Cooling Issues on Track, What is the solution?
 

Was out at Buttonwillow this weekend for the 1st time since by rebuild and it was ridiculously hot. Ambient was over 100 F most of Sunday and close to that on Saturday. One constant issue I had throughout the weekend was overheating. On my out laps car would come up to around 210 F and if I pushed it for a lap it would come up to around 225-230 F. (not comfortable with that) Needless to say, I did a lot of cool down laps in putting it around. The temps would always climb slowly and very with how long I was in boost throughout the lap. If I hammered it all the way down the front straight, temps would climb 5-10*F in that one pass. Cooling down would take forever on the slow laps (heat soak?)

Details of my current setup below. I may be forgetting some items but this is the bulk.

• 1.6 M45 motor (Fresh rebuild) with Ebay A/A Intercooler blocking approx half the radiator opening.
• 37mm Koyo Aluminum Radiator
• M-tuned reroute
• 180* Tstat
• Fresh water + water wetter
• Ducted radiator opening (Home Depot Special)
• Hood central vent and side louvers
• Water temp reading taken at rear block outlet
• Heater core bypassed with 1/4" restrictor in hose
• Only 1 fan on driver's side
• Factory undertray in place

So from this point I have run out of ideas for overheating caused by a failure or not having part of the equation not setup properly. My thinking is that I just didn't have enough radiator there with the intercooler to keep the car cool. Do you guys agree? Is that another root cause?

My thinking is improve venting from hood by added lips to the current vent and enlarging the vent all together (think it's too small) and upgrade to a thicker/larger radiator. If I upgrade the radiator, do I need to move all the way up to something like the TSE unit? Or will a 55mm Koyo/Mishimoto/Etc. do for my under 200whp levels?

Little ------ AIDS radiator is the problem. Get a bigger one, TSE if you have the cheddar.

Sounds like you have taken all the usual steps. I would have thought the 37 would be enough for an M45 1.6 but maybe H man is right, time for a 55mm Koyo or TSE's cross flow. I assume your we'll under 200whp?

Also, if you have any "cooling or intake openings in the front of the car that allow air to enter the engine bay without going through the rad core first, plug them. Little things like TSI's. sloppy rad ducting, holes in the bumper skin, etc, can undo all the hard work getting the cooling system to reject heat by not letting the core get enough airflow.

Pics of vents?

I was able to keep my 250whp car cool with a 55mm radiator, ducting, hood vent, and an FMIC blocking 90% of the "mouth".

The easy solution is just to buy the best radiator on the market - ours. ;)

Where are you pulling the air intake for the heaton? Getting the filter for it out of the engine bay and into cold air will increase your compressor efficiency and lower the heat overall and should help engine temps (this goes for any compressor in the intake but double for roots[technically not a compressor fucking bite me]). Also more fuel and more timing advance will help as well if you want to get another hot track day in before you get proper cooling mods done. Or switching to e85 or race gas with methanol in it will make a big difference as well. Heatons heat the car up fast. In sub-freezing temps I'd have my old car up to the thermo temp in under a 1/4 mile of 25mph driving just getting to the main road. So the fact that only a little m45 on a 1.6 is getting it cooking is not surprising.

Car is making 170whp. No other openings on the front of the car except the hood vent and louvers as previously mentioned. During the weekend I also had an on track collision so the drivers side headlight and turn signal were taped up with Gorilla tape, seemed to hold fine so I didn't think that was an issue. Was running real hot before the collision too.

Will post shortly. Think I just have a crappy cell phone picture but it will do. The center vent is located center on the hood and just in front of the valve cover. The side louvers are copies of the FM louvers. They are located at cylinders 1 & 2 over the wheel wells.

This was my thinking too. Save up to buy one. I really don't want to spend the time, money and energy to buy a 55mm that only saves me $100-200 and still may not be the answer. A lot more expensive to throw away a track weekend due to overheating.

Intake is located right behind the drivers headlight like most other NA cold air intakes I've seen. Nothing done to isolate the filter. Thought process is that if the intercooler is doing it's job, the air should cool down enough before getting into the motor. Don't know what my AIT's got up to. Is there a way to read that off the MS after the fact?

