foru2nv4

I have a 4.6 litre mustang with a saleen series IV supercharger on it with the saleen program on the PCM. I have upgraded to a smaller pulley a larger rearend 4.10 gear and a bigger throttlebody 78mm after the program.
My question is the car gets herky jerky shifting with my stick n 2nd gear and 3rd gear so it seems as if its not gettin enuff gas. Does anyone out there have 42Lb fuel injectors? If so do I need a bigger fuel pump? If so what should I b looking at purchasing? If not is the stock suffecient enuff 2 supply to bigger injectors? In my case 42LB injectors for my twin screw supercharger?

0949er

I have 42lbers and they work fine. What kind of fuel pump do you have? Did you get a tune after you added a smaller pulley?

MU71L4710N

if you didnt tune it you should probably ask these questions BEFORE doing mods unless you don't care about blowing your motor to pieces.

foru2nv4

Its a 2003 mustang and yes it was tuned by saleen ran fine with all of saleens supercharger stuff that came in the box from saleen which was purchased brand new. Has 30LB fuel injectors, saleens tune, saleen series IV supercharger, and saleens intercooler. Ran just fine but now I have a smaller pulley, 4.10 gears, bigger throtttle body. My thinking is now it needs more fuel like going to 42lb injectors and maybe a bigger fuel pump. The fuel pump is a stock pump I do believe its the 255 pump.

mrtstang

It's all in the tuning. I run 42's for both n/a and nitrous, and it works perfectly fine for both.

foru2nv4

Thanks mrtstang. I have been asking this question for a year now on this forum, cuz I dont drive the car in winter and why would you. Been tryin to get answers since then would like it resoved now its summer. impossible, especially going up a small hill. You have had the best answer since I been askin. So if I go to 42lb injectors I dont need to upgrade my fuel pump but I need to upgrade my tune? Thats how I take what ur sayin! I am just getting tired of ridiculous answers to questions. I car is a car and it should not b so difficult to geta straight answer. LIKE I SAID NUTTIN WRONG WITH THE CAR B4 THE UPGRADES AND NOW AFTER THE UPGRADES AND ITS HOT OUTSIDE ITS ACTING WEIRD.

masterofthepuppets99

did you get a tune after you put on a smaller pulley? if not then that is your problem. bigger injectors may solve your problem, but once again, a tune is necessary.

MU71L4710N

okay dude thats your problem. you cannot change things AFTER the tune and expect the car to run right. your putting in more air with a smaller pulley than your car was tuned for, your likely running lean right now...this can and will cause blown motors. if your going to change pulley sizes, you HAVE to get your car tuned. so either put the old pulley on or take your car to the shop and do not go into boost again without tuning it.

and since your so hell bent on injectors, if you put bigger injectors in without tuning for those your car will run even worse than it is now.

mrtstang

With any decent blower application, i would change both the injectors and fuel pump and then have it tuned accordingly. My pump was good till around 360 rwhp on the juice, but it was maxed out pretty hard.

Now are you saying that you have the 42's, but are still running the stock fuel pump or am i reading that wrong? Either way a set of 42's and a Focus fuel pump with a retune would be your best bet IMO.

uberstang1

It would probably be a good ideal to move to a 255LPH fuel pump and get it tuned.