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Ist there a reason not to spray at too high RPM's??

 
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GrandSportC3
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PostPosted: Thu Dec 28, 2006 8:17 am    Post subject: Ist there a reason not to spray at too high RPM's?? Reply with quote

I know that some people shut off the nitrous above 6000 RPM. Is there a specific reason not to run nitrous at too high RPM or is this just so that the spray isn't on during the shift???
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Big Dave
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PostPosted: Thu Dec 28, 2006 10:15 am    Post subject: Reply with quote

That would be a strategy based upon your build (parts and limitations due to those parts) and style of driving (I've seen a lot of people sand bagging).

Nitrous like a rising tide, lifts the power curve uniformly, across the RPM range, it isn't any more pronounced at the upper end of the band than the lower. I think of it acting just like boost in that it is similar to increasing the engines displacement. Would you feel safe putting part A combined with part B in your set up if you were running a 40% larger motor? In other words you don't put a TH350 behind a BBC and expect it to live; a SBC 355 running a 225 horse shot of nitrous acts just like a N/A 509 cid BBC in torque curve and peak horse power.

The distinct advantage nitrous has is that you can tailor your displacement as you race with multiple stages and ignition control so that you leave with the most motor your traction can support and cross the line like a BBC on steroids if your parts can support it.

Big Dave
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GrandSportC3
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PostPosted: Thu Dec 28, 2006 10:33 am    Post subject: Reply with quote

Big Dave wrote:
That would be a strategy based upon your build (parts and limitations due to those parts) and style of driving (I've seen a lot of people sand bagging).

Nitrous like a rising tide, lifts the power curve uniformly, across the RPM range, it isn't any more pronounced at the upper end of the band than the lower. I think of it acting just like boost in that it is similar to increasing the engines displacement. Would you feel safe putting part A combined with part B in your set up if you were running a 40% larger motor? In other words you don't put a TH350 behind a BBC and expect it to live; a SBC 355 running a 225 horse shot of nitrous acts just like a N/A 509 cid BBC in torque curve and peak horse power.

The distinct advantage nitrous has is that you can tailor your displacement as you race with multiple stages and ignition control so that you leave with the most motor your traction can support and cross the line like a BBC on steroids if your parts can support it.

Big Dave


Great Information, Dave!! Thanks!!
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pro60chevy
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PostPosted: Thu Dec 28, 2006 7:08 pm    Post subject: Reply with quote

It also has alot to do with what your rev limiter is set to. You don't want to be bumping off of it while you are spraying. My rev limiter is set to 8600, and my nitrous shuts off at 8200. I normally cross the lights at 7800, so there is still room left. If you happen to blow the tires off at the launch, which I did many times, and you buzz the engine enough to hit the top limiter, like I have, with the nitrous shutting off at a lower RPM, which it did, it sure keeps your intake from becoming a launching pad for your carburetor.

A window switch takes all the guesswork out by not letting it turn on until a specific RPM, and shutting off at a specific RPM. My ignition box takes care of all that.
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Big Dave
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PostPosted: Thu Dec 28, 2006 8:04 pm    Post subject: Reply with quote

I tend to overlook that, thinking everybody has an ignition module that will pull timing out whenever your juiced, kills it before the rev limiter and prevents it below a preset RPM limit OR a MSD 7AL 3 or better box. I've had one for six years; bought it before they invented digital boxes, so if your looking at one go digital.

Wouldn't attempt it without it. By the way anyone ever think of running nitromethane? If your running alcohol, and you spray, you are in effect running nitromethane whether you know it or not. Same chemical reaction occurring in the combustion chamber. Pour in enough alky-Haul and spray it, and you too can do a John Force burn out.


Big Dave
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clay
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PostPosted: Thu Dec 28, 2006 8:05 pm    Post subject: Reply with quote

Usually I lowered my shift points slightly when spraying. Nitrous usually generates more torque gain than h.p. gain - example a 150 h.p. shot probably gives 200 ft. lb. gain. Lowering shifts slightly still lets you get the benefit and be a little easier on parts. Like Big Dave said, it really makes it feel like a larger motor. The only other reason is what pro60chevy mentioned about the rev limiter. Clay
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GrandSportC3
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PostPosted: Fri Dec 29, 2006 8:17 am    Post subject: Reply with quote

Big Dave wrote:
I tend to overlook that, thinking everybody has an ignition module that will pull timing out whenever your juiced, kills it before the rev limiter and prevents it below a preset RPM limit OR a MSD 7AL 3 or better box. I've had one for six years; bought it before they invented digital boxes, so if your looking at one go digital.

