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Thinking about exhausts..... Imagine a standard 4 cylinder set up with a cast iron manifold feeding into a twin downpipe which then joins into a single system. I'm wondering if the twin pipes continued for the length of the system (with a small silencer in each pipe) there would any advantage? My reasoning is that 2 X 1.5" Dia. pipes (for example) would give the same flow as a single 3" pipe but without the noise level. Or am I barking up the wrong tree?
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... the only injury I sustained was a bumped head when I let the seatbelt of without realizing the car was upside down and that's not really the car's fault.
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Exhaust ideaDeleted
@Deleted
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i can kinda see your piont but you would get a much better result in using a a free flowing tubular manifold with a twin out let ie (4into 2 into 1) use it till it get to the 2 pipes then join your system from there if the engine is a 2.0 then 1.5/8" would be a better size to use hope this is of some help
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Last Edit: Dec 9, 2004 19:22:11 GMT by Deleted
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Exhaust ideaBenzBoy
@benzboy
Club Retro Rides Member 7
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Hmm, with the two pipes coming straight off the iron manifold, there might be some problems with gas flow. For example: with a cast iron manifold you would have to have one of the downpipes beneath cylinders 1 and 2, and the other one beneath 3 and 4. However with the firing order of 1,3,4,2 the charge from cylinder 3 relies on a certain mount of "vacuum" being created by the gas escaping cylinder 1, and drawing the fresh fuel into cylinder 3. If the manifold effectively paired cylinders 1 and 2 up, and 3 and 4, you could lose some of this effect... Having said that I guess if the two pipes were close enough together it may not make as much difference, although the exhaust might sound a bit funny! I'm kind of half asleep at the minute (staying up to bid on US eBay! ) so maybe I've got all that round my neck... will have to look again tomorrow when I'm more awake! ;D
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Dec 10, 2004 18:58:45 GMT
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I'm not very clued up on exhaust manifolds, but am I right in saying that a 4 into 1 design is only really good for high top end power and torque at the sacrifice of torque at lower revs, while a 4-2-1 is better for uses other than drag racing etc becuause it allows a good even spread of the torque so taht the car can pull well low and intermediate revs as well, or am I getting mixed up and talking sh*t? ;D ;D
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"He's not the messiah, he's a very naughty boy!"
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Exhaust ideaBenzBoy
@benzboy
Club Retro Rides Member 7
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Dec 10, 2004 19:16:39 GMT
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I think that's right Rev#9, but I'd think it depends on the engine / application. Skoda run two downpipes from a cast manifold on the Estelle and Rapid. The two pipes just go straight into a single silencer, so it must work! ;D I didn't get the part from US eBay . After staying up 'til 3am! Oh well...
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Last Edit: Dec 10, 2004 19:17:23 GMT by BenzBoy
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Dec 10, 2004 20:12:54 GMT
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Hard luck, now you can get some sleep though! ;D ;D Another thing I'm not clued up on is how the lengths of downpipes affect power and torque, wasn't there a feature in Retro Cars or PPC that talked about that a few months back? Not really something I've ever thought about as on an Imp there isn't a lot of room for experimenting with exhaust lengths, it has to be short as the exhaust starts not far from where it ends.
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"He's not the messiah, he's a very naughty boy!"
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Dec 10, 2004 21:26:14 GMT
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only example i understand is the LCB on a mini which works as Benzboy describes. also its thought that a side exit zorst delivers slightly more power than a centre exit, the side exit being a little bit longer, although i'm not sure if airflow is different at this point at the back end. oh i'm confusing myself now...IGMC
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Exhaust ideaBenzBoy
@benzboy
Club Retro Rides Member 7
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Dec 10, 2004 23:14:10 GMT
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I read that article too - the basic jist of it is that the point at which you siamese the pipes depends on the engine and is a very fine art. I've always thought that exhausts exiting at the rear of a car are better because you have the depression created by the aerodynamics of the car as it goes along. I don't know how much effect this has though - I mean, on an F1 car it'd be vitally important, but on other cars I don't know if the difference would be at all noticable. Mercedes have a side exit on the SLR so I suppose it can't make that much difference
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