TraviZ

iTrader: (2)

How much effect does your engine compression have on nitrous injection?

With my engine in my sig, I would like someday to spray at the track. Not sure though if my CR is too high. also I don't want to big of a shot on my poor hyper pistons.

automec

the main thing is to make sure you have high enough octane gas to run on when spraying. i have run a 250 shot on a 10.5 comp. 355 with hypers.( was told it had forged in it). they held up untill i hit it with a 350 shot , found out they were hypers when 7 of them broke.
my new motor is 13.9 to 1 , and i will be hitting it with 150 shot. i pull 6* of timming and run vp c-12 fuel.

83 Crossfire TA

iTrader: (2)

do a search, this has been covered loads of times here, I know I've replied multiple times to similar threads.

F-BIRD'88

Your compression ratio is quite high for pump gas as is.
I would not spray it with more than 100hp shot without changing to 110 octane race gas. that means 100% 110 or better octane fuel. Not a mix.
That means draining the tank completely. Or running a small fuel cell under hood to allow you to run the motor and N2O on 110 while spraying 'er.

If you planned on spraying 'er on pump gas you should have gone easier on the compression ratio. Your motor is going to be "'on the edge" as it is N/A.

TraviZ

iTrader: (2)

I only planned it for a 100shot when I hit the track, trying to nail a 10.xxx second quarter mile someday. I figured I can pick up the trick gasoline and back off the total timing 4 degrees. and see where that takes me.

However I need to ask this. Say I have my ecm tuned in perfect for spark and fueling. And of coarse I add nitrous, they say back it off 4 degrees. well is this recomendation from, say, a stock engine on stock ecm, or equivelent in which my hi output engine being tuned in with more advance timing curve. and still only removing 4 total degrees'? I was never sure about this one.

also then If I don't already have you confused, If i go from being tuned for the 91 octane, but jump up to 110 race gas, of coarse I can introduce more timing. but then again leave some out for the nitrous. how much on avg can you go advance on the timing on high octane fuel?

F-BIRD'88

Modern unleaded racing gas burns at the same rate or actualy faster than pump gas does. So it will want the same ignition timing for maximum performance. Maybe less actually. If you end up with more than 36deg, suspect something is wrong. You should make maximum power using 32 to 36deg.
As a general rule you can to take 2 deg timing out for each 50hp of N2O.
So for 100hp take 4deg out + 2 more and start there.
With nitrous haveing the timing a little retarded will not effect the performance much, but adds a lot of saftey. Then you can add in a few deg at a time and see the results. If more timing does not increase performance, don't use it.

izcain

other things will affect how much you can spray a motor with (aluminum heads, cam specs) all sortsa things. I have sprayed 125 shot with forged bottom end running 11:1 and pump gas just had to be careful and have the proper tune. I run 110 at anything more though.