Dyno day - worth playing with timing?
Old [Sch|F]ool
Joined: May 2001
Posts: 12,869
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From: Cleveland, Ohio, USA
O2 should always be measured pre-catalyst.
I run trailing ignition. I just don't run trailing *split*. One MSD box drives both coils.
I have been able to run stock or mild ports happily at AFRs as lean as 17:1 under cruise. The bridgey doesn't like it any leaner than 14:1 under cruise, period. It also won't idle at all leaner than about 12:1 (although that reads at about 15:1 due to all of the excess oxygen in the exhaust
)
BTW - AFRs are normalized for 100% gasoline. It should be noted that fuel in the US is usually 10% ethanol, at least in this part of the country it is. Stoich for that is 14.2 instead of 14.7, but O2s only read the lambda, and we convert that to an AFR, so it's easiest to go by a "100% gasoline AFR" instead of confusing everyone with .85, .91 lambda.
I run trailing ignition. I just don't run trailing *split*. One MSD box drives both coils.
I have been able to run stock or mild ports happily at AFRs as lean as 17:1 under cruise. The bridgey doesn't like it any leaner than 14:1 under cruise, period. It also won't idle at all leaner than about 12:1 (although that reads at about 15:1 due to all of the excess oxygen in the exhaust
)BTW - AFRs are normalized for 100% gasoline. It should be noted that fuel in the US is usually 10% ethanol, at least in this part of the country it is. Stoich for that is 14.2 instead of 14.7, but O2s only read the lambda, and we convert that to an AFR, so it's easiest to go by a "100% gasoline AFR" instead of confusing everyone with .85, .91 lambda.
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zuesskroph
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Aug 13, 2015 06:05 PM