Also, don't see a way I would route the intake to a cooler place in the engine bay. Cowl intake just wasn't going to work room wise.

How it was taped up and one side of the vent/louver
https://www.miataturbo.net/attachmen...ine=1348602837

Shakey but shows what you need
https://www.miataturbo.net/attachmen...ine=1348602837

Looks OK. I would maybe extend the hood vent a bit forward but that's not the cause of the overheating.

Maybe pressure test the cap. I like the 1.3bar Koyo cap which raises the boiling point a bit past the stock 1.1bar cap. I've seen caps with slightly damaged gaskets burn up engines more than once. As the engine heats and cools, it fails to draw a vacuum and pull overflow coolant into the system. The low pressure also allows hot spots in the head.

Emilio, can you explain how TSI's reduce the air flow through the radiator?

Any hole in the front of the car that allows air into the engine bay is adding pressure to it. What pushes air through the rad is a pressure differential. Vehicle speed increase pressure in front of the rad. More pressure in front of rad, less pressure behind it in the engine bay. Add more pressure behind the rad by adding holes to the front of the car and the pressure differential across the rad is lowered. Thus, less airflow through rad. TSI's don't hurt rad flow if they are completely sealed from the engine bay, only feeding into the induction system of the engine.

There are many detailed threads here regarding the Miata cooling system. comradefks has clearly read all of them and taken all the typical steps to inprove cooling in an F/I track Miata. Something is being missed though so we're kida brainstorming to try to figure out what it is. On paper at least, it shouldn't be overheating really.

I wouldnt think it was a weak rad cap. If you have a weak rad cap and the temp gauge shows your over heating the car is already toast because at that point its reading the temperature of the head and not the coolant.

Maybe a stupid question - but did you check for air in the system? The long M-tuned return can have a tendancy to trap air. Didn't see it mentioned, so thought I'd ask... I would 'assume' this was checked.

Haven't tested the cap previously but it as aftermarket, don't know the exact brand. Will put in on the list to replace if for nothing but to cross it off the list.

Drained the system and bled it after Saturday up at the track. Seemed to bleed out all the air (bubbles). Water was flowing cleanly at the radiator fill.

Just to confirm, we do not have a block coolant drain location right? Only the drain plug on the radiator correct?

How much "heat soak" in the engine bay is normal? When I come in off track everything in the engine bay is untouchable. That includes supercharger, valve cover, anything near the radiator, even the intake manifold is noticeably hot. I'm wondering if the louvers I installed are doing anything or maybe hurting me.

Also, I am starting to get more and more OK with just biting the bullet and going for a TSE unit before the next weekend out there. Gotta fit that in with planning for my wedding somehow....eep

If you don't have an oil cooler (supercharger owners, lol) then you have ~300*f+ engine oil in there so yeah, everything is going to be fire hot.

The vent in my hood makes everything surprisingly cool, but I can provide any specific data due to the confidentiality agreements with my race team, McLaren.

Yes on only having the drain on the radiator.

How are you bleeding the system?

Oil temps at the drain plug sensor got up to about 250F over the weekend. Don't know what the delta between that location and an oil cooler sandwich plate or the other locations for a reading are.

As far as bleeding, I fill the radiator with the nose of the car jacked up then run it until it's up to temp at idle. Keep filling radiator as needed. Then hold that car at between 2k and 3k in revs as it continues to purge out air. Basically stop when I stop seeing bubbles come out of the fill. Let the car cool down and top off the radiator/overflow as needed at the point.

That sound pretty good. The only thing I might add to the end is letting the car idle until the fan comes on and turns off 3 times to make sure all the air is out.

Understood. Only issue is that I'm running a MS now so the fan coming on and off is solely to do with coolant temp from the sensor at the back of the head and doesn't necessarily coincide with the thermostat opening, which is my understanding of what makes the coolant in the radiator dip and push water/air through to the fill at the radiator.

I think we got all or almost all the air out of the system. If there was some air in there, it was negligible.

You drive like a woman if your oil temps are 250*f and you're not running an oil cooler.
Buy , start the car, pour in water, relax, wait for the t-stat to cycle, then run records at every track. This funnel is magical.

