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Getting afr’s right with a big cam

Understanding AFR

Discussion and questions related to the course Understand AFR


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whats the best approach when dialling in afr’s at lower rpm’s with big cam’s, I find it had somtimes because of over lap playing with afr readings

In this situation, it becomes really hard to rely on the reading your O2 sensor is giving you. I've struck this tuning a single cylinder bike engine too, which was compounded by the pulsey nature of the engine. I got the mid RPM ranges tuned as the readings made sense there, and this gave me an idea of what the fueling curve for the motor should look like, from here I had to tune it by ear pretty much, adjusting things till the motor seemed happy.

Pretty much what iv been doing, I go to the rpm point where the cam starts to work then tune up the map, then get a good idle and interpolate between the 2. Just seeing if there are any other options?.

Can you post a screenshot of a log showing the AFR readings you are concerned about?

I don’t have one now but iv tuned a coulpe large cams in Ls’s they seem to fine with how I do it, I’m just after another method if there is one.

Any of hp academy guys care to chime in?

Hey Will, Zac is an HP Academy guy ;)

I agree with his comments. When you have a lot of overlap, the lambda sensor readings can end up being misleading at low rpm. It's most often an issue at or very close to idle and as you've mentioned, higher in the rpm range you're able to rely on the lambda sensor readings.