note: After finding the V8miata.net forum in 2014 we went back and and added the previous entries into our "Alpha" development project build thread here.

New Project Introduction : Many of you reading this already know about Vorshlag's history with installing American V8s into European sports coupes and roadsters, but that wasn't the first V8 swap that I contemplated. Back in 1998 I purchased a 1992 "NA" 1st generation Miata. I bought it wrecked, repaired all the bodywork, and had it painted with the intention of building a 302 Ford V8 powered "monster" Miata. That was right around the time when the LS1 engine was just being introduced into the new 1997 C5 Corvette and 1998 Camaro/Firebird.


A couple of BMW E36 chassis with our LS1/T56 swap kit, shown above. These can weigh 2550 lbs (without interior) to 3100 pounds (fully optioned)

At the time I owned this '92 MX5 we were moving from Houston to Dallas, so the Miata V8 swap was mostly ignored, then became a seldom used daily driver for a couple of years. During that time I also owned and raced an LT1 V8 powered '94 Corvette and a supercharged LT1 '94 Trans Am, but I noticed quickly that the all-new "gen III" small block Chevy LS1 engines were a cut above the "gen II" LT1 motors. Deep skirted all-aluminum blocks with 6-bolt mains, incredible cylinder heads, and lots of new technology - but the same narrow/compact architecture of a "cam in block", pushrod V8. I was quick to get my hands on LS1 parts, weighing blocks (109 lbs) and heads (21 lbs) and learning quickly that these things are very light. And they were making more power, dollar for dollar/mod for mod, than anything else out there.


Comparison of Miata drivetrain next to LS1/T56

We completed the move from Houston to Dallas and the plans for little Miata V8 project switched from Ford 302 to Chevy LS1 V8 power. I started to accumulate LS1 bits, but the Miata (one of a half dozen cars I owned at the time) was parked outside and got hammered badly in a hail storm. This was a big one - it blew out skylights, ruined our gutters and roof, and utterly destroyed two of my cars. I was "SOL" and sold the Miata for a bit of a loss. My V8 swap fascination changed focus to a BMW E36 with LS1 power, and in 2002 that project began with the same block I had rounded up for the Miata. Since then we've sold dozens of E36 BMW LS1 swap kits, made an E30 BMW LS1 (our $2011 GRM Challenge winner), Z3 LS1s, and are deep into a new E46 chassis LS1 swap. We have several E36 LS1 turn key swaps underway right now, too.


Even Mazda knew the 1.8L wasn't enough. Here's a factory built NB test mule with a Duratec V6. Why was this never built?

But this whole time that Miata LS1 swap was bugging me. It was an unfinished project that I had let slip by. A thorn in my side every time I saw people talking about the various LS1 Miata kits out there. Sure, the V8Roadsters LS1 swap kit sold by Flyin Miata looks very nice, and the new Boss Frog kit has a different take on it. They have fine products and I am not saying otherwise. But... I could see little improvements we could make, significantly different parts choices I was familiar with from my years of building/owning/racing Corvettes, F-Bodies, and Mustangs, and maybe some improvements that could come from our decade of working with LS1 V8 powered BMWs. The question I put to myself earlier this year was: Should we jump into this market with our own LS1 swap kit for a Miata??

Yes, we are making an LS1 swap kit for Miata's

As you might have guessed, we are going forward with this swap. Why would I start this thread if we weren't, right? Our BMW LS1 swap business has been growing lately and we have been taking on turn-key swaps in addition to the already robust E36 LS1 swap component manufacture and sales. We all love this Miata chassis, it is so abundant that it has become very affordable, but they are just... lacking in horsepower. An LS1 fixes all of that.


Our first Miata V8 candidate, or "Alpha" Miata, is a 1999 "NB" 2nd Generation Miata that weighed 2342 lbs with 1/2 tank of fuel

For now, we are going to concentrate on the 1999-2005 NB chassis and skip the 1990-1997 NA cars, just because they are getting a bit long in the tooth. The prices aren't that far apart for clean swap candidates, looking between the NB and NA Miatas. The 3rd gen NC MX5 chassis is significantly different from the NA & NB cars, and used car prices are still pretty high, so we are not going to delve into an NC LS1 swap right now.


Left: Miata "BP" 1.8L engine weighs 348 lbs. Right: Miata 5-spd manual transmission weighs 85 lbs

Some of the weights involved are shown above and below, from weights we have taken. Looks like the 1.8L Miata motor and 5-spd trans together weigh 433 lbs, with accessories. Not bad for an iron block 4 cylinder. By comparison the BMW E36 chassis' 4 cylinder M42 DOHC 4 and Getrag 5-spd are 429 lbs, which is almost identical. The big 5.7L LS1 V8 weighs 457 lbs soaking wet, with all accessories (and has more than triple the displacement and triple the power of the Miata 1.8L). The 6 speed Tremec T56 (from the 1998-2001 Camaro) itself is a portly 125 lbs, but it's a big strong transmission with two overdrives. That should give us a 582 lb drivetrain, if we stick with the T56, or an extra 149 lbs over stock. The combined "609 lb" weight shown below was indeed for an LS1 and T56 drivetrain with accessories, but also included a stock Camaro engine harness, MAF sensor, and engine computer.


Left: The M42 1.8L DOHC 4-cylinder and Getrag 5-spd is 427 lbs. Right: A fully dressed 5.7L LS1 + T56 at 609 lbs (click to enlarge)

Why do we love the LS1 V8 so much? Well, there are several reasons. It is a compact and light engine, as I mentioned before. It has been used in literally millions of cars and trucks worldwide since 1997, in so many variants - iron and aluminum blocks, and factory displacements that include 4.8L, 5.3L, 5.7L, 6.0L, 6.2L, 7.0L - that are all dimensionally identical. With aftermarket support that dwarfs almost every motor in existence, there are essentially no limits on power goals, which aftermarket engines that can make 8.5L and boosted engines pumping out 2500 hp. A common build is to use a nearly stock aluminum 5.7-6.2L LS1 series engine and make 350-450 whp, with a mild camshaft, good street manners, and great power under the curve. Even "only" 350 whp in a 2500 pound package can be a total blast at an autocross or track event. A little more displacement and/or compression+camshaft can get you to 500 whp, which is a LOT of fun.

Our first steps included finding a willing Alpha customer, which we found in Jason Toth. He was eager to become our first test customer and on his own he rounded up this highly optioned, 1999, silver 5-spd Miata that needed a little help and wasn't anything super rare, so it will make a great swap candidate. Once the car was here, we took a ton of measurements and fixed a few little things on the chassis that were going to stay. Then the OEM drivetrain was pulled out so we could take a closer look.



The car was coated in oil underneath from a leaky front seal, so we gave it the full pressure wash treatment under the hood and on the bottom. Once the car was in the air I noticed the relatively large transmission tunnel, so I was pretty confident we could make the Tremec T56 or something like it fit without too much trouble. We might go another direction with the transmission, with two other possible gear box candidates, but I will share more on that soon.

continued below

 

continued from above


First test fit of our mock-up LS1 and T56 transmission

Once the stock drivetrain was out, we shoved our "mock-up" LS1 engine and T56 into the little car. The initial fit wasn't half bad, but there are two corners in the firewall that really limit rearward movement of the V8 engine's cylinder heads. Our guys cut some small notches back there (which will be covered in steel when the final engine placement is locked down) and re-installed the LS1/T56 drivetrain farther back, and now it looked much better.


Well we're committed now! You can see the corners we trimmed to make the LS1 fit farther back, which lines up the shifter nicely, too.

After seeing this second test fit's engine placement, we were happier and now know which oil pan should work perfectly. We've also got a good idea on how we want to build the new front crossmember, which will be a custom tubular design utilizing mostly stock suspension geometry. Definitely some weight to be lost there. The rear differential was also mocked up with an aluminum Ford 8.8" 31-spline differential carrier from a 2003-04 Cobra. This will need another custom subframe to mount this diff carrier, plus some other parts we will discuss later.

