On the innovate forums I read that a 15.2-15.4:1 AFR will be ideal to improving fuel economy when cruising. This is according to Klaus the engineer who answers questions on the forums.

When I am cruising my AFRs are 14.3-14.8. How can I achieve a 15.2-15.4 AFR when cruising? Do I change the load values on the MAF table below load point 25? How much fuel should I take off below load point 25?

Thanks

 

your oxygen sensor should regulate your AFR when not WOT; should be ~14.7. I dont know how much the 10% ethanol in gas now will affect your AFRs but prob. not that much.

 

At cruise your car should be in closed loop, which means that changing settings on the XEDE tables will have no effect. The only way to affect closed loop fuel trims would be by fooling the ECU into thinking that 15.2-15.4 AFR is stoich. This can be done by using the LM-1 or LC-1 to simulate the stock narrowband O2 sensor, since you can adjust the voltage the LM-1/LC-1 supplies as its narrowband O2 signal.

heyzeus, unless you have adjusted the lambda multiplier in your wideband, you'll still read ~14.7 even with 10% ethanol...

l8r)

 

Um, why would you want to run >15:1?

d

 

I was told that running at 15.2-15.4:1 at cruising would improve fuel economy the most and it will not have any ill effects on the car. If that is the case, then why not do it.

 

That sounds nice an theory, but I'm not actually convinced that it will make much of a difference. Cylinder temp's will be higher, N0x emissions will be greater, and you could only possibly gain a little in mileage.

Note that EU VW GTI's have a lean-run mode, but it works completely differently. They are able to run like 65:1 AFR, but fire their injectors during the compression stroke.

d