Vortec EGR System?

[1project2many]

Sorry, Mark. Didn't mean to leave you hanging. Had a road trip to visit family.

Change that bit and you should see fuel trims follow only bank 1. I have been told the selection for 1 or 2 O2 sensors will do the same thing but haven't played with it.

Spent time with my cal. Problem was solved with engine displacement per cylinder. The displacement step size is 10CC so I bumped it from 630 to 640CC.

Imported trans module from 99 Envoy for faster response to throttle changes. I need it due to reduced torque at lower rpm. Much more driveable now and less fuel wasted. Still need to work on a few things but better overall. Didn't realize TC can do that until this weekend. V. Cool.

The EGR helping / hurting mileage has been a back and forth issue for years. Claims on both sides by respected individuals lead me to believe there are more than simple variables involved. I look at cam overlap and exhaust configuration to decide how much is needed. Decent overlap and mufflers indicate EGR already present at part throttle without opening valve so why add more?

[EagleMark]

Hope your trip went well.

I tried the bank fueling bit and no change? Still had difference on 1 and 2... I'll give it a shot again tomorrow. Also asked John at TC to verify it's purpose.

As you found TunerCat will do the Import Calibration of Engine/trans or... which others call a segment swap. It will also do it table by table if the table is open. The more I use it the more I like it.

The EGR helping / hurting mileage has been a back and forth issue for years. Claims on both sides by respected individuals lead me to believe there are more than simple variables involved. I look at cam overlap and exhaust configuration to decide how much is needed. Decent overlap and mufflers indicate EGR already present at part throttle without opening valve so why add more?

That is the first time I've ever heard a theory on why! Makes perfect sense as well.

I just can't pull the TB off right now to check EGR/diffuser issue you asked about, can't chance the vehicle being down. Have no idea when I may have to leave town and bring wife to OR for surgery... The Suburban just has to many issues for a trip...

[pmkls1]

Well Mark, I may be a little late chiming in here, but I just happen to be resealing the intake on my grandfather-in-law's '99 suburban. I snapped some pics of the bare intake to illustrate what I believe may possibly be the issue. The particular truck that I'm working on is a 1999 Chevy C2500 Suburban with an L31 5.7 (obviously) and a 4L80E. Mechanically, the '96-'02 L30 and L31 intakes are essentially identical AFAIK. Anyway, I've got a couple things to do and then I'll upload my pics to the computer and post them with a few notes showing the passages and such.

[Hog]

There are some small EVAP differnces between the 96-97 and 98+ intakes, but the 305 and 350 intakes are NOT differnt.

peace
Hog

[pmkls1]

Alright, the first pic is of an assembled manifold with a few things pointed out for anyone not familiar with the layout.

[pmkls1]

The next pic is of a bare intake in the same orientation.

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[pmkls1]

Sorry for having to post one pic per post, but I'm having problems with posting. This next pic is a close-up with the EGR passages pointed out.

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