jub jub

I did some scanning at the track this past Saturday and noticed my timing was around 19-20 degrees at WOT. IAT was around 125F. I figured I must be losing some HP because I had 28 degrees on top when the car was dyno tuned.

Does a high IAT cause the PCM to revert to the low octane table? Also, my injector duty cycle was around 114%. Is the PCM compensating so I don't run too lean? The actual outside temp was 90 with about 85% humidity. Any thoughts?

foff667

iTrader: (2)

iat is part of it...some tuners up how much timing is taken out dependant upon iat temps...when i was dynotuned some cells would take out up to 11*

SideStep

Hey jub... I checked an 02 ZO6 PCM .bin file for the timing pull at 125 degree IAT. The PCM is pulling 5-6 degrees timing at those IATs, here is the data (partial) for the 122 - 131 degree IATs. It is represented by amount of cylinder fill (g/cyl) vs. IAT...

This is where you are loosing your timing...

No, IATs themselves will not throw you into the Low Octane table, Knock will.

How do you know your injector duty cycle is 114%?

..............IAT Temps
(g/cyl).....122...131
0.08..........0......0
0.12..........0......0
0.16..........0......0
0.20..........0......0
0.24.........-1....-1
0.28.........-1....-2
0.32.........-2....-2
0.36.........-2....-3
0.40.........-3....-3
0.44.........-3....-4
0.48.........-4....-4
0.52.........-4....-5
0.56.........-4....-5
0.60.........-5....-5
0.64.........-5....-6
0.68.........-5....-6
0.72.........-5....-6
0.76.........-5....-6
0.80.........-5....-6
0.84.........-5....-6
0.88.........-5....-6
0.92.........-5....-6
0.96.........-5....-6
1.00.........-5....-6
1.04.........-5....-6
1.08.........-5....-6
1.12.........-5....-6
1.16.........-5....-6
1.20.........-5....-6

jub jub

Thanks for that info SideStep.

I have a PID for injector duty cycle that I monitor. Right now my injectors are stock so I will be rescaling the IFR table once I install the Accell 36# units that I have.

I really didn't know that IAT temps had such a profound affect on timing. Now I fully understand more the advantage to having a cold air intake. During the time I was scanning, I had temporarily installed the stock Z06 airbox with K&N filter because of some problems I've been having getting my LTFT's to settle down with the Halltech Stinger.

SideStep

I was wondering how the hell your IATs were so high with that Halltech...

RedHardSupra

iTrader: (1)

so you're out of injectors and you worry about pulled timing? you should consider yourself lucky and thank the PCM for doing it, otherwise you'd be making a 'blew up at the track' post.

get injectors, then we can take a look at the rest, i'm not gonna help you to blow up your engine sooner.

jub jub

I appreciate that!

I'm just trying to figure out the jist of all these variables so I can make more of an "informed" decision as to future mods.

DellZ06

Probably a dumb question, but

How does an injector duty cycle go over 100%? I thought 100% was like always open all the time...

"These injectors go to 11..."

John.

Patrick G

iTrader: (14)

The pcm will call for whatever the motor needs. If it needs 110%, it will ask for it. Whether the injectors can deliver more than 100% remains to be seen.

moehorsepower

iTrader: (3)

The injector duty cycle can go up to and more than 110%. The problem is that either you will not be able to get the AFR to the proper ratio and or the injector can and will lock up at WOT. It is best to stay at 85% at WOT...