Stall when coming to stop, LM7 5.3 Turbo TH400 swap Speed Density 2BAR

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Originally Posted by SiriusC1024

Try LTFT+STFT on the corrections.

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Can you elaborate on this? Take the difference of the two? I just want to make sure I'm not confusing anything.

Here is a log from this morning, I reset LTFT about 42 seconds into the log.

Attachment 152675

Here is the last log I grabbed from a lunch run. I was making small adjustments to the VE table and it seems the LTFT's did change, but the car drivability seemed to not like the changes..

Attachment 152676

It seems as tho on my deceleration the 30kpa row of all my logs is getting "bad or un-usable data" which I've read about filtering, but have not dove to far into this yet. I'm going to do some reading and see what I can do with it, but any help is appreciated. I did just check DFCO and its still on.. I'll turn this off and grab another log later on today and see where I'm at.

Something is deff. still off.
Could the RPM reading actually be accurate?
The MAP reporting can't be accurate, could it?

Are you sure you have the linear and offset correct for the MAPS?

LTFT's are still up against the guardrail at 25%. Are you sure there are no exhaust leaks pre NBO2's?

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Originally Posted by abc

Something is deff. still off.
Could the RPM reading actually be accurate?
The MAP reporting can't be accurate, could it?

Are you sure you have the linear and offset correct for the MAPS?

LTFT's are still up against the guardrail at 25%. Are you sure there are no exhaust leaks pre NBO2's?

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Stock PCM obviously, stock coils, stock wiring. I never felt that RPM was off from what HPTuners is telling me.. Seems inline..

-OEM ACDelco Truck 19418810 2BAR Map - Using data of 200kpa - 8.01kpa showing 93kpa but I'm at 2178 feet above sea level, 4746 density altitude. 76 degrees in my garage at the moment. I do see other settings, 10.33, 9, changed to base of 10.33 and MAP shows 94kpa.. seems right :/

-When I put another aftermarket Vacuum gauge on the intake manifold vacuum block port, it showed 17in in park, 15 in drive.. This does match up with the 34kpa or so reading from HPTuners.

-No Exhaust leaks that Im aware of, the actual only exhaust connection PRE O2's are where the manifold is bolted to the cylinder heads..

Heres another log, its damn hot out, so I didn't get as much data as I wanted, but the LTFT are now moving..


Attachment 152685

Still the car begins to have idle issues/drivability as soon as I change the VE, write and clear LTFT and start on a new log..

If you clear out a 25% long term fuel trim, it will struggle with fueling until the LTFT catches back up.

If the sensor's actual specs are 200/8, you do not diddle the offset to make it read what you think it should.

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Originally Posted by blindsquirrel

If the sensor's actual specs are 200/8, you do not diddle the offset to make it read what you think it should.

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Understood.

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Originally Posted by gtstorey

If you clear out a 25% long term fuel trim, it will struggle with fueling until the LTFT catches back up.

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Ahh, that tracks as they say. I'll make sure to try and only clear when in a better scenario.

and here is the longest log to date, with some LTFT getting sorted, but around cruise/idle they remain high.

Attachment 152703

Clear trims and log this, please.

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Originally Posted by SiriusC1024

Clear trims and log this, please.

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Got some logs in.

First one is the longest, nice 30 minutes.

Attachment 152739

Second is just a backup, JIC.

Attachment 152739

Car is idling way smoother, no heavy stalling when coming to a stop. RPMS do dip down very slightly, but very very reasonable. Overall the car acted very well in cruising around.

I'm going to review the edit you sent over Sirius1024 and see if I can make sense of what you did. Thank you.

What is the configuration of the front O2 sensors? Where are they installed exactly?

IAT sensor part number?

Front O2 sensors are about 2" on Passenger and 4" on Drivers side from the exhaust manifold stock flange location, which leads into a Y-Pipe into the turbo.

IAT sensor is a stock one from a Buick 3600 1998 unknown part number, nothing cast into housing. Was grabbed from parts car. If you're seeing any issues with the IAT Sensor I can always buy a recommended one if that is best.

Are you seeing issues with the readings? I'm in Vegas, where the temps are unreal lately.. even for Vegas.

Also, I'm not around my computer at all tomorrow, so I wont be able to log/report anything until Saturday evening at best. I appreciate the help.

How about the FPR? Before or after the rails?

FPR is before, roughly 12" before the stock fuel rail lines, adapted to 6an hose, return 6an regulator. Just got back to my computer, will do some logging tomorrow and report back.

FPR goes after with vacuum reference. Hopefully that explains the weirdness in the VE.

Attachment 152802

https://king6fab.com/how-to-technica...al-feed-setup/

Regulator does not need to be after the rails, it does the same thing as long as it's referenced to manifold no matter where it is located - even if it is inside the tank or in an external surge tank. Single-inlet rail with a referenced reg works fine.

Is it theoretically better if you can flow all the fuel through the rails first? Sure, but it's also theoretically better if you can plumb the rails in parallel (feed to Y to rails, rails to another Y to regulator). The ones where that truly makes a difference are edge cases (extremely high power, and/or restrictive fuel rails). 'Stock motor with a turbo' is probably not at any kind of level where that stuff makes any real difference.

Yes it does. It most certainly does. There's a reason I knew to ask the question. Think about how a reg is constructed.

The only time fpr before the rails is acceptable is when it's not vacuum referenced.

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Originally Posted by SiriusC1024

Yes it does. It most certainly does. There's a reason I knew to ask the question. Think about how a reg is constructed.

The only time fpr before the rails is acceptable is when it's not vacuum referenced.

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Based on what? Doesn’t matter if the regulator is trying to hold 58psi as fixed or a variable pressure. Either it’s accurate or it’s not. Might be advantage to after the rail, but a blanket statement of will work or won’t work is way to strong.

Based on the fact that there's an inlet and outlet labeled on the reg. Rail pressure is raised for higher MAP, such as boost or N/A WOT. When the throttle shuts the reg moves to lower pressure. Rail pressure remains high. The only way the reg would release rail pressure is if it was bidirectional because the outlet would now be an inlet. What happens is the pressure is released as the injector fire. Fuel is incompressible, but the lines expand a little. Not much volume is required to do this, but in the meantime injector flow is elevated. You end up with VE like the above because the O2's are calling for less fuel during this rich transient.

Or you could look at a regulator circuit. Study how the spring adjusts where pressure balances across the diaphragm and how this balance is achieved.

Then there's the fact that if you google "vacuum referenced regulator location" they all show what I said. For the reasons I've said.

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Originally Posted by SiriusC1024

FPR goes after with vacuum reference. Hopefully that explains the weirdness in the VE.

Attachment 152802

https://king6fab.com/how-to-technica...al-feed-setup/

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I do recall this being one the of way's to plumb in a VR FPR.. Maybe I may have to change things to see if that's what's contributing to the weird VE transition.

Got another log on the books tonight. Car seems to be responding very well.

Attachment 152829

The IATs are concerning. It didn't seem like they were dropping at all, when I was cruising around.. I may need to look into the pump and verify its flowing like it should.. Thank you for your assistance.