Vorshlag LS1 Swap Goals

I don't want our kit to be just another "me too!" option for the Miata V8 swap world. Although some of the steps and parts will be similar to the other kits out there, we plan on doing several things very differently. In order to make the drivetrain work how we want, some of the major changes will have secondary effects, including some upgrades to other areas of the car. These "forced" upgrades will work in harmony with the rest of the swap to keep up with the speed potential of the ~400 whp LSx powerplant that most customers want. Again, these upgraded components will be shown as it they are developed.


The factory NB Miata Power Plant Frame is shown in the pictures above (click to enlarge)

One major change I proposed was trying to keep the factory Power Plant Frame (see above), which is the big aluminum C-channel shaped structural member that attaches between the factory Miata transmission and rear differential carrier - giving the chassis much needed rigidity. All of the other V8 swap kits do away with the factory PPF and replace it with big slabs of steel in the form of subframe connectors, and another big hunk of steel that bolts between those to become the transmission crossmember. My initial idea might not work, but we're going to try it - as keeping a PPF could both save weight and keep the chassis stiffness using the same style components the Mazda engineers started with.

In the end, I want to see a 2500-2550 pound finished weight on this fully optioned, full interior, street car build. That means only +150-200 lbs total weight added over stock. And yes, if you are keeping up with my math that's barely enough added weight to cover the increase in drivetrain weight over stock (+149 lbs), so we have some weight loss to concentrate on. That's what makes this swap worth doing - light weight, lots of power, small car. I am hoping that the custom PPF, our tubular subframes, and some of the other potential differences on our proposed LS1 swap kit will help save some weight over the Boss Frog (+300 lbs over stock ) and V8Roadsters (+200 lbs over stock) swaps. Who knows - we might miss that goal, but we are going to try. Again, we're beefing up some other systems (that might add some weight on their own) to match the performance of the LS1 engine that most other kits completely ignore. Only way to know is to try our ideas and scale the parts continuously throughout the build. Every stock piece that comes off will be weighed and so will every part that goes back on.



Sharing The Build Online

As usual we will post updates on this project and share them with the online community during the Alpha build. Perhaps it is not smart to show our project this early in developmental stages, but that's how we've always done it. In the end, we always get good ideas from forum readers, as there is always someone out there that has run into something we might not be familiar with. We do have some very experienced Miata guys in house, as well as good fabricators and a decade of experience in the LS1 swap world. It would be foolish to think that "we know more than everyone", and we can always learn something from someone. If you see something that could be done better - feel free to speak up!



Since some of my ideas might crash and burn as we progress, I'm not going to give away all of our thoughts up front. Some will become obvious as the build progresses, and whatever we end up with will have tons of pictures and data shared along the way. We also reserve the right to change directions on a particular goal, part choice, or theory as we progress - because on this first build I am sure we will learn as we go. Whatever we do, we will try to post regular updates as the build progresses.

When Will It Be Done?

This is a question I hate answering, because the answer is vague: "It will be done when it's done". There are so many things going on at the Vorshlag shop, which is a company primarily focused around developing, building and supporting suspension products. The LS1 swaps are too much fun so we also spend a good chunk of our time building, developing and supporting these swaps now, too. We are already well underway on a new BMW E46 LS1 swap kit & Alpha build, have some new things coming for our BMW E36 LS1 swaps (as well as three turn key builds), and more.

Just know that this Alpha LS1 Miata build is not going to happen overnight. This is not a "one-off" build and it has the extra burden of a future production swap kit riding on it as well. We will take what we learn in this build to create production fixtures so we can manufacture parts in batches made to tight tolerances. Then anyone with some basic tools can use our kit parts on their NB Miata, install them in their own garage, and have them fit without major hassles. The users and production variables dictate how we can implement some of our V8 swap solutions, as always.

So if you absolutely gotta have a Miata V8 right now, then we aren't your source. Check the links I have included above for the competing LS1 swap kits, which are in production today and I'm sure they'd love to have your business. I'm going to stop here, as I have four other build threads to update or start (Pikes Peak STi, BMW E46 LS1 Alpha LS1, McCall's BMW Z3M LS1, and the Subaru BRZ build thread).

Thanks!

 

Project Update for October 1, 2012: Well we've had a busy few weeks since the last update, after the blur that was August (Pikes Peak hill climb event), spending September racing at the SCCA Solo Nationals, a Global Time Attack event, and some other autocrosses. But the LS1 Miata project hammered along with a few test fits, some changes, new parts arriving, and key decisions being made. We acquired several donor parts, weighed and tested each of them, and whittled down our options quite a bit. Let's get caught up:

Three Transmissions, One Winner

The transmission to use in this chassis was always an unknown. The tunnel is tight in some areas and we didn't want to require our end users to hack up the tunnel in their cars to fit the transmission. A little engine bay trimming isn't so bad, but slicing and widening the tunnel is major work that most people do not want to tackle - us included!

The first manual transmission candidate we tested with was the Tremec T56 6-speed transmission. This one is very well known, but with increasing demand and a finite supply from the 1998-2002 Camaros and Firebirds, the used prices have been creeping up towards $1500. The T56 "Magnum" (really just an aftermarket version of the 2010+ Camaro's TR-6060) is around $2800 new, but has increased torque capacity to 700 ft-lbs among other needed improvements. We used one of these in our E36 "Alpha" car behind a 490 whp 7.0L LS2 and it was a great trans. The Miata fitment testing we did on the LS1 + T56 fit "pretty well", but still had some width limitations inside the stock NB chassis' tunnel. We really do not want our LS1 swap kit to require tunnel surgery and we want the engine as far back as possible, so this gave us reason to think twice.


1998-2002 GM F-Body T56 weighed in at 125.8 lbs, dry.

The T56 also didn't have an easy way to attach the Power Plant Frame ("PPF" or Torque Arm) to the rear end. Also, this transmission is relatively heavy at 126 pounds. It is a great transmission, capable of handling some good torque (450 ft-lbs), shifts well enough, but has two overdrives... which is overkill for this chassis.

Next up, we purchased and tested with the ZF S6-40 6-speed manual from a 1989-1996 Chevy Corvette. This "ZF6" is a freagin' TANK of a transmission, used in several BMW models (with a different tail assembly missing the PPF mount) with either 650 or 1000 ft-lbs of torque capacity in stock form. It also has a provision for a very similar torque arm as the Miata, as used in the C4 Corvette. That was my favorite choice up front, but as some of you pointed out, it has a few flaws.


1989-1996 Chevy Corvette ZF S6-40 weighed at 153 lbs, dry.

First is that weight! Good grief this thing is heavy, even using a factory magnesium C4 bellhousing. That big torque rating comes with a lot more steel on the internal gears. It also has a divorced shifter that mounts to the body, unlike the T56 which has an internal rail shifter (which makes for better shift feel and easier swapping). We found a good specimen with a magnesium bellhousing made for the LT1/LT4 engine, but it was going to take an expensive adapter plate to mate to the T56 bellhousing made for the LS1 engine - and it would only gain weight.


The shifter location was not right and the clearance to the tunnel was non-existent.

Finding the ZF S6-40 new is impossible, as they have been out of production for over a decade. Finding them used is difficult because they only came in certain C4 Corvettes and rebuild costs were also high. Physically the remote mounted C4 shifter location was way too far forward and the transmission itself was WIDE. There was no way this big beast was going to fit the Miata tunnel without a major fight. The only feature it added was the potential to use a modified C4 PPF, but that was not enough to overcome the many other obstacles. So the ZF6 was a dead end. Hey, you sometimes have to try something to find out what works and what doesn't. We had seen weights listed all over the place, and now we know.

