Ok, I know this goes against normal thinking, but i need to decrease my boost and overall HP, I am running 14lbs of boost, 3" pulley on a KB 2.6 with 60lb injectors...so to say I have almost no gas mileage is appropriate, but I did not buy this for mileage , can I just increase pulley size? do I need to downsize injectors? Is there other info I need to provide ? I think that the motor is running on edge of HP, so i would like longevity and a little better mileage...I appreciate any help...Thanks.

 

Pulley swap and dyno tune.

 

What simon1 said. Don't just swap the pulley and not retune. Too much fuel.

 

Why to much fuel? These are maf based systems. Less air less fuel. Where am I wrong?

 

Because if it were that simple that's what everyone would do.

Pulley swap and retune. Put the 10 psi pulley and tune it to around 475 rwhp and you will be done.

 

Ok, I got the larger (10 psi) pulley and will be swapping it, KB said that for every 1 psi drop I would lose 20-30 RWHP, so that would put me 500 ish? I think that would be plenty. So, now I had to find a competent tuner in the mid state NY area...Thanks.

 

A somewhat agressive tune, the larger throttle body and a built motor makes right around 475 rwhp with that pulley. Anymore than that and you are taking some chances in the tune and with the motor.

 

I am making 617 ish at wheels, so 725 at crank, the motor has been built to take it , but why push the limits if i don't need to , I will start with increasing pulley size and retuning. Do I need to decrease in injector size also? I appreciate the help, Thanks.

 

You should still be able to use the injectors but with a new tune.

 

I'm not trying to throw you down but you are not making 617 rwhp with a 14 psi pulley from KB. Unless you have radical flowing heads and a huge cam, along with running c16.

For example, 18 degrees of timing, stock cams/heads, 16 psi through a manual tranny dyno'd at 540 rwhp on 91 octane. Tuned by one of the top tuners in the country. Same car, same pulley, different tune, 100 octane, race only with IATs at 76 degrees, 565 rwhp/560 rwtq.

The numbers on KBs website are over stated and not real world. They claim stage 2 10 psi pulley 05+ stangs make 539 rwhp. Thats BS. They make at most 500 and thats with a ragged edge tune, 93 octane.

Has your car been dyno'd and tuned? Been to the track? Just wondering, cause alot of people assume what their car makes but until they strap it on a dyno and find out for real they are just geussing. If you were to do that, you would know exactly where you are at and then have a better idea of the kind of power you are making. I would guess around 520 rwhp based on past experience with the KBs and being there when they are being tuned.

The 3.0 pulley should make 15.5 psi with the stock throttle body and 17.0 with the big one. Those PSI numbers seem to be right on. I forget what size pulley is on my car, I think it's the 3 1/8. It makes right 15.5-16 psi on the dyno and on the boost gauge.

What kind of short block do you have?