I was running a built a6/z6 motor with a dx tranny and 12psi. Yesterday i switched to an si tranny and installed some motor mounts. I went to drive it today and noticed that it kind of hesitated in 3rd gear at WOT like it was pig rich. I havent had a chance to hook the wide band up and check the a/f. When switching to a tranny with a shorter gear ratio will it change the a/f ratio and if so will it make it richer or leaner?

 

I don't think it could, unless it has to do with the vehicle speed sensor that is mounted on the transmission, it may be sending different signals to the ECU at in 3rd than the old one was, hence creating a limp-in setting on the ECU... But I seriously doubt that's what has happened.

Did you happen to pull on the wiring for the O2 sensor or anything? It's possible that during the swap you either ripped a wire inside of the insulator or perhaps damaged the O2 sensor itself..

 

no sensors or anything were damaged. Im running open loop. I was thinking that since the tranny had shorter gears that it would change the load on the engine hence changing the a/f. Something is obvioulsy wrong because when i did some pulls from 3rd gear it hesitated a few times. I guess ill have to throw the wideband on to check it out. Thats the only thing i can think of that would make it hesitate like that right after a tranny swap.

 

TTT

 

you are correct.. a tranny change will effectively change your af ratio. you are at a different load point on the map sensor at a given rpm.. example if you cruise at 3k rpm before the same 3k rpm cruise will show a different map reading..just datalogg a little.. you'll see it right away