Dies at full throttle

[CoClimber]

I have an S50 with headers, 3.5" MAF, 21 Lb injectors, and an AA chip set up for those changes. When I'm autocrossing and I'm near redline at full throttle in second, the engine will often cut out for maybe a second, catch, then cut out again. This isn't like the rev limit cutout in that it cuts out for too long to be the rev limiter. When I lift, the engine runs fine.

I'm wondering if the fuel pump is up to the task. The fuel pump was designed to deliver fuel to an engine that produces ~165HP and my engine is supposed to produce ~260HP.

Anyone have this experience?

[nando]

the fuel pump is fine, what it sounds like to me is fuel starvation from the fuel sloshing around in the tank. was it nearly empty?

[CoClimber]

Half tank. Didn't have this problem with the M20. The fuel filter was changed about a year ago. Filters are cheap so I'll order one with my next parts order (there's always something!)

[nrubenstein]

In my E46 race car, I get starvation at anything less than 5/8ths of a tank. A new filter is a good idea, but it won't solve your problem.

[CoClimber]

Worth a try. I have another race in a week so I'll fill up before I get there.

[Ara]

Im having the same problem with my S52 obd1 car. Let me know what you come up with. Im leaning towards fuel starvation on turns but it sometimes cuts off in a straight line too.

[CoClimber]

I'll have the car out at a race on Sunday so I'll fill up the tank and see if that makes a difference. Hate to haul all that fuel around but I need to figure this out. I'll also try to check the speedometer input to the DME as I heard that may make a difference.

[Ara]

Fuel pump relay was the culprit for my issue:
part # 12631729004

[CoClimber]

I didn't get the car out on Sunday. Rain and the need to cut firewood won out. I'll try again this Sunday.

Ara, I wonder why that relay would only fail near redline. Interesting.

[Ara]

I didn't get the car out on Sunday. Rain and the need to cut firewood won out. I'll try again this Sunday.

Ara, I wonder why that relay would only fail near redline. Interesting.

Im sure it wasnt the redline, it was the pressure that caused the fuel cut......the relay prongs looked a smokey brown when I pulled it. Ill do some tests in the meantime as well.

[CoClimber]

Raced the car with a full tank of gas. Still had the problem. I'll be at a DE on Wednesday and will replace the fuel filter before that. Conditions will be different there - full throttle in third through fifth rather than near redline in second - but I will hopefully have a better understanding of what is going on.

[Ara]

Well the relay wasn't it.......what a tease. Im looking at this thread and I might have to poke around a bit and test a few things. Its either vacuum or a tired pump :

http://www.r3vlimited.com/board/showthread.php?t=218200

[DTFE30]

Did you make sure you wired the vehicle speed output to the dme?

[CoClimber]

Speed is wired, I believe. More data: tracked it at Watkins Glen and it would consistently die at ~6200RPM. I would leave it in third into turn 9 and it would hesitate at the same point on the track. I would lift slightly before that and the engine would keep running fine. I'm fairly convinced I have a chip problem. I will contact the manufacturer.

[CoClimber]

Now I'm starting to second guess the speed input. The car is going up on the lift for a clutch job so I will spin the wheels scope the VSS signal at the DME to make sure it is there. It would be very cool if it is missing. There were some cars at the track that shouldn't have pulled away from me as quickly as they did and this might explain it.