Lean Upshift

[Jim Blackwood]

I'm sure this is an easy one for you old pros. Anyway on every upshift ('411 controller, manual tune, 300 Buick V8, full Monte SD) I get a lean spike that causes hesitation just as I'm hitting the gas pedal. Not so bad after it warms up but rather bothersome before that. I'm guessing it's a transient setting? Anyone care to point me in the right direction? Thanks.

Jim

[Alvin]

This will typically resolve itself with good VE tuning with a wideband

[SiriusC1024]

Make sure your fuel injector info and VE is correct, like Alvin said.

Then if there are still issues move onto fuel transients. Research fuel-to-wall impact and evaporation tables. If it's rich on throttle close and lean on throttle open (or vice-versa) changing these settings will give good results. If lean on tip-in AND lean on tip-out (or vice-versa) then look elsewhere.

Another thing to check is for knock on tip-in.

[Jim Blackwood]

Thanks guys, I have most of that sorted, I just get a lean spike on the upshift, I can see it flash to around 18 or 20 on the AEM WB. It makes the engine hesitate on re-application of the throttle coming out of the shift, but that does not necessarily mean it isn't leaning out on decel. I'll try to get a more accurate diagnosis today and also have a look at your suggestions. I can stretch out the throttle action and maybe get a better picture of the timing but I'm pretty sure it is going lean on accel.

Jim

[Jim Blackwood]

Definitely going lean on tip-in and rich on tip out. The lean spike is much more obvious which I suppose is to be expected.

"If it's rich on throttle close and lean on throttle open ... changing these settings will give good results."

Exactly. So I could really use a little guidance here, as to exactly which table to try, which direction to move the values, and a good initial increment to move them. Any suggestions about that would be most welcome.

Jim

[Alvin]

IMHO you are going down the wrong road looking at transient stuff. This screams to me that the VE table isn't tuned as well as it should or it has some holes in it.

I've done seriously radical setups with '411's and not needed to touch transient stuff. Like 502 big blocks, 460 cube individual throttle body setups, short runner destroked LS7's that turn 8000 RPM.

[Jim Blackwood]

What you say makes sense of course, and if it was something like a bog I'd totally agree with you. But it isn't, it just an irritating little stumble and I know for sure that guys have had success with tuning the transients where it was either a rich/lean or a lean/rich combination like this is. I can remember watching a video by that goat-rope guy about it one time and I'll go back and look for that if I can find it. I just can't remember whether he said to increase or decrease the settings or which ones to change. Clearly if it is a 3D graph it doesn't all have to be increased or decreased either but there has to be method to determine what cells are affected. I'm not yet practiced enough with the scanner to set that up. I've got the one for the VE deviation but that's about as involved as I've gotten with it so far. That all is pretty close and I continue to tune it in.

But one thing is certain. When you hit the gas if there is a lean spike it isn't getting enough gas in that instant, and that can be at a wide range of RPMs. If you raise the VE table across that band to make it rich enough for the lean spike to go away then it's going to be too rich at that rpm at a steady state. If it is not, that simply says that your transient settings are dialed in correctly for your setup. And that is probably pretty common anong LS engines.

However My engine is a Buick. So it needs different settings because first off it just isn't as efficient as an LS, and secondly because the intake system is much different.

So all due respect to you and everyone there, but I strongly suspect that trying to tune this out in the VE table would be heading down a rabbit hole with no end in sight. In any case I'd like to try the transient settings to see what can be gained by it. If it doesn't help I can always revert back to today and try something else.

And thanks again for helping. I sincerely don't mean to question your expertise.

Jim

[SiriusC1024]

Don't bandaid it. Be certain VE is correct.

Still running MAF? Read this:
https://forum.hptuners.com/showthrea...ot-tip-in-quot

Last resort adjust transients. Post #3 here:
https://forum.hptuners.com/showthrea...Transient-Fuel

[Jim Blackwood]

Not running MAF, it's a SD tune.
I continue to refine the VE table but the thing that is in the way of being able to lean out the cells for economy is this rich/lean transition on upshift with a manual transmission and it doesn't look very much like that can be tuned out in the VE table. Maybe you guys have had better luck but bear in mind you are tuning LS engines. I am not. I am tuning an old school Buick 300 and chamber, port and intake design has improved in the 30 years between the two engine types. So it's not surprising that something like the transition tables, which clearly are not there unless they are needed, may hold the key.

In the old carb days I'd just increase the accelerator pump shot and be done with it. Despite EFI's obvious advantages it appears that today it is not quite so easy.

As for the transition entries, first I am running the '411 controller and newer versions have much more settings, second it is becoming clear that not many people have much of an idea of what those settings do or how to manipulate them to get the desired results maybe because they don't need to change them, maybe because of the variations in the controlllers means they are talking about settings that I simply do not have. So I seem to be stuck with the old trial and error method which so far hasn't given any detectable results whatsoever. I would welcome something making it clearly worse at this point.

Jim