Stuttering or Popping at top end of track.

[DAVE94LIGHTNING]

Guys..on the Nitrous at the top end of the track I feel a definate popping or sssputtering. Do you think I am running too much fuel pressure or too little? I am not sure what it is yet, but I did not get a chance to make another run with higher/lower fuel pressure this last night. It seems like it is a fuel/exhaust sound and the truck runs great up to the top end of the track..just wondering?

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SVT# 3617 IN 1994

 

[Muddmann]

considering your runnin 4.56's, im guessing your right at the edge of hitting the limiter by the time you get to the far end?

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-all the bolt-ons
-Jacobs ignition
-full exhaust
-Level 10 tranny
-TFS Stage II heads
-Blowzilla...coming soon

if i stop runnin, the evil little clowns will get me...

 

[HotRod]

Before you make any more passes, do a few simply checks. Look at the plugs and see if there are any little specks on the porceline. That shows lean. Second you might want to regap the plugs to .35-.40, if its not there already. Any more and the spark can be blown out and a nitrous missfire is bad news.
About the fuel pressure, ALWAYS go higher as a start. If your borderline lean, and you take a pound or two out, you SCREWED! We dont want that.

If your rich, it will only slow you down, not a bad thing compared to lean.
And lastly, the rev limiter issue is very important also. If you have a chip with the limiters moved, then thats probably not a rev limiter problem. If you dont run a chip, you could be hitting the rev limiter and asking for a fireworks display. Again, not a good situation.

Let us know more about your combo and lets see what we can come up with.

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Rod K.

'93 Lightning #1529 NLOC #675
13.27 @ 101.55 Au Natural
12.67 @ 102.52 Kinda juiced..
'98 SVT Contour E1 #5782
'00 Suzuki Bandit S1200 10s??

 

[CAPTAIN]

I'm pretty familar with Dave's combo. I believe he's runnig the NOS 02116 under intake wet kit jetted @ 150. He runs 4:56 gears & has no chip that I can remember. Fuel pressure was at 45psi w/ vaccuum off & his plugs are gapped correctly at .35. he just put a torque convertor & 1.72 rockers recently too.

Seems to me that you're hitting the rev limiter, not the speed limiter. The speed limiter is a complete fuel shut-off & you'll be having more problems than "popping" if that happens! I believe (correct me if I'm wrong) that the factory rev limiter is also a fuel shut-off, but it will continue to feed fuel as the rpm's bounce back off the limiter. The "popping" sound you hear might be just the revs bouncing & fuel being burnt inconsistantly.
If the rev limiter is a spark shut-off, that would mean the fuel is still flowing, just not burning. The "popping" you hear would be the unburnt fuel igniting in the exhaust. This is what I would put my money on.

Either way, I think those gears, torque convertor & rockers are really making some rpm's at the top end, and you're hitting that limiter in the last gear (top end) too early.

Another scenario would be running too rich, but I think it would be doing it at the low end of the track too, and it wouldn't have just started to do this without you messing w/ the fuel pressure or nitrous & fuel jetting.

What MPH were you going through the traps at, and when did it start to "pop"? 1000 foot mark?

 

[DAVE94LIGHTNING]

Guys: Captain is on the money about my trucks combo, except that this time I was running "struckby's" chip which has the speed limiter removed and the rev limiter moved wayy high like 10kRPM.

On the pass without the chip I hit the speed limiter for sure..the RPM's were only about 3000RPM and it hit exactly at 90mph on my speedo which I had checked over and over again.

I'm thinking it is running a little rich right now..I will first try running about 48psi fuel pressure and see what happens..if that makes the popping worse I will try running about 40-42psi to see if that cures the problem.

My spark pugs look perfect thus far and the truck pulls hard all the way down the track. The popping is at about the 1000ft mark

If that won't get me 12's at 3000ft elevation I might bump the timing a bit as well..I am currently running 10* with Ed's chip but have been as high as 13* with a little high octane for safety.

Thanks for the help guys

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SVT# 3617 IN 1994

 

[CAPTAIN]

Keep us posted buddy!