briann510

My s/c setup installer did not put a boost a pump on and this has always bothered me that one wasnt installed when it comes with the setup. I was told a better high performance fuel pump was put on but cannot verify it was even after asking several times exactly what was put in.

My year means removing dropping fuel tank itself and from what Im told the exhaust and rear also to get to it and not sure why that would have been done instead of a simple BAP install. Only 1 person makes a high performance pump system for the late 03-04's and its over 1K or a 08 Z06 pump can be put in but if that was the case my pressure im sure wouldn't be this low. I unfortunately cannot verify what fuel pump is in there if it was changed unless I drop the tank.

Tuner did a conservative tune and car has run great since day 1 with no complaints but not sure why the low fuel pressure wasn't noticed and addressed or maybe it was and tune adjusted or it but 30 psi at 6-9 psi cant be good im thinking no matter how its tuned.

Results with 60 lb injectors.

60 lbs rock steady at idle and cruising/light throttle
52-58 going through the gears "normal" driving shifting at 3500-5500 out of boost

Once in boost the pressure begins dropping FAST
50-40 WOT from 2-4 psi
40-30 WOT from 4-9 psi

When I shift at 6K its at 30 psi or below in every gear but still pulls very strong.

If I stab the throttle at any rpm and hit boost the pressure drops to low 40's-30's.

All this checking coincided with my detonation I began having in higher bosot when the weather turned cooler and I attributed it at first to the higher % of ethanol in our winter gas here but now believe its also related to maybe low fuel pressure and leaning out.

My question is how would a tuner tune with that low of pressure at WOT and still get good AFR's or with injectors flowing correctly pulse wise? I watched it on the dyno and all looked ok although I did not see the logs to see what IDC's were and other parameters etc. Obviously for the last 3500 miles Ive been driving this car very hard always in boost so the low fuel pressure doesn't seem to affect the tune and really has me wondering how is it possible. AFR's have been checked and are within good readings but I don't see how thats possible with such low pressure at WOT.

I just ordered the Racetronix fuel pump upgrade harness today for a start and then can install a boost a pump off that.

BLOWNBLUEZ06

You can tune around fuel pressure drops to the point where the injectors no longer flow enough. When you get your fuel pressure back up, you'll have to re-tune because you'll be running pig rich. Andy's secondary fuel system should solve all of your problems!

briann510

I don't want to put a secondary fuel system on plus I have the fugged up FFS POS fuel system that only mid 03 and 04's got. One of GM stupid azz designs. If I have to remove the pump ill take the front seat out and cut a hole in the floor to get it out nice and easy instead of dropping the tank and all the connections and then fab a removable sealed cover there for floor.

So would you think doing a tune with the low pressure is fine the way it is or should the fuel pressure be upped with BAP and tuned for it? I cant imagine injectors running that low on fuel pressure is good but maybe it doesnt matter as long as AFR's are good.

I wanted a DD car without having to put all sorts of extra stuff on just to make 525-550 rwhp. It shouldnt need anything more I would hope. Andy said a BAP should be all thats needed but it just pisses me off it wasnt put on and maybe tuned around the low pressure is all. I guess im just venting here... I know the BAP and Racetronix harness will fix it according to A&A but was just curious how it was tuned for the pressure it has.

95vettski

Your options in order from easiest and quickest to most difficult.

1. Add bap to increase voltage to stock fuel pump

2. Add secondary fuel system (A&A or ECS)

3. Drop tank and replace pump

You can also add meth to compensate for lack of fuel volume, but not recommended. Also, I beleive even if you cut a hole behind the passenger seat you will encounter a steel cross member or something.

briann510

I think the pump thats in there is fine. Stock pump was replaced by GM once when my brother in law ran the car out of gas twice and burned it up I guess. I bought the car after they fixed it and have never run it lower than 1/4 tank so I doubt its gone bad.

No tune should be adjusted for 30 psi at WOT at 8-9 psi.

Ill have the Racetronix fuel harness upgrade in soon and see what that does as maybe its losing voltage through the stock wiring and then ill add the BAP next.

I don't mind if I have to drop the tank to redo something as I have a lift at home and can do it easily but I really don't wanna do that if I can just add a BAP and be fine with a new tune to that.

I saw where someone had cut a hole in a 03 before and got the pump out that way or tried to anyway.

MIKE-C5

I had the same issues, then I went with an ECS fuel system that Arnold modified and now Im seeing pressure like never before ! !