Yes, some of you figured out this was the transmission I eluded to in my first post, and yes, you were right that it is not a good swap candidate. I am not always correct.

Our third choice was the Tremec 3550/TKO series 5-spd, and I think we have a winner. This 5-speed has an internal rail shifter and only weighs 95 pounds, but the two aftermarket TKO versions have 500 and 600 ft-lbs of torque capacity. They are hard to find used, but only cost $2200-2300 brand new. Of course it has no provision for the PPF, but I have pretty much given up on this as an impractical goal. Sure, we could hobble together something that attached to the back of the TKO, but we already have enough custom fabricated parts in store for this swap to make all of our other "wish list" items work.



We have seen these TKO's in all manner of race cars and kit cars, including a Cobra with a Ford big block that was in our shop for some work for about a week. We got to measure the trans, drive it, and this trans is pretty slick. It is so compact, yet so strong! The only question left was which aftermarket version to use?

continued below

 

continued from above

TKO 500 vs TKO 600

There are actually 3 choices when it comes to the GM pattern Tremec TKO transmission. The differences in torque rating and costs all come from some internal gearing differences. But there are key reasons why we want to use the 600:

• Tremec TKO 500 Chevy/GM - TCET4616
• Transmission is rated at 500 lbs. ft. Torque
• 3.27, 1.98, 1.34, 1.00, .68
• Tremec TKO 600 Chevy / GM - TCET5009
• Transmission is rated at 600 lbs. ft. torque
• 2.87, 1.89, 1.28, 1.00, .64
• Tremec TKO 600 Chevy / GM Road Race overdrive - TCET4618
• Transmission is rated at 600 lb-ft. of torque
• 2.87, 1.89, 1.28, 1.00, .82

When you look at the ratios the "normal" TKO600 actually has a much more usable first gear for a car like the Miata. That tall first gear works better when you are using these transmissions in a light, powerful car with not enough tire (we won't ever have "too much tire" on these cars, heh). Way back when I was racing a Mustang 5.0L with the factory T5, it had "3.35" first gear. Later I went to a T5-Zcode, which had a taller "2.95" first gear and the change was very noticeable. The taller 1st gear was much easier to launch with at an autocross and the gap between 1st and 2nd was closer - for a more normal feeling gap. This TKO600 looks like that same upgrade over the TKO500.



So the TKO600 is where we would go, just for the better first gear. It also has a slightly taller 5th gear, for better highway cruising. There is also a TKO 600 "road race" version which is the same box, with the same taller first gear, but a lower 5th gear, for using all 5 gears in anger on a road course (much tighter ratio 4th to 5th). We don't think there's any road course where this would be needed on a Miata with a big thumping V8, and it wouldn't have as much of a "street friendly overdrive" as the .68 or .64. So the TKO600 with the .64 5th is what we think is ideal.

The TKO's synchros are big beefy brass units, which are a bit unusual in construction; we have heard stories that they don't shift well above 6500 rpm, but then other racers using them say they work fine. We talked to a local Tremec rep that came by our shop last week and he said he can make these TKOs with a custom carbon blocker rings and synchro package so that they will shift like butter at high RPMs. For this build the engine we have in store isn't a super high rpm buzz bomb and will likely make peak power at 6000, so this isn't a concern this time.

Other Parts In Store

We are still exploring possibilities with the rest of the swap, but we do know the Ford 8.8" aluminum IRS differential housing from the Ford Mustang Cobra is what we will build the back of the car around.


Left: The BMW E46 188mm diff next to the aluminum 8.8" Ford. Right: RX8 front parts (top) will be used, but the rear uprights are 5-link and wrong (bottom).

Development on the front end is starting with a pair of Mazda RX8 uprights and hubs. These feature 5x114.3 bolt circle hubs, with much stronger hub assemblies than the 4 lug Miata. The uprights are nice aluminum units which we will build control arms to fit, and feature large front disc brakes (12.5" diameter). We still have a lot of work to jig up for these, and we will increase the wheel and tire size to work with the bigger front and rear uprights/hubs/brakes.

Engine Being Built

We have several swaps going on with stock LS1 drivetrains, but the customer for this Miata wanted something more. His 400 whp minimum power level meant that it would be a pretty hotted up 5.7L LS1, or one with some better head work and internals. We contacted HK Racing Engines in Houston and they came up with a potent little combination based around an LS1 5.7L block we sent them. It will have CNC ported heads, a small duration but high lift hydraulic roller camshaft, and extra beefy internals. The machine work is complete and they are assembling the longblock now. We are using one of two oil pans on this engine...



The pans above have a much lower front profile than the Camaro LS1 pan that people tend to (cut up and modify) in these Miata swaps, but are nowhere as expansive as custom fabricated oil pans.



You can see the massive improvement in the front of the sump area, where the steering rack would be. That picture we took is showing showing the factory F-Body LS1 oil pan ghosted over the GM LS1 swap oil pan. Hopefully the Holley or GM swap pan will clear the stock steering rack placement, and more than likely the Holley version will be what we use. We have all three pans here for mock-up test, which we will do as soon as the TKO600 arrives.

OK, that's all we have for now. We have the transmission nailed down, three oil pan options, new front uprights/hubs/brakes to work off of, the rear differential picked, and a few more things in the works. We still have a LOT of work to do, but this swap is being attacked between other LS1 swap jobs underway at the shop right now (five cars). Just wanted to give a few updates on where we are headed with this Miata swap.

More soon,

 

Project Update for January 4, 2014: Wow, over a year without an update? Yikes. While it looks like I have been avoiding this build thread, we have been plenty busy working on this project and many others over the past 14 months. Most of the work we have been doing on this project over the early part of 2013 had to do with upgrades to the shop and building fixtures we needed to delve further down the rabbit hole on the Miata LSx swap. Later in 2013 we also tried a number of oil pans, designed and built a new tubular front crossmember, did all of the geometry calculations then mounted the new front suspension bits, and then we finalized the wheel and tire package. We also worked on a lot of other customer cars in that period, built a few race cars, developed our BMW E36 LS1 swap kit extensively, released our BMW E46 LS1 kit, and a number of suspension development projects in the same time period.


All pictures in my posts can be clicked for higher rez versions

We also had a very busy racing schedule in 2013, running 15 events with NASA (among many other groups' track and autocross events) in our TT3 prepped Mustang, shown below. We won 13 of those, got one 2nd and one 3rd, setting 8 track records along the way, while testing all sorts of aero and suspension work (we race to test, and test to race). Another project that kept us busy was developing a new set of NA/NB Miata shocks shown below. These are custom built with Bilstein Motorsports components, using massive 46mm monotube pistons, machined and assembled at Vorshlag, then custom valved by Maxcyspeed & Co. We just finished our final round of track testing last weekend, testing the latest valving package for a dual purpose street/track set-up. I had a blast hooning around in the tester's 2001 Miata below at Eagles Canyon Raceway. These dampers should be in production in Q1-2014 and we will have more information about these in the New Damper Offerings forum thread.



One thing to note about this post: starting in early 2013, I started making ALL of the pictures in all of my forum posts click-able for larger sizes. With a photographer like Brandon on staff it is a shame to only show the little "small" versions in our posts. So if you see an image you like, click it for a higher resolution version of the same image.

Before I get going on this update I wanted to shout out to V8Miatas.net - Just found this forum which looks to be a great resource for V8 Miata swaps, as the name suggests. Our build thread was added there today at this location. I already learned a few things reading build threads there, so if you have plans for any sort of V8 swap in any generation of the MX5 chassis, you should head over there and sign up.

Shop Upgrades Lead To LSx Swap Progress




So one of the things we needed to work on this Miata LS1 car was a 4 post lift, which we finally ordered and installed in early 2013. This made it easier to do drivetrain mockups. We quickly realized that we also needed a chassis dolly to make the Miata easier to move around once the subframes were out. So we built that in summer 2013, and soon modified it to fit two other chassis. Now that dolly thing gets used on a daily basis (should have built one of these sooner) to move a car around the shop that has no suspension, crossmembers, or wheels.



