There is an episode of Engine. Asters where they run though this exercise. There are a lot of variables to figure on and the best way to do this is dyno the engine while trying different lengths of header collector extensions. That’s expensive!
What the show concluded I’d have to research.
Below are pictures of what the rest of the exhaust should look like. While YOU can not duplicate this because it is on a. Or eggs and your car doesn’t have the real estate available to duplicate, but is shown, you’ll just create a pressure wave cancellation box which simulates an open tube exiting the ex exhaust to the atmosphere. Like what you see on engine Masters, just an open exhaust.
Pressure wave cancellation box shouldn’t number at the minimum the same number of cubic inches the engine is in its size. So an example, if you have a three 60 in.³ motor, each cancellation box should be at least 360 in.³.
After that, the pipe exiting the pressure wave cancellation box can be reduced in size though I don’t suggest it if possible. But it should go into either your glass packs or your mufflers that flow 2.2 in.³ of air per horsepower being made.
This means, each muffler on a 400 hp engine should flow at least 400 CFM. That is a tall order, I know. But a reduction in CFM could very well limit the maximum amount of upper RPM horsepower to be made.
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