Guys I need some help on transition fuel.

[Dewayne Smith]

I've tuned a few boosted vehicles and have had really good luck overall but this one is kicking my tail.

I'm working with a P01 with 3 bar. This setup starts making boost early and under mild acceleration at say 32% throttle @ 125kpa then lift to 22% @94kpa to level out it goes very lean to the point that the engine is basically free spinning for a few seconds before picking back up again.
If i add fuel to the really lean cells then the next time when I'm accelerating its extremely rich and chokes down.

I have got to be overlooking something simple but I've been fighting this for a few weeks now and have yet to smooth it out.

I'm posting my tune as well as 2 short log clips.

Thanks guys!

69 Buick Turbo 6.0 4l80 3 BAR OS 11.8.22. 1.hpt
7.1.hpl
7.2.hpl
1660407987351.jpg1660407987333.jpg

[Dewayne Smith]

Looks like those that may know are busy.

[SiriusC1024]

Maybe...

Looks like what might be happening is when you suddenly decrease throttle the pressure buildup, while being too small to be vented out the blow-off valve, is being sent through the IAC.

Try doing an IAC/TPS relearn.

If that doesn't help then maybe it's Idle Reset Position. I have one of those style throttle bodies, and Idle->Airflow->General->IAC Reset Position had to be changed from 310 to 160. Do a relearn after changing that.

[Dewayne Smith]

Maybe...

Looks like what might be happening is when you suddenly decrease throttle the pressure buildup, while being too small to be vented out the blow-off valve, is being sent through the IAC.

Try doing an IAC/TPS relearn.

If that doesn't help then maybe it's Idle Reset Position. I have one of those style throttle bodies, and Idle->Airflow->General->IAC Reset Position had to be changed from 310 to 160. Do a relearn after changing that.

IAC/TPS relearn hasn't helps. I've never really understood what the Idle Reset Position does but I'll dang sure give it a try.

BTW, I hate this throttle body and the intake. I think a 102 TB is overkill for this application and the engine has a lazy response because of it.

Thanks!

[Alvin]

Try PE settings like this. You may need to go over the tune a bit after this change.


69 Buick Turbo 6.0 4l80 3 BAR OS 11.8.22. 1.2.hpt

Otherwise I'd make sure fuel pressure isn't doing something weird right there.

Your blowoff valve is closed at idle on this right?

[Dewayne Smith]

[QUOTE=Alvin;706432]Try PE settings like this. You may need to go over the tune a bit after this change.


69 Buick Turbo 6.0 4l80 3 BAR OS 11.8.22. 1.2.hpt

Otherwise I'd make sure fuel pressure isn't doing something weird right there.

Your blowoff valve is closed at idle on this right?[/QUOTE

The blowoff valve is closed closed at idle an just the slightest blip of the throttle will try to open as the throttle blade closes. I've ordered a lighter spring but I don't think I can go any lower without idle vacuum pulling the valve open.

The tune needs going over anyway, I had it nice and smooth but chasing this issue over the past few weeks I've let it get a bit rough.

About to see what you changed and give it a test. Thanks!

[Alvin]

IMHO a turbo blow off valve should be hard to open sitting still revving. Had a turbo car dropped off with a blower spring in it so it was open at idle and acted as you described

[Dewayne Smith]

IMHO a turbo blow off valve should be hard to open sitting still revving. Had a turbo car dropped off with a blower spring in it so it was open at idle and acted as you described

The PE adjustments you made didn't help the issue but I didn't have time today to mess with it much at all. I do like how you lowered the throttle and raised the map for PE.

Maybe I'm looking at the blow off valve the wrong way, I'll add spring pressure and see what happens.

[Dewayne Smith]

I know its been a few days but I finally got to spend some time on the Buick today.
I added a stiffer spring to the BOV and also added a pressure transducer to the fuel rail. The fuel pressure is holding steady, no drops or spikes. The stiffer BOV spring did not help. If anything, its closing the BOV sooner because now I can see the MAP pressure rise back up some. I'm gonna see how light of a spring I can run and still keep the BOV closed at idle. I still feel its transition fueling but just can't figure out how to adjust from above 100kpa back down to 90ish. Can't help but wonder if its something to do with the fuel to wall impact factor due to this intake that I like less and less.
I'll update again soon.

[Dewayne Smith]

I may be on to a "work around", gonna use the minimum injector pulse table to keep the injectors from dropping too low. I've watched injector pulse across today's log and I'm gonna start at 2400 RPMs and set min pulse to 4.0 the rest of the table. In my head this should work but may need to fine tune the numbers a little. I'll report back after I've tested this.

[SiriusC1024]

What don't you like about the intake? My only complaint is increased valve noise. That thin sheet metal acts like drum. Put my hand on top and it's quiet.

Might hop over to where we're working on an issue like you have:
https://forum.hptuners.com/showthrea...Transient-Fuel

[Dewayne Smith]

What don't you like about the intake? My only complaint is increased valve noise. That thin sheet metal acts like drum. Put my hand on top and it's quiet.

Might hop over to where we're working on an issue like you have:
https://forum.hptuners.com/showthrea...Transient-Fuel

That's exactly why I don't like it. Ill check out that link, thanks.