Believe it or not, the lack of the 4 post lift and chassis dolly were big impediments to this Miata LSx project. Since we are still in a somewhat small shop space we couldn't afford to have the Miata stuck on one of our lifts for more than a day or two, which kept us from pulling the front subframe out for more drivetrain mockup (ever try to move a car around without even subframes in it?).

The Real Engine Swap Work Begins



Once the lift and chassis dolly were built we rounded up the hardware needed to get the TKO-600 transmission mounted to another LS1 block we have, then put that mockup drivetrain in the car for some testing with the REAL transmission. Before we had eyeballed the TKO in the tunnel but not while attached to the block. This helped us see what the next piece was in the way...



After we did that round of LS1+TKO mockups we quickly realized that the OEM front crossmember was a HUGE hindrance to this swap, as even heavily modified and hacked up it would be in the way of the engine, oil pan and exhaust headers. We refuse to accept the huge compromises that come with "block header" exhaust headers on any of our swaps, so a new tubular front crossmember was going to be required.



You can see above some of the structure of the frame fixture that bolts to the body dolly, which Ryan built for the NB Miata. There's actually a lot of steel rectangular tubing you cannot see in this pic. The rolling cart attaches to this frame fixture from underneath the lift. This fixture was built to allow the car to sit at the desired ride height w/o suspension while sitting directly on the lift, with the rectangular tubing setting the chassis height. He then mocked up some 265/35/18 tires at both ends for a quick look. If you shove them in hard enough they almost fit under the fenders, heh.



continued below

 

continued from above

Choosing Tires and Suspension To Build Around

We knew early on that we wanted to upgrade all of the factory (and very weak) 4 x 100mm NA/NB hubs hubs to 5 x 114.3mm RX8/NC hubs. The 4 x 100 hubs are a common failure point up front on Miatas that see any track time, and keeping the rear 4 x 100 hubs would limit the halfshaft strength greatly. Going to 5 x 114.3 bolt pattern opened up a lot more wheel and brake choices as well. Doing this "hub upgrade" is more work than you might think - this meant new uprights and control arms, so the NB suspension pick-up points on the crossmember were no longer sacred... so we might as well ditch it, right? Well we tried to keep the stock crossmember, probably far too long into the swap development. We tried cutting it to make room for this or that (like some of the kits are fond of doing), modifying the pick-up points, but it was getting weaker and more customized.



Meanwhile we had been mocking up this RX8 front control arms and uprights and even tried an 18x10" wheel and later a wheel and tire. Ryan put in several days of work, and with Jason's help, they did a lot of measurements and calculations and got the front suspension sorted out fairly well. At this point we knew we would be able to re-use the RX8 front spindles, brakes, and control arms. I was worried we would need to fabricate control arms, but it all fit very well with the forged aluminum RX8 arms. Small victory.


Video we made for the customer, showing the RX8 suspension and 18x10" wheel in action

In the video linked above we were showing the customer the current location of the wheel and suspension with the big 18x10" wheel, to which we later mounted a 285/30/18 tire. This video shows the front 18x10" wheel turning at ride height, and we later made some adjustments to clear that wheel at full lock, inboard (obviously the fenders will need to be cut and flares added to cover the tire). Our customer has had regular e-mail updates every 2-4 weeks, showing all of what you see here and more. We send these email updates with pictures and videos to all of our long term project customers - basically anyone that has their car in our shop for anything more than just "day work".



Later a set of 18x8" Mustang wheels (from my 2013 Mustang GT) were installed, shown above left. We noted that these barely fit under the stock fenders, but they didn't have enough positive offset. We might pick up some higher offset RX8 18x8" wheels (above right) and tires, which would sit farther inboard. This could possibly avoid the need for cutting and flares for some folks. Luckily, our Alpha customer is going with the 285mm tire option. Why so much tire? Well the LS1-based 5.7L motor that was built for this car will make 425-450 whp, and in a 2600 pound car with a short wheelbase, that is downright hair raising... we felt that a 285mm tire (Hoosier!) was going to be barely enough to keep it on track when the loud pedal is cranked up to 11.



One thing that had me a little worried during our wheel and tire mock-up was tire height. Most NA/NB Miatas are using a 23" tall tire, which is SUPER SHORT and only come in sizes out to about 215mm or the occasional 225mm. We went away from the typical 14-15" wheels to clear larger RX8 front "sport" rotors, which at over 324mm diameter are too big to fit inside a 15" or 16" wheel. Then tire width choices started to come into the picture... there just wasn't anything wide enough in 14, 15, 16" or even 17" diameters (the last two diameters tend to top out at a 255mm tire width for most brands), so we jumped straight to 18" - which currently has the most options for wider tires in both street and race compounds, covering widths including 275, 285, 295, 315 and beyond. We're building our TT3 Mustang around a 345/45/18 in the 2014 season, for instance. You can almost never have too much tire width on a race car...



Turns out there wasn't any tire anywhere near 23" tall once you left the skinny options in the 14-15" wheels, so we chose the shortest tire that is also wide that we knew of - the 285/30/18. This tire is normally the magic solution to "going wide" on track or autocross cars, and we've used this 24.9" tall monster tire on lots of BMWs (see above right, which has a bit more tire height room), EVOs, Subarus, and more. They even are used on RX8s and NC MX5s, but those cars have a lot more "wheelhouse" room than the NA/NB chassis. So we will likely cut the front upper frame horns for more clearance at full bump travel (then add back more structure with welded steel tubing). The above left picture shows the suspension at about 1.5" of bump, which isn't enough. Oh well, using a 2" taller than stock tire causes some problems we will have to overcome, but they aren't anything we haven't tackled before on other chassis.

New Crossmember Development

Once the tire was chosen and the front hubs and suspension components were tested and mocked up, we were ready to start burning in the pick-up points onto some sort of crossmember - either the stock piece or a custom design. At this point it was obvious that the OEM front crossmember was the next big stumbling block and it had to come out, once and for all. We just couldn't save it (it was already cut-up so much to clear the engine that it would need major reconstructive surgery), we didn't need it (we were changing all of the suspension pick-up points), and it was just in the way. So first the Vorshlag crew fabricated a crossbar that held the front of the engine from the top, which rested on a part of the upper chassis that wasn't going anywhere. Then they made a similar and also temporary rear transmission crossmember that was bolted in place, so the driveline position and angles were set. In the step above you can see the OEM crossmember out of the car for a bit, but now it was time to be fully replaced.



Now that the drivetrain was where it needed to be we connected the dots to build our new front crossmember. Using lengths of 1.75" diameter x .120" wall DOM steel tubing, Ryan measured then mandrel bent the new fore-aft frame members. These tubes were spaced inboard enough to maximize exhaust header space as well as set the final lateral and vertical locations for the RX8 lower control arms, which had geometry already determined above. These main fore-aft tubes bolt at both ends of the engine bay, onto factory chassis mounting locations that have substantial strength. Unlike the stock front crossmember, which mounts at the rear of the engine bay and at the midpoint (where the suspension parts mount), the new tubular design would mount at those points plus forward at the front tow hook tie down mounting plates. Our crossmember should make for a more rigid chassis when it is completed, with less cowl shake and more stable suspension mounting.

continued below

 

continued from above



You can see Ryan welding the front mounting position of the crossmember tubing at the tow hook mounting plate, which is a beefy piece of plate steel bolted to the front of the chassis with plenty of bolts on both sides. With these two main crossmember pieces in place several things were then test fit. First, 3 different LSx oil pan designs were fitted to see which provided the best clearance to the lateral tubing member that was still needed as well as clearance to the NB Miata steering rack.



