so I got tuned the other day and I wanted to get better gas mileage the car is an 01 with ap2 motor swap comptech supercharger with 9 psi boost aem ems v1 id 1000 injectors sos tb larger sos aftercooler t1r exhaust and test pipe comptech header mishimoto cooling system . so at wot my afr is 11.7 but under light throttle /load situations the afr is in the 15.5 to 17 range car isn't acting up or running hot and it is getting stock or better gas mileage just curious what you guys think. as you go up a hill the afr goes into the 14's and if you give it any gas 13's so I guess I will scope the motor over the next few weeks and check plugs it has 1 step colder ngk copper plugs.
I know a lot of the cars that come factory with wide band use this strategy I just don't want to hurt the motor I have played with the tune at steady state running and you can feel the car run bad when the afr drops to 11to1 and stumble at 18to1 so maybe I can pull this off any thoughts would be appreciated . here is a pic of my dyno pull had some belt slip at the top end and was 100f air temp 70% humidity

 

lean light load cruising is fine as long as you have the correct ignition for it as well. If you got professionally tuned and he set your cruising AFRs for around this area, I would imagine he did the timing as well. Timing needs to be a little more advanced in the areas that you are running less fuel.

When I tuned my own car, in the highway cruising areas, I bumped the timing up about 3-4* and leaned the o2 feedback to 15.5 which means that is what it was sweeping for, so I would have AFRs sweeping between 14.8 and 16.2 in general. I got slightly better mileage by doing this, but this was on an N/A engine. I hear on turbo cars you can lean it out and advance the timing even more, I would imagine S/C cars would be similar to tuning N/A

 

I also did that when I had the AEM V1. I would cruise between 15.5:1 and 16.5:1 depending on load. I could get over 30 mpg on the highway even with a built motor...

TIm

 

lean it out at cruise till it drives funny, then add a little back till it drives right.

 

thanks guys

 

is the o2 feedback map the best way to do the lean crusing? i get terrible mileage currently and i am desperate for some better mpgs.

current o2 feedback map is basically 14.7 below 87kpa, then it goes to 13.4 around 90kpa then 13.1 at 100+

i am NA

 

I don't use o2 fb

 

I put the car on the dyno and simulated highway low load conditions and I gave the aeromotive fpr a half turn got me out of the 17's so cruising at 65-75 mph on flat land my afr is 15.5to16.1 so I am happy and it looks as though the car will get 27mpg highway if I keep my foot out of it

 

If you're on AEM, I think most of your MPG problems are in the Accel/Decel trim tables. Fiddling with these drastically improved MPG for me when I was using the 1052.

Now that I'm on Kpro, Hondatas version of fuel tip in is much more basic and appears to be more in lines of where it should be anyways, part throttle is 300% better than it was on AEM and mpgs are through the roof compared to AEM. I'm talking 23 hwy on AEM and 28 on Kpro (and thats without lean cruising on Kpro)

 

If your mpg difference is that big you didn't have the aem tuned very well.

Especially on a turbo car you can get wayyyyyy better milage with aem than kpro.

Also keep in mind that if you lean it out too much the power will drop off enough to make you use more throttle to maintain speed. That will cost mpg as well. Typically if the car drives well it'll get decent milage