90hp Power Cut on Corner Exit (Straight Line) - Fuel Starvation or Limp Mode?

[ogtega]

I’m trying to diagnose a peculiar power cut I experienced with my B48 Supra at COTA. I’m hoping someone here can recognize this issue and provide assistance.

As I exited Turn 20 at COTA, I straightened the steering wheel and accelerated out of the corner. Suddenly, the horsepower gradually decreased, eventually reaching a hard “floor” of approximately 90 hp (as indicated by the sport displays).

This incident didn’t occur during the corner itself but rather immediately after, as I straightened the car and began pulling down the straight.

The problem went away once I completely released the throttle, and then I immediately got back on it - all 255 hp (I know) returned instantly.

- I’m driving a B48 (2.0L) Supra equipped with a ram air intake (using OE piping and channels to the stock air box). I haven’t tuned the car.
- Sport+ mode was enabled, and I was running with it on.
- I had the TCU flashed using xHP for faster shifts with some customizations.
- DSC and Traction Control were both activated.
- I was also running with about half a tank of fuel.



I would greatly appreciate any assistance or help in identifying what the issue might be.

Additionally, I’ll mention that no CEL appeared, and my mechanic attempted to use his code reader after my session to check for any issues, but nothing was detected.

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[Rocksandblues]

right hand turn, not a sweeper but still guessing fuel starve

 

[razorlab]

right hand turn, not a sweeper but still guessing fuel starve

That was a left hand turn

What were ambient temps? I am guessing high IAT started bringing down torque/load target big time. Where you logging at all?

 

[ogtega]

That was a left hand turn

What were ambient temps? I am guessing high IAT started bringing down torque/load target big time. Where you logging at all?

I only got around to ordering a data logger after this track day, so I'll likely have to wait till the weather warms up before I'd have any data on the issue.

Which is unhelpful, but I just wanted to see what else I might have to investigate or look out for before the weather gets good enough to hit the track again.

 

[tracer bullet]

There's a chance there's a code associated. Even if it didn't do a light on the dash there may have been something stored indicating what it didn't like, assuming that the ECU cut power because it didn't like something (it might not have done so).

Interesting that power came back quickly, that might say it wasn't the ECU doing anything, I'd think a restart or cool-down period or both would be needed to make an ECU happy again. Common BMW power cuts come from engine temperatures but they don't recover so fast as what you saw.

On the line of thought on fuel, it might be a factor to know how full your tank was?

 

[itzTang]

There's a chance there's a code associated. Even if it didn't do a light on the dash there may have been something stored indicating what it didn't like, assuming that the ECU cut power because it didn't like something (it might not have done so).

Interesting that power came back quickly, that might say it wasn't the ECU doing anything, I'd think a restart or cool-down period or both would be needed to make an ECU happy again. Common BMW power cuts come from engine temperatures but they don't recover so fast as what you saw.

On the line of thought on fuel, it might be a factor to know how full your tank was?

- I was also running with about half a tank of fuel.

Additionally, I’ll mention that no CEL appeared, and my mechanic attempted to use his code reader after my session to check for any issues, but nothing was detected.

 

[razorlab]

Which is unhelpful, but I just wanted to see what else I might have to investigate or look out for before the weather gets good enough to hit the track again.

Might be unhelpful, but without that or a deep scan for codes ( with bimmerlink or protool) everyone here is just guessing.

 

[tracer bullet]

I missed the tank level for sure.

On the codes, I wasn't clear, but meant to try scanning again if this mechanic had a generic code reader. I feel like anyone with a car with a BMW engine should have Bimmerlink to do the best job. You can go from zero codes on a generic reader to suddenly seeing 50 codes and having to start wading through the ones you actually care about instead of some implausible reading that happened once 6 months ago. You probably know that part yourself, but I was trying to suggest it to the OP to scan it again because there may yet be something there.

Might be unhelpful, but without that or a deep scan for codes ( with bimmerlink or protool) everyone here is just guessing.

Exactly. You were more clear though.

 

[Rocksandblues]

That was a left hand turn

What were ambient temps? I am guessing high IAT started bringing down torque/load target big time. Where you logging at all?

Guess that is why i am shit driver.... I keep turning the wrong way and can't read a simple track map.

What oil is the OP using? Maybe that is it.

 

[Mdstx]

Considering how many people have gone into the wall after apex of T20 at COTA, I would posit that more than likely it was your traction control. But as the others have said, without the data, it's just a guess.

 

[ColonelAdama]

This incident didn’t occur during the corner itself but rather immediately after, as I straightened the car and began pulling down the straight.

I'd think it was more related to EGTs or IATs than fuel starvation, but datalogger will tell.

There are various reasons the car could go into a "soft limp mode"

 

[razorlab]

Considering how many people have gone into the wall after apex of T20 at COTA, I would posit that more than likely it was your traction control. But as the others have said, without the data, it's just a guess.

That wouldn't last all the way down the straight though.

 

[Mdstx]

That wouldn't last all the way down the straight though.

So, I watched some of the video on a larger screen. You have good point. He had a little bobble coming out of T20, but the TC should have not been retarding throttle that far down the straight. Data would be informative.

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