Each oil pan design had some advantages and disadvantages, with the total depth of the pan's sump driving how low we could get the drivetrain in the chassis, and the front section of the pan limiting where the steering rack would end up. In the end we chose the oil pan from the 1998-2002 Camaro, which is commonly available from the aftermarket. The Holley swap pan and the GM Muscle Car swap pan both had issues that could not be overcome. Luckily we didn't have to settle on a fabricated oil pan (these always seem to leak), the GTO double-hump pan (we have used that one and do not like it) or another cut-up OEM pan. There are good baffle/trap door kits made for the Camaro pan (Improved Racing's unit is preferred) and we have a lot of miles on track with this oil pan and baffle in BMW E36 LS1 swaps.


This is our prototype front NA/NB engine swap crossmember - additional gusset plates and tubing will be added before final welding

The final LSx oil pan we picked ('98-02 Camaro) is shown above, after the lateral tubing member was tack welded in place. Two vertical tubing members were also added, welded mid-way from front-to-rear and landing on some plate steel that bolts to the stock crossmember front mounting holes (which doubles as the upper control arm inboard mounting point). This makes for a completely bolt-in tubular crossmember, with extra mounting bolts/locations, once we get it into production (we will replace the OEM tow hook tie-down plates with a new, Laser Cut plate version). It also has a LOT more room for the engine and exhaust headers, so we can develop real exhaust headers - which can make upwards of a 50 horsepower difference on an LS1 V8 over the block-hugger super shorty headers some kits are stuck with. And this crossmember could work with a LOT of other engines as well.

We weren't going for the "lightest crossmember on the market" here, as I cannot count how many lightweight tubular crossmembers I have seen bend or fail. No, we wanted the STRONGEST possible fabrication we could come up with. The .120" wall thickness on the 1-3/4" DOM tubing we used might be overkill, and we could step that down to .095" wall on a later prototype piece (we will surely make some tweaks to this design before it is ready for mass production), but when it is completed we will weigh this first tubular unit vs the stock OEM stamped sheet steel fabrication and see where everything shakes out. A crossmember is not somewhere you want to skimp on.

Throttle Body Clearance, Air Cleaner Routing, Possible Hood Ducting?



Of course before the oil pan and engine heights were finalized we tested with an intake manifold and throttle body on the mock-up LS1 engine, then tested with the stock hood in place. We had plenty of room up top, but realized that due to the short length of the Miata engine bay the intake inlet tube would have to go "over the top" of the radiator support (yes, this means we have to lose the factory hood latch). We've done this type of air inlet re-routing before, like on our TT3 Mustang shown below.



This was one of the many custom tweaks we had to do on that car to make room for a deeply ducted hood, which vented the back of the radiator and made the front splitter much more effective. This had an accidental side effect of offering a lot more cooling capacity (and front downforce) to that car, so we might do something similar on this LS1 Miata, and of course use a bigger radiator at the same time.


Ducting the Mustang's hood made the front splitter we built MUCH more effective, both for cooling and front downforce

There are plenty of Corvette style air filter housings we can choose from, which was the air filter we ended up with on our TT3 Mustang. So after the intake manifold was fitted the Miata's engine height was locked down, and the driveline down angles were set at the transmission. Next up it was time to burn in the RX8 suspension mounting points to the new crossmember...

Final Welding of Suspension, Brakes Added



Our fabricators Ryan and Olof made some steel mounting plate sections on the bench that were then fitted to the tubing and tack welded in place on the crossmember. Then the suspension was mounted up, the wheels were added, and everything was set to ride height... to re-check camber, caster, toe, and then camber and caster change with suspension travel. Obviously you don't want caster change with suspension travel, so that was dialed out.



It doesn't look like much but dozens of hours were burned getting these mounting points welded in, measured, moved, and tweaked. Mazda-sourced eccentric bolts are used at the same suspension mounting locations as the RX8, to be able to adjust camber and caster. And while some of you suspension savvy readers might point out that the upper arm's mounts aren't perfect (we wish they were about an inch higher), they are as perfect as we could make without cutting the frame out of the NB chassis or going to custom control arms.

continued below

 

continued from above

There's a lot to be said for re-using OEM forged aluminum arms, which can make for easier service and maintenance down the road. We checked the dynamic camber change and it turned out to be pretty reasonable, too. Remember: Vorshlag specializes in suspension development, so this was an area we really made sure to get right. And we could see something in track testing that might make for future changes before this kit goes into production, too.



Seeing the old front suspension and brakes on the shop floor next to the new stuff is quite a difference. We're upgrading from a 254 x 20mm vented front Miata front rotor to a 323 x 24mm RX8 Sport front rotor. Going with RX8 hubs gives us a lot of Big Brake upgrade kits to choose from down the road, if needed. This customer wants a car he can track, autocross and street drive across country - and it will have 450+ hp and sport 285mm tires, so it will have some extraordinary braking requirements for an NB Miata.



These RX8 calipers and rotors are all Centric premium units that we sourced new, so it should make for a good starting point for track and street testing. We will also add front brake ducting, at a minimum, before it sees any track testing. That makes a huge difference on most road course cars we deal with, and it doesn't cost a lot nor does it have any downsides for street driving.

What's Next?



With the front crossmember, brakes and suspension nailed down and in prototype form it is time to move to the rear suspension. The front bits had so many variables that all cross over each other, but without steering involved we're hoping the rear will go more smoothly and quickly. As you can imagine the customer is getting anxious to drive his car, and wants to run events this year, so we've got to get crackin!



None of the OEM rear control arms, brakes, and hubs will be re-used. Again, we felt that the small-ish rear hub's inner spine size would limit the power capability of any halfshaft that could be built for these cars. I've seen fellow racers shred axle after axle in LS1 equipped Miatas, and I don't want to get stuck with those limitations on our swap. So this means it all has to come out and we get to start over. Yay.



The diff housing we are using is of course the 31 spline Ford 8.8" aluminum IRS casing that was used on the 1999-2004 Mustang Cobra. This was also the same housing used in Lincoln MarK VIIIs, and steel versions were used in the Thunderbird and Explorer chassis. The new S550 Mustang chassis looks to have the aluminum version as well (we should have one of these Mustang's soon for chassis/suspension development in late 2014 and a full season of racing in 2015). All this means is these diff housings are both common and affordable, not to mention strong as an ox. Aftermarket choices abound for gearing and internal differential options, too. We also have the rear uprights chosen, which are a commonly used unit for Cobra kit cars.


The real motor needs to be installed, of course, along with the accessories/brackets and clutch system

For now we will use the OEM rear subframe to mount things to, at least during mock-up. Once these uprights and the diff housing are mounted and set at the right heights and locations, we will fabricate upper and lower control arms, check the suspension geometries, then move to the halfshafts. This will entail a lot of fiddly work, measuring and calculations, of course, but compared to the front bits (which had to have an engine, transmission, suspension and crossmember all mate up) it should be a little less work.

Until next time, thanks for reading.

 

Thanks for posting up Terry! I very much appreciate you taking the time to share this project with us here at V8M.net! We all, obviously, enjoy anything V8 Miata related whether it's Ford or GM. And to have a mfgr take the time to post great pics and a well-written thread is just pure icing on the cake for me, at least! I've visited your company's site a few times, but it has been awhile. I think I remember reading about the start of this project - perhaps on your site, but I had forgotten about it since. Not anymore. Your approach to suspension choices and concern for high HP strength/abuse are refreshing - and will be appreciated by your customers, for sure!

Thank you again & we wish you the best with your Miata conversion kit (and other projects) success! Alpha project is going to be bad @ss...

Almost forgot to mention my one point of contention with you, LOL, and that is the first generation NA's being "long in the tooth"... Some of us are sorta passionate about our Miata body-style preferences! The NA's are older, no doubt, but they need love too... I would take a guess that many of your NB items should retrofit our prehistoric Miatas too!

