Ignition Coils to run in IT7 / Engine dead spot?

[TomL]

I think RX555 may be onto the answer. If your fuel pickup is toward the right side of the cell/tank, the long run through Turn 7 may be uncovering the pickup and emptying the float bowl enough that the engine dies just after you get onto the straight (which would occur somewhere near start/finish). Then, once you're going straight for a bit, the fuel pump catches up and the engine runs normal again.

By the way, you mention running up to 8500 rpm. Where are you doing that, and what gear and final drive? I don't quite hit 8000 in 5th, even with a 5.12 rear, and I was going faster on the front straight than you last weekend.

On the coils question, I've used both MSD Blaster2 and stock coils, and I've never had a problem with either.

[mackguy]

I think RX555 may be onto the answer. If your fuel pickup is toward the right side of the cell/tank, the long run through Turn 7 may be uncovering the pickup and emptying the float bowl enough that the engine dies just after you get onto the straight (which would occur somewhere near start/finish). Then, once you're going straight for a bit, the fuel pump catches up and the engine runs normal again.

By the way, you mention running up to 8500 rpm. Where are you doing that, and what gear and final drive? I don't quite hit 8000 in 5th, even with a 5.12 rear, and I was going faster on the front straight than you last weekend.

On the coils question, I've used both MSD Blaster2 and stock coils, and I've never had a problem with either.

Will try to get a better look at the fuel pickup. Stuff in the fuel cell did get moved around during the "incedent" on Saturday. But it seemed like it was happening about midway down the straight, though I had not considered there being a lag.

Yes, you were faster than me on the straight. Every IT7 car there was faster than me on the straight, and I was routinely at 8k+ in 5th on the straight. We counted 2.5 driveshaft revs for one wheel rev (open differential). I know I was slow all the way around the track but when you get passed when you're already at "top speed" (I know I was passed by you, Steve Rose, and the Hines car when I was in 5th and feathering the throttle around 8500).

Part of the answer there I think is tires... we are running 45profile R888's. I know Steve was running a taller profile (60 maybe?) RA1.

[team-gpracing]

We counted 2.5 driveshaft revs for one wheel rev (open differential).

I know this isn't a response to your question and maybe open diffs are different, but doesn't that mean that you have a crazy low rear gear? 2.5:1 ???

[mackguy]

I know this isn't a response to your question and maybe open diffs are different, but doesn't that mean that you have a crazy low rear gear? 2.5:1 ???

We went around in circles about that but apparently for an open diff you x2, so it's about a 5:1.

If we had 2.5:1 I'd have been going about 190mph in the straight!

[joeracerx95]

We went around in circles about that but apparently for an open diff you x2, so it's about a 5:1.

If we had 2.5:1 I'd have been going about 190mph in the straight!

"I'd have been going about 190mph in the straight!"

Yeah, I'm pretty sure you wouldn't. But you probably would get better gas mileage.

Anyway, put in a fuel pressure gauge and look at it as you come out of the last turn before your problematic straight. You'll probably see little or no fuel pressure. It then takes from there to your hesitation spot for the fuel lines and float to run out of fuel and then the engine goes dead. Meanwhile the gas sloshes back because you are now going straight and the pressure rebuilds and refills the float, and then you have your engine back. Happens to me on left hand turns if I run less than five gallons in the stock tank.

I've always used stock coils and never had one go bad. I've been told by people that know more than me that the stock 12a ignition is more than adequate for stock engines. Now a turbo motor at 9000+ is a different story.

[mackguy]

well Yes, I'm sure you are right but if I was turning 8krpm with a 2.5 rear and a .83 overdrive... that would be quite fast.

Good observation. The cell did get jostled around so that could be part of the issue. What is strange is that it didn't exhibit that issue anywhere else on the track except on the straight, thus I didn't think about it being a fuel issue.