Cool me down to take another round

[tomfree]

Points to whoever gets the easy song lyric reference first…Why another thread on "my car runs too hot on track" Tom? I'm glad you asked!

EDIT: I'll do my best to be diligent and update this first post with relevant solutions proposed in the thread.

Goals

1. This thread will be easy to search for the future and either reference fixes directly or link to fixes here in the forums or elsewhere
2. "Tiered" solutions with something resembling data to back it up (stock power level, upgraded turbo, etc.)
3. Identify stuff that doesn't work or absolutely isn't worth the money/effort, also with something resembling data

Per our huge track thread, I was at CMP last weekend, 2 drivers, ~80deg ambient, and the ECU pulled fuel/timing after we tried to run consecutive 25 min sessions, and even sessions that weren't consecutive. It was like hitting a wall. Even when we didn't get the "hit a wall", we were still getting the "Engine too hot" on the display which took FOREVER to go away. Lots of others have had the same issue, and varying fixes have been applied.

Bryan's assessment is IATs that are obscenely high due to heat soak. Other possibilities are high oil temp and coolant temp. The real problem is likely a combination of all of them. Which one is the root cause? Do I have data? Nope. I need to address that as well.

Stuff people have tried:

Wagner Intake Manifold/Intercooler (and other IMs)
https://www.wagner-tuning.com/produ...uer-toyota-toyota-supra-gr-mk5-200001175.html

This is probably one of the most effective mods…if not THE most effective mod to battle heat soak and get temps down. It is also a significant chunk of money, and a fairly involved installation. Bryan has a bunch of data on how this impacts IATs as well as a whole bunch of other stuff in his build thread.
https://www.supramkv.com/threads/razorlab-2020-le-build-thread.12426/

Turbo Heat Shield
https://www.supramkv.com/threads/verus-heat-shield-functionally.18607/
Cheaper, easier install, questionable if it does much, even though Verus does provide some data for it.

https://www.bimmernetwork.com/produ...JDlwgGUV2to0_PaIuaNoYmLkwmY3Hsq8XCaMqLq-XwR6V
Another option per @i3igpete

Bryan has also suggested a very effective cheapie heat insulation/blanket material
https://www.supramkv.com/threads/razorlab-2020-le-build-thread.12426/post-379603

I've used this flexible adhesive heat sheld stuff successfully on my Mustang to shield the floor from the exhaust heat, as we were melting race shoes.
https://www.amazon.com/gp/product/B00029KC2K/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Oil Cooler
https://www.supramkv.com/threads/staying-cool-to-avoid-power-loss.14275/
A lot of talk about the issue and some discussion of solutions, but not much depth in "I tried this…it didn't/did work." References CSF radiator (probably not worth the $) and upcoming oil cooler solutions (Verus).

2025.07.08 Edit: The Verus oil cooler is in the wild: https://www.verus-engineering.com/shop/a0262a-oil-cooler-kit-mk5-toyota-supra-4958?category=57#attr=


Radiator / Fan
See link above…I didn't do an exhaustive search on aftermarket radiators, but my quick search didn't find much with data to support a rad that provided much value, and data to support it.

Bryan's recommendation for the OEM 1000w cooling fan. A direct replacement for the Supra fan, but not cheap. Scour eBay or used parts sites for a good used unit. BMW P/N 17-42-8-666-819 2022
https://www.fcpeuro.com/products/bmw-engine-cooling-fan-assembly-genuine-bmw-17428666819#fitment


Hood venting
Lots of threads on this all over the place. I have ducting and a vent on my Mustang, and it's worth 15-20 deg for coolant temp, and I’m sure oil temp benefits as well, but I don't have a "before" for oil temp. I'm looking at the Verus hood vent for the Supra…and another hood. I want to be able to return the car as close to stock as I can because I change cars…too often.

RaceLouvers vents...they test their stuff. Proven to not just vent, but extract as well.
https://racelouvers.com/toyota/toyota-supra/supra-mk5-2020-2023/

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[razorlab]

While it has the highest cost of entry, everything else is a band aid except for an intake manifold.

The other option before dropping cash for a manifold is meth/water mix injection, however, while meth is more capable of lowering IAT compared to water, it's also a fuel and will change combustion air/fuel ratio. So on a stock tune, you would need to monitor fuel trims to make sure you aren't spraying/using too much meth. You would also want a charge pipe with a 1/8 NPT bung.