Patrick

 

Patrick - thanks for the kind words. Wasn't sure how this thread would be received here, whew.



As for the different Miata generations, we have some NA aficionados here within our walls. Much of our Miata suspension testing has been in NA chassis MX5s, too. The white NA above got the very first set of AST coilovers for any Miata, which were developed at Vorshlag, and they are still on there 5 years later. I'm hooning one of our Mustangs in the background of this shot, heh. That was Turn 11 at Eagles Canyon Raceway, where we do much of our suspension track testing. We do work on all manner of late model sports cars like BMWs, Corvettes, Subarus, even stick axle pony cars.



We also tackled some 302 V8 swap fabrication work on an NA Miata last year. The problem is our LS1 swap kit is so extensive that it will likely be a bit expensive. And as we've seen, some of the NA owners tend to be a bit more thrifty than NB owners? Not knocking it - that's just how it usually falls out. So since we don't know how many of our kits will end up in the NA chassis we have been concentrating our development with the NB chassis.... but as you said, much of the the LS1 swap bits we develop will swap over to the NA.

Cheers,

 

Any updates?

 

Hey Terry. Are you selling the front sub frames now? I'm interested in the RX8 hub/brake conversion for my project. Dave

 

Project Update for June 25th, 2014: Long time no post on this project once again, but with some recent changes and progress we have regained some lost momentum and we are pushing to get this prototype LS1 NB Miata on the road by this Fall. After a spurt of work in January and a little more in April, some real time was spent on this project in May. Let's get caught up.



The biggest progress of late was a new milestone that was started and finished since the last post - the rear subframe and suspension was constructed. Right now the car still sits on 18x10" wheels and 285/30/18 tires at all 4 corners, with the new RX8 front suspension tacked up as well (see above). The front obviously needs more negative camber (and more adjustment range), which we're working on next.


Ryan, that started fabrication on this project has left us (left) but our new fabricator, also named Ryan, is on the case (right)

We had a few delays on this project in the months since the last post, due to a few unforeseen changes here at Vorshlag. For one, our lead fabricator Ryan B (above left) left us after almost 3 years of great work to pursue his college degree full time. He was working here part time for the past year and whenever we had to steal him for major fab work at our shop he didn't get to focus on the Miata swap often or for long. After he left we searched for over a month and found another great fabricator to join us, Ryan H (above right), who joins us with lots of race preparation and fabrication experience from a Daytona Prototype team and other previous race shops.



As soon as Ryan H started here we buried him in fabrication work on a customer's V8 swapped race car, then he spent 100 hours working on the Pikes Peak Subaru above. Once those pressing deadlines were passed he got to spend about a week and a half working on the LS1 Miata and a lot of progress happened, back in late May.

Custom Rear Subframe Construction

We weren't sure which way the rear subframe and suspension would go until we just dove in and started mocking up parts. We knew the factory rear hubs were going away, as we wanted to fix the problems we've seen in our V8 swaps to this chassis when we made ours - namely, busted halfshafts out back and fragile hub bearings at both ends.



There wasn't much to start with when Ryan got to the back of this 1999 Miata. We had looked at using part of the old factory rear subframe structure and cutting it up to fit the Ford 8.8" aluminum center section. The problem was the new diff was so large that most of the top of the old subframe had to be removed and very little structure would be left.



The stock differential housing, rear subframe and rear control arms were removed so we could mock-up the new parts we wanted to add. The rear hubs/uprights were ordered then we mocked up the Ford 8.8" IRS diff housing...



There was no way that 75 pound aluminum diff housing could fit without hacking the stock rear subframe beyond recognition, so it was set aside intact and fabrication of an all new rear subframe was started. The Ford diff housing was mocked up using some straight tubing passing through the new rear hubs and uprights we chose for this new set-up. These were chosen for their "high torque capacity" sizes on the hub bearings and the splined size for the halfshafts. Nothing that uses the OEM rear NA/NB Miata hubs or input spline can live much beyond about 250 ft-lbs of torque for very long, at least not with grippy R-compound rubber. The LSx motor that has been built for this Alpha car will make more than double that (450 ft-lbs+)



The uprights (below) we used are aluminum, very strong and work with the 5 x 114.3 mm bolt circle hubs shown above. This rear hub will work with the same wheel bolt pattern we're using up front, which we borrowed from the best OEM Mazda front bits. The entire front suspension is based on the beefier RX8 hubs, uprights, brakes and forged aluminum upper and lower control arms.



We also switched to a different rear cover for the Ford 8.8" IRS housing, which is shown above, deciding not to use the 2004 Mustang Cobra cover. This dual ear "winged" mounting style cover used is similar to the style that comes on the BMW E36 chassis and somewhat like the C4 Corvette Dana 36/44 housing - both cars we have worked with and raced hard for many years without issue. This style cover is easier to work on and mount to than the "clamped center mount" '99-04 Mustang Cobra rear cover used in our earlier mock-ups. This newer cover also has both fill and drain plugs on the cover, for use with a possible differential fluid cooler (common for heavy road course use).

continued below

 

continued from above



The goal was to be able to use stronger OEM based and commonly available hubs, brake parts & other consumables (not one-off fabricated or race-only parts), and have the same wheel bolt circle front and back. This way if you blow through your brakes or wear out hubs at a track event, you can run to a local parts store to get replacements fast.



Ryan jumped into the new rear suspension and subframe design with both feet and spent a full day making measurements (see above) and checking suspension geometry using 3D node software, to check camber change through suspension movement. Using the short upper and long lower arms and moving the pick-up points in computer space, then checking the camber change under movement. The final pick-up points and geometry chosen looked great and the dynamic camber change was well within normal parameters.



This is major fabrication work coupled with suspension design, and not something usually done by just "anyone that can weld". Luckily it wasn't too challenging for our crew - we are primarily a suspension shop and all of us are racers - and the new subframe and suspension design was knocked in a little over 70 logged hours.



The start of the upper structure of the rear subframe is shown above and left. The beefy new subframe unit will bolt to the 6 factory mounting studs in the rear of the chassis, without any cutting or welding. Once it is finish welded I will share the final weights vs the OEM bits, but it should add little to no weight over the stock rear assembly. The picture above right shows some of the tubular steel custom rear lower control arms going together. These are adjustable and feature polyurethane mounting bushings for some cushion but nowhere near the slop of a rubber mount. This should be suitable for a dual-purpose street/track car, but we could also make these arms with spherical ends for track-only set-ups.



These hub-mounted stands worked well during geometry checks and suspension mock-up and fabrication. Lots of fixtures and welding jigs were built to be able to make the parts uniformly and mirror imaged from side to side.



Here you can see the aluminum 8.8" diff housing starting to be fitted to the tubular steel rear subframe structure. Polyurethane (red) bushings were used in the front and rear mounting locations for this housing.



The front diff mounting brackets are shown below at right. There is a gusset to add on each side but otherwise that section of the subframe is finished.



You can see the rear chassis studs and bolt holes that the new subframe mounts to, below. There are some scalloped areas that will be added for more bolt/nut clearance, and small tubular gussets here and there, but this is the final layout we're going with.



There are a few gussets to be added, then final welding can be done and the subframe removed for powder coating.

What's Next?

We've already had started on the front subframe and it was mostly done. Now we are tweaking the front geometry to allow for more camber and caster adjustment, using the RX8 eccentric bolts/washers and OEM style "cages" around these bits. Once the front subframe is completed we will design and build the LSx V8 motor mounts (takes about a day and a half). After that the prototype header fabrication and a driveshaft can be built. We have an aggressive schedule to finish this car this year, so stay tuned for more updates. We will be making production runs of both subframes, for use with LSx V8 swaps as well as racers with boosted Mazda engines that want the reliability and durability of the higher strength hubs, halfshafts and diff housing we're using.

