Unexplained Fuel Cut WOT 1st gear pull
 

MS2PNP, 1994 1.8l. turbocharged

rev limiter is coolant temp based and set up properly.
overboost protection is spark only and set at 190kpa or higher.

For some reason whenever I do a WOT pull, especially at an autocross in 1st gear WOT, the engine LOVES to fuel cut on me and I have no idea why. I finally had time to re-create the scenario today. Was happy for a moment until I checked the datalog and well the plot thickened.... Because it IS a fuel cut. (PW = 0) but there is absolutely no reason to back up why. It's not OBP because it always happens well lower than the target boost level. Just seems to mostly happen on WOT events right when the boost starts to build and RPM is high but not that high. Any suggestions or guesses guys? Ty

post your tune too.

Thanks here's my tune attached. I'm hoping to have this problem fixed by the next autocross coming next Saturday morning.
I did some looking stuff up online tonight but couldn't find really someone having the same exact problem. It's getting late so I figured it'd be smart to post a topic to read back at in the morning. Have you ever seen that before? It's Pretty odd... I'm hoping it's not like it could be a gremlin somewhere on my overall setup or the MS hardware.

Didn't open tune cause mobile, but is traction control on?

MS2PNP has freaking traction control?!!! You gotta be kidding me. Not that I'm aware of. Launch control isn't on

May/probably not. Unlikely that would be it anyway, dumb suggestion.

Nah that could definitely be it if it were on! =( but nope

Don't see anything glaring in the tune - but my gut tells me it's probably a VR conditioner trimpot (r56 / r52) - but I don't see any sync losses occuring in your log at the same time. Either way, bust it open and turn it a few directions one way, see if it gets better. If it gets worse, turn it the other way.

I would rather not mess with anything inside the megasquirt case if i don't have to. It should be setup properly. The unit is less than a year or two old. I just purchased it 2 months and 1 year ago. I mean I'm comfortable with checking if there's any cold solders and stuff but i think it's setup as it should. Every single thing else has no problems. Car runs great all the features and option pin ports do as they should. It's just weird and having that one problem only with WOT and as it comes onto medium boost quickly.

And also I'm not playing a prank or anything trying to waste ur guys time, that IS my current tune. But nonetheless that issue has been there from the beginnings, it's taught me to stay off WOT and enjoy the car without doing wot from the very first time it happened I've kinda been scared lol. But i always thought it was boost cut or something.

Just since recently I've been doing autocross and going WOT in 1st has made it very apparently consistent. So i want to explore fixing it. Yet my overboost protection is set as spark cut. So what could this be lol

Is it possible to be something car part related like bad fuel pump, fuel pump relay etc, even tho it shows up on the data log like It's being commanded to happen from megasquirt?

Haven't looked at tune yet cause mobile but it's not predictive over boost is it? Does MS2PNP support that?

It feels like that. Not sure if it supports it either. Would like to find out tho so i can turn it off for autox

I bet it is the AFR safety time, causing a quick spike and then triggering the safety. increase the delay by .5 seconds and try.


work computer, cannot open tune, but I will later.

Thank you Ryan, please let me know if you can find out if it's that.

That happened to me this morning. Was worried till I realized what it was.

Where do you find that in tunerstudio to change?? I have ms2pnp.

Nope, looks like it's not in ms2. Is it just WOT, or can you part-throttle your way past 6000 RPM?

Yes, I can part throttle my way everywhere lol I've been doing so for around 8 months now. Part throttle anywhere from 0 to like 60 or 80% it'll hardly ever happen. Anytime it's in the area of 90% or above TPS, it does it.
I can part throttle my way to my rev limiter, my boost target, or even have the overboost protection happen at times with it not happening. It's so freaking weird.

I never realized how weird it was until yesterday because I never investigated it through a data log lol always assumed I was just hitting a safety net of my own
yet I did start thinking to myself more recently when it happens that it couldn't of overboosted, so I assumed it was AFR or Acceleration enrichment related. But now that I've got more into fining out the edges of the tune, it doesn't explain for it.

It might possibly be a AFR safety net feature inside of MS2pnp's code that isn't accessible through tuner studio perhaps?

1 random suggestion for what it could be but i don't know the answer.
Fuel tank was on about 1/4th full. Maybe the fuel pump pickup hit a patch of air, but is mega-squirt 2 PNP capable of sensing when that happens, and cut's the PW / injector duty cycles until fuel pressure is back?? o.O

That's about the ONLY bright idea that I have

Nope definitely not that.

Status2 and Status3 show spark cut and fuel cut. After looking at your tune the obvious setting that cuts both is your rev limiter setting. You have a coolant based rev limit set for 5k when over 90% TPS which is where the cut is happening. It doesn't look like it should be triggering at the coolant temps your log is showing but try changing from coolant based to normal.