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By splitting the pipes, you are decreasing the volume of air that has to go through a muffler. Since you now would have 2 mufflers "splitting" the total volume in half and sharing the load, this in effect causes LESS back pressure on the exhaust system and increases performance UP TO A POINT. Also a factor of this is how much restriction is built into the muffler (i.e. how much resistance is built into each of the 2 mufflers versus the 1 muffler). The system can also be designed with a crossover pipe to balance the back pressure on each of the individual exhaust pipes.
The deficiency of a dual exhaust system comes into play when you reach a point where there isn't enough back pressure to create a vacuum in the system to help exhaust gases escape the combustion chamber on the exhaust stroke. Yes we all know that the engine "pushes" the exhaust gases out of the combustion chamber, but a well designed exhaust system actually creates an initial vacuum to help with the initial and final draw of the gases when the exhaust valve opens and closes. This vacuum helps pull the gases away from the cylinder head so that the next cylinder that opens the exhaust gases is actually initially "sucked" or "pulled" out of the combustion chamber before the piston "pushes" the remaining gases out of the cylinder. I believe the proper term for this is scavenging.
Normally you would only see true dual exhaust (2 into 2) systems on larger displacement engines since they move larger amounts of air. Some larger V-6 high performance engines will use 2 into 1 into 2 systems to improve the flow and decrease back pressure while still maintaining a good initial vacuum. I can't ever recall seeing a factory 1 into 2 system on a small displacement engine. I've seen plenty of aftermarket systems (particularly on PT Cruisers) that are 1 into 2 systems.
So the bottome line is, a true dual exhaust system on a small displacement engine is more than likely overkill.
posted by 68.45.24...
, Wed, 21 May 2003 07:58:07
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