Thanks,

 

Terry - This is going to be amazing when you get done. I wish the project was moving at break-neck speeds, but I can understand you all have so many other commitments to make. Thank you for not letting the Miata project get mothballed! Best of luck to you - and glad it is coming together!

 

Can you let me know who makes the piece you are using for control arm adjustment there? I am working with tie rod pieces from an HD truck, and its less than ideal. I knew people made specific stuff like this but hadn't found anything.

I love the project. I'm just doing custom control arms to accept a better spindle, but keeping the OE geometry due to lack of resources to design a better system. I like what you guys have done, the rear subframe looks much stronger, boxing itself in instead of leaving it open on the bottom like the OE unit. And a dozen other things, too, I'm sure.

**Still would love to know the brand you are using, I found some good stuff, however. I'm going to start drawing this up, pretty excited to fabricate what I have in my head!
http://www.speedwaymotors.com/Search...End%20Bearings
http://www.southwestspeed.com/?sec=v...Male%20Threads

 

Any updates?

 

Yea, wow.... long time no update. I will make a point to write-up what we've been up to next week and post it here. We moved shops (doubling in size), but have been plugging away at the Miata LS1 (and the Scion FRS LS1 and others). Here's a couple of quick pics...


Engine in place with a different manual trans, plus with front accessories


Prototype tubular front crossmember finish welded and ready to go back in

Those last two pics were from just this past week. So much has changed, improved, and been completed since my last update. Front subframe done, all new front uprights/control arms are done, trans crossmember done, motor mounts done, new trans in place of the TKO, rear subframe done, rear suspension done, etc. Its now time to make headers and finish the plumbing.

More soon!

 

Wow that is sweet Terry. Make headers? Any plans to market them? You guys still in the DFW /Plano area?

Any plans to take this car to mitty in April...?

 

Yes, we plan on making a kit for all of this - tubular front subframe, tubular rear subframe for 8.8" Ford IRS, control arms, motor mounts, transmission crossmember, driveshaft, steering shaft, and headers - on the first round. Much more after that is in production. That's how we've done all of our BMW kits (120+ kits sold) in the past. Prototype header design and fabrication work is next on the Miata LSx swap. We just went through this on the FRS/BRZ swap we're doing, shown below.


Header mock-up started. We can go through dozens of iterations fast using this snap-together kit


One side mocked-up in plastic tubes, ready to go to steel


Going into steel, mocking up tube by tube. This looks easy, but takes 35-40+ hours


Final prototype headers set of FRS/BRZ LSx swap, stainless, long tube, 3" collector, 1.75" primaries, with V-bands

We find its more economical for everyone if we make the prototype headers here in-house, then have them replicated by a production header maker here in the USA, where they can CNC bend the tubes. That's where we are at in the FRS - the manufacturer we use made their first "production" set off of a fixture made from our prototypes, and we just test fit them on the car, then we will have them tweak a tube or two. It takes a couple of iterations, which takes a couple of months. But everything else we make in house, like the mounts, trans crossmember, and on the Miata the subframes and control arms. Here's some production pieces from our other V8 swap kits...


After we make the prototypes we put CAD drawings together for each piece, which is then CNC laser cut


We weld these in our production fixtures in house. Here's the production BMW E36 LSx Swap Motor Mount kit


Typical inventory of BMW E46 & E36 stainless long tube headers


We make driveshafts for each chassis, to fit T56 or T56 Magnum transmissions


Production motor mounts and Transmission crossmember for Scion FRS/Subaru BRZ LSx

More soon,

 

Thanks for the update. You guys look to do amazing work. Sorry, but where are you located, again? Would love to see you guys at an event and check out the projects. Very nice.

Also, thanks for leading me to the holy grail of header fab. wow. genius engineering there.

 

Me too bring the Miata to Mitty in April!!!

 

Project Update for June 25th, 2014: Long time no post on this project once again, but with some recent changes and progress we have regained some lost momentum and we are pushing to get this prototype LS1 NB Miata on the road by this Fall. After a spurt of work in January and a little more in April, some real time was spent on this project in May. Let's get caught up.



The biggest progress of late was a new milestone that was started and finished since the last post - the rear subframe and suspension was constructed. Right now the car still sits on 18x10" wheels and 285/30/18 tires at all 4 corners, with the new RX8 front suspension tacked up as well (see above). The front obviously needs more negative camber (and more adjustment range), which we're working on next.


Ryan, that started fabrication on this project has left us (left) but our new fabricator, also named Ryan, is on the case (right)

We had a few delays on this project in the months since the last post, due to a few unforeseen changes here at Vorshlag. For one, our lead fabricator Ryan B (above left) left us after almost 3 years of great work to pursue his college degree full time. He was working here part time for the past year and whenever we had to steal him for major fab work at our shop he didn't get to focus on the Miata swap often or for long. After he left we searched for over a month and found another great fabricator to join us, Ryan H (above right), who joins us with lots of race preparation and fabrication experience from a Daytona Prototype team and other previous race shops.



As soon as Ryan H started here we buried him in fabrication work on a customer's V8 swapped race car, then he spent 100 hours working on the Pikes Peak Subaru above. Once those pressing deadlines were passed he got to spend about a week and a half working on the LS1 Miata and a lot of progress happened, back in late May.

Custom Rear Subframe Construction

We weren't sure which way the rear subframe and suspension would go until we just dove in and started mocking up parts. We knew the factory rear hubs were going away, as we wanted to fix the problems we've seen in our V8 swaps to this chassis when we made ours - namely, busted halfshafts out back and fragile hub bearings at both ends.



There wasn't much to start with when Ryan got to the back of this 1999 Miata. We had looked at using part of the old factory rear subframe structure and cutting it up to fit the Ford 8.8" aluminum center section. The problem was the new diff was so large that most of the top of the old subframe had to be removed and very little structure would be left.



The stock differential housing, rear subframe and rear control arms were removed so we could mock-up the new parts we wanted to add. The rear hubs/uprights were ordered then we mocked up the Ford 8.8" IRS diff housing...



There was no way that 75 pound aluminum diff housing could fit without hacking the stock rear subframe beyond recognition, so it was set aside intact and fabrication of an all new rear subframe was started. The Ford diff housing was mocked up using some straight tubing passing through the new rear hubs and uprights we chose for this new set-up. These were chosen for their "high torque capacity" sizes on the hub bearings and the splined size for the halfshafts. Nothing that uses the OEM rear NA/NB Miata hubs or input spline can live much beyond about 250 ft-lbs of torque for very long, at least not with grippy R-compound rubber. The LSx motor that has been built for this Alpha car will make more than double that (450 ft-lbs+)



The uprights (below) we used are aluminum, very strong and work with the 5 x 114.3 mm bolt circle hubs shown above. This rear hub will work with the same wheel bolt pattern we're using up front, which we borrowed from the best OEM Mazda front bits. The entire front suspension is based on the beefier RX8 hubs, uprights, brakes and forged aluminum upper and lower control arms.



We also switched to a different rear cover for the Ford 8.8" IRS housing, which is shown above, deciding not to use the 2004 Mustang Cobra cover. This dual ear "winged" mounting style cover used is similar to the style that comes on the BMW E36 chassis and somewhat like the C4 Corvette Dana 36/44 housing - both cars we have worked with and raced hard for many years without issue. This style cover is easier to work on and mount to than the "clamped center mount" '99-04 Mustang Cobra rear cover used in our earlier mock-ups. This newer cover also has both fill and drain plugs on the cover, for use with a possible differential fluid cooler (common for heavy road course use).

continued below

 

continued from above



The goal was to be able to use stronger OEM based and commonly available hubs, brake parts & other consumables (not one-off fabricated or race-only parts), and have the same wheel bolt circle front and back. This way if you blow through your brakes or wear out hubs at a track event, you can run to a local parts store to get replacements fast.



