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Compressor Surge?

Road Tuning

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At about 7000rpm, my MGP/MAP spikes, fuel leans slightly (despite adding fuel) and power falls off. No knock or fuel/ign cut. Turbo is a VF48 with a billet compressor wheel.

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Any chance you have a 7000 RPM rev limiter? Or could it be a rich misfire? What did the ignition timing look like on that run?

At a guess I'd say you're suffering a rich misfire since the AFR is incredibly rich at high rpm. It starts around mid 11's which is probably ok but ends up in the low 10's and high 9's. Compressor surge will typically at low rpm where the turbo first makes peak boost and not near the rev limit.

Sounds like missfire, late/slow/light off in the exhaust can push boost higher than target if the turbo still has much left in it.

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