setting cruise afr with dyno?

[guest]

Mike, my dealer was running a $20.00 dyno base run special and I asked if he would check my cruise afr using the dyno. He said at 70mph i was at 14.7 afr using 18% brake this is a dyno 250or 250i. at 80mph he said I was 14.4 at 18%. does this sound in the ball park. I am using a cv40 on a mild 95 build. does 18% brake seem right or should he have been at a higher percent brake? thanks guest

[Mike]

Those numbers are what we would be looking for with gas prices as they are today. 18% is a good number depending on what gear was used. Some would use a higher load with lower gears and vice-versa. Some use 20 or 25%, this just puts more load on the bike and means you are checking AFR at a slightly higher throttle opening for the same rpm at each sample point. With the 250 dyno's a stetp test can be perfromed where the dyno autmatically stops at preset points, samples and then moves to the next. This gives a broader picture and can be more controlled but it is still a judgement call on which load you wish to tune to because, with a carb, the numbers may be good in one area but not so much in another, yet our change affects all areas.
Mike

[guest]

Mike - 2007-03-16 7:10 PM

Those numbers are what we would be looking for with gas prices as they are today. 18% is a good number depending on what gear was used. Some would use a higher load with lower gears and vice-versa. Some use 20 or 25%, this just puts more load on the bike and means you are checking AFR at a slightly higher throttle opening for the same rpm at each sample point. With the 250 dyno's a stetp test can be perfromed where the dyno autmatically stops at preset points, samples and then moves to the next. This gives a broader picture and can be more controlled but it is still a judgement call on which load you wish to tune to because, with a carb, the numbers may be good in one area but not so much in another, yet our change affects all areas.
Mike

Mike, so 18% is what you would want in 5th gear? The tech said he checked it in 5th gear using 18% thanks for sharing your information.

[Mike]

Yep!!
Mike