Has anyone tuned a 2003 8.1L silverado before?

[gtp2k2]

Since I got my software activated I've been itching to mess with my 2003 silverado 2500 HD, with the 8.1L and allison 5 spd. I seen one or two files posted, that weren't in the repository, and have downloaded them to check out soon, but were from a 2002 IIRC. Just wondering if anyone had messed with these.

[Rinkrat456]

Did you find my files when searching?

[gtp2k2]

I found your thread. I wonder if there were any differences between 2002 and 2003

[Rinkrat456]

I used many '05 files to compare to when trying to figure out if something was ok to change initially. I got rid of the "traction control" dip in the timing tables that kill timing down low in the '02 I tuned by using an '05 as my base spark table to start at.

I ended up tuning for the small percent of ethanol we find in MN fuels at the owner's request.

[RWTD]

Make sure you set PE delay RPM to 0 on any Gen 3 truck. Many 8.1 trucks are set to not go into PE at WOT, due to a PE Enable Timer (HPT doesn't have this parameter, but setting PE Delay RPM to 0 will bypass it) that is often set to 60 sec. This RPM value does not affect the Gen 3 V8 cars, as the Timer is set to 0 on all of those. Also, rework your PE Enable TP table(s), as well.

[gtp2k2]

I just got the file off the truck last night. I will check into the tables as well. Going to be quite the learning curve going from spending 5 years tuning 3800's with DHP to this platform.

Rinkrat: I noticed from your thread that you couldn't change the value in the PCM to accomodate a larger tire size. I also see that it's blanked out on mine. Did you ever find a way around that?

I also scanned the truck, and seen that I have a weak o2 sensor B1S1, and I'm getting a maf code. Do you think the maf code could be contributed to the K&N intake?

[Rinkrat456]

Rinkrat: I noticed from your thread that you couldn't change the value in the PCM to accomodate a larger tire size. I also see that it's blanked out on mine. Did you ever find a way around that?

I also scanned the truck, and seen that I have a weak o2 sensor B1S1, and I'm getting a maf code. Do you think the maf code could be contributed to the K&N intake?

The tire/gear change calculator just scales the trans numbers by the % change. Switching to say...265/75R16's from 245/75R16's is a difference in 3-4% so the trans tables are all scaled up by that difference. If you were switching to a smaller tire, it scales down by that percent instead. Same with gear changes. I ended up multiplying most of the shift mph vs TPS vs gear tables by 7% to accommodate for the owners' choice in 285's, and then I fine-tweaked the trans shift points from there. The owner asked for earlier upshifts around highway speeds under light throttle so in those columns I didn't apply the straight-forward 7% scaling. Comparing stock tune vs my final tune, looks like I only changed it by 1-2 mph in those cells.

The 8.1 I played with also had a K&N FIPK and I didn't get any MAF codes.

[JonathanLeskewich]

Hi Rinkrat, any chance I could look at the 8.1 Allison file? My 8.1 is turbo and I?ve had my tune complete for awhile. I have always wanted to check the torque and trans tables to make sure I got them right?