Lean Spike when Accelerating - 0411 Swapped Pickup

[Obsolete489]

When you say something weird with the os, do you mean like being corrupted somehow?

[Obsolete489]

Also, I did confirm that if I stay below 75 kpa this doesn't happen. I'm going to log map sensor voltage next time I try.

[anniversaryss]

Also, I did confirm that if I stay below 75 kpa this doesn't happen. I'm going to log map sensor voltage next time I try.

Did you figure this out?

[Obsolete489]

Did you figure this out?

So I have been working on a rear mount turbo for this thing, tuning it in a 2 bar SD OS, so I had kinda been ignoring any fueling issues as I work out bugs and dial in the VE. At first recollection I thought I hadn't seen this issue since converting to 2 bar, but now digging through logs again it is still there, just not quite as noticeable. It doesn't look like it is going quite as lean - maybe 16-17 afr, but then again that could be because I'm still running OL and it's probably sitting a touch rich..

Have you encountered something similar?

[anniversaryss]

So I have been working on a rear mount turbo for this thing, tuning it in a 2 bar SD OS, so I had kinda been ignoring any fueling issues as I work out bugs and dial in the VE. At first recollection I thought I hadn't seen this issue since converting to 2 bar, but now digging through logs again it is still there, just not quite as noticeable. It doesn't look like it is going quite as lean - maybe 16-17 afr, but then again that could be because I'm still running OL and it's probably sitting a touch rich..

Have you encountered something similar?

In speed density open loop I get a hard lean spike that lasts 1 or 2 seconds. Usually only happens before the car is full warmed up and when I slightly hit the throttle around 2k and 13 to 15% throttle.
It isn't as noticeable when the car is warm, did it in maf also just not as bad

[Obsolete489]

Sounds pretty similar to what mine does. I always thought the transient fueling was to blame but no amount of messing with it seemed to fix the issue. Switching between maf and SD really didn't make a difference for me.

Im working on a pressure sensor to log fuel pressure at the rail, to confirm if it's the tune or something physical.

[anniversaryss]

Sounds pretty similar to what mine does. I always thought the transient fueling was to blame but no amount of messing with it seemed to fix the issue. Switching between maf and SD really didn't make a difference for me.

Im working on a pressure sensor to log fuel pressure at the rail, to confirm if it's the tune or something physical.

That's my next step

[Obsolete489]

Definitely report back if you find anything, and I'll do the same. At this point I almost hope it's a physical issue but I doubt it. What style fpr do you have? My has a return and vacuum reference.

[anniversaryss]

Definitely report back if you find anything, and I'll do the same. At this point I almost hope it's a physical issue but I doubt it. What style fpr do you have? My has a return and vacuum reference.

I'm running a return and referenced regulator. Unfortunately its winter here and I cannot do much at the moment.

[Obsolete489]

I'm running a return and referenced regulator. Unfortunately its winter here and I cannot do much at the moment.

Yeah it's not great working weather here either. Since you're running the same style fpr that does seem suspicious.. I figured yours was different.

[anniversaryss]

Yeah it's not great working weather here either. Since you're running the same style fpr that does seem suspicious.. I figured yours was different.

No its a 97 Lt1 with a 24x conversion and 0411 pcm

[anniversaryss]

anything come of this?

[Oleblu]

What about serious changes to your transient tables. Obsolete I know you said you changed transients and got nowhere. Have either of you gotten drastic and doubled the 12283 table (fuel to wall impact factor) At first I was changing transients and getting nowhere but only by 25-50% make serious changes and at some point you should see your (pump shot) increase. Or choke out the engine with to much fuel. At that point start stepping back your changes by 10% increments. This worked for me, but it was strictly a trial and error process.

[Obsolete489]

I was waiting to do another log and confirm this, but the last time I drove it I could not find a correlation in fuel pressure drop with the lean spike, so it pretty much has to be the tune - likely the transient tables.

Oleblu I did try some pretty aggressive transient changes, I'll have to go see if I saved any of the old tunes with those changes and the logs corresponding. If I remember correctly it would go rich right when I get on the throttle then the lean spike would still follow a couple seconds later.

[Oleblu]

Possibly your gain table for impact factor. It's based on airflow, I massaged mine a good amount above 60 up to 150

[Obsolete489]

I think i messed with the gain some, but I should probably do some retesting here. The lean spike also doesn't seem as bad this time around, but i could be imagining that too.

[Obsolete489]

Just to update, it is definitely independent of fuel pressure.

[anniversaryss]

What do you mean?

Have you tried anything with injection timing. I know you got a small cam but hey never know..

[Obsolete489]

I was fairly certain that the lean spike wasn't related to a fuel pressure drop, and I confirmed that with a better Data log. The fuel pressure stays nice and steady through the spike.

I have made some adjustments to injection timing based off fuel trims, but haven't specifically played with it to try to fix this.

[anniversaryss]

I was fairly certain that the lean spike wasn't related to a fuel pressure drop, and I confirmed that with a better Data log. The fuel pressure stays nice and steady through the spike.

I have made some adjustments to injection timing based off fuel trims, but haven't specifically played with it to try to fix this.

There was an old post i had found guy had exaclty the same symptoms as i. Lean tip in, bogs hard for at lest 3 seconds and goes way lean. He ended up changing his injector timing and says his issue went away.
We also have fairly large cams, him 10?, i have 19? overlap.
We assume bc the ls1 injection style happens so early that any cam with overlap will have some sort of issue, i would believe especially swapped cars like ours being an lt1 with and ls1 pcm which have completely different designs than an ls1
You have your motor.
Even the 2002 Express van which is a SBC with an 0411 pcm has way different injector timing than an ls1.

Now could i be way off and be wasting my time, possibly. But i found a guy who had the same exact issues as i and its def worth a try.