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Old 06-21-2011, 11:30 AM   #1 (permalink)
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Air fuel ratio

I just got my 08 Z06.
I previously had an 08 C6 w/LS3.
I installed my predator to do some custom tuning and notice that the Z06 @ WOT had a 12.6 Air fuel ratio.
Is this air fuel ratio set from the factory?
On my C6 LS3 it was 11.7 from the factory @ WOT.
I added fuel and got it down to around 12.3@WOT.
Wanting to know if 12.6 was the original tune from factory.
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Old 06-21-2011, 01:11 PM   #2 (permalink)
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Re: Air fuel ratio

Sounds like your car may have already been tuned. The factory A/F tables vary with rpm and throttle setting. Since you're talking WFO, let's take a look at what the typical stock Z06 would be...
2300rpm.....11.71
2400..........11.24
25..............11.01
26..............11.20
27..............11.27
28..............11.31
It bounces around for the next 4000rpm with a lean of 11.86 (3900rpm) to a rich setting of 11.01 (2500rpm.)
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Old 06-21-2011, 01:32 PM   #3 (permalink)
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Re: Air fuel ratio

I had that feeling.
I guess I can do some data logging and watch for knock and lean it out little by little if it was tuned and set at 12.6. I'm assuming that's the max it can be before any spark knock.
As of now I'm not getting any knock at 12.3 which is the leanest (at around 3400 rpm)
Thanks for your help and info Norty.
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Old 06-21-2011, 02:32 PM   #4 (permalink)
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Re: Air fuel ratio

Where are you putting the wideband? If it's after the cats, it will show a little lean. Optimum AFR for making power on the dyno is around 12.8:1. You can run that AFR safely on these engines.
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Old 06-22-2011, 04:11 PM   #5 (permalink)
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Re: Air fuel ratio

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Originally Posted by jub jub View Post
Where are you putting the wideband? If it's after the cats, it will show a little lean. Optimum AFR for making power on the dyno is around 12.8:1. You can run that AFR safely on these engines.
As Jub said, wideband after the cats is not very accurate.

Any welding shop can have a bung put in the exhaust before the cats and the wideband sensor can go into the bung.

Mike
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Old 06-22-2011, 06:33 PM   #6 (permalink)
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Re: Air fuel ratio

Quote:
Originally Posted by DarkZ View Post
I just got my 08 Z06.
I previously had an 08 C6 w/LS3.
I installed my predator to do some custom tuning and notice that the Z06 @ WOT had a 12.6 Air fuel ratio.
Is this air fuel ratio set from the factory?
On my C6 LS3 it was 11.7 from the factory @ WOT.
I added fuel and got it down to around 12.3@WOT.
Wanting to know if 12.6 was the original tune from factory.
For one the predator is not the best tool to be getting facts.
That is a commanded AFR, not a true AFR.

Since GM is forced to warranty the CATs for 8 years by EPA law and depending on the run done, weather, and gas used the PCM could have been doing COT, which dumps in extra fuel to cool the CATs down to protect them

Other run can be done and happens at that time COT was not commanded on so AFR would look different
Also if E10 gas is used or not requires a richer/leaner AFR throughout RPM range.

AFR has to be tuned as to mods the car has, the elevation, type of gas used and if the CATs are installed or not.
Car at sealevel in 90 degree weather needs a totally different AFR then a car at 6,000 feet and 65 degree weather
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Old 06-23-2011, 06:56 AM   #7 (permalink)
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Re: Air fuel ratio

Ls7s like the air fuel 12.2 12.4 is optimum for ls7s dont touch it. The computer will learn and correct also. Chuck Cow even recommends that af ratio on ls7s.

Just see if theres any timing being pulled out...
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Old 06-23-2011, 07:27 AM   #8 (permalink)
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Re: Air fuel ratio

COW is a moron and the last person to listen to
PCM is not "learning" as WOT is a non EPA function and ignores the o2 sensors and fuel trim cells.
12.2 AFR is too rich UNLESS tuner cranked in too much timing causing engine knock and richer AFR used to attempt to reduce that knock

My C6 Z06 has 12.7 AFR with no knock and does just fine
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Old 06-23-2011, 08:02 AM   #9 (permalink)
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Re: Air fuel ratio

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Originally Posted by racingvette View Post
COW is a moron and the last person to listen to
PCM is not "learning" as WOT is a non EPA function and ignores the o2 sensors and fuel trim cells.
12.2 AFR is too rich UNLESS tuner cranked in too much timing causing engine knock and richer AFR used to attempt to reduce that knock

My C6 Z06 has 12.7 AFR with no knock and does just fine
Would you look at that. For once we're in agreement!
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Old 06-23-2011, 11:04 PM   #10 (permalink)
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Re: Air fuel ratio

Well guys I wasn't trying to start A tune war about Chuck Cow. Dont know the hate Torwards the guy but that's your deal. Now I was Just saying about the tune because I was also skeptical on my tune I was 12.2 12.5 ended up with final run. 488 468 torque with cats. with just headers. But again it was 100 degrees outside. Pulled the belt just for giggles hit 501 478 lol. So you are saying that the computer doesn't learn at wot if there's cold or hot weather.
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Old 06-23-2011, 11:17 PM   #11 (permalink)
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Re: Air fuel ratio

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Originally Posted by Zeueses07Z06 View Post
Well guys I wasn't trying to start A tune war about Chuck Cow. Dont know the hate Torwards the guy but that's your deal. Now I was Just saying about the tune because I was also skeptical on my tune I was 12.2 12.5 ended up with final run. 488 468 torque with cats,with just headers. But again it was 100 degrees outside. Pulled the belt just for giggles hit 501 478 lol. So you are saying that the computer doesn't learn at wot if there's cold or hot weather.
Also I know what your saying about it not learning. But only when in Open loop at wot the car can not learn, because wot is open loop correct. So with my tuning I have seen cars with a 13.0 a/f and same car detuned to 12.5 and dyno higher than when at 12.5. So my second question how much of a difference will you see from lets say yours 12.7 to his 12.6 or 12.3 4 and ect......


Thanks guys just was trying to help.....
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