4.8 Hot Start and Fuel Trims / VVE

[DanN]

Losing my marbles a tiny bit. I've been chasing my tail for quite a while now, and I think I must be missing something basic.

I have a 4.8 with the "low buck truck" cam: Lift .552/.552, Dur @.050 212/22X, LSA 107 Deg. I have a TBSS intake with the flex fuel injectors.

I have reverted to my starting point, and have attached it with a basic idle log and a hot start log.

I have been trying to follow Cringer's method, but my LTFT and my charts don't seem to jive.

I am logging lambda from the AC input with this math: ((([7101.10]/0.5)+10)/14.7)

I could use a leg up.. feeling pretty defeated at the moment.

[LS ROB]

I'd get the part number off of the injectors and make sure you have the correct data in the tune for the injectors you have. Have you done any VVE tuning yet?

[DanN]

I'd get the part number off of the injectors and make sure you have the correct data in the tune for the injectors you have. Have you done any VVE tuning yet?

Just checked my Injector data - it got changed somewhere along the line. Updating...

Haven't tried VVE tuning. Call me chicken. Ha.

[DanN]

Updated tune with corrected injector data, and a quick around the block log. It is definitely better.

I'm reluctant to fiddle with the VVE table until I'm a little more confident my data isn't garbage.

[RDF1]

Whats your injector part number?

[LS ROB]

Add cylinder airmass to your channels.

[DanN]

Whats your injector part number?

They are 12594512, which are listed as 38# for a 5.3 w/ flex fuel.

Add cylinder airmass to your channels.

Will do.

[DanN]

Fresh copies of the tune and log.

[RDF1]

They are 12594512, which are listed as 38# for a 5.3 w/ flex fuel.



Will do.

Here is LMG injector data.

[DanN]

MANY thanks RDF1.

Here is the latest tune and log. I have updated to the LMG injector data and made a small tweak to the MAF tune.

[DanN]

Still working on this with limited.. success?

At one point I thought I had it, but it seems I don't. My hot start is over 5 seconds (no throttle input).

I tried some suggestions from Cringer's Youtube for the Cranking VE vs Map vs RPM and Idle Startup airflow vs Run time (off time) vs ECT. It seemed to work the one time I forgot to log, but not so much since.

I also did a little dabbling in the VVE.

Seems it needs more fuel on cranking?

[LS ROB]

Give this a go to see if it helps at all. If it starts, let it idle for a good while.

DN_9_July_4800_Startup-3-idle-airflowrobtest.hpt

[DanN]

Give this a go to see if it helps at all. If it starts, let it idle for a good while.

It did start; I let it idle for a full 10 minutes. Then I stopped it and restarted, and logged another 3 minutes. The restart was quite good I'd say.

So..all you did was set Final Idle Airflow Min vs RPM vs Gear back to stock. I didn't think that would really matter given it's a manual with no gear feedback...