Track overheating
 

I'm running a 1995 Miata with a FM II hydra turbo kit and new Miata 1.8 crate engine. I have FM cross flow radiator, dual fans, tight radiator shrouding, hood louvers, and 3" wide opening slot cut in the bumper to feed air directly to the top of the radiator. The coolant is distillers water and Waterwetter.

On short tracks and cool temperatures the car runs fine with coolant temps about 210. However at Road Atlanta and 90 degree days I watch temps slowly climb to about 230 at which point I gt out of it. When I do this temperatures quickly drop to normal.

I can sit in 100 degree stop and go traffic all data with the a/c running with no issues.

Do I need to go to the M-Tune route. I'm freaked at the tight installation and multiple points of potential failure.

Any advise? Thanks.

A reroute will increase the flow of coolant to the radiator leading to more capacity. A reroute will also even the cooling through the engine (i.e., gives #4 some cooling). It does not have to be the M-tuned though. There are plenty of lower-cost/fewer-failure points options. Search on it. I've got good pictures of mine in my build thread.

BTW, the flip side of increasing the flow through the radiator is decreasing flow through the heater core. In winter, you'll notice that your heater doesn't work as well after a reroute. It'll still be warm, but not hot -- if that's a concern.

Are you running the shroud on the FM dual fans? That significantly impedes airflow through the radiator on track -- although it works great for using the A/C as you mentioned.

M-tuned reroute, the shroud is not helping but probably not enough of a restriction to make it overheat. The cut in the bumper is probably hurting you and you don't have shrouding on the front of the radiator. The hood louvers are probably too far back to work right and are hurting flow rather than helping it.

Step one is to box or shroud the front of the radiator. Step 1a is the reroute. Step 2 is removing the shrouding on the back-side of the radiator.

Do you have the under pan installed???

Removing radiator fan shrouds will probably help and tie the fans directly to Radiator without shroud.

If your temp sender is located at the back of the head where the least coolant flow is, then a simple reroute *might* solve your problem.

Could you please confirm for us that you haven't deleted the heater core coolant path from the cooling system.

The most significant thing you can do to improve performance at speed is to fully duct or "shroud" the front of the radiator, so that all air that flows in through the mouth of the car can only exit the mouth of the car if it goes through the radiator. Simply having a small gap where air can escape around the sides of the radiator is enough to significantly lower the airflow through the radiator. I would also recommend testing the effectiveness of the slot cut in the bumper by taping it up and observing on-track temps. The effect of that slot cut is going to be somewhere between significantly bad to negligibly good. The top of the radiator is fed with air entering the mouth of the car. It is not a linear flow. As the car drives at speed, the volume of space in front of the radiator is pressurized. Once pressurized, this air looks for ways to de-pressurize. It can't escape out the front of the car because the mouth is designed to pressurize the cooling air, unless you changed this by cutting an air escape hole at a lower pressure region such as the front of the nose. This would have the effect of lowering the pressure of all of the air in front of the radiator. Pressurized air instead must escape through the bottom of the car beneath the engine. The easiest way to escape is to go around the radiator, this includes above the top, beneath the bottom, or around the sides. If air cannot escape around the radiator, it must go through the much more restrictive path of the radiator itself, which is how your car cools itself.

There are ways to improve the airflow through the radiator - if you have a well engineered hood louver designed to maximize and improve the natural lower pressure zone towards the front of the hood, it can increase the vacuum of the engine bay thereby increasing the velocity of the air through the radiator. A much better option would be to run a front splitter. Splitters work to improve car handling by reducing the air that can get underneath of the car. Basically you take the high pressure which naturally piles up in front of a car and add a splitter to the bottom of the front of the car to use that pressure to force downward on the splitter. The splitter also helps handling by reducing the air which can get under the car creating more natural vacuum underneath of the car. Both of these things, more high pressure at the front of the car (and thus into the nose and through the radiator) and higher vacuum under the car (thus higher velocity through the radiator) help your cars cooling ability at speed.

