GR Yaris (Gen 2) GR Yaris GEN 2 - Heat soak issues

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Micke_b

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Heat soak / boost cut at track days, anyone solved this?

I haven't seen many others mention this, but a few friends and I are all having serious heat soak issues on track days, and I'd want to get to the bottom of it.

The scenario:
  • Arrive at the track, drive the first heat, all good.
  • Second heat, after the car has been standing in the pits heat-soaking for ~45 minutes: no boost. The boost bar in the dash stays under +1, where it's normally close to +2. Noticeably reduced power.
  • No CEL, no warning message, nothing. Just less boost. Sometimes the car recovers mid-session, sometimes it doesn't.
  • Sometimes driving a while, pitting, and restarting the car brings boost back, but not always.
My car is on a stock ECU, no tune, but with an upgraded intercooler (AIRTEC) and the AIRTEC auxiliary cooler kit. One of my friends runs an EcuTek tune that supposedly addresses this, plus every cooling upgrade available, and he still gets the same issue (he even got it in his first heat after just driving to the track and standing for an hour in the pit with the car).

Our current suspicion is the MAF sensor getting heat-soaked: there's a heater pipe about 20 mm from the sensor that radiates heat onto it while the car sits in the pits. My next step is wrapping that pipe in insulation to block the radiation. I added a small heat shield next to it before my last session, and I've been using a leaf blower to cool things down before each heat, it seems to reduce the problem slightly and the car recovers more often, but nothing has been a 100% fix.

Has anyone solved this completely? Found the root cause? Any ideas welcome. 🙏
 

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  • GRY-heat-soak-maf.webp
There was some talk about this in another thread that the maf sensor got heat soaked. Piras have a duct for this problem.

www.pirasmotorsport.com

PIII GR Yaris MAP Sensor Cooling Duct

Stop GR Yaris track-day power drops. This 3D-printed MAP sensor cooling duct prevents ECU cuts by lowering heat-soak temperatures. Shop the OEM+ kit now.
www.pirasmotorsport.com www.pirasmotorsport.com
 
GRnewb said:
There was some talk about this in another thread that the maf sensor got heat soaked. Piras have a duct for this problem.

www.pirasmotorsport.com

PIII GR Yaris MAP Sensor Cooling Duct

Stop GR Yaris track-day power drops. This 3D-printed MAP sensor cooling duct prevents ECU cuts by lowering heat-soak temperatures. Shop the OEM+ kit now.
www.pirasmotorsport.com www.pirasmotorsport.com
Click to expand...
Yeah but the duct wont do much in the pits. Maybe it will help recover fast though. 🤔
 
Never had such issues on track, and don't have any MAF cooling. I'd say the issue is something else. what fuel do you use?
I am typically bonnet open on pits after track sessions just to get rid of excess heat.
 
Michael Knight said:
Never had such issues on track, and don't have any MAF cooling. I'd say the issue is something else. what fuel do you use?
I am typically bonnet open on pits after track sessions just to get rid of excess heat.
Click to expand...
I use 98 octane that is the highest you can get here in Sweden. Always open bonnet after session. Something is heat soaking and then the ECU is restricting the boost. Just not 100% sure on what. But that MAF seems to be the most likely. But could be something else as well. But not sure what that could be? 🤷‍♂️
 
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Micke_b said:
I use 98 octane that is the highest you can get here in Sweden. Always open bonnet after session. Something is heat soaking and then the ECU is restricting the boost. Just not 100% sure on what. But that MAF seems to be the most likely. But could be something else as well. But not sure what that could be? 🤷‍♂️
Click to expand...
someone with access to ecu could see what is happening. You could always visit at Toyota service center and they can check if everything has been running smoothly. I think ecu stores certain data (at least they were able to track my power steering issues even though it gave no fault code as such to the dashboard). worth asking, at least?

I'm quite sure ecu has stored something as that is not a normal behaviour.
 
Not on trackdays, but in repeated runs up Alpine passes in >25°C ambient I've kept an eye on the various IAT readings when having a rest to see what aided cooldown and reduced heat soak the best.

In order from worst to best
  • Idling, bonnet closed
  • Idling, bonnet open/Engine off, bonnet closed (both similar)
  • Engine off, bonnet open
The surprising thing was that while idling may help distribute heat around the engine, it does not help prevent heat soak in the intake system, and in fact may exacerbate it.

On pulling away again after the stop you see the IAT readings spike well over 50°C (the alarm temp on my phone dashboard) until the flow of air through the engine compartment starts to lower things. During that time you definitely feel the car running less boost and less aggressive timing. Sluggish would be the word.

I've learned just to take it easy after a stop until the temps drop back down, but I'll be honest and say that this only takes a few minutes once moving, and I've never had the car not regain full performance fairly quickly. Seeing someone leave their car idling during a rest stop and then immediately gun it away again makes me wince!

Interestingly, it seems that using at least some boost helps bring the readings down more quickly. Not sure I quite understand the mechanism going on there, but it is noticeable and repeatable.
 
I'm experiencing the same issue with mine in normal traffic, if I stop after a long drive and the engine is fully up to temp, leave the car off for a couple of minutes then get back in and drive, it'll give me at most 0.8 of boost for the first minute or so. I've always presumed it's just heat soak in the intake system and it seems driving + getting it into boost gets rid of it the quickest because you cycle as much air as possible through the intercooler, but I have no data to back it up.
 
Very frustrating when you do TimeAttack and you have no boost and need to delver a fast lap. 🤦‍♂️
 
I measure intake temps using a stand alone set-up. I started by placing the sensor in the pipe between the IC outlet and TB. Cruising down the Hwy I was getting readings of 50-60 C°. This was purely from heat soak. I ended up repositioning the sensor to the silicon hose on the IC outlet.
I insulate this pipe now with reflective tape and the pipe to the turbo inlet.
Cruising down the HWY my intake temps are around 2 °C above ambient
Theres no doubt in my mind this vehicle suffers badly from heat soak.
 
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When driving slowly or parked in the pits. Turn the A/C on with cabin fan on low. This forces the rad fan to a higher and constant speed which cools things down faster without adding too much heat from the condenser.
 
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