RedHot99T/A

Ok,so i have an ms4 cam with all supporting mods;springs,rods,pump...i also havetrue dual exhaust,1:7/8 headers fast 78mm intake.i went to get my car tuned,and the tuner found my fuel pump is on its way out so in order to keep the engine from leaning out while i drive it he kept the injectors open longer to supply what the pump couldnt do itself...long story short i made 365whp at 6500rpms and 321whp at 6100rpms once he turned the limiter down because it was starting to lean out at 6500.he said get a new pump and bring it back he will redo the whole tune....can i really see over 400whp with just a pump swap?the new pumps in but it doesnt feel faster but it drives ALOT smoother....i know im rambling but is that possible? i havnt had a chance to bring it back up to him yet ater the new pump.also the heads have a 3 angle valve job if that makes any difference.

RedHot99T/A

also the car is a 6speed

Redbull87

iTrader: (3)

If the pump was truly the problem Im hoping the tuner or someone check the fuel pressure at the rail.Having a new pump in there and a tune for a failing pump will still have poor results and you need to go back and retune.A well running ls1 ms4 cam and supporting mods should see 400whp easily.

What heads are you using?

hcb1700

iTrader: (9)

Not with just a fuel pump.what year is your car, and do you have an LS6 , or better, intake? My brother's '01 Z28 barely hit 400rwhp with PRC Stg. 1 LS6 heads, MS4 cam, bigger injectors, headers, etc...

badazz81z28

iTrader: (6)

You most likely have some more potential horsepower if you truly do have a tuning and fuel pump issue, but what do you expect????

I suspect you have the stock 98-99 LS1 heads. Your power is about on par considering the stock LS1 will dyno around 305 RWHP. A 60 hp gain is pretty good to me.

DONAIMIAN

iTrader: (18)

How did he figure the fuel pump was going out? Or did he mean you need a higher volume pump to support the HP? I'm confused.

RedHot99T/A

he said the car kept leaning out on him while he was tunning it,he said the more he kept the injectors open the more power he was getting,so he said the pump is on its way out,and alos i running a Fast 78mm with 241 heads with a 3 angle valve job.once said and done i checked the pressure and it was 37psi at the rail

slammedc5

iTrader: (1)

Hum, I have a 01 ls1, ls6 intake stock. I installed a mayhem cam 630 lift and associated parts and short tube headers with staight pipes. That's it I dynoed sat at 395whp. My tuner said I was leaning out too, but thats because my injectors are to small not the pump going bad. My duty cycles are at 95 at 5800rpms. So when i get my new injectors, we'll Max out the tune. He says at least 25whp left in it. I have a really good tuner.

RedHot99T/A

hmm,well he said the injectors are fine,and i made 321 untuned running crazy lean he said....i need to get the car back up to him ASAP and see what it does again...your at 395 and have 25 to go possibly? sounds like a great setup man!

slammedc5

iTrader: (1)

Thanks, yours will turn out good too. Cant remember what your cam specs are, mines pretty big. I have a 6 speed as well, stage 2 clutch. If you look at my dyno sheet, even with small injectors, the torque and horsepower curve is pretty flat, the car pulls hard.
See if your tuner will tell you what the duty cycles are a like 6100rpms or higher. I had to hae my rev limiter temporarly set at 6100, after my new injectors, it will be 6900rpms.
You have a good cam, i love my mayhem 2 cam

RedHot99T/A

Thanks,on the cam card it reads .651 to a .611......i just want the car to meet my goal of 400a it drives great for a cam of its size so making 400 up top and drivability down low ill be happy,i just hope its the pump that screwed it all up

dodson55

iTrader: (18)

if you were only making 37psi of fuel pressure your tuner is an idiot for even starting to tune it that is just asking to burn a hole in a piston you need 58psi of fuel pressure and the low fuel pressure can cause low hp numbers and with fuel pressure that low i could see it being 30-40 hp less then it should be also before you retune it go with some bigger injectors because stockers will max out with that cam

RedHot99T/A

We checked the pressure after he tuned it,i checked it out....and yea my friend is selling 38lbs injectors to me for 120