bennyhonda7

k on my basemap before i had closed loop only and was getting like 11.1 afrs not boosting...and 11.5-12.5 in boost...if i leave open loop on will i still be able to boost without leaning out?

tranceminister

If you disable closed loop (running strictly open loop) you will need to retune your vacuum maps in order to achieve a 14.7:1 or stoich ratio and gradually tune your way into boost. If you leave it in closed loop your ecu will be trying to control a stoich mixture until a certain throttle percent is reached etc. This can be good in some situations and can also be bad in boosting situations.
So essentially if your running open loop you should have no problems boosting or driving in vacuujm as long as it's tuned. If your running closed loop just monitor your AFR's especially when part throttle cruising/boosting on the freeway etc.

bennyhonda7

so in open loop will my gas mileage be better even with 450's? right now im gettin about 18mpg? is this normal?

tranceminister

No, in closed loop your gas mileage will more than likely be better because the ecu is doing a fairly good job at keeping an economical fuel supply. You could probably tune it out just as good if you disabled the closed loop and run open loop though, but expect it to be on the rich side otherwise.

Rory

If you want to be lazy, you can leave O2 trim enabled in vac. and disable it for boost. The downside to doing this is that the transition into boost is a bit less nice than if you just leave O2 trim off all the time.

Also, unless something new happened since I stopped paying attention, this only applies to OBD0.

tranceminister

Correct, it's being worked on for OBD1 apps. though. Just needs some more work, I've tested a few scripts for this and it's getting there but not official yet.