Wouldn't attempt it without it. By the way anyone ever think of running nitromethane? If your running alcohol, and you spray, you are in effect running nitromethane whether you know it or not. Same chemical reaction occurring in the combustion chamber. Pour in enough alky-Haul and spray it, and you too can do a John Force burn out.


Big Dave


I do have a retard system that will be activated when I'll use the juice.. I'll pull 3 or 4 degrees of timing with the 100 shot..
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GrandSportC3
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PostPosted: Fri Dec 29, 2006 8:19 am    Post subject: Reply with quote

clay wrote:
Usually I lowered my shift points slightly when spraying. Nitrous usually generates more torque gain than h.p. gain - example a 150 h.p. shot probably gives 200 ft. lb. gain. Lowering shifts slightly still lets you get the benefit and be a little easier on parts. Like Big Dave said, it really makes it feel like a larger motor. The only other reason is what pro60chevy mentioned about the rev limiter. Clay


I'll definetely watch out for the rev limiter.. I'll set it up to 7200 (from 7000) to be sure that I won't run into it...
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86GN
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PostPosted: Sun Dec 31, 2006 12:12 am    Post subject: Reply with quote

A lot of the torque deal has to do with the system being a constant flow deal. At 1000 or 10000 rpm the system is flowing the same amount. The difference is that at 1000 rpm there's more time for the cylinder to fill, so there'll be more nitrous and fuel to burn, creating HUGE amounts of cylinder pressure. That cylinder pressure is torque. This is why, typically, when running nitrous the car will be quicker short shifting as compared to running NA.
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GrandSportC3
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PostPosted: Thu Jan 04, 2007 2:13 pm    Post subject: Reply with quote

86GN wrote:
A lot of the torque deal has to do with the system being a constant flow deal. At 1000 or 10000 rpm the system is flowing the same amount. The difference is that at 1000 rpm there's more time for the cylinder to fill, so there'll be more nitrous and fuel to burn, creating HUGE amounts of cylinder pressure. That cylinder pressure is torque. This is why, typically, when running nitrous the car will be quicker short shifting as compared to running NA.


I'm actually planning on shifting 300 - 400 RPM earlier than without the nitrous!
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af2
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PostPosted: Thu Jan 04, 2007 7:08 pm    Post subject: Reply with quote

GrandSportC3 wrote:
86GN wrote:
A lot of the torque deal has to do with the system being a constant flow deal. At 1000 or 10000 rpm the system is flowing the same amount. The difference is that at 1000 rpm there's more time for the cylinder to fill, so there'll be more nitrous and fuel to burn, creating HUGE amounts of cylinder pressure. That cylinder pressure is torque. This is why, typically, when running nitrous the car will be quicker short shifting as compared to running NA.


I'm actually planning on shifting 300 - 400 RPM earlier than without the nitrous!



You are also limited with the MSD 6 you are running as far as limits! I am book savvy and not real world. From what I have read you have to anticipate and incorporate other safeties!
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af2
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PostPosted: Thu Jan 04, 2007 7:10 pm    Post subject: Reply with quote

Post twice! Waited 4 minutes. Oh well! Laughing
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GrandSportC3
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PostPosted: Thu Jan 04, 2007 8:18 pm    Post subject: Reply with quote

af2 wrote:
GrandSportC3 wrote:
86GN wrote:
A lot of the torque deal has to do with the system being a constant flow deal. At 1000 or 10000 rpm the system is flowing the same amount. The difference is that at 1000 rpm there's more time for the cylinder to fill, so there'll be more nitrous and fuel to burn, creating HUGE amounts of cylinder pressure. That cylinder pressure is torque. This is why, typically, when running nitrous the car will be quicker short shifting as compared to running NA.


I'm actually planning on shifting 300 - 400 RPM earlier than without the nitrous!



You are also limited with the MSD 6 you are running as far as limits! I am book savvy and not real world. From what I have read you have to anticipate and incorporate other safeties!


for my current setup, the 6AL is more than adequate.. Once I'll get my next setup, I'm pondering getting a 7AL...
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