Custom tuned and hitting limp mode

[Kingamer]

View attachment 201683 View attachment 201684 View attachment 201685 I recently was custom tuned for flex fuel at e30 with 91oct the tune was very smooth on the dyno but when I tried my first 4th gear pull I hit limp mode and had a p0087 code.

I removed some boost by ethanol air charge and turned on fuel duty limit max 92% yet the datalog shows 100% fuel duty.
Heres the log screenshots
I wanna make this tune as stable as possible so some insight would help greatly.

 

[AdamD19DFK8]

I think with flex fuel you have to run less boost as it taxes the fuel pump more. Have you tried lowering your torque targets by 5%?

 

[boosted180sx]

welcome to flex fuel and the garbage stock fuel system.

not much you can do except to keep lowering aircharge/torque request until your not.

i'm surprised your tuner didn't put a lock on his custom tune and you were able to change the values.

 

[kefi]

Set the fuel pump limit to 88%, not 92%.

It is normal for the pump duty to overshoot the target value, so the target value should be much below 100%. Ideally you want to pump to touch 100% but the fuel pressure not to drop. Since the fuel pump piston stroke is not linear from camshaft rotation even if you limit the fuel pump to 90% duty you are actually at 97.5% fuel pump flow.

In testing I found that values of 88% for the target and 88% for the hysteresis worked for our vehicles.

Also what boosted said. The pump limit is kind of a backup bandaid because of how many factors can ultimately affect the required fuel, you really want to get your tune to the point where the limit isn't needed. Wherever your fuel pump is hitting 100%, you should reduce the maximum aircharge table. Note that the aircharge table INDEX can be changed as well, unlike most tables.

 

[NoKz]

welcome to flex fuel and the garbage stock fuel system.

Facts.

i'm surprised your tuner didn't put a lock on his custom tune and you were able to change the values.

Any tuner that does that is an asshole. I'm not just paying you to tune it, I'm paying you for the full, unlocked tuning file on my vehicle.

 

[boosted180sx]

Any tuner that does that is an asshole. I'm not just paying you to tune it, I'm paying you for the full, unlocked tuning file on my vehicle.

You are actually paying for the tune and not necessary the file. As much as I would LOVE to have an unlocked file, alot of tuners do LOCK their tunes because they have to protect their work. You also don't want the end user to be adjusting parameters they really shouldn't be and blame the tuner if something does happen. There can also be a custom tune tailored to one car that's going to get passed around from person to person just because they have the same mods. These things have happened before.

There's a reason why these "locks" were made available. A few years back, Flash pro didn't even have an option to lock tuners work in the beginning and all the values were all out in the open. It was actually great. I was doing an Etune with Vit on my 9th gen and was able to compare each calibration and see parameters he changed. I hate it but i don't blame them for wanting to lock their work.

Now, if you express your concerns, and they dont want to fine tune parameters, then yeah they are assholes.

 

[Kingamer]

I being a tech know what not to do when it comes to keeping my engine safe.
I understand fuel trims so I know not to mess with what the tuner did because he smoothed my trims for keep me from leaning out and blowing apart the engine.

What I didn't do is increase anything only reduced. And for the air charge limits I decreased the tables by 5% from 7k to 5500

I set the fuel pump duty to 92% as a test because I hit limp mode with the tuners base air charge and no fuel duty limit

For torque tables can anyone show me a pic of what to change so I don't mess anything up

 

[boosted180sx]

I wasn't referring to you with my post btw. I was just surprised he left it open.

the fuel pump duty limit is a gimmick at best. It will still overshoot and on some people have caused oscillating AFRs. Best not to rely on that and work on actually making the tune not hit.

i only see screenshots of the logs and not the log itself so i can't tell you what to change but go to your throttle maps and lower the values to reduce torque request on where you want to lower fuel needs. Also change the aircharge tables in your ethanol section.

 

[Kingamer]

I did lower my boost by ethanol by 10% but I never touched the tq tables because I don't know tables to change.
I would upload my datalog but it will not allow the extension

 

[boosted180sx]

I did lower my boost by ethanol by 10% but I never touched the tq tables because I don't know tables to change.
I would upload my datalog but it will not allow the extension

yeah unfortunately the forum doesn't support it. you have to upload it to a google drive first.

the y axis is rpm and the x axis is throttle input. Find where you are maxing out and drop the values in there. The far right column would be 100% throttle.

from my experience when i was running like 27% ethanol a while back, you had to reduce the aircharge values quite a bit even from their base maps.

 

[Kingamer]

I see and when I load it to google drive I can upload it to here after?

 

[boosted180sx]

yeah. itll give you like a shareable link and can just link it here or in the messages. whatever you prefer.

i had flex fuel for a few months but i ended up going back to 91. i may mess with it again once a more affordable fuel system is available.

 

[Kingamer]

Ok I think I got it figured out now

 

[AdamD19DFK8]

For torque targets each gear may respond differently. For example, after I installed PRLs charge pipes for their intercooler, all of a sudden 3rd gear was maxing out the fuel pump baaad with settings I had been using for awhile before hand. I had to reduce everything drastically to get it to not drop fuel pressure long after spool up. First I just reduced everything by a certain percent throughout the power band. Would log, and look at areas after spool up where it stayed tapped out and kept reducing until I could do pulls with it only briefly maxing out, at spool up, which is fine. 4th gear on I could keep the higher targets i'd been using.

 

[boosted180sx]

Ok I think I got it figured out now

yeah looks to be there now and not private. ill take a look once im home from work.

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