Ryan jumped into the new rear suspension and subframe design with both feet and spent a full day making measurements (see above) and checking suspension geometry using 3D node software, to check camber change through suspension movement. Using the short upper and long lower arms and moving the pick-up points in computer space, then checking the camber change under movement. The final pick-up points and geometry chosen looked great and the dynamic camber change was well within normal parameters.



This is major fabrication work coupled with suspension design, and not something usually done by just "anyone that can weld". Luckily it wasn't too challenging for our crew - we are primarily a suspension shop and all of us are racers - and the new subframe and suspension design was knocked in a little over 70 logged hours.



The start of the upper structure of the rear subframe is shown above and left. The beefy new subframe unit will bolt to the 6 factory mounting studs in the rear of the chassis, without any cutting or welding. Once it is finish welded I will share the final weights vs the OEM bits, but it should add little to no weight over the stock rear assembly. The picture above right shows some of the tubular steel custom rear lower control arms going together. These are adjustable and feature polyurethane mounting bushings for some cushion but nowhere near the slop of a rubber mount. This should be suitable for a dual-purpose street/track car, but we could also make these arms with spherical ends for track-only set-ups.



These hub-mounted stands worked well during geometry checks and suspension mock-up and fabrication. Lots of fixtures and welding jigs were built to be able to make the parts uniformly and mirror imaged from side to side.



Here you can see the aluminum 8.8" diff housing starting to be fitted to the tubular steel rear subframe structure. Polyurethane (red) bushings were used in the front and rear mounting locations for this housing.



The front diff mounting brackets are shown below at right. There is a gusset to add on each side but otherwise that section of the subframe is finished.



You can see the rear chassis studs and bolt holes that the new subframe mounts to, below. There are some scalloped areas that will be added for more bolt/nut clearance, and small tubular gussets here and there, but this is the final layout we're going with.



There are a few gussets to be added, then final welding can be done and the subframe removed for powder coating.

What's Next?

We've already had started on the front subframe and it was mostly done. Now we are tweaking the front geometry to allow for more camber and caster adjustment, using the RX8 eccentric bolts/washers and OEM style "cages" around these bits. Once the front subframe is completed we will design and build the LSx V8 motor mounts (takes about a day and a half). After that the prototype header fabrication and a driveshaft can be built. We have an aggressive schedule to finish this car this year, so stay tuned for more updates. We will be making production runs of both subframes, for use with LSx V8 swaps as well as racers with boosted Mazda engines that want the reliability and durability of the higher strength hubs, halfshafts and diff housing we're using.

Thanks,

 

Project Update for December 17th, 2014: We've been busy on the Miata over the past few months but I've just been too busy to get caught up on the forum updates. We just finished construction and a big shop move for Vorshlag, doubling our available space, which ate up a lot of my time. This move has made for some extra room to work on projects like this, to add some new fabrication equipment, and just this past week for two CNC machines (lathe and mill) to finally make our machined Vorshlag products 100% in-house.



Right after the move in November a majority of Vorshlag folks also went to SEMA and then we were competing in OUSCI (Optima Street Car shootout) in our TT3 Mustang. Then Jason went to the 2014 PRI show and took 100 pics of cool new parts. Ryan stuck around at our new shop in Plano, Texas, and worked on the Alpha Miata V8 and made some really good progress. Then he found some more days in late November and early December as well. Anyway, we have all been slammed, but big progress has been made on the Alpha Miata.


The 2014 SEMA show and the OUSCI competition were fun but ate up a lot of time I where could have been updating various build threads

Front Suspension Follies!

Last time we updated this build thread, Ryan had finished re-checking the geometry on the rear bits, tweaking the rear subframe and making new rear control arms. That was back in June. In August he was freed up a bit and finish-welded the custom rear rear control arms. They are ready for shock mounts, cross bracing and custom half shafts at that point, but the rear subframe still needed to be final welded. He wanted to tackle the front before "locking down the design" (track width, ride height, etc) out back.



Now we move ahead to some time he had in August, when he moved to the front, to re-run the 3D geometry on the RX8 spindles/arms that we already had mocked up and tacked in place to the custom tubular front subframe. Well... while it looked fine to the naked eye, once the wheel was at the proper ride height (now visible with the RX8 hubs mounted to the new hub-stands, shown above) the geometry was less than ideal. Once the pivot points were input into suspension analysis software it was obvious that anti-dive and bump steer were terrible. Still, I wasn't giving up on keeping the suspension/brakes "all Mazda" up front, so I had him stick with the RX8 bits a little longer and try to move the pick-up points to try to dial some of this out.



Ryan cut off the previous pick-up points and made new ones, then rolled the mounting points as far as he could within the constraints of the stock front Miata tub and the RX8 arms. After sourcing some factory Mazda RX8 eccentric bolts and making the new control arm mounts that mimicked the factory subframe mounting points, it looked great and had the adjustments we needed, but the geometry still wasn't getting much better. He did some 3D measurements, saw some room to improve, then yanked the subframe and started over - making an all new front subframe section, from scratch, to gain some room for our the RX8 suspension at the lowered ride height and to fit with the big tires we had in mind. Two steps forward, one step back - that's how it works sometimes. The second, new subframe was tack welded together and had several improvements, and we would end up sticking with that through the next suspension iteration.



After he re-installed the RX8 bits it still wasn't good enough, so our engineer Jason and I asked Ryan to just fabricate new control arms to use with the RX8 uprights and hubs, but after an exhausting search the OEM style ball joints for the RX8 (very funky taper and size - nothing like anything supported by the aftermarket) were not available separately, so this was a dead end. Bah! I finally pulled the plug on the RX8 spindles and pretty aluminum control arms. We had already acquired brand new RX8 brake parts, too. Oh well, some ideas just don't pan out. Lots of fabrication hours were wasted based on my notion of using OEM RX8 spindles, brakes and front control arms.

After this latest wild goose chase we had Ryan stop working on the car for a few weeks while engineer Jason and I regrouped, to look for other front suspension and spindle solutions we could utilize. After this debacle we realized that swapping in another set of control arms wasn't going to work inside the narrow confines of the Miata without several miracles, so instead we focused our search on a good OEM uprights that was made for a double-A Arm suspension. The result was we found something much better than the RX8 bits - lighter, forged aluminum, even more common to find, with tons of aftermarket support, beefy front hubs, and dozens of OEM and aftermarket big brake options. So, what did we use?

When In Doubt, Just Use More Corvette Parts

Corvette C5 spindles were the chosen upright this time (C6 are virtually interchangeable, too) and the first one we purchased looked great - and proved to be significantly lighter, too. And honestly we don't care where the parts come from, if it meets the criteria for use on a hybrid build like this: use the best parts available, that can be purchased at the best price, with good aftermarket support, easily procured consumables, and the best materials/strength/design.



The C5 aluminum upright was 5.6 pounds (13.96 pounds, with hub and ball joint installed - and the unit bearing hub is BEEFY!) compared to the 15.5 pound RX8 steel upright and hub. The nice thing is that the front and rear spindles on a C5 (and C6) are interchangeable (RF and LF are the same, LF and RR as well), which doubles your chances of picking them up second hand. Once we had one of these forged C5 spindles on hand, new ball joints were ordered next (we first made sure first that they were available separately!) and Ryan started making a whole new set of upper and lower control arms.



These would be tubular, the right lengths, and after some analysis, end up with better geometry, and have more range of alignment adjustment than the "eccentric" bolts of the RX8 arms. We could now adjust camber and caster through a larger range and achieve proper geometry at the ride height we wanted without cutting up the Miata tub. The lower arms would house the C5 ball joints and the upper arms would accept the matching C5 upper. The ends we chose were firm polyurethane bushings and the lengths were to be adjustable. A lot of pieces were ordered, many more were custom machined, and a lot of hours were spent calculating, fabricating and measuring.

continued below