I just got a 1992 GT.. its a alright car, came with dual flowmaters, and headers cowl indution hood, and a vortech s/c. The car starts up and runs fine, but if you floor the car it sputers around 3500rpms. The check engine light works but dosent come on. I unhooked the intake tube from the s/c and the car revs fine. I/m not to sure if the owner before me did all the proper mods it needed. so if if anyones got one and knows what i should look for it would be appreceated.
Need Some help with s/c 5.0
- Thread starter snoprohowe
- Start date
BK_CAULEY
it's built for speed not longevity, woman
Proper fuel supply for sure. bigger pump, injectors, and some kind of FMU like an adjustable fuel pressure regulator. and make sure the mass air meter is matched to the injectors if they have been upgraded. and check your plugs,wires,cap and rotor also to make sure you are getting good spark.
need more info. What other mods are done to the car? Fuel pressure reg, fmu, what size maf and inj, are they calibrated, custom chip, etc etc
JChalfan
Member
We definitely need more info on your combo.
Going just on what you said, I agree with BK_CAULEY. With a SC, you need to be sure you are giving it plenty of fuel. You need a high volume fuel pump (255lph), and either big injectors with a matching MAF (preferably with a custom tune), or if you are using stock injectors, you MUST have a FMU (fuel management unit). The stock injectors can't flow enough fuel with the stock fuel pressure. The FMU responds to a boost signal by progressively restricting the return fuel line as boost increases, increasing fuel pressure to the injectors, forcing more fuel through them than they are designed to flow.
When you say you unhooked the intake tube from the SC, do you mean you hooked the MAF (mass air flow sensor) directly to the intake, like on a stock setup, simply bypassing the supercharger? And when you did that, it works fine, and you can go wide-open past 3500 with no problems?
One other thing, it's possible you are blowing out the spark with the supercharger, if your plugs are gapped to large. You could gap them down smaller (maybe around .035) and see if it makes a difference. But FIRST, I would figure out if your fuel system is adequate. If you are running it lean with the supercharger, you run a good chance of blowing your head gaskets.
So before you do anything else, tell us about your fuel system...
Jeff
Going just on what you said, I agree with BK_CAULEY. With a SC, you need to be sure you are giving it plenty of fuel. You need a high volume fuel pump (255lph), and either big injectors with a matching MAF (preferably with a custom tune), or if you are using stock injectors, you MUST have a FMU (fuel management unit). The stock injectors can't flow enough fuel with the stock fuel pressure. The FMU responds to a boost signal by progressively restricting the return fuel line as boost increases, increasing fuel pressure to the injectors, forcing more fuel through them than they are designed to flow.
When you say you unhooked the intake tube from the SC, do you mean you hooked the MAF (mass air flow sensor) directly to the intake, like on a stock setup, simply bypassing the supercharger? And when you did that, it works fine, and you can go wide-open past 3500 with no problems?
One other thing, it's possible you are blowing out the spark with the supercharger, if your plugs are gapped to large. You could gap them down smaller (maybe around .035) and see if it makes a difference. But FIRST, I would figure out if your fuel system is adequate. If you are running it lean with the supercharger, you run a good chance of blowing your head gaskets.
So before you do anything else, tell us about your fuel system...
Jeff
Well i have been looking at it and it appers to have stock injectors. But acording to what i could find on the vortech website , it clams i dont need fuel upgarde or chip with the sc. I think i'm going to rebuild the bottom end of the engine so i know it can handel the sc. also with that vortec clams to have a stock set up... but i wanted to beef it up some. but not to sure, i have been a heavy equipment mechanic so i'm not really up on what the car needs.. thanks for your help!
JChalfan
Member
According to this page, even the base 5.0 kit comes with a FMU:
http://www.vortechsuperchargers.com/product_variation.php?pvk=571
If you're running stock injectors, you have to run an FMU or you will blow your head gaskets at the very least.
You didn't say which SC you have, but a stock bottom end can easily handle 5-6psi. If it's otherwise in good shape, you don't really need to go through it just for the SC.
Jeff
millhouse
Founding Member
If the fuel system is indeed up to snuff your ignition system certainly could be the culprit. The easiest thing to check would be the spark plug gap. Make sure your plugs are gapped down to around .028-.034 as in boosted apps (with a stock ignition) you are prone to spark blowout at higher rpms. After you have that sorted out be sure your wires and coil are in good condition (Ohm them out).
