Well I noticed that some people pulls the timing (ignition?) 3 degrees back when spraying, while other people just spray with standard timings..
Could someone please explain what it "means" to retard the timing and why you'd do that when on the juice?

Thank you.


BTW: I keep seeing people talk about split-shot (2x 20 shot, or 2x 30shot) what does that mean??

Supposedly for a small shot (40 shot for example) you can get away with leaving the stock timing of the engine as is.

If you wanted to get a little more horsepower from your engine and you were naturally aspirated you could possibly advance the timing a few degrees and pick up a couple of HP.

With nitrous though you'll usually need to retard or pull back the timing a few degrees. Depends on the amount usually and what else you have done to your motor.

Phantom12 runs a 40 shot with stock timing.

I run a 40 shot but have the timing retarded 3 degrees. If I don't run nitrous I have 175 hp on the correct map. But if I run no nitrous YET still have the nitrous map then I only get about 172 hp. Part of the power loss is due to retarding the timing, the other part is due to being a little too "rich" or too much fuel.

My shop erred on the safer side as I also got colder spark plugs.

If you are just using the nitrous, say for drag racing 1/4 mile or 1/8 mile or just for a couple of seconds then you'd be fine with stock timing with a small 40 shot. I had mine set back for safety since I will be spraying from 2nd gear till 6th...almost a good 20 seconds! It doesn't take long to mess up your motor so I didn't want to take a chance. Phantom seems to be having no problem running his to 200+ mph with stock timing.

Another busa with a 60 shot had 4 degrees of timing taken out. Some people don't take out as much timing per shot of nitrous, all depends.

And I mention 2 x 20 shot because the way I have mine set up is after the nitrous bottle goes to the solenoid it gets split into 2 lines and is routed to both ram air tubes for better distribution to all 4 cylinders (theoretically speaking). This way all 4 cyl supposedly get roughly the same amount of nitrous instead of shooting it @ one side and having ..... say cyl 1 and 2 get most of it and cyl 3 and 4 not as much. More hp and more reliability...theoretically speaking of course. It only cost me 40 more bucks to go that route so I said screw it! Normally a 40 shot is just 1 line that gets directed @ the airbox or sometimes down 1 ram air tube. Retarding the timing helps avoid pre-ignition/detonation.

Ali

Why is the risk of detonation bigger when you spray nitro?
I know that when you retard the ignition you ignits it more degrees from TDC (top dead center) than when not retarded, and therefor at a lower temperature.. And the later the ignition comes the hotter it gets inside the cylinder which equals a higher risk of detonation.. But I dont see why putting nitro + more fuel into the cylinder would make it self-ignite, I mean it shouldnt get hotter just because you add the nitro/fuel (when not ignited that is).

So why would it detonate due to more nitro/fuel??

Guess Im a little confused but please help me out here :roll:

It isn't "nitro". It's nitrous oxide. It isn't a fuel.

Read this entire site:

http://www.diy-nitrous.fsnet.co.uk/

...if you really want to know what's up.