ok 1st off you guys might not remember me havent posted here in a long time but ive been workin on the car and just got it tagged again for the 1st time in probly 3 years. its a 97 trans am with a forged 355 trick flow heads a 224/236 cam 60lb injectors a vortech s trim fmic etc ect. i had a cheap turbo style filter right on the charger intake and it somehow came loose and i guess the hose clamp or something got sucked in and destroyed the impeller. well after researching a bit i decided to go with the 928 motorsports billet impeller, built a 3.5" intake setup and just took it out for a couple runs tonight. before with the 7" crank pulley and 2.75" upper pulley it would make maybe 9lbs. now its climbing to around 11-12lbs. it was tuned by bryan herter from pcmforless at jds performance in PA. Ran into a few problems during the dyno session belt was slipping only made 5lbs and it only reved to 4500 rpm but he tuned it i guess assuming what it should do. i have a fuel pressure guage and a wideband and in the upper rpms it starts leaning out. used to b around 11.5:1 at WOT (so his tune was pretty good) now it starts dipping into 12-13:1. i backed out as soon as i saw this (kinda hard to keep an eye on all this stuff and the road im sure u guys know). but anyways im guessin my single walbro 255 isnt enough anymore. what do you think about this whole situation go with a dual 255 setup or sump the tank and big pump?

 

Get it re-tuned. An s-trim and a single walbro should fuel your needs sufficiently at 12 psi. You cant just add 3-4 psi more boost and expect the tune to compensate. Its setup for the way you had it before, and u were lucky there. I think they say 1 psi of boost is worth about 20hp, so do the math, you added roughly 60 hp. You need to raise the value of the %change to fuel vs. rpm @ WOT where its leaning out and up. Find someone with tunercat or lt1 edit or ask bryan for a re-tune based on the changes.

 

As stated above, get another tune.

 

thanks. gears were still turnin in my head when i posted that i guess. thought of the same thing later on