Safe optimal cruising A/F ratios
 

I have a wideband and just purchased an AFC II. I have a new fuel system and engine. I am running very rich at idle and on the interstate, at 70 mph 10.8:1-11.2:1 So my question is, would it be dangerous to run as high as 15.5:1 at 70mph? I basically bought the AFCII to increase my gas mileage. I'm getting 18 mpgs at 10.8:1 lets see what happens after I hook it up!

No such thing.
Your wide-band cannot tell you the EGT's are getting hot.
If you run too lean, it'll hesitate.


-Ted

uhh sounds like you have a bad O2 sensor. You should be closed loop between 14 and 15. You can't really change your cruising AFR's on a stock ECU.

Presuming that his original 02 sensor is actually still hooked to the car and functional that is.

To answer the question, you can lean out the cruising AFR's as high as it'll go before it starts to buck, which will vary with your port configuration, but is usally up around 15:1-16:1.

Is this car N/A or turbo?

The car is a turbocharged, the factory 02 sensor is removed to install the wideband 02 sensor. I am installing an AFCII to correct the fuel.