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Lisle magic funnel:
https://www.miataturbo.net/attachmen...ine=1348678778

I generally have my fans set to come on at 210 degree Fahrenheit and then off at 200. So I know what they are coming on and off with the thermostat being open. It is probably a bit overkill to burp this way, but it has always worked for me.

[QUOTE=hustler;931956]You drive like a woman if your oil temps are 250*f and you're not running an oil cooler.

I was...because I was overheating. Do about 1 hot lap for every 3-4 cool down laps in a session. Cool down laps were about 20 seconds slower than a fast lap.

[quote=comradefks;932009]I've never been there, but I bet it felches abraded poz dump to deal with that crap.

It really did suck. Almost packed it up early a couple times on Saturday night and Sunday morning but decided why not go out there.

Ended up playing the drive it 4th gear everywhere and pedal it on the straights while catching my friend in his slow ass 240sx single cam around the track. Proved entertaining :)

So I guess my consensus is to upgrade the radiator, make sure my radiator cap is replaced and has a pressure rating that is adequate and bleed the system thoroughly. Also want to revisit my radiator ducting and see if I can improve on it.

Oh, and I drew this up real quick. I will make it up at work and rivet around the vent opening in the hood to promote heat extraction.

We have one of the Lisle magical funnels here but never use it. John prefers to lift the nose of the car up. One trick I've found for burping is to put the back cap on just before the tstat opens. Pressure builds in system and helps push bubble out back of engine.

wouldnt hurt to add some shrouding and "box-in" the radiator.

I have done by best to duct the inlet to the radiator at this point but I do think there is some room for improvement. Have been reading a few different ways to attack the problem and going to try my hand at some of the solutions when I address the radiator issue.

Pics of your setup? im trying to work out the best way to attach the ducting at the bumper and such? I had hoped to mess with my ducting this weekend, but we had crap weather.

I'll try to take some pictures of the ducting when I get a chance, don't have any currently. Basically had to get it done quickly so it's a combination of the factory undertray, cut of plastic sections of For Sale signs riveted together/ to the bumper skin and a ton of Aluminum tape connecting pieces together and sealing all the small openings. Also sealed off the top openings under the hood.

https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
https://www.miataturbo.net/attachmen...ine=1349123560
Most of this is ghetto because I rushed to get the car on track in just a few days.

Nice ducting techsalvager*.

*I vote we replace "peasant" with techsalvager. Especially when used to describe copious amounts of zip ties.

thanks hustler! That plastic looks way thicker than the stuff you recommended the other day, where did you get it? Did you have to pull the bumper? i have mesh in there to keep the IC safe and i also have to deal with that pita bumper opening.

You need to get a factory under tray on that thing, that single piece of plastic with no sides is doing little to protect the low pressure side of the radiator. IMHO I would rethink your shrouding as well, the plastic wall at the bottom of the radiator is doing nothing to direct air into the radiator. It is simply blocking off an area for the air to bypass. Proper ducting directs air smoothly to the radiator, and gives it no choice but to pass through the radiator.

I am looking at possibly participating in the SV Miata Challenge at ACS in mid November, about a month from now. I do not currently have the funds to upgrade to a TSE radiator as discussed previously. I would like to upgrade/replace my radiator cap with a Koyo 1.3 bar and add the lip/riser in from of my hood opening to help with heat evacuation.

I expect the weather at ACS next month to be considerably cooler than BRP in Sept when I was overheating. Thinking 70-80 degrees ambient. That would be 20-30 degrees cooler than BRP. What do you guys think my chances of overheating at ACS would be? I have never been to the track. Do I have a shot of not overheating with those long full throttle straights? Thanks.

Explain what that is? Are you talking about raising the rear of the hood and hoping that it extracts heat?

See my post #30. Basically a sheet metal lip to kick air up as it passes over the hood at the opening behind the radiator. My understanding is that makes the pressure differential greater and extracts more heat.

Anybody?

How does a 20 degree drop in ambient temps relate to coolant temps? Thanks.

Depends on the placement of the range of 20 degrees compared to the target temp of the thermostat.

