Pulling timing for Nitrous on LT-4
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On The Tree
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Pulling timing for Nitrous on LT-4 1996 LT-4 Vette
Have an old NOS fogger plate, max 150hp. Sent it to Induction Solutions for blue print and flow. Need to figure out if there is a good solution for pulling timing only when on the bottle. I can tune the timing map to accommodate, worse case scenario, but then I have to drive around daily with that. It has a brand new Opti but otherwise stock ignition.
Have an old NOS fogger plate, max 150hp. Sent it to Induction Solutions for blue print and flow. Need to figure out if there is a good solution for pulling timing only when on the bottle. I can tune the timing map to accommodate, worse case scenario, but then I have to drive around daily with that. It has a brand new Opti but otherwise stock ignition.
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On The Tree
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From: Euless, TX
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MSD digital 6 plus and an adapter harness for your coil. Plug it in and wire it up. 12 volt hot triggered off of the nitrous wiring will trigger the box to pull the timing from base. I have always ran my nitrous kits this way on LTX cars over the years. The ignition box also helps with spark energy. Make sure to gap the plugs to ~.030 non projected tip ~8 heat range. I would pull 8-10 degrees from stock assuming you are running 36 degrees total if on pump fuel. Remember excess timing and fuel kills engines on the nitrous.
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TECH Resident
Joined: Oct 2006
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From: Euless, TX
You wire a 5 pin relay into the IAT sensor. IAT goes to the normally closed pin. Signal wire to the PCM on the switched pin. IAT fixed resistor to the normally open pin. The other end of the resistor ties into the other IAT wire. When the nitrous arming switch is energized it substitutes a fixed resistance for the IAT. I generally use a very high ohm resistor. This tells the PCM that the intake air is extremely cold ~ -20°F. Then program the intake air temperature timing compensation tables to give the desired timing retard. You can lookup the IAT temperature sensor temperature. You can datalog and test to make sure the correct amount of timing is being removed before spraying.
Thread Starter
On The Tree
Joined: May 2018
Posts: 144
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You wire a 5 pin relay into the IAT sensor. IAT goes to the normally closed pin. Signal wire to the PCM on the switched pin. IAT fixed resistor to the normally open pin. The other end of the resistor ties into the other IAT wire. When the nitrous arming switch is energized it substitutes a fixed resistance for the IAT. I generally use a very high ohm resistor. This tells the PCM that the intake air is extremely cold ~ -20°F. Then program the intake air temperature timing compensation tables to give the desired timing retard. You can lookup the IAT temperature sensor temperature. You can datalog and test to make sure the correct amount of timing is being removed before spraying.
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From: Euless, TX
Teching In
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I converted over to FAST EFI and didn't have this issue when I had my LT1 pulling large amounts of timing. However prior to that YES it was all done with an MSD Digital 7 box jumpered in between coil, and opti. I believe I used the Trans brake as the signal for changing limiters (launch rpm vs total rpm). Timing was all pulled the second the first kit came on....
The FAST made it much simpler with a crank trigger.....and a true distributor like what we all ran..
The FAST made it much simpler with a crank trigger.....and a true distributor like what we all ran..