Foot to floor, but data sez big "accel pedal %" dropoff

[ZDan]

I've been getting what I *thought* was fuel starvation, but after actually looking at data it seems like somehow I'm getting a throttle command dropoff dropoff despite foot to floor. But only after a few laps!

This happened at NHMS in May, *every* time I went out, with a full tank, after a few laps power would dropoff a LOT, but very smoothly, no hiccups or anything like that. This would *reliably* happen coming out of T6 which is a ~180degree banked left, about 5 laps in. *Obviously* fuel starvation, right?!

I installed the Verus fuel door before next event at Palmer (clockwise, aka "remlaP"). Same damn thing happened again, *reliably* coming out of T9 which is, you guessed it, a 180degree banked left!

Next event was Thompson (CT) Speedway, a CW circuit. Same thing again, this time it seemed to happen at different spots, but at least a couple of times exiting T1, which is a *right*-hander after a long straightaway! WTF...

Just ran Palmer (CCW) this past weekend, and again after ~3-6 laps power would drop, usually (always?) exiting T2 (T1-T2 = extended left-hander).

Here's some data from NHMS in May and from Palmer this past weekend. Red rectangles around the place on the track where it happened. Note that in the earlier laps that "Accelerator Pedal" is at 100%, but on the last lap it drops WAY off, in a place where I *know* my foot is to the floor.

Can also see weird little dips in "Accelerator Pedal %" in other laps as well despite being on a part of the track where foot-to-floor is no problem and honestly I'm mashing the damn pedal hard as my skinny leg can!

Why this only happen after a few laps? Maybe I should replace the accelerator pedal assembly? Throttle body assembly?

[Petah78]

Not of any help here but didn't you have problems with TC/brakes lock up a while back? TC/VSA certainly has the ability to pull throttle, no? Could it be related?

[ZDan]

Originally Posted by Petah78

Not of any help here but didn't you have problems with TC/brakes lock up a while back? TC/VSA certainly has the ability to pull throttle, no? Could it be related?

Don't think so, I've been pulling the 40A ABS fuse (the bigger one) at every event since then. No nannies whatsoever, including ABS!

Honestly I was looking to see if there was a discrepancy between "accel pedal" and "throttle position" which would (I think) indicate what you're talking about, was shocked to see the "accel pedal" dropoff when I *know* my foot was on the floor!

[CSG Mike]

Accel position is your pedal. Throttle position is the throttle's literal position.

They're directly related but not 1:1, as there is a torque demand aspect to the engine's output.

Care to email the log? I'd like to look a bit deeper.

[soundman98]

have you inspected the accelerator pedal assembly? is it loose, or is the wire connector solidly in place?

the drops aren't equal, or consistent within each full-throttle event, which would mean that there's a dead spot in the accelerator travel. it seems to indicate a loose-something than a bad component.

it could also have to do with the g-forces you're experiencing on those right-handers, and pushing the pedal at an odd angle.

it might be worth logging at a standstill while physically playing with the pedal -- put a side load on it at 100% throttle, or wiggle the electrical connector under the same circumstance.

[ZDan]

Forgot to update this! The tune was cutting back on throttle at 275F. Had the trigger bumped up 10 degrees to 285. See how it goes at Watkins Glen in a week!

[blsfrs]

Isn't 275F a bit warm?

[ZDan]

Originally Posted by blsfrs

Isn't 275F a bit warm?

Some people definitely think so! Personally, running known good 5w30 synthetic, it doesn't worry me too much. I keep an eye on the gauge and it always settles in just above 270F indicated, if it kept going up I would worry. Actually glad to learn that it's in the tune, and honestly 285F for me is a good time to call it off, even though the oil can certainly handle temps that high. That said I don't expect it to get to 280F during extended lapping sessions..

[Shoebox]

Originally Posted by ZDan

Some people definitely think so! Personally, running known good 5w30 synthetic, it doesn't worry me too much. I keep an eye on the gauge and it always settles in just above 270F indicated, if it kept going up I would worry. Actually glad to learn that it's in the tune, and honestly 285F for me is a good time to call it off, even though the oil can certainly handle temps that high. That said I don't expect it to get to 280F during extended lapping sessions..

the issue with hot oil is oil pressure. Not the oil breaking down. Something is seriously wrong with your oil cooler setup, if you’re seeing temps that high… fix the issue instead of creating moronic workarounds

[ZDan]

Originally Posted by Shoebox

the issue with hot oil is oil pressure. Not the oil breaking down. Something is seriously wrong with your oil cooler setup, if you’re seeing temps that high… fix the issue instead of creating moronic workarounds

Like I said!
Oil cooler setup is, nonexistent...
I'm not worried about 5w30 at 275F. Oil pressure should be about what it is for 0w20 at 250F. Or 5w30 at 250F with an oil cooler, at least according to this data:

https://www.ft86club.com/forums/showthread.php?t=91820

[blsfrs]

When you say "Oil cooler setup is, nonexistent...": You mean that you are not running an oil cooler?

[ZDan]

Originally Posted by blsfrs

When you say "Oil cooler setup is, nonexistent...": You mean that you are not running an oil cooler?

Correct.

[blsfrs]

You are braver than most. If you're not blowing up engines on a regular basis then what you are doing may to be working.

[86league]

Originally Posted by ZDan

Forgot to update this! The tune was cutting back on throttle at 275F. Had the trigger bumped up 10 degrees to 285. See how it goes at Watkins Glen in a week!

Aftermarket tune? The stock tune has something like this as well?

I thought I remembered reading reports of the ECU cutting power with high temps, but a quick search didn't find what I remembered from years back.