Rev Limiter
Thread Starter
Team Owner
Joined: Aug 2000
Posts: 24,099
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From: Spring Texas
Rev Limiter
Is the rev limiter done by fuel cut off or by coil pack cut off? I think the coil pack cut off would be quicker than fuel cut off. My vote is for coil pack cut off.
Melting Slicks
Joined: Jul 2001
Posts: 2,188
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From: not speeding just flying low
Re: Rev Limiter (Godspeed)
Fuel cutoff, that's why it can be so damanging on nitrous.
Thanks
[Modified by SAXN8R, 6:44 PM 1/5/2003]
Thread Starter
Team Owner
Joined: Aug 2000
Posts: 24,099
Likes: 1,327
From: Spring Texas
Re: Rev Limiter (SAXN8R)
I was told it was coil pack shutdown last night because the fuel cutoff would be too slow. After all, the fuel runs at 40-50psi and would take a relatively long time to bleed down. Plus, electrical shutdown of the coil packs would be much quicker from the PCM.
Drifting
Joined: Mar 2001
Posts: 1,270
Likes: 0
From: Rockford IL
Re: Rev Limiter (SAXN8R)
Fuel cutoff, that's why it can be so damanging on nitrous.
I knew it was fuel cutoff, but explain how it can be damaging on nitrous? If there is no fuel to burn or detonate, then how can there be a problem. I am sure you know more than I do on this subject, but I just want to learn more.
[Modified by SAXN8R, 6:44 PM 1/5/2003]
I knew it was fuel cutoff, but explain how it can be damaging on nitrous? If there is no fuel to burn or detonate, then how can there be a problem. I am sure you know more than I do on this subject, but I just want to learn more.
[Modified by SAXN8R, 6:44 PM 1/5/2003]
Thats why a window switch is important, you can set it to shut off your nitrous before you hit the rev-limiter.
A lot of guys do damage by not shutting off the traction control too. If you spray it with T/C on, it spins the tires so fast that T/C kicks in, shuts off the fuel, but you are still spraying nitrous into the motor. Not a good combo!
:nono:
Melting Slicks
Joined: Jul 2001
Posts: 2,188
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From: not speeding just flying low
Re: Rev Limiter (kwik8racr)
Okay,
Thanks for the explaination, but I am still confused. Does nitrous burn on it's own? I thought that nitrous wasn't flamable by itself. I must be stupid or somthing, because I don't understand if there is no fuel for combustion, how can you have detonation? Thanks again for trying to make the explaination idiot proof!
CP, the fuel is cutoff at the injectors. There is still fuel preassure, but the injectors stop spraying fuel, so there is no fuel going to the cylinders immediatly at fuel cut-off. This instantly will shut down the engine.
Thanks for the explaination, but I am still confused. Does nitrous burn on it's own? I thought that nitrous wasn't flamable by itself. I must be stupid or somthing, because I don't understand if there is no fuel for combustion, how can you have detonation? Thanks again for trying to make the explaination idiot proof!
CP, the fuel is cutoff at the injectors. There is still fuel preassure, but the injectors stop spraying fuel, so there is no fuel going to the cylinders immediatly at fuel cut-off. This instantly will shut down the engine.
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Melting Slicks
Joined: Jul 2001
Posts: 2,188
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From: not speeding just flying low
Re: Rev Limiter (CP)
OK. Got it. It's not shutting down the fuel pump. I thought they just interrupted the signal to the coil packs.
Le Mans Master
Joined: Jan 2001
Posts: 6,444
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From: Maryville TN
St. Jude Donor '06-13,'16-'17, '19
Re: Rev Limiter (SAXN8R)
CP, the fuel is cutoff at the injectors. There is still fuel preassure, but the injectors stop spraying fuel, so there is no fuel going to the cylinders immediatly at fuel cut-off. This instantly will shut down the engine.
Tom
Drifting
Joined: Aug 2002
Posts: 1,317
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From: Lancaster CA
Re: Rev Limiter (TCW)
CP, the fuel is cutoff at the injectors. There is still fuel preassure, but the injectors stop spraying fuel, so there is no fuel going to the cylinders immediatly at fuel cut-off. This instantly will shut down the engine.
Right on! The ECM simply quits firing the injectors. Also, the command to quit firing the injectors happens about 6020 (LS1) rpms but the tach will be at 5800 rpms cause the tach lags the actual rpm.
Tom
Right on! The ECM simply quits firing the injectors. Also, the command to quit firing the injectors happens about 6020 (LS1) rpms but the tach will be at 5800 rpms cause the tach lags the actual rpm.
Tom
:cheers:
Race Director
Joined: Aug 1999
Posts: 15,299
Likes: 33
From: Houston Texas
Re: Rev Limiter (SAXN8R)
Okay,
Thanks for the explaination, but I am still confused. Does nitrous burn on it's own? I thought that nitrous wasn't flamable by itself. I must be stupid or somthing, because I don't understand if there is no fuel for combustion, how can you have detonation? Thanks again for trying to make the explaination idiot proof!
CP, the fuel is cutoff at the injectors. There is still fuel preassure, but the injectors stop spraying fuel, so there is no fuel going to the cylinders immediatly at fuel cut-off. This instantly will shut down the engine.
Thanks for the explaination, but I am still confused. Does nitrous burn on it's own? I thought that nitrous wasn't flamable by itself. I must be stupid or somthing, because I don't understand if there is no fuel for combustion, how can you have detonation? Thanks again for trying to make the explaination idiot proof!
CP, the fuel is cutoff at the injectors. There is still fuel preassure, but the injectors stop spraying fuel, so there is no fuel going to the cylinders immediatly at fuel cut-off. This instantly will shut down the engine.
Here's my stab at it. Other members feel free to correct me. N20 release 2 oxygen atoms, so even without fuel under the pressure and heat, the 02 atoms are still going to burn. Also, wouldn't the spark plug still be firing?
Safety Car
Joined: Oct 2001
Posts: 3,504
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From: Insert Wittty Comment here
Re: Rev Limiter (rschiltz)
The air we breathe is about 12% oxygen. Nitrous is 2 parts Nitrogen which makes up 80% of our atmosphere, and 1 part oxygen. Hence you get 33% oxygen vs 12% in the same ammount of space (your cylinder). Well, all that oxygen needs fuel to combine with. No fuel mean you go lean...
If you run a motor lean what you get is a rapid rise in chamber heat. All that oxygen acts just like the oxygen enrichment on a blowtorch it simply blows a hole through the piston just like a torch...
One thing, lean engines make more power. In racing lean is mean... But lean is also dangerous. You have to be on top of your game or dead holes is the result....
If you run a motor lean what you get is a rapid rise in chamber heat. All that oxygen acts just like the oxygen enrichment on a blowtorch it simply blows a hole through the piston just like a torch...
One thing, lean engines make more power. In racing lean is mean... But lean is also dangerous. You have to be on top of your game or dead holes is the result....