DenzSS

Using Autotap, we're seeing a loss of timing. It drops from normal range to 0 degrees after the truck is taken to WOT. Fuel pressure is good, with absolutely zero KR.

The truck is a 2001 Silverado.

Thoughts?

[ November 14, 2001: Message edited by: DenzSS ]</p>

Pro Stock John

iTrader: (34)

Keep in mind that our cars have base timing, not sure what it is but it's probably 10 degrees.

This truck have mods?

DenzSS

Doh--I forgot to mention that.

It has an ATI Procharger that went just went on. Guess I should have mentioned that. A buddy of mine owns a shop in the KC area thats doing the install right now. He's done a LOT of LS1 FI and has never seen this before. The truck was basically stock other than a PCM modified by Ed Wright to up the speed limiter. They did a baseline dyno run before the Procharger, but did not ATAP. They've never done a 6.0, but have done several 5.3 ATI kits. Everything looked ok during the dyno, perhaps a little low ~240RWHP SAE corrected. The kit then goes on, everything looks kosher, falls flat on its face. No codes are being set, zero knock retard, fuel pressure is good. Plugs have been gapped and changed. The truck idles fine, but falls on its face as soon as it goes WOT. Using Auto-Tap, it idles at 35 degrees or so. As soon as you hit the throttle, it drops to 25, then 20, 15, 10, and eventually 0 as the RPM's climb.

Any thoughts? I'm out of ideas.


Thanks,

Denzil

[ November 14, 2001: Message edited by: DenzSS ]</p>

DenzSS

Other mods--custom exhaust. Nothing else.

Ragtop 99

iTrader: (7)

I would first call Ed Wright and find out what he programmed for. You might also ATAP and get your MAF flow and MAP for him.

DenzSS

They talked to Ed. All he changed was the speed limiter and modified for the lift kit and wheels.

DenzSS

ttt

Neil 6.0

Does the ATI come with a 'piggyback' computer?

DenzSS

AF looked ok on ATAP. The truck is at an exhaust shop right now getting a bung welded in for wideband O2.

Replacing the PCM--well, swapping it like you suggested--is the next plan of attack.

Neil: Nope. No piggyback computer. None is required as long as you're using the standard kit. If you move to the "tuner" kit and up the boost, you're going to need programming. So far, the ATI Gen III kits are pretty good. F-bodies are a bit of a pain to get everything mounted, but that's nothing but time.

Neil 6.0

Is the MAF stock (untouched)? Could it be the torque management? What has ATI said?

Sorry, I'm just shooting in the dark...

DenzSS

MAF is stock. We're working with ATI(they're just down the road a ways), but they're as lost as we are it seems. Nobody has seen this situation it seems. Oh well, nothing like breaking new ground. <img src="images/icons/smile.gif" border="0">

I'm not sure about TM. TM should only be pulling timing on a shift if I remember correctly. This is a steady consistent drop.

Neil 6.0

Dang, that is crazy. <img src="images/icons/frown.gif" border="0"> Just out of curiousity, is a HPP3 being used on the truck? (I doubt it since you said the PCM has been to Ed Wright).

DenzSS

Nope. No HPP3. Although its always nice to blame. There's nothing quite like removing HPP# Power Programming and watching the HP jump. LOL

really slow truck

so your o2's and ltrims and all your air-fuel stuff look good, and there are no other problems... <img src="images/icons/confused.gif" border="0"> have u tried swapping pcm's? like borrowing another trucks if you know anybody to see if it still does it? that just seems odd