A/f ratio
01-05-2006, 06:38 PM
#1
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A/f ratio I was messing around with my car today looking at my data through a scanner and my a/f ratio is 14.6 at idle isnt that running rich?? i have just recently put headers on it and havent got to get it tuned yet but i was just wanting to see if that sounded rich or if they just run high at idle.
01-05-2006, 06:48 PM
#2
14.6 is approximately the stoich A/F ratio, which is exactly what your car should be shooting for. Congrats...looks like you haven't killed your O2 sensors yet.
As long as you run in closed loop, your car will always shoot for ~14.63:1 AFR.
As long as you run in closed loop, your car will always shoot for ~14.63:1 AFR.
01-05-2006, 07:22 PM
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nice that it was i was hoping for since im trying to get it to pass emissions now but i cant seem to get it out of readiness mode since i put a new battery in 150 miles ago. but thanks for the info man.
01-06-2006, 06:07 PM
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just a question for you, is this the actual AFR (i.e. does it fluctuate slightly even while keeping the RPMs/load the same)? The reason I ask is because there's also a commanded AFR, meaning the AFR that the computer WANTS to see, but in most cases it's not the ACTUAL AFR. Having your AFR 100% dead on after putting headers on seems a little strange.
01-06-2006, 06:10 PM
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He's talking about closed loop. Closed loop always corrects to lambda/stoichiometric/whatever you want to call it, regardless of what mods or what you are commanding. Gasoline is 14.6ish. Commanded A/F ratio only affects open loop.
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01-06-2006, 09:35 PM
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Originally Posted by Bombguy99z28
He's talking about closed loop. Closed loop always corrects to lambda/stoichiometric/whatever you want to call it, regardless of what mods or what you are commanding. Gasoline is 14.6ish. Commanded A/F ratio only affects open loop.
At least that's my experience.
01-06-2006, 11:37 PM
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Damn, your car tuned itself! wish mine did that.
I agree with Zeus though. If you're looking at the stock O2 sensor voltage it will be going up and down and never settle. Does your scanner average this out to get the est. afr?
I agree with Zeus though. If you're looking at the stock O2 sensor voltage it will be going up and down and never settle. Does your scanner average this out to get the est. afr?
01-07-2006, 08:34 PM
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I don't know if this post was directed at me, but a) there were no smart-*** comments directed at anyone on my part, and b) you and I are saying the same thing. I thought it was odd that his AFR would be AT precisely 14.6:1. At idle my LC-1 fluctuates up and down slightly, and hardly ever stays AT 14.6, it goes 14.8, 14.1, 14.3, etc. If I were to plot the data points 14.6 would only be the average. I also have a big lopey cam in there, but even stock, or even when I just had headers it was like that too (just not as bad). Narrow bands are even worse. That's the only thing I was trying to say.
01-07-2006, 09:05 PM
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My O2's do fluctuate and there is a cam in the car maybe its just a freak hell i dont know lol thas why i was asking anyways i wasnt tryin to start a fight and i dont see any smart-*** comments either maybe i missed something
01-08-2006, 06:37 PM
#15
Just because the pcm is commanding 14.6 and are in closed loop in no way shape or forum guarantees your even in the ballpark of stoich. The more mods you have the more likely the pcm will not be able to fully and accurately correct fuel trims. This is where tuning would come in.
01-09-2006, 02:27 AM
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Yes, however thats the essence of fuel trims. Fuel trims indicate how far from your tune the pcm has adjust. If you had no fuel trim learning, then yes, whatever your tune says is what you get. Granted, the more the computer has to adjust the more off from you will be, however, .500 mv is always 14.6 no matter what your tune says or how out of tune your car is, and .500 mv is what your car strives to achieve in closed loop (assuming your narrowband o2s are properly functioning and not too far removed from the engine).
The point being, if his car is achieving 14.6 at idle average, then his computer is operating completely normally and with a degree of accuracy.
The point being, if his car is achieving 14.6 at idle average, then his computer is operating completely normally and with a degree of accuracy.
01-09-2006, 02:37 AM
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Sorry to offend you, and not the thread starter who evidently took nothing by it. Afer all, it was a smart *** comment directed at him right? sheesh
I don't think I'm the one trying to be a smart *** here.
I don't think I'm the one trying to be a smart *** here.