I have shrouded the air inlets, intercooler and radiator with with plasticore shrouding and weather stripping. The area over the top of radiator support are covered with aluminum plate. Any air entering the car has to go through the intercooler and/or radiator (to the best of my ability). The louvers are installed as Flyin Miata shows in a low pressure area as far forward as practical. I would love to cut in a radiator air extractor in the hood directly behind the radiator but it would cut into what looks to be critical support structure for the hood.

I hate to keep pouring good money after bad into this project. The question for me now is rerouting a proven or required solution to this problem. When I see comments on Flyin Miata's web site that say "try" rerouting I get concerned.

Thanks.

The slit in the top of the bumper did in fact help based on past track events. I don't have a front lip spoiler or splitter so that sounds like a promising idea. Anything to lower the pressure behind the radiator should help.

How do you tell if you have an inadequate cooling system vs. a problem of just getting heat out of the motor that the reroute would help?

I have a temperature gauge installed that is looking at coolant temperatures entering the radiator. I have not deleted the heater core coolant path.

Thanks again folks.

If you have a thick radiator, duct the front of the head exchangers, use a belly pan, and run a reroute out the back of the head, the car will run cool on the track. Do these things, if the problem persists remove the fan shroud. I've done it, Savington did it, Spoolin2Bars...it's not a mystery; we have a working formula.

The people who don't recommend a reroute are the people who get lapped. There is a reason that every car which comes out of TSE, every car that 949 races, and every fast Miata in Texas is running the things I listed, even on NA cars.

Listen to Hustler.

A reroute will (not might) help you. It puts more heat into the radiator rather than into the mixing manifold and back into the motor. Not to mention the benefit of cooling cylinder #4.

Anyone had any experience with Begi racer coolant re-route? Looks like a simpler and more reliable install than the M-Tune. I can live with longer warmup times (I always warm up before I drive anyway).

Also, I have a temp gauge sensor on my upper radiator hose. Begi advised that it was their experience that this read hotter than if the sensor was on the engine side of the thermostat or line leading from the back of the motor to the heater core(!?).

When I ran a Begi racer reroute and an ebay radiator without proper ducting during the winter in VA my car would never reach proper operating temps at speed. I could sit and let the car idle for 45 minutes and temperature gauge in dash would get up to 11:30 perfectly. As soon as I got on the I-60 and was doing a constant 50mph or higher the temp gauge would drop back down to the "C" line. I never tracked the car like this, other then local auto crosses. I also do not remember ever getting out my laptop and looking at temps when it would do this. While driving to my parents one Christmas it felt colder in the car with the heater on then with it off. You have not stated your location so I do not know how cold it gets where you live, nor do I have any clue if you drive the car on the street at all. This is just my experience with only the racer reroute.

Thanks. I just found the thread dealing with the "racer" reroute and that seems to be the major opinion.

Looks looks M-Tune is the best way to go.

Thanks.

It's the only one available that fits, the first time.

You can easily piece together a system with BEGI's spacer for less than the M-tuned unit. Everything on it works fine, don't get me wrong, however I'm not a fan of the hose, or the remote thermostat dangling around. If you wanna save ~$100 (I think), you can get BEGI's spacer, a Kia water neck, and a GM hose from an auto store.

I am a little spooked by the numerous hose clamps on the M-Tune. Changing the oil filter looks like it will be more of an issue also.

I'm going to follow up with my mechanic. The skin on the top of my hands is awful thin and this install looks like a killer.

Let's talk about BEGi's spacer. It doesn't fit right with a six speed, the threaded fitting doesn't let the OEM sensor sit flush and seal so you need sealant, the one I recieved didn't clear the accessory CLT sender so I had to mount it 180'd. You also basically cannot take it out with the head in the car so you want the remote t-stat housing. M-Tuned is the better choice. I fucking hate the one I bought.

Be a man.

Oil filter should come out through the passenger fenderwell anyway. The M-Tuned reroute adds two more hose clamps to a system that already uses 16 (NA) or 18 (NB), so I'm struggling with your logic there too. The install isn't fun, but it's not undoable, and it does make a difference.

I'm on board and will order the M-Tune and band-aids. Thanks again folks for your help.

I love learning from Hustler, he's like an abusive, alcoholic Scoutmaster. Thanks for the review, Looks like 949 or Trackspeed will be getting more of my cash. :burncash: