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

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?

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!

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.

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.

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!

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..

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:
http://i.imgur.com/m8H5JBA.jpg
https://www.ft86club.com/forums/showthread.php?t=91820

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

Correct.

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.

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.

Custom tune. Seems I've read that the factory tune might cut power around 300F? Not sure on that.

Well, that's an interesting data point, given the recent discussions on whether an oil cooler is needed.
Might as well explain why your oil never gets too hot :)

It's also interesting that your tune implements the "oh the engine is too hot" by faking the accelerator pedal position, rather than something else, such as altering the lookup in the drive-by-wire table.
If the accelerator pedal is pressed all the way, one could argue any data logging must show 100% accelerator pedal position.

Which OBD PID / CAN ID does your data logging system use for the "accelerator pedal position"?

I would consider 275F to be an absolute upper limit for 0w20, but low for good 5w30.
It seems like I've read that factory setting for calling things off is at 300F, for sure before the tune I never ran into any cutoff.

Yeah, that data is sort of misnamed, should be "throttle commanded by ECU" and not "pedal position".

I don't know, but confirmed that it is *not* actual pedal position but rather what the ECU is dictating for throttle.

Use CAN ID 320 (0x140 hex), first byte, divide by 2.55 to get 0...100 range.

I'm not much of a data jockey... I use the ECUtek software to view data, that's it. Again, it's been confirmed by the tuner that tune applies a multiplier to applied pedal at high oil temps and high rpm, so it's known to be controlled by the tune at that point and not actual pedal position.

I wasn't aware there was a table for this - any idea what it's called?

Yeah my oil almost never gets over 230F, with an oil cooler. It regularly got over 275F before an oil cooler. It’s cool if you want to drive around with limited power. And oil pressure at idle is irrelevant…..

Who's talking about oil pressure at idle?

FWIW I had same max speeds at COMSCC Palmer event 1 this year vs. a car very similar to mine with slightly more peak power and slightly less midrange torque (he has 4-1 EL catless, I have 4-2-1 catless) and he has an oil cooler, so...

By "limited power" do you mean the factory tune cuts timing advance at some oil temperature? Dunno if my aftermarket tune does or not but in any case our max speeds were similar to when we were running full factory exhausts and tunes anyway...

Watkins Glen event on Mon/Tue went GREAT (except for a couple of partially stripped wheel studs :confused0068:)!

I was able to run extended sessions, no problemo :)
Did a 2:14.870 on day 1 and 2:15.335 on day 2 (headwinds, everybody was slower) and TT'd 2:15.688 which was enough to take the win in T50 by 2+ seconds vs. Miata I've been going back and forth with this year :D
https://www.comscc.org/events/result...?id=2021-09-14

Having the oil temp trigger reset to 285F resulted in never running into the tune cutting back on commanded throttle. Oil temp on the factory gauge remained at the same normal level of just over 270F indicated.

Sweeet...

Time for some proper studs and open ended lugs! Which I suppose is annoying given your road salt and stuff...

I have the shorty ARP studs so I can run closed-ended lug nuts on the street.

I got some purty rainbow-colored Muteki lug nuts for track for this year for max disco. Before going to the Glen I noticed one of them hanging up a smidge while changing wheels/tires for the trip. Ran down one of my street lugs on that stud by hand, no problemo, so I "cleaned up" the Muteki lug nut with a tap and then it installed fine by hand. *At that moment I should have removed all the Muteki lug nuts*.

At the track while removing the left front wheel on day 1, one of the Muteki lugs was dragging, and then halfway through removing it, it totally siezed up. Took a big-daddy impact to remove it. Cleaned off the outer half of the ARP stud but the inner threads were fine and I was able to get a few good turns on it. Took max torque with my street lug nuts no prob.
Day 2, exact same thing happened on the right rear.

TL/DR: Muteki lug nuts are *shite*. WAY worse than off-the-shelf "tuner" lug nuts from Pep Boys (the "street" lug nuts I've been using street and track for a few years now).

So in your situation, what do you think would be the better fix out of these two examples?

1) Increase the thermal safety limit so that the ECU can't limit the power output of the engine when the oil reaches the original temperature setpoint,

or

2) Install an oil cooler so that the oil temperature doesn't reach the original thermal limit in the first place.

But that's not what actually happened. The original temperature setpoint was _lowered_ by the custom tune on the ECU. So as I see it, the question should be "which of the following is the most effective for engine longevity":

1. No action - factory oil temperature setpoint and 5W30
2. custom tune to lower temperature setpoint
3. oil cooler to reduce oil temperature well below setpoint

I'll admit I've glossed over this thread... But why Not buy an oil cooler? regardless of the oil's thermal capacity itself it literally is cheap insurance for a motor seeing track use.

For me, for my usage, option 1, by far.

The tuner's 275F limit is appropriately conservative, presumably assuming 0w20 weight oil. Personally I haven't seen anything to suggest that 275F should be a problem running good synthetic 30-weight.

FWIW I never encountered any factory oil temp cutoff running the same oil temps. I've read that there may be one around 300F?

But again, it's not the oil breaking down that's the danger here. It's the worry that the viscosity of the oil drops low enough that it's unable to provide adequate lubrication to the bearings. I'd recommend sending your oil out to Blackstone for analysis if you plan on not running and oil cooler.

Just out of curiosity, did you verify with your tuner what the stock temperature limit is, whether it be 300 degrees like you've read somewhere, or some other value, and that he specifically lowered this limit in his tune?

If he indeed lowered the limit, then I agree with you that you should be fine in the short term. However, if you're regularly tracking your car, I agree with @Kelse92 in that for the overall life of your engine, you should still install an oil cooler. If I were in your shoes and in the same situation, I would.

Just curious if anyone has actually seen the oil temp based compensation tables in their tunes. In romraider Ive seen and played around with the coolant and IAT based timing compensation tables with some success but I’ve never found any tables that pull timing based on oil temps.

You pick oil viscosity based on operating temps. At 275F, I think 30-weight is fine, at least for limited track usage. If I was track-only, I might go 40-weight. Probably HTHS more relevant anyway, 5w30 Redline is 3.7 HTHS.

I haven't sent oil out for analysis because I've seen reports of others who have. After typical HPDE-type track usage, "high" oil temps, with no oil cooler, the reports I've seen show little to no degradation of the oil, and normal amounts of wear metals.

No, and frankly I don't see any need to bother him about it. I know that my custom tune specifically commanded reduced throttle once ~275F was reached above some rpm limit. I wanted that feature removed, he instead bumped it to 285F, which is fine as I know it never continues upward from ~270-275F anyway and yeah, if it *does* start to go higher in retrospect I'd like the cutoff about there.

I think that the risks of running 3.7 HTHS 5w30 synthetic at 275F for 15-20 minute track sessions are minimal. The risks of having an aftermarket cooler are non-zero and in fact we have seen *plenty* of reports of leaks (oil dropped on track = bad, also fire hazard!) and even engine failures. My oil temp reliably goes up to just over 270F indicated and it *stays* there. Data logging confirms this. Spending time, $$$$, effort while introducing multiple new possible points of failure for me, for my usage, makes zero sense.

Understood, good luck. And congratulations, I hope you keep kicking ass at the track.

If I were to start tracking my car after supercharging, I think I would try to introduce some additional cooling in the form of a distilled water mist directly into the intercooler/radiator/air conditioning condenser stack during mid to high RPMs. It wouldn't be too difficult to set up. I did notice that when I was installing my intercooler that the upper 1/3 of the radiator was very clean compared to the lower 2/3, as if air wasn't passing through it. Probably due to the design of the grille and the crash bar behind it. This might be a safer and inexpensive alternative that you could consider for those hot track days.

Thanks! 2 points up going into last event which is at more of a Miata track, New Hampshire Motor Speedway (South Oval config).

My approach would be to see how it goes with the stock cooling. If oil and coolant temps remain in check, I wouldn't bother...

As I think about it, my *first* mod would be to vent the hood, which should improve cooling while reducing front lift. Hell maybe I should do that anyway, it's a zero-point mod with my club!

Dan, I'm getting close to hood vents as well. Let's chat at NHMS.

That's not his car though lol. Every engine is different and the use case and climate is vastly different. I'm just saying it's pretty cheap insurance - like an oil cooler.

:thumbsup:

Do you have a sawzall?