Corvette 2009 LTFT question

[c6vette]

Dear all, i was trying to tune my corvette with the diablo predator. 

i have completed four data logs, and run them through the dslogredux

the first log,

said raise injector slope 8%      so i did 
second log said raise injector slope 2% 
third log said lower injector slope 1%
the forth log said raise 3%     

what am i doing wrong?  why is it taking so many runs to dial it in? and why cant i move on to the WOT  adjustments?

chris

[GrumpyAeroGuy]

I don't think you are doing anything wrong.

what mods do you have, if any. That can have an effect on things. No trick MAF, no throttle body spacer, etc.. (hopefully).

LTFT is a function of alllll kinds of things including temperature/humidity... ambient conditions, etc..

Make sure you do a true cruise log 1800-2300rpm, NO cruise control. Drive as steady as you can. Are you ever going to get it dialed in perfectly? nope. Get it as close as you can. I am ignorant as to whether vettes have AFM. If they do, make sure you log in a gear (if auto) such that it doesn't kick in. Usually one notch down from drive is good.

You CAN move onto WOT adjustments. the software will allow it. the RECOMMENDATION is to get your trims dialed in first, as they effect WOT fueling as well....

I think you are pretty close. I don't too get crazy with my truck (CAI and exhaust), I try to get it as close as I can within reason, then go ahead and adjust WOT fueling.

Hope this helps.

[c6vette]

thanks for the reply ill break it down

ls3 engine,
cold air intake
the diablo tune (not the 91 octane tune) I think this is the right tune
today, in charleston sc
first three runs were between 10am-2pm
fourth was at 4pm (i bet thats the difference)

cruise was on same stretch of road, i ran the car for 30 miles exactly before each run to dial in the changes. the rpm was at 1900 5th gear 60 mph 6 speed manual

i used cruise control, but the road is dead straight.

later this week ill be adding a ported throttle body (im sure ill have to do this all over again)

thats all i can really think of. if its off a little will it damage anything? and is cruise control really that bad ?

chris

[GrumpyAeroGuy]

no damage...fuel trim is a bias to look-up tables in the control. It is basically telling how much the control has to CORRECT to get to the right AFR.

If your trims are 0, your control gets everything correct out of the box. If they are off, it's basically saying this is how much fuel needs to be trimmed to get to the target AFR.

Either way you're running ok. If trims are set correctly, the control doesn't have to work as hard to get it right. That's all it is.

The control has default look-up tables (i'm sure), and the trim setting biases the table to get closer to the target without haveing to add or remove too much fuel.