OEM DME strategy in order of temps for power pull:

1. IAT
2. Coolant
3. Oil

2021+ is more aggressive compared to 2020 on ignition timing reduction based on IAT/Coolant. This is #1 in the list above.

I made this handy spreadsheet below (showing 2021+ DME programming) to easily see how much ignition timing will be pulled depending on the IAT and Coolant temp. The two tables on the left are the OEM calibration in the DME. The top table is a lookup percentage table for the bottom table.

So, for example, if the car is at 134F IAT and 212F Coolant, it will pull 7.46 degrees of ignition at 5500 rpm, which is significant. Even at 116F IAT and 203F coolant, which most oem supras will see on track easily in summer ambient temps, it will pull 5.55 degrees of ignition timing.

 

[i3igpete]

two less frequently mentioned options.

The BN heat shield is much less frustrating to install:

https://www.bimmernetwork.com/produ...JDlwgGUV2to0_PaIuaNoYmLkwmY3Hsq8XCaMqLq-XwR6V

RL has both a 3-piece and singular setup. Lots of test data, Albert recommends the 3-piece as having better trends across many cars

https://racelouvers.com/toyota/toyota-supra/

also

https://occamsracers.com/2024/08/24/miata-hood-vents/

https://racelouvers.com/content/Race-Louvers-Hood-Vent-Tech-Tips.pdf

 

[J29DB03]

And the only part of this thread that I know… AC/DC

 

[tomfree]

And the only part of this thread that I know… AC/DC

Now that you've ID'd the band, I'm back in the ring for another swing...

 

[tomfree]

While it has the highest cost of entry, everything else is a band aid except for an intake manifold.

The other option before dropping cash for a manifold is meth/water mix injection, however, while meth is more capable of lowering IAT compared to water, it's also a fuel and will change combustion air/fuel ratio. So on a stock tune, you would need to monitor fuel trims to make sure you aren't spraying/using too much meth. You would also want a charge pipe with a 1/8 NPT bung.

OEM DME strategy in order of temps for power pull:

1. IAT
2. Coolant
3. Oil

2021+ is more aggressive compared to 2020 on ignition timing reduction based on IAT/Coolant. This is #1 in the list above.

I made this handy spreadsheet below (showing 2021+ DME programming) to easily see how much ignition timing will be pulled depending on the IAT and Coolant temp. The two tables on the left are the OEM calibration in the DME. The top table is a lookup percentage table for the bottom table.

So, for example, if the car is at 134F IAT and 212F Coolant, it will pull 7.46 degrees of ignition at 5500 rpm, which is significant. Even at 116F IAT and 203F coolant, which most oem supras will see on track easily in summer ambient temps, it will pull 5.55 degrees of ignition timing.

First of all...thank you for sharing (as you always do). A good friend put a small blower on his Focus years ago, and shocker...had stupidly high IATs on track. He made a meth injection setup using the windscreen washer bottle and pump. I don't remember what he used for the squirter, but whatever it was, it was on the cheap. That lasted for about a season, as he constantly looked for the highest alcohol content washer fluid for his meth choice. My takeaway from that was the added requirement of having to find the fluid and remember to top it off before each session was a big pain. I'm probably not the right person for that solution.

On to the IM...I'm a decent wrench...and have friends who are pretty good wrenches, so I'd consider a DIY install for the IM. On a 1-10 scale of difficulty, 10 being most difficult, what would you rate it, and how long did it take you?

 

[tomfree]

two less frequently mentioned options.

The BN heat shield is much less frustrating to install:

https://www.bimmernetwork.com/produ...JDlwgGUV2to0_PaIuaNoYmLkwmY3Hsq8XCaMqLq-XwR6V

RL has both a 3-piece and singular setup. Lots of test data, Albert recommends the 3-piece as having better trends across many cars

https://racelouvers.com/toyota/toyota-supra/

also

https://occamsracers.com/2024/08/24/miata-hood-vents/

https://racelouvers.com/content/Race-Louvers-Hood-Vent-Tech-Tips.pdf

Ah...thank you for the heat shield recommendation. That one wasn't on my radar.

I'm 99% sure we have racelouvers hood louvers on my Mustang, not sure why I didn't look at them for the Supra.

 

[razorlab]

First of all...thank you for sharing (as you always do). A good friend put a small blower on his Focus years ago, and shocker...had stupidly high IATs on track. He made a meth injection setup using the windscreen washer bottle and pump. I don't remember what he used for the squirter, but whatever it was, it was on the cheap. That lasted for about a season, as he constantly looked for the highest alcohol content washer fluid for his meth choice. My takeaway from that was the added requirement of having to find the fluid and remember to top it off before each session was a big pain. I'm probably not the right person for that solution.

