What will spray add?, Time reduction wise?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: What will spray add?, Time reduction wise? (skateparkdave)
Well, my feeling is that if you build 400chp with NOS, blower or N/A you get the same cylinder pressure, as that's what builds HP...burning fuel to build pressure to drive the piston.
That said most books suggest dropping CR, enhancing exhaust port flow, and going to forged internals. I guess it depends on what will be your resultant HP. Also if you just dump a 150 shot into a relatively stock L98 you won't likely get 150 CHP gain.
If I were going to experiment with NOS I would start with a nice wet system with all the safety bells & whistles at a 50 shot and work up. If you make a mistake with a 50 shot your engine might survive but not likely with a 150 shot.
BTW, the rule of thumb that Frank quoted, i.e. 100 HP == 10 mph & 1 sec, refers to HP at the crank. HP at rear wheels would be about 83% of that number, at least with my A4 it works out that way. That rule of thumb is for a car weighting around 3,350lb-3,400lb at launch, like our C4s.
The actual equations are:
CHP = ((Trap Speed) / 234)^3 * Weight,
ET = 1357 / (Trap Speed),
where CHP is crank HP, Trap Speed is in MPH, ET is in sec. and Weight is launch weight in lbs.
That said most books suggest dropping CR, enhancing exhaust port flow, and going to forged internals. I guess it depends on what will be your resultant HP. Also if you just dump a 150 shot into a relatively stock L98 you won't likely get 150 CHP gain.
If I were going to experiment with NOS I would start with a nice wet system with all the safety bells & whistles at a 50 shot and work up. If you make a mistake with a 50 shot your engine might survive but not likely with a 150 shot.
BTW, the rule of thumb that Frank quoted, i.e. 100 HP == 10 mph & 1 sec, refers to HP at the crank. HP at rear wheels would be about 83% of that number, at least with my A4 it works out that way. That rule of thumb is for a car weighting around 3,350lb-3,400lb at launch, like our C4s.
The actual equations are:
CHP = ((Trap Speed) / 234)^3 * Weight,
ET = 1357 / (Trap Speed),
where CHP is crank HP, Trap Speed is in MPH, ET is in sec. and Weight is launch weight in lbs.
Thread Starter
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
Re: What will spray add?, Time reduction wise? (65Z01)
Ok, thanks Frank and James and all. I think I'll wait and see how it all works at the track before doing it but if I do, a 50 shot sounds like the best place to start. I was never planning on using it off the line but maybe for just a boost like after hitting second gear in a race that counts.
One more question..Is it better to spray before throttle body or through a plate after..or what? I have no MAF (it's speed density) so does it matter? I've heard conflicting stories. I'm such a novice
Thanks again.
[Modified by skateparkdave, 1:00 AM 7/5/2004]
One more question..Is it better to spray before throttle body or through a plate after..or what? I have no MAF (it's speed density) so does it matter? I've heard conflicting stories. I'm such a novice
Thanks again.
[Modified by skateparkdave, 1:00 AM 7/5/2004]
Race Director
Joined: Feb 2004
Posts: 12,517
Likes: 19
Re: What will spray add?, Time reduction wise? (skateparkdave)
The Nos 5151 kit is a wet style "plate" ystem. A plate goes between rear of throttle body and plenum. Nitrous is injected in the plate. Fuel is also. The fuel is connected to the pressure valve. The Nos and fuel mix in plate and sucked into motor. Simple system and easy to hook up. The plate is jetted like a carb for different levels of power. 50-175 hp is available depending on jetting. Bigger kits are available but not common.
Thread Starter
Melting Slicks
Joined: May 2004
Posts: 2,524
Likes: 10
From: Lufkin Texas
St. Jude Donor '05-'06
Re: What will spray add?, Time reduction wise? (Pete K)
Thanks Pete, yeah I looked at something like that and it seems like a pretty versitile system but I have a Power Tower there and I'm going to have to remove it or rig a way to move throttle linkage forward yet even further if I put a nos plate there and spray post throttle body. A guy I know was telling me I could mount a spray tip in the plastic accordian tube inbetween air filter and TB, right in front of TB. Does this work??
Race Director
Joined: Feb 2004
Posts: 12,517
Likes: 19
Re: What will spray add?, Time reduction wise? (skateparkdave)
I remember seeing that done on a mustang a while back. I am sure it can be done.Some guys drill the bottom of the plenum and put the jet in there to have a stealthy approach. I dont have a power tower, but the kit gives you longer throttle body bolts and a bracket to relocate the throttl linkages foward the thickness of the plate. It worked very well for me.
