Lean Spike when Accelerating - 0411 Swapped Pickup

[Obsolete489]

So the injector and o2 changes had no effect on the lean spike. I do like the o2 sensor changes at cruising speeds, needs a little tweaking at idle yet though. I'll try OLSD tonight.

[Oleblu]

If the issue persist in OLSD i would definitely start leaning on the transient tables. Fortunately someone just bumped the transient fuel how to to the top this morning.

[Obsolete489]

Yeah I saw that. It's looking more and more likely that this is a transient issue. I'll keep you posted.

[Obsolete489]

Still have the lean spike in SD. Time to read more into transients.

[GHuggins]

Transient - Impact Factor - Gain - your issue is happening up in the 120+g/s area from a brief glance at your log... If you notice in this table - transients are taken away with air velocity and volume - try either changing these to 1's or increasing them up towards 1 where they are below a setting of 1 in this table...

[Obsolete489]

Thanks for the help, I'll give this a shot and report back. Appreciate it.

[Obsolete489]

Lean Spike - Then Rich Spike.hpl

This is sorta a long log, jump forward to 11 minutes and 40 seconds in to see where I test the lean spike issue.

So it looks like the lean spike may have gotten worse? Certainly no better. Also, when I let out of the throttle I get a huge rich spike.

[Obsolete489]

L29.Channels.xml l29.Layout.xml

Here are my layout and channel files.

[Oleblu]

When I take a break I'll check your log and post my tune for you to reference my transients. I've gotten mine to where it has a slight rich tip in with a bit of a lean tip out. Remember mine is setup for a different intake and a small block. so just use the data as reference. I significantly changed my fuel to wall impact factor table and tried to leave the gain table close to factory.

[Obsolete489]

Maybe I should try a drastic change then, I'll try adding a bunch to the impact factor and see what happens.

[Obsolete489]

Alright so I added 50% to the impact factor in the high map areas, it might have improved things a little, but now I get a rich tip in haha

I'll probably add more and see if i can get the lean spike to go away.

lean spike.PNG

[Oleblu]

well atleast you can worry less about lean tip in. sorry i took so damn long to get back to you. here is my tune for reference.

4l80e swap tune dialed in tune 3.hpt

If you have a rich tip in, but a lean off throttle try to now manipulate the gain table to dial it in. Iv'e never gotten mine perfect but I tend to nit pick. I settled for a slightly rich tip in, and deal with a little bit more of a lean tip out than I honestly like. But id'e rather have lean off throttle than worry about a lean tip in.

Remember to keep the impact factor table smooth.

[Obsolete489]

No worries man. I'll check it over.

If I could get it to something like that, I would just let it be probably. That lean spike is really annoying because it happens pretty much every time I pass in od, and I can feel it.

[Obsolete489]

So I tried adding quite a bit to the impact factor table in the high map areas, and still get the lean spike, along with rich tip in. I'm going to try messing with the fuel boiling time.

[Obsolete489]

No luck so far. I did check, and the lean spike does exist at WOT as well. It goes about the same percentage lean, and it also occurs approximately 2 seconds after the throttle change for both WOT and overdrive pull at ~40% TPS. Also, I have yet to make this happen below 75kpa MAP.

[Obsolete489]

Any thoughts on what to check? Is it possible this is somehow not a tune issue? Perhaps something weird going on with the injectors? My rationale for it not being injector or fuel pressure related is that it just spikes once, then comes back to where it should be, aside from a rich spike after I let off. If it were injectors on fuel pressure, I would imagine it to completely screw up the fueling at high MAP, right?

[Oleblu]

Process of elimination, start with fuel pressure rig up a gauge from the rail. Once that's ruled out move to injectors and all injector data. Make sure your running the correct data per your fuel system, vacuum operated regulator or pressure operated regulator. If nothing is found this route its more than likely a tunable issue. Really sucks chasing problems.

[Obsolete489]

Well, I've checked fuel pressure at idle, I haven't checked it when this condition comes up though, suppose I should do that.

Injector data should be good, I double checked all that. Same deal with the regulator referencing the manifold pressure, already checked that.

It does though, sure gets old.

[GHuggins]

Not to step in here, but if it's happening that late - transients most likely aren't the issue... Could be something weird with the OS, but who knows at this point on that? Post your latest tune if you don't mind. Does it feel at all like it's got a stumble or possibly a misfire or anything like that?

[Obsolete489]

By all means, please step in, and don't be afraid to call me out if I'm doing something stupid haha

That is what I've kinda thought all along, 2-3 seconds in just doesn't seem like a transient issue.

The tune I posted on page 1 in the first post is pretty much what I have in it right now. I went back to the original transient settings (though they might need some work), pretty much everything else in the tune is what I'm running now.

When running normally, no stumble or misfire that I can ever feel. The only noticeable hiccup is when that lean spike hits, I can literally feel the power drop when it happens at the 40% tps pulls. When I'm in PE, the spike isn't big enough to feel though I would imagine you could see it on a dyno.