What causes timing to be pulled @ WOT?
Thread Starter
TECH Enthusiast
Joined: Dec 2003
Posts: 535
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From: Warner Robins, GA
What causes timing to be pulled @ WOT? 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?
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?
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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
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
Last edited by SideStep; Sep 27, 2005 at 08:33 AM.
Thread Starter
TECH Enthusiast
Joined: Dec 2003
Posts: 535
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From: Warner Robins, GA
How do you know your injector duty cycle is 114%?
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.
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.
get injectors, then we can take a look at the rest, i'm not gonna help you to blow up your engine sooner.
Thread Starter
TECH Enthusiast
Joined: Dec 2003
Posts: 535
Likes: 0
From: Warner Robins, GA
Originally Posted by RedHardSupra
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.
get injectors, then we can take a look at the rest, i'm not gonna help you to blow up your engine sooner.
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.
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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.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
duty cycle 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...
