How rich before you see its effects on dyno?
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From: olathe, ks
How rich before you see its effects on dyno? What is the approximate A/F prior to seeing black smoke from the tail pipe? Also at what point do you really start losing power due to a very high A/F ratio, 10:1?
I saw a dyno A/F graph and it got really rich. The power did not have a power sag where the A/F got really rich. It was the mid part of the dyno the A/F was showing rich. I did not see black smoke for the 3 runs - no cats.
winpep was the software used on the dyno. I do not recall the model of the dyno.
I saw a dyno A/F graph and it got really rich. The power did not have a power sag where the A/F got really rich. It was the mid part of the dyno the A/F was showing rich. I did not see black smoke for the 3 runs - no cats.
winpep was the software used on the dyno. I do not recall the model of the dyno.
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From: Kansas City, MO
That is a very complex question. As with many threads on here, too much is involved for a simple answer. Basically, "it depends".
Combustion can occur from 8:1 to about 18:1 air/fuel ratio. Common ratio for a naturally aspirated street motor at WOT is 12.8:1 - 13.2:1. Common for forced induction is 11.5:1 - 12.5:1, leaning heavily toward the richer ratio.
When does black smoke start to appear? Who knows. All that tells you is you have incomplete combustion. Could be a timing or fuel issue.
Combustion can occur from 8:1 to about 18:1 air/fuel ratio. Common ratio for a naturally aspirated street motor at WOT is 12.8:1 - 13.2:1. Common for forced induction is 11.5:1 - 12.5:1, leaning heavily toward the richer ratio.
When does black smoke start to appear? Who knows. All that tells you is you have incomplete combustion. Could be a timing or fuel issue.
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when I tuned my stroker my AFR was below 10:1 don't exactly know where it was but i made a change and from where it was to 11:1 it was a quick 30 rwhp gain! I picked up about 60 rwhp total from dynotuning my stroker. 434 to 494 rwhp
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From: olathe, ks
Originally Posted by DenzSS
That is a very complex question. As with many threads on here, too much is involved for a simple answer. Basically, "it depends".
Combustion can occur from 8:1 to about 18:1 air/fuel ratio. Common ratio for a naturally aspirated street motor at WOT is 12.8:1 - 13.2:1. Common for forced induction is 11.5:1 - 12.5:1, leaning heavily toward the richer ratio.
When does black smoke start to appear? Who knows. All that tells you is you have incomplete combustion. Could be a timing or fuel issue.
Combustion can occur from 8:1 to about 18:1 air/fuel ratio. Common ratio for a naturally aspirated street motor at WOT is 12.8:1 - 13.2:1. Common for forced induction is 11.5:1 - 12.5:1, leaning heavily toward the richer ratio.
When does black smoke start to appear? Who knows. All that tells you is you have incomplete combustion. Could be a timing or fuel issue.
Is it possible the A/F reported by the dyno be wrong. IE you have lots of overlap and at certain RPM ranges the ehaust is over scavenging the CC, then the raw fuel makes the readings high?
I am not suggesting that is the explaination for a rich condition, but a contributor to the observed A/F.
That was helpful - thanks.
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From: Kansas City, MO
Sure, most A/F ratios on dynos are incorrect by a little bit, but not that far. A malfunctioning wideband is incredibly easy to diagnose.
As far as A/F ratios go, once again that is an incredibly complex issue.
If you're getting raw fuel across the overlap, you have an actual rich condition. It reads high because the a/f ratio is too rich. You can draw enough fresh air and fuel across a superheated exhaust valve to cause spontaneous ignition as well.
You should see how much the A/F ratio fluctuates during the load transition between shifts. As the load uncouples, the cylinder pressures spike and A/F goes lean. The computer compensates, adds fuel, the load goes back on the engine and the cylinder pressure drops...creating a rich condition. Then the computer compensates and evens out the A/F until the next shift.
As far as A/F ratios go, once again that is an incredibly complex issue.
IE you have lots of overlap and at certain RPM ranges the ehaust is over scavenging the CC, then the raw fuel makes the readings high?
You should see how much the A/F ratio fluctuates during the load transition between shifts. As the load uncouples, the cylinder pressures spike and A/F goes lean. The computer compensates, adds fuel, the load goes back on the engine and the cylinder pressure drops...creating a rich condition. Then the computer compensates and evens out the A/F until the next shift.