You need to experiment with your particular combo. But it is well known that the burn speed of a fuel air mixture plus nitrous increases. So, if your timing was optimal in the first place, it will be too advanced when nitrous is added and pulling back timing usually INCREASES power, not decreases it as suggested by 01Z. The stock timing curve on both the LT1 and LS motors is pretty aggressive. GM puts a lot faith in the knock sensor to protect from detonation. Adding nitorus does not cause detonation - it causes a quicker burn and increases cylinder pressures. This MAY be picked up by the knock sensor as knock (the KS is an acoustic pickup) but I wouldn't count on it. I do not agree with the above suggestion, I think it gives up "free" hp.

Rich

 

You didn't get my point at all.

 

Elaborate?

Rich

 

Since it's you....

In my parting sentence I wrote "I'm not saying he is right" as my disclaimer so at least part of my point is not a suggestion but a regurgitation from someone from some place that would surprise you. I regurgitate because I have no authority and little experience.

My point is about the pesky initial knock count that in some installations occurs without exception when the nitrous first hits and not about overall timing under nitrous; the inference is being taken wrong because I had diverted to solving a problem which has the side benefit of causing timing to be automatically pulled.

As I'm sure you know, when the PCM pulls timing it gives it back slowly. So in essence what the speed shop tech, who is also a successful manufacturer and seller of excellent products told me they use that initial timing retard as an automatic method of setting timing back under light shots of nitrous. Not everyone is unlucky and gets this first hit knock count. But in some situations this particular tuner cannot solve that problem so they use it to their advantage.

In other words, sometimes we can pull away too much spark advance even under nitrous and thereby forfeit some level of performance. That is what I took from what he said when I asked about adding a length of nitrous line to insure that the faster-than-petrol moving liquid n2o does not create an initial lean condition that causes knock that causes the pcm to pull up to 15 degrees of timing. So, my point is about timing already being pulled and then a device that pulls even more - hence too much timing being pulled.

If you don't have this initial burst of knock then pulling timing is a good and safe thing. If you consistently get this brief moment of knock then pulling even more timing is diminishing performance.

IMHO all nitrous installs should be monitored for knock and watched with a logged wideband but first timers usually start with just the nitrous and sometimes move on to worry about really getting the timing right. I'm and I'm

 

Thanks, I see a bit better now what you meant. The issue with timing and N2O isn't detonation so much as power though. You potentially leave power on the table by not retarding the timing. Since the burn is faster, peak cylinder pressure appears too soon w/nitrous and power is lost. The peak cylinder pressure also may be very high, damaging parts in a way very similar to detonation.

Rich

 

Okay, I learned something new here - thanks for explaining. Timing retard isn't just for detonation, got it now.

Oh and another thing your explanation illuminates. I have been talking with a tuner that charges an extra $100 for nitrous. To me this seemed unnecessary because I can do that myself. However, if he is experimenting with the correct amount of spark retardation in order to increase the power effect then that tells me he would tweak in the correct timing in order to get the full blow from the hit rather than just keeping the engine from hammering itself. Thanks again man!