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Old 01-18-2005, 09:09 PM   #1
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Default exhaust cutout

does anybody use these... are they a good idea or are they useless
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Old 01-18-2005, 09:10 PM   #2
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It might kill backpressure if you decide to race with the cutout open. But it sure would be fun to blast people on the streets.
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Old 01-19-2005, 01:44 AM   #3
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I am not sure what you are speaking of, but if they are the same as "dump tubes," then they will give you more than you think....(and not just noise). Your basic dump tube is a Y-shaped 1-into-2 adapter that is either solenoid operated, or just a flange (plate) held on by wing nuts. They are usually located ahead of the cat for the least amount of backpressure. When you get to the track, open the tube for max performance.

The L67 is a good candidate for one. They work really well on FI cars (ask any serious GN owner). Also, backpressure isn't as much of an issue with a bigger motor like the 3800. There is enough displacement to keep the combustion chamber full at low RPM'* (again, something that L67'* don't have to worry about). USUALLY (and I say this sparingly) the only time you have to worry about having enough backpressure is in small displacement four-bangers (especially ones with fart cannons). You may notice a difference at low RPM'*, but will notice that the engine breathes much better as the tach swings to the right.
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Old 01-19-2005, 02:28 AM   #4
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Backpressure isn't good on any engine, at all. Going with too large an exhaust pipe lets the exhaust gases expand and cool so they don't go as fast.

You will run faster with it in the 1/4, you may lose some low end torque, but 3800'* have plenty IMO, and need more ontop (where you are going WOT). If you put it right before the muffler you're not doing as much as if say at the front of the pipe. Turbo'* do better then blowers with a huge exhaust because it helps keep the turbo spooling easier.
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Old 01-19-2005, 03:23 AM   #5
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Quote:
Originally Posted by BonneMeMN
Backpressure isn't good on any engine, at all. Going with too large an exhaust pipe lets the exhaust gases expand and cool so they don't go as fast.
look at the exhaust on this http://www.goarmy.com/racing/nhra_top_fuel.jsp
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Old 01-19-2005, 10:41 AM   #6
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Quote:
Originally Posted by dblack1
That'* alittle different. That thing is running boost levels that would grenade a 3800. Not to mention that on top fuel dragsters, the blower takes over 1000hp just to turn it!

I would say a cutout would only be good for track runs, but there are some mighty fast B'villes that run stock or slightly modified exhausts with cat & mufflers. One that comes to mind is Rogue with a [email protected] and, as far as exhaust goes, he only has an aftermarket cat.
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Old 01-19-2005, 12:06 PM   #7
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actually the army top fuel dragster uses nitro instead of a blower.... if our exhaust is too open then we need to install a smaller sc pulley
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Old 01-19-2005, 12:32 PM   #8
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Quote:
Originally Posted by dblack1
actually the army top fuel dragster uses nitro instead of a blower.... if our exhaust is too open then we need to install a smaller sc pulley
Nitro for fuel, blower for boost. See the pulley right behind the drivers helmet... That'* the */C pulley.
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Old 01-19-2005, 01:33 PM   #9
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yea i guess that one does have a blower on it... and nitro isnt fuel from what i understand about it, when it burns it releases oxygen therefore rasing compression
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Old 01-19-2005, 01:38 PM   #10
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Top fuel cars don't burn nitrous oxide, if that'* what you're talking about. They use nitromethane (more specifically, a nitromethane blend) for fuel. Every Top Fuel and Funny Car on the circuit has a blower. They wouldn't even come close to winning without it. You might be able to visit some other sites to check out the specifics, because I really don't know all that much about it. I know the History Channel had an awesome Modern Marvels episode about drag racing. They rerun it every now and then, so definitely look for it if you get the History Channel.
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