5.3 let me down..or maybe it was the tuner

[chvy=power]

So today as i was sitting around the house with nothing to do i decided to take my truck to the local dyno..I did one pull and it was running so lean they wouldn't let me make any more pulls because they were scared i would melt a piston or somthing. It put down 253.89 hp and 259.40 torque. the afr was around 15:1 then when it got to about 5500 rpm the afr was really close to 16:1..wtf. Sounds like its time to ditch the mail order nelson tune and get a live tune?

[pl4yboy]

HOLY GOD. Your AFR should be around 12.7 WOT...

[SCIV]

I doubt the tune is off that much...

Something else is wrong, or you didn't give the proper info when getting the tune, or you changed something since then. That's my $0.02

[farmtruc]

Check your fuel pressure as well, a tune won't account for low pressure if that's the cause, neither will it account for a maf reading on the lean side, so many variables.
That's why it's up to the customer to get a wideband reading and report back.

Ya, a live tune is better than a mail order tune, so if there's someone local that has a good reputation, I'd go for it.

[chvy=power]

yea im not bashing nelson performance by any means btw just dont see how tune can be spot on when you dont actually have the truck in front of ya to work on... I checked the fuel pressures and its running around 56-58 psi. the guys at the shop also told me my timing was way off also. here is my dyno sheet some of ya'll can prob read this a lot better than i can

[farmtruc]

Getting an a/f ratio reading is the first step, so that's some good feedback. Injector duty cycle needs to be recorded also, you could be out of injector.
You have a 2000 truck, that means it probably has a few things that could be done.
Check the ltrims, if they are way off, something like a vac leak could be causing the lean condition.

The maf controls a/f ratio as well, if that's reading a little off that would cause a lean condition.

Every shop out there will talk crap about the next tune or shop, how was timing measured? It's impossible for the timing to be off if the truck is running fine. Timing without a doubt is higher than stock, so to say it's way off, what does that mean? Timing can't be off, it can be low or high, caused by detonation or temps, but to say timing is off, please explain what the dyno operator meant by that.

Once we get some answers we can richen it up. But for me to just send out a tune that is richer, when in fact it shouldn't be, is just covering something else up.
The tunes we send out are setup to run on the rich side, if anything your truck's wb reading should have been a little rich, if it isn't, steps need to be taken.

Most trucks are on the edge of running out of injector with just a cam and exhaust, so that's my guess.

let me know and we'll take the next step.