What air/fuel ratio is considered too lean?
11-23-2006, 10:15 AM
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What air/fuel ratio is considered too lean? from my post below,
'02 A4 Z28 w/PTB dynoes@298...after SLP lid, dynoes@303...after SSRA2, dynoes@318!,
my air/fuel ratio of 14.1 is considered lean. Is my air/fuel ratio lean enough so that I shouldn't run the car in the quarter without first getting a tune to richen out? or am I okay? If so, then what air/fuel ratio is considered too lean so that there's a risk that the engine can detonate? Thanks in advance for the info.
'02 A4 Z28 w/PTB dynoes@298...after SLP lid, dynoes@303...after SSRA2, dynoes@318!,
my air/fuel ratio of 14.1 is considered lean. Is my air/fuel ratio lean enough so that I shouldn't run the car in the quarter without first getting a tune to richen out? or am I okay? If so, then what air/fuel ratio is considered too lean so that there's a risk that the engine can detonate? Thanks in advance for the info.
11-23-2006, 02:22 PM
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I don't know. When the car was bone stock, the air/fuel ratio was at a factory rich 12:1. The ported throttle body and the SLP lid leaned it out significantly.
Last edited by damon_Z; 11-23-2006 at 02:38 PM.
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11-23-2006, 05:16 PM
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i think you're overreacting. you did all those mods back-to-back, correct? the mods were thrown on and the car immediately hit the dyno, correct? if this is true, the PCM never got a chance to readjust. if you were to hit the dyno now that the car has been driven and has adjusted, i bet your A/F ratio would be significantly richer.
11-23-2006, 05:26 PM
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Originally Posted by sidewayz28
14.7?!?!!?!?!?!?!?!?!??! are u serious?
http://en.wikipedia.org/wiki/Air-fuel_ratio
http://www.knfilters.com/airfuelmonitors.htm
http://auto.howstuffworks.com/question257.htm
A gasoline engine burns gasoline in the presence of oxygen (see How Car Engines Work for complete details). It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1
11-23-2006, 06:30 PM
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Originally Posted by ChocoTaco369
i think you're overreacting. you did all those mods back-to-back, correct? the mods were thrown on and the car immediately hit the dyno, correct? if this is true, the PCM never got a chance to readjust. if you were to hit the dyno now that the car has been driven and has adjusted, i bet your A/F ratio would be significantly richer.
11-24-2006, 01:40 PM
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Originally Posted by Rhino79
12.8-13.0 at WOT is your target, 14.1 is way lean. I set the WOT fueling around 12.5 around peak torque and lean it back to 12.8 after that.
3.0-5.9, 6.0-8.4, 8.5-13.0, 13.1-17.0, 17.1-19.0
Flooded,Way Rich,[U]Rich-Lean[/U],Way Lean, Engine damage
11-24-2006, 01:43 PM
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Originally Posted by Rhino79
12.8-13.0 at WOT is your target, 14.1 is way lean. I set the WOT fueling around 12.5 around peak torque and lean it back to 12.8 after that.
3.0-5.9, 6.0-8.4, 8.5-13.0, 13.1-17.0, 17.1-19.0
Flooded,Way Rich,Rich-Lean,Way Lean, Engine damage
11-24-2006, 01:53 PM
#13
Originally Posted by ChocoTaco369
i think you're overreacting. you did all those mods back-to-back, correct? the mods were thrown on and the car immediately hit the dyno, correct? if this is true, the PCM never got a chance to readjust. if you were to hit the dyno now that the car has been driven and has adjusted, i bet your A/F ratio would be significantly richer.
thta is a good point anthony!
11-24-2006, 04:31 PM
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choco is probably right sinc ethe ecu will learn after mods, but I'd get the car dynoed again, or some how figure out what the a/f is just in case, it'll probably be cheaper than killing the engine.
11-24-2006, 04:33 PM
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Originally Posted by Black Z28 M6
This guy is right.12.8-13.0 is your target to get all the power you can.
3.0-5.9, 6.0-8.4, 8.5-13.0, 13.1-17.0, 17.1-19.0
Flooded,Way Rich,Rich-Lean,Way Lean, Engine damage
3.0-5.9, 6.0-8.4, 8.5-13.0, 13.1-17.0, 17.1-19.0
Flooded,Way Rich,Rich-Lean,Way Lean, Engine damage
11-24-2006, 04:37 PM
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Originally Posted by BrandonDrecksage
choco is probably right sinc ethe ecu will learn after mods, but I'd get the car dynoed again, or some how figure out what the a/f is just in case, it'll probably be cheaper than killing the engine.
11-24-2006, 11:07 PM
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Originally Posted by damon_Z
I know there is a risk of damaging the engine, but I also know that there are plenty of people out there who never gets dynoed, but just run with whatever mods they have on the dragstrip. I mean, have you ever heard of anybody damaging their engine just from running WOT with a ported throttle body, SLP lid, and an SSRA2? I'm going to take the risk tomorrow at Atco's annual winter wonderland.
only difference between you and I is taht you know your way to lean.either way, good luck, hope you trap that 110mph
11-25-2006, 03:13 PM
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Originally Posted by Rhino79
12.8-13.0 at WOT is your target, 14.1 is way lean. I set the WOT fueling around 12.5 around peak torque and lean it back to 12.8 after that.
11-25-2006, 08:41 PM
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Originally Posted by 5550racing
Yeah, I was wondering what was too lean. I dynoed 320, 309 at 15.2 AFR!
I thought 14.7:1 is considered perfect.
I thought 14.7:1 is considered perfect.
This is rarely (if ever) perfect for peak performance.
11-26-2006, 02:55 AM
#20
12.8-13.0 is correct for WOT. 14.7 is correct for normal operation.
Your car is constantly trying to shoot for 14.7, to burn all the gasoline and recover all the energy, for maximum fuel economy. This, however, does not produce the most power. When the car senses over a certain throttle percentage at a certain RPM, it enters PE territory. PE stands for "Power Enrichment", which is simply a number that 14.7 is divided by and the computer then shoots for as the commanded AFR.
Technically, PE should be about 1.14, which would command us a 12.9 AFR, but we usually have to tweak it untill it's right.
14.7 is as lean as I'd go. Anything richer than that is "safe".
Damn I'm going off here....
And that's all I have to say about that.....
Your car is constantly trying to shoot for 14.7, to burn all the gasoline and recover all the energy, for maximum fuel economy. This, however, does not produce the most power. When the car senses over a certain throttle percentage at a certain RPM, it enters PE territory. PE stands for "Power Enrichment", which is simply a number that 14.7 is divided by and the computer then shoots for as the commanded AFR.
Technically, PE should be about 1.14, which would command us a 12.9 AFR, but we usually have to tweak it untill it's right.
14.7 is as lean as I'd go. Anything richer than that is "safe".
Damn I'm going off here....
And that's all I have to say about that.....