Does timing have anything to do with Air fuel ratio?
05-19-2006, 04:22 PM
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Does timing have anything to do with Air fuel ratio? If a wideband O2 sensor is reading 11:1 if I advance the timing shouldn't that ratio go up as more fuel is being burn?
05-19-2006, 04:35 PM
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Originally Posted by blackbird345
If a wideband O2 sensor is reading 11:1 if I advance the timing shouldn't that ratio go up as more fuel is being burn?
Andrew
05-19-2006, 05:07 PM
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Originally Posted by blackbird345
If a wideband O2 sensor is reading 11:1 if I advance the timing shouldn't that ratio go up as more fuel is being burn?
There will be a point of advance where this no longer works due to misfires, and or preignition.
05-20-2006, 07:52 AM
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Originally Posted by blackbird345
So I was correct then. Thanks. The wideband O2 reads the amount of air vs unburned fuel correct?
It's comparing the outside atmosphere with what you have in your exhaust and only looks at the oxygen.
It has no idea how much unburned fuel is in the pipe, just the amount of unburned oxygen.
It is common to see your wideband read richer when you lower your spark advance, and leaner when you increase the advance... but like I said up to the point of misfires.
The type of exhaust you have also matters. Manifolds and long-tube headers look very different on your wideband when you get to the point of misfires.
Manifolds allow the unburned fuel and oxygen to burn up faster in the exhaust. Long tubes allow them to stay unburned longer.
05-20-2006, 10:30 PM
#7
also..in general..if you advance timing your A/F will go leaner..if it doesnt go any leaner then you are most likely at the most spark that you need for that particular cell...
its a good way to tell on the street when your spark advance is far enough and stops making power...
its a good way to tell on the street when your spark advance is far enough and stops making power...
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05-21-2006, 01:06 AM
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Originally Posted by soundengineer
also..in general..if you advance timing your A/F will go leaner..if it doesnt go any leaner then you are most likely at the most spark that you need for that particular cell...
its a good way to tell on the street when your spark advance is far enough and stops making power...
its a good way to tell on the street when your spark advance is far enough and stops making power...
Andrew
05-21-2006, 09:27 AM
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Timing will not change the AF/R. Not enough to matter anyway. I have seen dyno test of this. You can change the timing 20 degrees and you might see a .1 change. Which is nothing.
05-21-2006, 10:01 AM
#12
Originally Posted by Red99C5
Timing will not change the AF/R. Not enough to matter anyway. I have seen dyno test of this. You can change the timing 20 degrees and you might see a .1 change. Which is nothing.
I have seen the exact opposite. When I dyno 5-6 degrees of timing has moved my AFR by half a point.... and yes I was the one on the dyno and yes I was the one making the changes, 80 pulls.
You get to a point (for me it was 28.5 degrees) where no more advance moves the AFR. I brought timing all the way up to 32 degrees and got no more power but my AFR did not move either...
Last edited by SideStep; 05-21-2006 at 10:09 AM.
05-21-2006, 05:39 PM
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Originally Posted by SideStep
20 degrees!
I have seen the exact opposite. When I dyno 5-6 degrees of timing has moved my AFR by half a point.... and yes I was the one on the dyno and yes I was the one making the changes, 80 pulls.
You get to a point (for me it was 28.5 degrees) where no more advance moves the AFR. I brought timing all the way up to 32 degrees and got no more power but my AFR did not move either...
I have seen the exact opposite. When I dyno 5-6 degrees of timing has moved my AFR by half a point.... and yes I was the one on the dyno and yes I was the one making the changes, 80 pulls.
You get to a point (for me it was 28.5 degrees) where no more advance moves the AFR. I brought timing all the way up to 32 degrees and got no more power but my AFR did not move either...
I seen it on the same run. They programmed the timing to go up and down at different rpm steps. This way there is no variation in air density from one run to the next.
05-21-2006, 06:49 PM
#14
no change in air density...
just in A/F..big difference..
more complete burn....and when it doesnt burn any better...thats where you get the most and cant get any further....
you will see A/F differences with spark changes..
I've puhed it around on a loaded and locked dyno so that I could show somebody before the differences and show how I found max power on the street..without a dyno being necessary...
just in A/F..big difference..
more complete burn....and when it doesnt burn any better...thats where you get the most and cant get any further....
you will see A/F differences with spark changes..
I've puhed it around on a loaded and locked dyno so that I could show somebody before the differences and show how I found max power on the street..without a dyno being necessary...