155 -> 135 with a 190 degree t-stat is probably drastically different than 80 -> 60 with a 160 degree t-stat.

i don't think that is what he meant. i think he is asking if he had coolant temps of 220 on a 95-degree day and hits the track on a 75-degree day can he expect to run significantly cooler.

I'd assume so, ambient temps have a big impact. I once ran my Boss 302 on a 110 ambient temp summer day at the track and it went into limp mode due to overheating. the same car, on the same track with 95 ambient temps was fine to beat on all day turning similar lap times.

Exactly the answer I'm looking for, want to get peoples opinions and experiences with this. Preferably some of the SoCal guys can chime in with how difficult Autoclub Speedway is on the cooling system versus other local tracks that I have been to (Willow Springs, BRP, etc).

So I went back and looked at post 30 and read what you have written. I am still confused on what exactly you are trying to do. Are you saying you are going to duct off from the bottom of the radiator all the way up to the vent and then all around? If so then I think that would well. If that is not what you are planning on doing, then I need a simpler explanation for my 5 year old brain.

Whatever you do, do not duct the front of the radiator and add an extractor in front of the hood-hump. Everyone is lying about the effectiveness. Only you have absolute truth.

Ducting is only in front of the radiator from the mouth of the bumper to the radiator itself. The opening in the hood behind the radiator but in front of the valve cover is to lower engine compartment pressures because the location of the opening is a low pressure zone and the engine compartment is a high pressure zone. The lip in front of the opening that I want to add should decrease the pressure further and make the delta in pressure from the engine bay to over the hood greater at that location, hopefully pulling more air through the hole in the hood.

End goal is to increase the delta in pressure from in front to behind the radiator. Higher the delta, more air passes through and more cooling is done. To a certain extent.

Run-on sentences over.

Got lucky! Found a used TSE radiator that I could get the money together for. In the mail already and should be getting installed on the car next weekend. Stoked!

Do you have a fan shroud around the radiator? In order for an electric fan to cool properly you must run a fan shroud

I am using the OEM cooling fan and shroud combination and will be using the same fan setup on the TSE radiator as long as everything fits. I aim to not have the fan be a big portion of my cooling at speed, only really need it to cool down when coming off of track and to work while driving to/from the rack track.

I believe conventional wisdom is that on track cars you do no want a fan shroud behind the radiator. I believe that they end up blocking more air then they let through. Honestly with the TSE radiator, proper ducting before it, and the undertray, you should not be having over heating issues.

That's what I'm hoping for! Only one way to find out.

Got the lip/riser added to the hood this weekend. Came out a little taller than I originally thought but it should do the job well. Man my car is looking more hoopty every day...

https://www.miataturbo.net/attachmen...ine=1352149117

Thanks for posting those pics Hustler. Your ducting looks almost identical to mine, except for the oil cooler hole and the fact that yours is made out of plastic instead of Aluminum.

Were did you get the plastic?

Fans are for street cars, A/C function, and idling in the pits. They will not help when you are on track.

Theseus doesn't run a fan shroud, and neither does Rover. I don't understand why people continue to buy them.

+1

When we tested shrouds several years ago we found they only improved pressure differential and engine temps a little when stationary. As soon as the was over about 20mph, they blocked flow even with fans on. Almost no OEMs use full coverage shrouds and you will never see one on a top level race car.

Quick question on the subject of fans, when having some overheating issues, do you guys find that running the fan is better than having it off at speed? Or does the movement of the fan have a negative/negligible effect?

When I was overheating last time out, I lowered the temp at which the fan comes on to just have it running all the time basically. Thought it might be better to have the blades moving some air rather than just blocking airflow.

If the airflow across your core is bad enough, the fan will help a little. It's a band aid and warning sign though. If a fan lowers clt temps at speed, you have an airflow problem. Case in point, most bone stock Miatas with A/C will run hotter at 80mph steady state than accelerating hard at autocross speeds. The reason is the airflow leaks around the rad progressively raise the air pressure in the engine bay with speed until it just about equals that in front. Lots of leaks and poor exhaust from engine bay. Address those things and fans are superfluous once moving.