why does everyone turn on the spray at 3000? in my other cars i used to bring it on at 2500. just currious cause this is my first gm car... lt1 at that lol

 

If you spray in too low of an rpm, you can cause very serious engine damage. That is why 3000rpm is usually a common setting for the low end of the window switch setting.

 

Too much nitrous and not enough engine vacum. Nitrous sits in the intake and then boom! no more intake. So no N2o before 3K.. got it?

 

because, it is the 'safe' thing to tell people over the internet. even the nitrous companies have it in their manuals now that say no lower than 2500 rpms. i've hit it as low as 1800 rpms in my cars.

 

vacuum? when you are at WOT, there is no vacuum.

 

Sorry, more details needed i guess.
The cylinders don't draw in enough N2o to burn it all, some gets left behind in the intake. The same amount of N2o gets spray'd at 1,000rpm as 6,000, depending on how much cylinder volume you have and how much n2o your spraying will effect how soon you can begin spray the N2o safely. 3,000rpm is the "safe" area for all engines. Your engine, your choice.

 

http://nitrousforum.com/forums/showthread.php?t=38

nx description is the best one.

 

so it seems 2500 is the safe limit they speak of. i know it has to be at WOT. i am not a nitrous newbie by any means. just have never sprayed a lt1.

 

a 50 shot at 2000 would prolly be ok, a 100 at 2500...but thing is the lower rpm you hit it that bigger the tq spike...and that wil be what kills your motor...a 50 shot with a stock stall at say 1500 rpm will probably make 125 ft lb of torque...a 150 shot at the same condition would probably make 350 ft lb of tq...
add 350 to your stock 300 or so, and thats 650 ft lb on a stock bottom end...
ls1tech talks about this a few differant times...exspecially robert56, he dailed in a stock ls1 bottom end to stay together for over 2 years on a 250 shot...by breaking it up i think 150 at 300, and another 100 at 4500...trying to keep both tq spikes under 650 ft lb...

that all is only about keeping your motor together...that has nothing to do with the possibility of detination or backfire...

 

I've sprayed 2,500 RPM for three seasons now without any problems. However, I have a 2800 stall Vigilante that won't load the motor as much as a stock converter.

 

a 50 shot is closer to 175 ft lbs of torque at 1500 rpm and a 150 shot would be over 500 ft lbs of torque at 1500 rpm. A lot more extreme a change than it initially seems. a 200 shot at 1500 rpm would be well over 600 ft lbs of torque, all of these numbers are in addition to the torque the engines already producing. to contrast at 3000 rpm a 200 shot would be a little over 340 ft lbs of torque while a 150 shot would be around 260 ft lbs of torque.

 

The cylinder pressure increase is proportionate to hp and inversely proportional to rpm.

Example: engine makes 200hp at 2,000rpm, producing "X" lbs of cylinder pressure. At 4,000rpm, the engine makes 400hp, cylinder pressure also = X.

Add a 200hp nitrous shot at 2,000rpm and cylinder pressure doubles to 2X. Add it at 4,000rpm and pressure increases to just 1.5X. The lower you bring the nitrous in, the greater the increase in cylinder pressure, which is what breaks stuff.

Rich