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AFR and Boost

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There are many topics that ask what AFR to run under varying boost conditions, but does anybody know how to determine when you are actually running lean enough to damage the turbo?


This would've been a question I would ask until I just watched the "Understanding AFR" class. It will clear up any previous misconceptions about certain boost levels and specific AFR.

I would be much more concerned with damaging the engine before I worried about damaging the turbo.

The turbo life is dictated to a large degree be exhaust gas temperature at the turbine inlet. Most turbos will end up being damaged if they are exposed to EGT exceeding 1000 deg C for extended periods. AFR however is not the only parameter to consider here. For example if you're running on E85 your EGT will be far lower than what you'd see on petrol. The EGT will also be affected by your ignition timing and if you're retarding the timing to stay away from knock, this will artificially bump up the EGT without having any affect on the AFR.

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