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Where's my n20 mph?

This is a discussion on Where's my n20 mph? within the Nitrous forums, part of the LSx Technical Help Section category; I'll try to give as much info as possible. Mods: All boltons, Tsp tv2/5.3 h/c pkg, edge 3400 stall, rebuilt ...

  1. #1
    Another Slow LS1 shortdog's Avatar
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    Pewter
    99 Z28 A4

    Where's my n20 mph?

    I'll try to give as much info as possible.

    Mods: All boltons, Tsp tv2/5.3 h/c pkg, edge 3400 stall, rebuilt tranny, 3.73s, racetronix pump & lucas 42 lb injectors. Full weight car at around 3650 lbs.

    Before my passes, I've installed a new n20 line, filter, no.4 line from the noid to the nozzle cleaned the filter in the noid with a air compressor. Plugs are gapped at .032-.033.

    Track temp was around 55-60 degrees, 40% humidity give or take. Window switch pills set at 3200 on, 6400 off.

    Wed, I got in four passes, two n/a and two n20. My h/c car ran a new best of 11.86 @ 114, 1.64 60' on motor which is still low. Now, on the spray, it ran a best 11.07 @ 119, 1.53 60', 1/8 6.98 @ 96.50. So close to those damn 10s.. This was on a nx 150 shot. Though, I dropped 8 tenths, it only picked up 5 mph from my n/a mph. The psi was at 1000 and the bottle was about 3/4 full. I know the faster you are on motor, the more it takes for the car to pick up on n20, but not this bad. I was running that mph on a 100 shot with a stock cam, stock ported heads and tci 3800+! Something's not right, so what could be the problem?

  2. #2
    Senior Member Zboner's Avatar
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    no idea, but up the shot to a 200 and get your 10's

  3. #3
    Nitrous Tuner LS2Tuner's Avatar
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    The tune would be my guess! If it is too rich it will NOT mph. Who tuned it after the cam and those inj....?
    Do you have a hand held or any way of monitoring the A/F ratio on the big end?
    Also what kind of timing is in it.....?
    Your running a dead head style fuel sytem still or a adj. return style regulator..?
    It's on drag radials?
    Stock rear springs still.........................

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    Senior Member mrr23's Avatar
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    dark bowling green
    2000 corvette

    if you are going into the traps above the 6400 rpm shift point, that's where your lose can be at.

    case in point: my car. .4 gain, no mph. window 3500/6000 shifting at 6500 way too late starting and way to early shutting it off.

    time ------- NA ---------- N2O
    60ft ------ 1.791 -------- 1.838
    330 ------ 4.964 -------- 4.877
    1/8 ------ 7.611 -------- 7.464
    mph ----- 92.38 -------- 95.13
    1000 ---- 9.908 -------- 9.638
    1/4 ----- 11.841 ------- 11.479
    mph ---- 117.02 ------- 117.85

    next round window 3500/6400 shift 6500 still way late starting, but appropriate shut off.

    time ------- NA ---------- N2O
    60ft ------ 1.791 -------- 1.830
    330 ------ 4.964 -------- 4.810
    1/8 ------ 7.611 -------- 7.313
    mph ----- 92.38 -------- 98.85
    1000 ---- 9.908 -------- 9.427
    1/4 ----- 11.841 ------- 11.189
    mph ---- 117.02 ------- 128.24

    next thought is bottle was lower than you thought on the last run. when the bottle isn't full, the pressure drop is more severe. this will cause you to run rich on the big end and slow you down as ls2tuner is eluding to.

  5. #5
    Another Slow LS1 shortdog's Avatar
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    Thanks for the replies.

    Mrr23, I'm not sure where my rpm is at the end of the 1/4, but I'm shifting around 6600-6700. I've tried both msd 6000 and 6400 off pills with no luck.

    LS2Tuner, it was tuned after the cam and injectors. Unfortunately, I don't have a handheld or wideband, but the tuner had one. The A/f is around 12.6 n/a, but was rich (10s wot) on a 175 shot, so we leaned it out by putting in a .033 150 shot jet and that got it around 11.3-11.5 wot. BUT, it was hot outside and my bottle psi was very high, around 1150. Nx told me that the nitrous noid could possibly not open if the pressure is too high, causing the system to run rich. I was "probably" getting an inaccurate reading due to that, not sure though. The fuel pump and injectors are my only fuel upgrades. Stock springs with 255-50r-16 Et street radials, but I have BMR lcas, brackets, tq arm, sfc. My timing is set at 27*, but I do have a switch to reduce the timing by 4*. I forgot to turn it on n20 mode at the track Wed.

    The bottle is full and will give it another shot next week. I wanna go with a smaller fuel jet, but don't wanna risk it since I don't have a wideband.

  6. #6
    Nitrous Tuner LS2Tuner's Avatar
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    This has nothing to do with your problem but Please do yourself a favor and buy a pair of V-6 springs and put in the rear. It will make night and day difference. I would get it back on the dyno and get that A/F correct on what ever shot you plan on running........
    That window switch is for the birds for me!! I only put them on customers cars if they are 6 speeds and they are
    I have to have total control with a button in my hand!
    Don't be afraid of the bottle!!! Be afraid of your tune!!!

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