I have a huge radiator, dual electric fans and a 180 thermostat. In light traffic the cars does fine. It will warm up in heavy traffic. I noticed the fans are quiet so maybe I can upgrade the fans to noisier, but better air flowing blades.

The car does not have an air dam or a radiator shroud. Does this make a difference? What are the best flowing electric fans to use. Maybe this would help? Any ideas?

 

To cure my slow speed overheat I did three things, 1st; wrap headers with fiberglass header tape to reduce the underhood heat gain. 2nd; sealed the radiator top, bottom and sides so that all air coming in the front passed through the radiator. Both things made a noticeable improvement. BUT by far the greatest improvement was getting heat out of the engine bay with the hood vents you see in the images. Do a search on hood vents, lots of reading.

lots of info also posted on fans, the best junkyard fan comes from a Ford Taurus. I can't quote details but search is your best friend for this type info.

Good Luck!

 

Ahh great ideas! So the hood vents did the best out of the 3 mentioned? Interesting.

 

If you check the online catalog of a vendor (maybe Summit or Jegs) that sells a lot of different choices in fans, I think you will find they list the cfm flow rating for each model. That may help you make some comparisons.

If you get a couple of little tornado-makers, keep an eye on amp draw. You might need to use two relays rather than one to stay within their allowable switching load. Probably best not to exceed around 75% of their max rating if you want them to have long, trouble-free life.

 

All of this stuff^^^^^. Also be sure that you are not using any underdrive pulleys. AND the factory Miata temp gauge is not the most accurate thing in the world. You may want to install a real temp gauge to see what is actually going on. I have an overdrive water pump pulley that I am going to try on mine.http://www.summitracing.com/parts/as.../model/mustang I also added an over-ride switch on the fans so I can turn them on myself in traffic BEFORE it gets hot & the fans cannot recover it.

 

Just a comment about the cfm ratings on the fans. I have seen elsewhere in this forum that the cfm ratings that the manufacturers claim are basically made up. So, I would just suggest using recommendations on that one, not just specs on a webpage.

 

Good point about inconsistencies between fan manufacturers cfm ratings. The only thing that matters to the user is the cfm moved under a reasonably high static load, i.e., as installed and pushing air through a maze of radiator cooling fins. Some manufacturer's may rate the flow with unrealistically low static pressure.

I wouldn't be surprised if they also fudge on voltage, justifying by assuming their 12V fan is installed in a car whose electrical system MAY be providing 13.8V under running conditions, so we'll just use that voltage to rate performance, along with no static pressure. Uh-huh... Anybody but me old enough to remember the time in this country when most people thought telling the truth wasn't optional?

My '90 has a stock 5.0L HO except for a Ford E cam, and is installed with Martin's kit. The headers are not wrapped and the hood not vented. On the car's trip home from the Carolinas to Florida, I got stuck in a freeway stop and go traffic jam for over an hour in mid-90's ambient temperature. Engine temperature never rose above the point at which the fans turn on. That's with the Martin-supplied fans pushing through an A/C condenser as well (A/C not running). So for those using Martin's set-up, unless you have substantially more cubes and/or higher compression, it ought ta' cool it. If it doesn't, the first thing I'd check is the voltage at the fan terminals while they are running. Could be getting some voltage drop that's slowing the fans. Maybe the wire size could be too small, relay overloaded, weak alternator output at idle, or whatever. Maybe double check engine timing at idle, too.

For the bigger cube/high compression motors with more BTUs to shed, I've wondered if this set-up might be a good choice: Derale Dual High Output Rad Fan 16825 | eBay The shroud would get at least some of its total 4000 cfm moving over the entire surface of the radiator fins, rather than only the area directly behind the fans. Sticking a measuring tape on it just now, it looks like the 3.5" mounting depth may be possible by slightly trimming some sheet metal and replacing the hood latch with pins. It looks like the shroud could cover the A/C condenser completely (if you have one), although creating that effectively smaller plenum would likely reduce flow efficiency some.

Obviously a person could fabricate the shroud if they are handy with sheet metal.

 

Please don't get me started.

 

I had the same problem when I first bought my Monster. The fans were wired wrong so they were trying to push air forward rather than pulling air. Reversed the polarity of the wires and the problem was cured.

 

Hi,

I will assume that the water pump is OK and the thermostat is OK and is (a 180deg F unit).

So overheating is generally function of either cooling capacity of the radiator or poor airflow from fans.

Many of the cheap Chinese made aluminum radiators that might look "big" are actually rubbish at absorbing and shedding any heat. I would steer clear of any cheap crappy radiator. My preference is to use a two or three core unit made of brass (heavy but can sink lots of heat).

The fans I would recommend are SPAL, they are the best. Simply get the largest most powerful unit that you can fit. The fans need to be setup to PULL and NOT PUSH. PUSH fans are not efficient and wont move the air you will need.

Having a good shroud for the fans will be a must to ensure that all air the fans are sucking is getting pulled through the radiator core, and not getting around it.

Also make sure the intake is getting fresh air from outside or by shrouding the intake filter. An exposed element will just suck hot air. My analysis with thermocouples had shown that the underhood temps can go as high as 70 degrees on a warm day at idle and when the engine ingest that hot air it will accelerate the heating up and intake temps that high lead to detonation and other nasties.

if the radiator, shroud and fans are top notch then there will be no need for any additional hood vents, shrouding etc.

I have had my car idling in traffic when the temps were 105 deg F and the needle never moved even after 3 hours in that traffic. Car has never moved off the thermostat temp (180 deg F) position (middle of the gauge) in 7 years.

See my build thread for details of what I did.

cheers