O2 Sensor Safety Fudge Factor?

[free5ty1e]

Just random thoughts here... has anyone thought of forcing the O2 sensor to read slightly leaner than usual under heavy boost conditions, just for a kind of fudge factor safety margin thing? How would it be best to accomplish this? Discuss.

I'd rather lose a bit of power and run slightly rich than have a holey piston. Those don't compress air very well.

[Del_boy]

The Lambda sensor is only used for idling and cruising to maintain Stoich. On wide open throttle the ECU reads from fuel map from load calculated from MAF sensor/Throttle position sensor etc.

Cheers

[vrg3]

Yeah, under heavy load the sensor's usually reading very rich anyway.

In any case, you couldn't use a regular narrow-band oxygen sensor to do this. I do know that the TechEdge wideband oxygen sensor controller has a "simulated narrow-band" output signal and you can adjust its "stoich" signal to be richer or leaner than stoichiometric. But I think most people that dare to muck with that do so in order to lean mixtures out a little when cruising.

[Del_boy]

From all the subaru maps I have seen they tend to run very rich on heavy load (nominally ~10 AFR) to provide a safety barrier against DET.

Cheers

[aspect]

10! yeesh. Well, that is a nice safety net I guess.

[free5ty1e]

well thats good, but how far do these maps go? I mean, the car was only running 9 pounds of boost from the factory, do the fuel maps have any concept of high boost? How much boost can we run before our MAF sensor's flow measurement is maxxed out?

[vrg3]

The fuel maps don't go much beyond 10ish psi. But, they're not volumetric efficiency tables like on speed density ECUs. They're just correction factors to computed fueling, so you can somewhat reasonably run outside the maps.

There's still a long way to go before the MAF sensor hits its rail, though, so you still run pig rich.