After installing ARH 1 7/8" ARH headers and ORY on my 08 Sierra Denali, I installed an Innovate LM2 to monitor the AFR. I'm getting 11.6 to 11.8:1 @ WOT. I'm thinking I should be nearer to 13:1, but I'm not certain what these motors like to run at. Anyone know this from experience?
I think what's happening is that the headers and ORY, along with the VaraRam leaned the mixture out so much that the ECU is dumping a bunch of fuel in to compensate and is over richening the mixture. A friend of mine who is a tuning guru (on the LS1 vettes and such) says that we need to fatten up the fuel curve a bit and then zero the fuel trims til we get nearer to 12.8 to 13. Does this sound right? Anyone have this issue before? If so, what did you do? I have HP Tuners but haven't gotten around to familiarizing myself with it as yet, so keep the answers as simple as possible for my feeble mind, ok? Thanks for any input on this.

 

yes 12.8-13 is optium at wot. dial in ur fuel trims than adjust ur fuel curve cause the fuel trims control how mush fuel u spray at wot too.

 

I like 12.8.

 

I had mine tuned about a month ago and it was set at 10.7 from the factory. My tuner set it at 12.8 and at the far end of the RPM range he ramped it up to 12.5. He also used HP Tuners. I do have one issue. I have been getting a check engine light because my front O2 sensors are reading slowly, probably due to the fact that they are father from the engine. He recommended rear O2 sensors from a Corvette or similar vehicle. He thought they might have a higher wattage heating element to help with this issue. Good luck!

 

12.5 - 12.7 is what i felt was the best SOTP.... 13 AFR is good for midrange, but richen it up near the end as these 6.2s knock a little more then anything else...

 

From what I hear for N/A on the LSx platform is you need more fuel at peak torque and less fuel at peak HP so a flat AFR through the RPM band is not the ideal set-up. My 408 tune (yours will be different of course) starts at 12.6 up to 5100 RPMs then sloped to 12.9 at 6300 RPM's then fattens up to 12.6 by 6500 and then to 12.4 at 7000.

I haven't been to the dyno to verify this however after extensive MAF tuning with the wideband, I am within a very small percent AFR error during a WOT pull and the truck seems to like this curve (again, seat of the pants deal).

You can command whatever AFR you want however if your MAF (or Ve) is not tuned properly, you will never acheive your commanded AFR without "estimating" with your Pe values. Dialing in your Ve and MAF is the foundation to a great tune.

 

Thanks for the replies guys. I have been playing with the tune for the last couple of weeks with a friend of mine who is very good with EFI Live on the LS1s. The E38 seems to be a little bit trickier to tune though, and so far we have it doing pretty much what we command (12.85:1) when it goes into PE mode but the AFR drops at pretty much a constant rate from there to 12.0 - 11.9 at the upper end of the RPM range. We've just started playing with the VVE tables, but it looks like it will take a bit of work to get it optimized. He says we need a day or so of logging to get the VE dialed in right. From what I'm hearing, it looks like the best curve for me would be like 12.6 or so at peak torque and vary it to about 12.8 at high RPMs.
I'm certain that would wake my truck up pretty good. Right now the damn thing is running like 10.7 or so on the spray, so I know there's more HP left on the table.
Thanks again.