Ksths2

iTrader: (1)

I've got a 500rwhp LS1 C5 I drag race etc and I have been only spraying 100hp wet shot throw a Harris speed works perimeter plate, anyway I originally had fuel pump problems on the dyno as the stock pump couldn't keep up with the demand. So i upgraded to the LPE high flow pump and the problems went away.
The car runs 10.80's @ 128 in the 1/4 and i'm progressively turning on the juice. It activates at 3500 for 50% then 1.5 seconds later it goes 100%, only reason i'm doing this is traction (long story)
I have a FAST digital A/F meter that logs all the passes and its always about 10:1-11:1 on spray. And the plugs look great. My timing twister only pulls -2 degrees out.
As I'm in 3rd gear spraying right at the stripe and about 6400-6500 it starts breaking up or fluttering and you can tell it lays down a bit but i can't figure out what it is?
My window switch shuts off the spray at 6500, but i can't figure it out. It can't be valve float since it doesn't do it between shifts. The rev limiter is set at 7000 and it doesn't shift into OD either so i can't imagine its the rev limiter.
It doesn't seem to be detonating as the plugs and A/F meter looks great

Any suggestions on what is going on?

Beer99C5

iTrader: (21)

Does it do it N/A or throw any Misfire codes?

I had something similiar (did it NA and threw a code) and it turned out to be broken Valve Springs.

10-11 seems very rich, but if the plug readings are good perhaps your wideband is a bit off.

Jim

NitrousExpress

iTrader: (4)

Not only is that rich but a full point is a BIG spread. It shouldnt very that much during a run.

What do the plugs actually look like? Wheres the timing mark? Color?

Also You might want to do a calibration on the wideband. My lm1 was off and its made nearly a .5 difference once calibrated correctly.

N20GMC

10.0 to 11.0 is rich especially on a 100 shot.

The reason it gets worse at the end of the run is it has less bottle pressure. So it goes even richer.

Ksths2

iTrader: (1)

Nope, doesn't do it N/A, smooth and pulls all the way. & no codes.

Jim @ speed inc (the tuner) said my FAST A/F meter read a step richer than what his dyno a/f said. I mainly just use to it keep an eye to make sure both banks are the same so i don't go lean and BAM! And actually i do have 2 jet sizes richer than what was originally suggested by HSW jet size card.

Yeah the full point is not exactly correct. It doesn't vary hardly at all during the run, i was just giving the ranges i've ever seen when spraying it. It's normally 11:1 i believe.

Plugs are clean, porcelin is white w/ no spots, ground strap is tan & color change mark on strap is back where it bends down that joins by the threads of the plug. I don't have an actual plug reader tool.

How do i recalibrate my FAST a/f meter?

Ksths2

iTrader: (1)

I agree on the less bottle pressure but i've got 2 bottles w/ heaters and it doesn't seem to ever drop much. But why would it do it exactly at the same time and rpm if it was pressure related?

NitrousExpress

iTrader: (4)

On the FAST I am not sure. Give those guys a call. The people at COMP are pretty good guys. Do you mean the timing is where the strap meets the threads?

Do you have any way to datalog?

N20GMC

If it has 2 jets sizes bigger than what HSW recomends I would put the jets in it that they say and run it.

ryarbrough

iTrader: (18)

If you put in jets bigger than what HSW reccomends it's PIG RICH....

Drop it down to their suggested jetting and see what it does. I'd be willing to bet it's still rich.

Ksths2

iTrader: (1)

Sounds good on calling FAST, and the mark is on the flat of the ground strap but its just before the radius starts down to the threads. The only dataloging i can do is just recording the dual 02 sensor readings per a/f meter.

I agree, i will run the correct jets per 100hp shot and see what happens. Only reason i changed it from original is Speed inc and I were trying to find out if the stock fuel pump was keeping up or not. It wasn't so i installed the new LPE high flow and left the jets in since they tested it on the dyno and they said it was safe.

Nick@HSW

iTrader: (4)

Only 3rd gear? If you bump the window up does the studder move with it? I would imagine that with those jets you're going to be way rich...did you register the dyno a/f when the old pump was in there?

Nick

Brad@NANO Direct

iTrader: (18)

Sounds like you need a good'ol fashioned NANO system to me.

It still can get rich up top with heaters. It does sound like your jetting is rich. You need to get that up in the 11.7-11.8 range for sure.

Also, what plugs and what gap are you running?

Ksths2

iTrader: (1)

yep only seems to do it at the very top of 3rd gear in the 1/4, not sure on the window switch change, i was just playing it safe so the N20 wouldn't be on if it ever hit the rev limiter. No i got the FAST a/f meter after i found out on the dyno it was running out of fuel pump.

LOL on the nano, i agree!!! Plugs are NGK's BR7EF and for the life of me i'm blank on the gapping......I check and let you know.

Ksths2

iTrader: (1)

1 thing I was wondering, if its super rich like that would it make that fluttering i'm discribing though? I mean, wouldn't it just not be as much of a hp shot? I was thinking last night about it and that makes sense cuz my car was 453rwhp N/A and with 100hp jets and -2 degrees of timing it was only 508rwhp = 55hp difference with the 6 speed and now with the automatic & 3600 stall converter it was 423rwhp N/A and same shot and timing it was 485rwhp = 62hp difference rather than approx 100...........

NitrousExpress

iTrader: (4)

Very possible. Try recommend jetting and go from there.

Ksths2

iTrader: (1)

sounds good, i'll let you know how it goes and hopefully not cook it lol Thanks!

Nitro Dave's Nitrous Outlet

iTrader: (25)

Does the car have a fuel pressure gauge on it? If it does is the fuel pressure staying solid on the top end?

If I am understanding you correctly and the timing mark is close to the threads of the base of the plug you need to out some timing back into it. This is ofcourse only if you are pulling the plugs after wot and instant shut down. If the plugs were old it hard to get an accurate reading as well.

A good safe area will be about 11.8 on the airfuel.

Nitro Dave's Nitrous Outlet

iTrader: (25)

And does the car have a fuel pressure safety switch?

Ksths2

iTrader: (1)

Yes car has fuel pressure gauge but its on the fuel rail so a bit hard to ready going down track lol & no fuel pressure safety switch i used to run those on bike but I always had troubles with it.

Yeah pretty close on the plugs, and i will pull them right after next run w/ N20 to give an update. Thanks!

Nitro Dave's Nitrous Outlet

iTrader: (25)

Ok, The reason I asked about a fuel pressure gauge is because everyone jumped on board about it being to rich based off the info you have given, which is more than likely the case but a fuel pressure issue on the top end could be the issue as well. So I wanted to throw that out there for you to keep in your mind as you rule out possibilities.

When the car "flutters" does it pop out the exhaust of intake any? Or does it just nose down on power?
Dave