dark-evader

I have been spraying my built lt1 383 recently with no timing pulled, i tried to pull some timing out and it went lean as in 14s air fuel and started backfiring so i put all the timing back in it and no more popping and good air fuel ratio, i have a msd 6al--with in cabin timing control... is the thing pulling timing on its own?

Injuneer

Has the timing already been pulled back in the tune?

Is the knock sensor still functional?

dark-evader

the timing was original pulled 4 degrees, via the original instructions i got with kit 1 deg per 50 shot (200) at the time, I took car back to the tuner to put the timing back in ecu, car pulls harder now, and i put 250 shot on it and pulled 10 deg via the control ****, i got really bad popping and 14s air fuel ratio, i tried to pull 8 then 6 and same thing, so i just put all the timing back in and afr is richened up and no back firing at all, and i do believe the car still has knock sensor.

Injuneer

Logically, you don't pull the timing in the program, if you want the car to have max performance without the spray. You use the external adjustment as you are now. Do you know how much advance is in the program now (RPM vs MAP)?

Do you have any visible black smoke at WOT w/N2O? Running it extremely rich would minimize the risk of detonation, if they actually returned the timing to optimum non-N2O values. If the knock sensor is still there, it may have the stock settings in the PCM allowing it to pull 15-deg max. Or someone may have modified the stock limits, or the stock attack and restore settings.

Without knowing what was done in the tune, it's impossible to say what is happening.

What do the plugs look like after a pull, starting w/ fresh plugs, and examining all 8 of them for indications of detonation? Shut engine down immediately after letting off the throttle. Look for a ring on the porcelain w/ tiny black or metallic highlights. This is the step I've always left to the professionals, after watching them work on the tune, examining a fresh set of plugs with a magnifying viewer after each engine dyno pull.

Sounds like so far you've been extremely lucky.

dark-evader

thats correct i took it to dyno and they pulled timing from the computer 4 deg, and then i took it back and they put the timing back into the computer, so i could pull it with the ****. it's not black smoking on a pull, i haven't pulled plugs after a pull it's a street car, i have pulled plugs after many pulls and 100s of miles running on the street and mechanic said it was rich on the old tune with 4 degs taken out.

The pulls i have done on 960 bottle pressure the wideband was reading 13s 12s then 11s towards the end, I ran some vp fuels octanium additive in it as well because i am unsure of the tune octanium raises the octane 8 points, im going to put one step bigger fuel jet in it and raise the bottle pressure up 1000, best 60 foot was 1.41 with bad nitrous leak. and the knock sensor is still on the car.