Long story short is Im build APS TT.. Im heating up on track very quickly. With in a few laps I'm at 220F coolant and have to back off. I have seen the coolant as high as 244F for few seconds before backing off.

I have a koyo 36mm rad, OEM fans, OEM thermostat, Custom bleed/swirl pot.

Heater blows full hot, Care does not overheat under road driving conditions (even sprited runs only when thrash on track)

Fans work and cycle as they should.

Car has L19's and HKS HG.

Any one have any input on my issues?? Im swapping to a low temp thermo next week and coolant flush.

It feels fine to drive, idle is fine, no smoke from exhausts, power is strong.

Any ideas guys?? Ive been reading ALOT but I'm not pushing any coolant ether?? May be a very small amount as the APS overflow is hard to set up a running level as there is not min/max marks on it and Ive just topped it unto what every i though looked ok.

Im hoping its not the HG

 

You need to run an oil cooler for track use.

 

Sounds to me you are getting air in the coolant system, which accounts for the quick spikes.

 

Not sure how you have your overflow tank set up, but when it cools is there any way for air to get sucked back inside? Have you tried burping it?

 

I would say try evans coolant.

other thing you can try is to add an expansion tank back where the turbos feed back into the heater hose. I had a long thread on it last fall.

maybe a higher pressure radiator cap.

what are your oil temps when the car gets 220+ water temps?

 

On a 25 row Mocal with -12 lines

 

Yeah I burped it the other day with a spill free funnel. Still no good.

 

The thread you had a while back I think was based of my expansion swirl set up iirc. I spoke to you via PM and sent you drawings of mine.

That still works well.

I may look into evens then mate, do you run this?? What are your coolant temps??

Oil temp follows coolant very close, if I'm at 220F coolant oil is 230-235F....

 

I'm not sure exactly the case with vq rads, but I've heard of mishi moto rads causing heat issues on the track, and essentially not being "high performance." Depends on the car though, and I've read they had some bad batches of radiators.

I think I recall reading something about the aftermarket radiators for our cars usually being crap (not in their quality, but as a downgrade thermal performance from oem).

Not sure, can't recall 100%. I remember reading that there was one radiator that was discontinued that was very good. Could have it backwards, but might be worth looking around.

If you have air in the coolant system I would suspect you would have over heating issues on the street too.

One thing you could try is full water with water wetter (this lowers surface tension of the water, and helps it grab the edges of the coolant passages, pulling heat off more efficiently). Or even just dawn dish soap. How much dish soap however, not sure. The higher latent heat of mainly water should help lower temps at least a little bit.

Next it's really critical to have proper ducting for a track car, especially into, and out of the radiator. Vents in hoods, proper clean path into the radiator makes a big difference.

 

I agree i don't think its air in the system. I have ducted the front to the IC with all plate but its hard to vent the back of the rad... I have a vented hood too..

I currently run a 70/30 water/glycol with water wetter. Im hoping it is a rad/airflow issue but the speed at which the temp comes up I'm not getting my hopes up.

I may ditch the ac condenser to see if that helps too.

 

Try with OEM coolant radiator and fans. We had exactly the same problem on customer car, and this is the 3rd time I hear about overheating problems with thick "performance" coolant radiators.

 

^ OEM does not compare to a thick radiator and larger SPAL fans.

The 36 mm Koyo is not the largest. For an FI racing car, the thick Koyo and dual 12" or larger SPAL puller fans with custom shroud is what I would recommend.

You could try Evans - it can run very high temps without vapor formation, which will protect your engine. I had the fans go out on an airstrip event and it handled close to 300 degrees without issues (at idle, before I realized something was wrong).

Ultimately I think for racing your cooling set up is sub par. Switching to aftermarket fans is kind of a PITA because then you need a PWM controller to get both fans to operate at low speed and high speed settings as originally designed from Nissan. Having just one fan run high speed vs 2 fans as some people hook these up is suboptimal imo. The IPDM does offer separate low and high speed control lines which you can tap into to serve as input signals to a controller.

http://www.dccontrol.com/constant_te...ontrollers.htm (this is not the controller I use, but the one I will use as my DIF controller is now discontinued)

This is the fan I use: Spal 30102044 (two of them)

 

I have been told OEM fans are fine for track use as once your moving the air flow via the bumper opening is far grater than any fans system?

Evans I have thought about this but I think it will compound my cooing issues as its far worst at picking heat up from the motor than water, Also the fact its flammable is an issue for me too.

Im pulling my AC condenser this week to help improve rad airflow.

 

That Oil Cooler is also probably not large enought. You have 4 layers of cooling that you are trying to use, which is rediculous. The air is having to go through the oil cooler, AC condenser, Intercooler, and lastly, the radiator. I would recomment trying to get a bigger oil cooler, or get two, and put them to the sides of the radiator with some extra ducting/ widening the front opening. Removing the AC condensor will help, along with the thicker core koyo radiator.

A thicker radiator will help, along with making sure that your hood vents are functional and pulling air from between the radiator and engine. Having a lip along the front of the vent can help their effectivness.

A higher cap and watter wetter will also help some, but things like that will only help 10 degrees or so, and the cap will only allow the system to still operate effectively at a higher pressure, not lower the temps.

You could also consider running a water/methanol sprayer onto the intercooler and radiator similar to the subaru STIs that you could spray when it starts to get hot to get the temps down. This can pretty easily be run from your stock windsheild sprayer pump/system.

You could also consider an internal methanol/water injection that would increase power and keep the temps down.

Lastly, detune a little and run it rich can keep things cooler but thats not really the best solution and more of a limp mode solution.

 

Oil cooler and have you thought about installing a full ride fan switch? Also opening up some vent holes for better flow. stock Z's aren't the most open nosed car.


Also look into hood spacers. Might help a tiny bit with bay temps while at speeds assuming you have enough in flow. Again refer back to adding more air flow ducting to the nose.


Also whens the last time you did and oil change? What oil are you using?

 

I would think oil cooler placement is a variable.....

 

I think you have solid evidence to suggest that your particular set up is insufficient. You can decide what the most likely primary contributor is and test one by one - water pump, restriction in coolant flow, OEM fans, etc. I would submit that my first choice would be to swap out the fans and shroud.

Any glycol based coolant has a flash and flame point, even std 50/50 antifreeze. Unless your track prohibits it, I would run Evans to prevent vapor formation at the cylinder heads. Evans does not have the heat carrying capacity of water but it is the better coolant for racing. If your water pump is weak, radiator insufficient, fans insufficient, then it is true that Evans can make the situation worse.

 

Any know if running less boost (3-4 psi less) will have a decent effect on reducing temps??

 

That would definatly help, but it still seems like something isnt right. Have you verified that your stock thermostat is working as it should?

 

I would consider a different fuel vs changing boost and setting the rev limit lower. My car definitely runs hotter on 93 oct vs E85 - ambient oil temps appear to be about 5 degrees warmer with other conditions the same. Of course nothing spikes the temps like keeping the engine constantly between 5k-7.5k.

EDIT: a simple thing to try might be to just run a little richer mixture; you might lose a little power but you probably have plenty to spare