BIG backfire through exhaust when nitrous activates
BIG backfire through exhaust when nitrous activates Car runs perfect n/a, tune is dead nuts 12.8 a/f and runs like a scalded dog. Arm the nitrous and as soon as it starts spraying (3500rpm) the motor cuts out and I get a HUGE backfire out the exhaust (verified by chase car). I let off obviously, car catches itself and then runs fine. I've tested the kit in the driveway under pressure and both nitrous and fuel are spraying. WTF is happening? I know a 20F jet would probably be closer to the ideal tune but still........Details:
forged 370ci, 12:1 compression, 110 octane fuel
direct port, big NOS solenoids, 24N/22F
HSW low press standalone fuel system, 110 octane, 5 psi (have tried everything from 4.5 to 6psi with same result)
900psi bottle pressure (full bottle)
NGK -8 plugs gapped at .033 (tried .025 with same results), no detonation signs on plugs
Timing tuner used as window switch (3500-7000rpm) and pulling 9* timing, have tried pulling the timing in the tune instead with same results
Anybody have any ideas?
forged 370ci, 12:1 compression, 110 octane fuel
direct port, big NOS solenoids, 24N/22F
HSW low press standalone fuel system, 110 octane, 5 psi (have tried everything from 4.5 to 6psi with same result)
900psi bottle pressure (full bottle)
NGK -8 plugs gapped at .033 (tried .025 with same results), no detonation signs on plugs
Timing tuner used as window switch (3500-7000rpm) and pulling 9* timing, have tried pulling the timing in the tune instead with same results
Anybody have any ideas?
try going down 2 on the fuel side and see if it clears up a little bit. jetting setup looks kinda rich. other than that is the is the fuel system a return style and not dead heading? it could be building up alot of fuel pressure before the solenoid opens and causing a rich backfire...
just throwing some ideas out there to think about.
good luck
just throwing some ideas out there to think about.
good luck
Thanks for the replies.
Fuel system is a Harris Speed standalone setup (return style, aeromotive reg, low press spring). It only sprays for a split second before it cuts out and backfires, hard to get any useful data at all (wideband/plugs) in that little amount of time. Guess I'll try a 20F jet and see what happens?.....
Fuel system is a Harris Speed standalone setup (return style, aeromotive reg, low press spring). It only sprays for a split second before it cuts out and backfires, hard to get any useful data at all (wideband/plugs) in that little amount of time. Guess I'll try a 20F jet and see what happens?.....
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Car runs perfect n/a, tune is dead nuts 12.8 a/f and runs like a scalded dog. Arm the nitrous and as soon as it starts spraying (3500rpm) the motor cuts out and I get a HUGE backfire out the exhaust (verified by chase car). I let off obviously, car catches itself and then runs fine. I've tested the kit in the driveway under pressure and both nitrous and fuel are spraying. WTF is happening? I know a 20F jet would probably be closer to the ideal tune but still........Details:
forged 370ci, 12:1 compression, 110 octane fuel
direct port, big NOS solenoids, 24N/22F
HSW low press standalone fuel system, 110 octane, 5 psi (have tried everything from 4.5 to 6psi with same result)
900psi bottle pressure (full bottle)
NGK -8 plugs gapped at .033 (tried .025 with same results), no detonation signs on plugs
Timing tuner used as window switch (3500-7000rpm) and pulling 9* timing, have tried pulling the timing in the tune instead with same results
Anybody have any ideas?
forged 370ci, 12:1 compression, 110 octane fuel
direct port, big NOS solenoids, 24N/22F
HSW low press standalone fuel system, 110 octane, 5 psi (have tried everything from 4.5 to 6psi with same result)
900psi bottle pressure (full bottle)
NGK -8 plugs gapped at .033 (tried .025 with same results), no detonation signs on plugs
Timing tuner used as window switch (3500-7000rpm) and pulling 9* timing, have tried pulling the timing in the tune instead with same results
Anybody have any ideas?
I know its hard to data log anything prior, but what are you seeing after?
Nick
-9* should put you somewhere around 19-20 total right? That should be a good starting point with a little wiggle room.
The wideband shows stoich as I'm cruising along at 3k rpm. At the moment I smash the throttle, MAP drops to 100kpa and fuel stays at ~14:1....by the time it reaches the next cell it has already backfired and the wideband reads in the 13's, then starts trailing off toward rich as the motor stumbles and settles back down to idle. I never get any crazy rich readings. No knock retard at all. Responses are appreciated, thanks!
What are you using to log? Are you meeting your commanded timing? I was having a problem last year with commanded vs. delivered timing. You might have something pulling a bunch of timing and you don't know it.
