Quick qestion... I'm running stock setup besides a STI axle-back, and I also have an auto meter boost and a/f guage. I recently noticed after installing muffler and restting the ecu that the a/f guage shows lean just before the turbo starts spooling up at 3000rpms. I don't know if its because its been hot and humid here in new england or what. Anyone know if this is normal?

Thanks
Dave

 

Im not positive on this but I think the car will run more lean at lower rpm's and add fuel to the ratio as the load increases. I know that is what Cobb does with their stage maps to help with low end. Like I said, I dont know for sure but I think you have nothing to worry about. An egt gauge may be a better way to know if you have anything to worry about. Where did you install the probe to your a/f gauge?

 

I had the a/f guage connected to a separate o2 censor at the bottom of the down pipe. Just to clarify.... as i accelerate the guage goes up then when it hits 3000 rpms it goes back to lean then back up.

Dave

 

MO REX is correct. The engine tries to run as close to stoic as possible when manifold pressure is below atmospheric (vacuum). Rich fuel ratios are only used and needed under boost in our cars.

 

So its not a big deal unless a CEL comes on.

Dave

 

Yup, that's normal behavior and nothing to worry about.

 

you actually want to run a bit lean which is good for pre-spool and for spool-up. as for cobb's stage 2 map, it runs pretty lean which gets that stock turbo spooling quick, which is why the car feels a bit quicker. then as you get more load, it tends to run a bit fatter up top. you can fully see this if you have an EGT gauge. gas temps rise fast from 400-650C then slows to about 800C. that actually constitutes a good tune. hope this helps.

 

I heard that running lean on boosted cars can do some pretty good damage to the motor, is this true?

 

As long as it's not lean when your WOT. I would also say that as long and there is no noticeable detonation it should be ok. Granted tyou can have det and not notice it. From what i have heard unless your super rich all the way through the throttle there may be slight(maybe normal) detonation on even stock subaru's. This however hurts performance. I would say get an egt gauge and just watch your temps. A/F gauges have beens notorious for being wrong. Thats why most good tuners hook up a good A/F meter when they are dyno tuning.

 

As long as there is no detonation or pinging i think he's safe.

 

Thanks for the response guys!

 

Thanks for all the info guys!


Dave