On to the IM...I'm a decent wrench...and have friends who are pretty good wrenches, so I'd consider a DIY install for the IM. On a 1-10 scale of difficulty, 10 being most difficult, what would you rate it, and how long did it take you?

Yea, honestly meth injection is a whole other layer of things you need to keep an eye on. I've been pretty against it for awhile, however when setup well and used for cooling, not power, it can work well.

Yea IM is DIY if you have wrench experience. Honestly, it was pretty straightforward overall. I took my time and I think i did it in around four hours. That is with taking breaks, etc. I would put it at a 3 or 4 maybe? It's really just bolts and such. The part that took the longest and was the biggest pain was disconnecting the coolant lines to the OEM manifold. It's tight in there.

 

[i3igpete]

one thing to be aware of is that certain IMs require you to hack up the wire harness bracket or use a spacer. i believe wagner is one of the ones that do not, luckily.

 

[razorlab]

i believe wagner is one of the ones that do not, luckily.

Yea I didn't need to do any of that.

 

[razorlab]

Another cooling mod to mention is upgrading to the G series M 1000w radiator fan. Our Supra one is 800w and a different blade design.

The M series 1000w fan is what they use on the Supra GT4. BMW also uses it on the M240i/M340i/M440i with the cooling package.

It's a drop-in mod and helps the whole front cooling stack (radiator, heat exchanger and trans cooler). The negative is it's $1100 or so new. You can try and find used ones off wrecked cars on ebay and get them for about half the price.

 

[tomfree]

Another cooling mod to mention is upgrading to the G series M 1000w radiator fan. Our Supra one is 800w and a different blade design.

The M series 1000w fan is what they use on the Supra GT4. BMW also uses it on the M240i/M340i/M440i with the cooling package.

It's a drop-in mod and helps the whole front cooling stack (radiator, heat exchanger and trans cooler). The negative is it's $1100 or so new. You can try and find used ones off wrecked cars on ebay and get them for about half the price.

This looks to be the part (plugged in a '22 m440i xDrive for compatibility):
https://www.fcpeuro.com/products/bmw-engine-cooling-fan-assembly-genuine-bmw-17428666819#fitment

I'm starting the search for a used one.

I'll update the first post with the suggestions so far.

 

[razorlab]

This looks to be the part (plugged in a '22 m440i xDrive for compatibility):
https://www.fcpeuro.com/products/bmw-engine-cooling-fan-assembly-genuine-bmw-17428666819#fitment

I'm starting the search for a used one.

I'll update the first post with the suggestions so far.

Yup, that is correct. Same as on G series M2/M3/M4.

 

[Z4m40i]

I added a BM3 phenolic spacer along with my wagner manifold. I can't quite say if it helped at all, but I can say that it at least didn't hurt. My overall impression is that the differences are negligible. When I track, I'll sometimes take long data logs just to see how IAT's and temps trend throughout a session.

This isn't quite an apples to apples comparison. The data logged were at two very different racetracks. Laguna Seca is in central-ish california, and LVMS is in the desert but ambient temperatures were similar at the time of logging.

Laguna Seca w/ phenolic spacer 75F ambient temp
bootmod3 datalog - MultiMap Stage 2
IAT range 122-126F, delta 4F log time is 29 seconds

LVMS w/o phenolic spacer 76F ambient temp
bootmod3 datalog - MultiMap Stage 2
IAT range 135-140F delta 5F log time is 25 seconds

Same tune running e50. I think the best way to analyze this data is:

accel pedal, ambient temp, boost, coolant, engine speed, IAT, intake air before throttle, oil temp, trans temp, and vehicle speed

There are a lot of caveats to this data. The race tracks are very different, I'm unsure as to what point each log started (half way through a session versus beginning etc.) I assume that the log at LVMS was taken later in the session based on the oil/coolant and pre manifold temps. Maybe the best way to look at this is to compare how the IAT's trend over time.

 

[tomfree]

I added a BM3 phenolic spacer along with my wagner manifold. I can't quite say if it helped at all, but I can say that it at least didn't hurt. My overall impression is that the differences are negligible.

The phenolic spacer is a "while you're in there" thing, I guess. If I'm going to do the Wagner, might as well do the spacer if it's not prohibitively priced. I've seen plenty of data points where the material has knocked down temps in other places, so the theory is sound.

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