Just bought my '90 - 347 Monster...need to get through emmisions as I want to register the car. Car has no catyltic converters. My understanding from talking to a state emmissions rep is that I need an visual inspection on the cats and to pass the emmissions through a test designed for the original vehicle...I don't have much more details than that...Here is what is on there State web site...


"If your vehicle is a 1995 or older, and has a GVWR, that is less than 8500LBS, it will be tested using a method called Acceleration Simulation Mode (ASM 25/25). This type of test simulates driving at 25 MPH using the dynamometer while applying a 25% load equated to your vehicle make and model. The inspector will insert a probe in your vehicle’s tailpipe to measure the emissions while the vehicle is driven on the dynamometer."


My mechanic friend and I agreed that I should find the cheepest ones that will fit and then remove them after the test. I'd rather not remove them as I need to be tested in another two years.

my requirements are passing the test, keeping performance while the cats are on and leaving them on, and ground clearance...

So...

Will a small cheap set of Cats pass emissions in CT with a ford Stroker 347 set-up - RPM performer - EFI...with a stock A9P...Any thoughts on the above would be great...Meierznutz...your in CT right? any experience here you can share?

There is no OBD required testing for this year car...

Thanks in advance.

 

My mustang with a similar set-up passes the same test every year here in Georgia. The stock converters are in place, but were gutted years ago. You could try welding a set of converter heat shields over your pipes & see what happens. It should pass the visual test with those. If it fails on the dyno, then install some of the Magnaflow high flow cats & try again.

 

All of mine have passed a similar test with two magnaflow high-flow cats and a functioning EGR system. I do not run a smog pump as the newer style of cats makes it almost redundant. Also, the visual inspection looks for the equipment that a Miata came with which does not include a smog pump (and no EGR if your car is 1993 or earlier).

The reason it is possible to pass this test is that the acceptable limits are raised each year for every make/model of car to account for normal wear and tear. What this means is that all you have to do is make the car cleaner than a 20+ year old Miata with 200K miles on it. A clean, rebuilt 5.0/306/331/347 with new cats will fly through the test.

If you are running a stock Ford computer I would leave the cats in place. The computer depends on the backpressure and my not know what to do without it. If you're running an aftermarket ECU (MegaSquirt) it’s up to you (and your conscience) whether you leave them on or not.

-Jason

 

My 5.0 Mustang would pass with gutted cats, F-cam, 24Lb. injectors, TFS heads, & a 12psi Paxton supercharger.

 

Well it was a push...I went to the testing center and the performed the dyno test, but even with a large fan in front of the car, the temperature reached an uncomfortable levels before the test machine came back with a pass/fail answer. The temp ran to just over 220 before we called it quits. I'm really not sure were the limit on this should be on this. Any thoughts would be welcome.

I'm going to add 'Water Wetter' to the cooling system, and try again later today before investing in a more aggressive fix.

 

Make sure that you have some sort of shrouding in place to seal the grill opening to the radiator. You want all of the air that enters the front of the car to go through the radiator. This makes a huge difference.

 

Does it have cooling fans? Usually Monster Miata are built with two pusher fans in front of the radiator that are triggered via the original Mazda thermo switch.

-Jason

 

It has the cooling fans and they were turned on. I'm going to take out the thermostat, and add water wetter and go back for another try later today. Will see what I can do about a shroud too. A friend advised me that I could probably run a little hotter for the test...maybe in the two thirty range for a for minutes...

 

Excessive (advanced) ignition timing will make it run hot, also. Is your temp. gauge correct? What temp. is the ECT sensor showing?

 

I passed...very low polluter it seems...embarassingly low...go FORD EFI....

still have a few very minor kinks to work out machinically...Then the interior...but still pleased to be an owner...6k or so in to the 'decision' so far so good....

Car is now running in the 180's with the changes to the coolant- water wetter... and the thermostat removal...3G alternator is now giving me grief..whatever...fun car to drive..can't complain....

S

 

Andy...sorry I havent been on in a while.
Here is what I went through... the car was registered and insured before the swap so I went to emissions just before the stocker came out. That gave me two years to complete it. Three years later I am up and running ;-)
Here in the State of Taxation, we have to pass the emissions standard of the original car or the engine build date, whatever is newer.
Magaflow makes a nice small high flow cat that wont hurt performance and has only a 4" shell. Place them as close to the header as you can and install your O2 after them.
Water wetter is a great idea to keep temps down, just be sure you use no more than 30% glycol in the mix for best results.
If you dont have the air diverter in front of the rad, find a way to get it in. It guides the incoming air to the rad. I am running Flyin Miata's hood vents now and they dropped temps a lot.
PM me if you need a hand!

 

All good ideas but the o2 sensors MUST be before the cats, not after. They will not be able to accurately read the fuel ratio if the cats come before them.

-Jason