4.6 DOHC Cutting out
 

I have a 97 Cobra 4.6 with Paxton supercharger, it was dynoed @ 486 rwhp @6000
It is very strong, but it wants to cut out and backfire when I get into the throttle. The problem starts @4500 on up. I have changed the fuel filter and fuel pump, same issue. The problem seems to get less as the engine warms up. I'm running 10lbs of boost @ 30 psi fuel pr. Any suggestions would be appreciated.

what gap do you have on the spark plugs? you may need to close it up. Not to uncommon to get spark blow out on a boosted car. our turbo car has the plugs closed up to .028. The fuel press also seems low to me what size inj. are you running and what are the AF ratios?

For 10lbs you want to run a .032-.035 gap. Either NGK TR6 plugs or BR7EF plugs will work just fine.

Why only 6k? They should be pulling the car to 6700-6800 rpms? Maybe add a smaller pulley so you can use the entire range of RPMs.

If the car is backfiring that is detonation and needs to be corrected in the dyno tune. If you continue to beat on the car the stock rods will break or you will melt a piston for sure.

Give us the mods you have that support the superchager. IE fuel pump, inline fuel pump, injectors, MAF, intercooled, aftercooled, powerpipe, blower pulley size. Stock long block or has it been forged?

As said above more details please, did this just start or has it been ongoing? and yeah 30 lbs seems way low on a boosted motor.

PS make sure you have an aligator stuck in the air intake :D

Some of the mods are: Forged pistons 8.5:1, H beam rods, adj fuel reg, hd main bolts, long tube headers, BBK Cats, 42 lb injs, 255 lph fuel pump, NGK TR6 plugs, 90mm Mass air meter, BBK 62mm throttle body. This is a car I just bought, so I don't know if this just started or is on going. I tried a new fuel pump with no difference. The engine has a surge @idle, not real bad but noticeable. I have a dyno scheduled for the 21st of this month. The car has been sitting around for the last 8 years. They only put 3000 miles since the upgrades whiche were done in 04.

That motor will make a lot of power once its properly tuned!

Not sure if those 42# injectors will keep up. I've seen some people get them to work in the 550 range but 500-520 is about the max to keep the duty cycle in the 80% range.

Also, your fuel system will be labored as well. Check out SVTP and read up in the blower bistro for fuel system upgrades on 98 cobra's. You have a return style system, which is great, but I think you need more pump to handle the power that this motor and blower is capable of.

Since the car is making 10#'s at 6k I will take a stab that it has a pulley that will make about 15#'s at 6700-6800 rpms. If it makes that kind of boost your car should be in the 540-550 range in horsepower.