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Size Of Downpipe And Exaust

Old 03-10-2005, 07:19 PM
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I was thinking a 3" DP and either a 3 1/4 or 3 1/2 inch y-pipe to a pair of the new Racing Beat mufflers.



Does that sound about right for a FC with a mild port engine and a To4B, FMIC, etc..??

my thoughts were if I ever upgrade to a larger turbo the exaust would be set up already
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Old 03-10-2005, 08:14 PM
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is the turbine outlet 3"?



if so I'd just stick with that down to the Y, like your saying. I'm not sure what you mean about the 3 1/4" "y" Maybe if I saw the mufflers it'd make more sense.



I think the Idea is anytime you "Y" you want to step down in diameter to keep exhaust velocity up. My setup is 3" dp to borla xr1, and jr modified the apexi n1 Y (opened it up and added a couple wedges) to accept the 3" now, and it's not restrictive at all. So it goes from 3" to 2- 2 1/2" pipes to the n1 mufflers. Can't really say if it's helped or hurt because this is the only exhaust i've had on this turbo, but it sure sounds good.
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Old 03-10-2005, 08:30 PM
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turbo out is 3", so I guess a 3" DP, then a 3.5" pipe that splits into 2 3" pipes, then steps down to the RB mufflers that I believe are 2.5"



I can have 3" inlet put on the RB mufflers if I want as well,I want to keep the dual muffler layout of the FC along with the use of the RB mufflers



Kooks has developed thier own mufflers that are all stainless but I know they will be even louder then the XR1s I have on there now
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Old 03-11-2005, 09:24 PM
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The bigger the better; pressure guages don't lie.

Reducing restriction/backpressure is what you want.
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Old 03-12-2005, 03:51 PM
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I got a a 3 to 4 inch transition coming right off of the turbo to two 3 inch out the back. Going up to a 4 inch system made a big difference in just about everything turbo related. Power, boost threshold, lag, boost creep lol. I recomend going bigger after having a straight 3 inch system and going to 4 inch.
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Old 03-24-2005, 06:38 PM
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Below is my opinion. I base it upon the fact that most factory exhaust pipe diameters reduce as they get farther from the engine.



Hotter is bigger. Duh.



Big at the end is a sales tool either as to show a big pipe or to have a certain sound.



After right after the turbine, the need for a larger pipe than the turbine exit is diminished. The farther away from the heat, the smaller the pipe can be.



Larger than needed is more loud than it could have been.



I think a 3 to 4 is fine right after the turbine.



I think that two 3's to the mufflers is a lot more than is needed and much louder than it could have been.



My opinion is just that.



[quote name='Crusader_9x' date='Mar 12 2005, 04:50 PM']I got a a 3 to 4 inch transition coming right off of the turbo to two 3 inch out the back. Going up to a 4 inch system made a big difference in just about everything turbo related. Power, boost threshold, lag, boost creep lol. I recomend going bigger after having a straight 3 inch system and going to 4 inch.

[snapback]684875[/snapback]

[/quote]
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Old 03-24-2005, 08:07 PM
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I think opposite of Mike Hot gasses flow easy, cold gasses don't. The hotter the exhaust is the smaller it can be.



I think factory exhausts get smaller towards the tip to keep velocity up and heat in.



My thinking anyways.
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Old 03-24-2005, 08:30 PM
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Where are the engineering students when we need them?



I was told once by an engineering graduate, that a 3" pipe is good for about 550 hp.



If so, and you don't have twice that hp with two 3's, noise is the result.

Mike



[quote name='setzep' date='Mar 24 2005, 09:07 PM']I think opposite of Mike Hot gasses flow easy, cold gasses don't. The hotter the exhaust is the smaller it can be.



I think factory exhausts get smaller towards the tip to keep velocity up and heat in.



My thinking anyways.

[snapback]690540[/snapback]

[/quote]
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Old 03-25-2005, 06:32 PM
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I have read .025 in^2 of cross sectional area per hp recommended for rotaries in aircraft. I think 0.020 in^2 per hp is a little closer to ideal for a car given packaging constraints.



Now, keep in mind this is an ideal cross sectional area. It wil take a good bit more hp(flow) for a given pipe size to start to become restrictive in any measurable amount.
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Old 03-25-2005, 06:36 PM
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unless you know an excellent exhaust shop or can do it yourself, I have no seen that many well done exhaust systems in toronto area. If i were doing a custom exhaust, i would buy the turbo back racing beat system, sell the downpipe, and have that part custom made to fit your needs.
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