WhiteDiamond

I have been calling around locally to see who can do air/fuel measurments on the dyno and just about all the good shops around here can. However, they put the air/fuel monitor in the tailpipe(if standard O2) or they can use a wideband O2 if I can get a O2 bung set in place. I don't have room to get one in the factory exhaust before the cat, so my question is how do the air/fuel measurements compensate for the cats altering the hydrocarbon mix in the exhaust? It must work, as plenty of LSx's are running around tuned this way, so I would like to understand how it compensates for the cats burning off some of the hydrocarbons.

Todd

davidfarmer

I agree that it seems like burning off the extra fuel would cause post-cat O2 readings to be much leaner than true readings, but appearantly it isn't that simple.

I'm no chemist, and don't know if O2 sensors read oxygen, fuel, or some obscure by-product that corelates to a specific AFR reading, but it seems that tail-pipe readings are good enough for proper tuning.

Wish I had a more definite answer for you.