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Old 30th March 2008, 12:17   #1
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Default Why aren't 4 x 4 exhaust layouts used?

I've usually seen 4 cylinder cars using 4x2x1 or 4x1 exhaust layouts. How does a 4x4 layout affect performance? Has any of the tuners tried this?

I couldn't find any articles on 4x4 headers on the net so there must be something seriously wrong with this design...but what???

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Old 30th March 2008, 12:28   #2
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Default 4x4 exhaust

I'm guessing that a 4x4 exhaust design would reduce the amount of back pressure (so to say, not sure of the exact term) at lower revs and would seriously reduce the drivability, except for the higher end of the rev band (>5000 rpm ) , a 4x2x1 would help solve that. I may be wrong on this one though....
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Old 30th March 2008, 12:55   #3
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A pipe system will be similar to having open exhaust[it'll be LOUD], there will be very less back pressure, when low end torque will be very low, and the area it will need to be routed will also increase.
The NHRA dragster have a system what you are asking, Have seen them ON ESPN2, They are loud, [CV8 engines with *exhaust pipes]....even on track only cars it's loud.
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Old 30th March 2008, 13:16   #4
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I'm guessing it has to do something with the exhaust pulses being used for cylinder/exhaust scavenging, rather than noise levels. Even F1 engines use a 4-1 layout for each side of the V8 (where sound isn't much of an issue).

Space, noise and weight might be 2ndry.

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Old 30th March 2008, 13:43   #5
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The negative pulse from one cylinder can't be used to scavenge the gases from the other cylinder. Less efficient.

Packaging?
Four header pipes, four cat cons, four mufflers.

The early multi cylinder motorcycles like the original CB750 had four independent pipes. And so did other bikes of it's time.
But later they went for a collector type design. And some bikes had their header pipes interconnected alternatively with each other.

The top fuel dragster's exhaust is supposedly designed that way because 1) it just needs to expel the gases with minimum restrictions 2) it's supposed to produce downforce.
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Old 30th March 2008, 14:00   #6
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Where would the oxygen sensor be placed - on which exhaust manifold? And then there's the issue of cost - 4 pipes and 4/2 mufflers will be more expensive than all-in-one.
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Old 30th March 2008, 14:03   #7
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Quote:
Originally Posted by theMAG View Post
Where would the oxygen sensor be placed - on which exhaust manifold? And then there's the issue of cost - 4 pipes and 4/2 mufflers will be more expensive than all-in-one.
O2 sensor can be placed in any one of the pipes. It's placed the same way in your car now.
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