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.

[chvy=power]

at WOT there is no manifold vaccum so i dont see how that could be it..at WOT the lt and stft are both 0.0. just easin around town they run anywhere from -1 to -10. i took the screen out of the maf so maybe that threw the reading off?? As far as timing he said something about how the hp and tq curve were wavy at higher rpms meant that the timing was off. maybe that guy was an idiot? idk all this tuning stuff is new to me so i'm still learning. When you drive the truck it just makes a lot of noise at high rpms and dont go anywere, guess its starving for fuel? And are those hp numbers a little low? if i cant put down more than 300 to the rear tires then thats just sad......

[farmtruc]

I just went to their website and read up on their view of tuning wild cams. The term wild cam is relative, so I don't know what they mean, but for any wild cam that I've tuned for, I never turn off the o2's and they don't run rich.
I'm talking street vehicles here, race setups are different, but there are many cars out there with "wild cams" that are street driven.
If anything, for "wild cam" setups, I SD tune the vehicle.

here's what they said:

"
In cases where wild cams are present, custom tuning with no O2 feedback at idle is necessary to greatly reduce or eliminate the extreme rich conditions experienced with these cams. Generally, 02 feedback must be turned off with wild cams even after tuning is completed in order to keep the ECU from wanting to idle extremely rich again. Even though you may hear that running rich at idle and cruising is normal with wild cams from other individuals and tuning shops, don’t be fooled, it’s not safe and you shouldn’t have to deal with it. At TDC, we are perfectly capable of greatly reducing those extreme rich conditions and it's negatives affects on gas mileage safely and efficiently through custom tuning."


I'm not saying they don't know what they are doing, but they leave this open to speculation. Running a car in open loop all the time will eat tons of gas, plus it will be a never ending tuning battle to nail down a/f ratio and ltrims. This is called OLSD tuning and it's a headache for those looking for gas mileage. Of course if the customer has a wild cam, he's probably not that concerned about mileage.

In a street car with a wild cam or not, o2's are important. They give feedback to the pcm at idle and wot, and are important during normal driving to maintain stoich.

I just finished tuning an 08 LS3 vette we installed a cam in. It was a big one, like a 235/251-.640 lift. We left the o2's on and maf tuned it. Customer just reported it's running great with no idle issues and still has great manners on the street. That's what got me to read tdc's website and their ideas on tuning. I realize they can't put everything about tuning, but that paragraph was a bit vague and questionable.

[farmtruc]

at WOT there is no manifold vaccum so i dont see how that could be it..at WOT the lt and stft are both 0.0. just easin around town they run anywhere from -1 to -10. i took the screen out of the maf so maybe that threw the reading off?? As far as timing he said something about how the hp and tq curve were wavy at higher rpms meant that the timing was off. maybe that guy was an idiot? idk all this tuning stuff is new to me so i'm still learning. When you drive the truck it just makes a lot of noise at high rpms and dont go anywere, guess its starving for fuel? And are those hp numbers a little low? if i cant put down more than 300 to the rear tires then thats just sad......

How was map/vac measured at wot?
The 0 ltrims are correct at wot. If the ltrims are negative before PE mode, then they will go to zero, which is what you want.
Be sure the maf wasn't damaged in any way when the screen was removed. It sound odd, but the position/clocking of a maf will cause a lean or rich condition as well, but not in this case, just mentioning it.

The graph doesn't look bad to me, has a nice curve to it. It's a bit shaky, but that doesn't or have anything to do with timing.
Maybe his pick up or probe or however they measure rpm had some interference.
You won't see those tiny spikes like that because timing is off.

If a/f ratio is dead on, i don't think 300hp is reachable. You're asking for 40hp or so.

See if you can get some realtime data sent over, maybe someone has hptuners and can send over a scan.

[chvy=power]

yea thats one of the local tuners around here...he mostly does ricers and imports but everynow and then does a camaro or two..so idk if i'd trust him with my truck.. I've been very pleased with nelson performance and have reffered a lot of friends to you so if we can get this right through a mail order tune then i'd be extremely happy