Hondata

I'd like to know if the stock '04 RSX Type S pseudo wideband 02 sensor is suitable for tuning a supercharged engine running E85? It was recommended to use the stock sensor since it is wideband and the ECU is a PRB K-series one, so...sort of plug and play.The builder thought it was more reliable than an aftermarket wideband Bosch unit.

I ask because I've read that AFR's for E85 should be down in the 9.5 range, and perhaps even a little richer if supercharged.

I've also read that the stock 02 sensor for the 04 RSX, while called wideband, only reads down to about 11.7.

Yet, I was told that it should be suitable.

Car is a 2004 Honda S2000 K-Pro and the 04 RSX TypeS PRB ECU with the stock pseudo wideband o2 sensor. Max boost will be about 10-12psi.

What do you experienced guys think?

In short, yes. The stock wideband is not as accurate at richer air fuel ratios, but you need to understand how widebands work before judging the effectiveness of the stock wideband on E85 vs gasoline. It is no worse on E85 than straight gasoline.

Widebands don't read the air fuel ratio, they read the oxygen content of the exhaust and convert that to an equivalence ratio. So gasoline at stoichiometricacy looks identical to ethanol at stoichiometricacy, both being 1.0, even though the ethanol is a much richer air fuel ratio. And thus the accuracy is the same for gasoline and ethanol at the same lambda.

Do you got the sensor installed and working?
I think you need to do some substantial re-wiring to get it up and running in a S2000 setup.