torpedox

wanting to build a top fuel style Drag boat. I have an older BH Hanson G23 race engine, nearly new but 20 years old. I want to include a dummy Hemi engine, and hate that the tuned pipe is going to stick out the back. and using a standard muffler would kill the performance of the engine. I've been thinking that if the pipe was tightly curved and tucked under itself, like a dog with its tail between its legs, then I could even "tap" off the sides of the pipe to make functional "zoomie" style exhaust pipes coming out of the dummy engine. If I'm correct in my thinking, then it doesn't really matter where I "exhaust" the gasses as long as the reflective convergent cone is at the correct distance from the exhaust port. but how LITTLE radius can you go in a bend without it "becoming" the convergent surface? Hopefully I explained this good enough. if needed I will sketch what I'm thinking and add it.
Thanks!

av8tor1977

My Feedback: (6)

You are correct in assuming that the convergent cone is important, however, what is called the "bleed pipe", which we know as the exit pipe is also critical. It's i.d. and length both are part of a tuned pipes calculated proper proportions. Get it too small or too long, and you can toast the engine.

That is a very popular engine. You might look into offerings for helicopter, r/c car, and full size scooter tuned pipes and come up with something you can work with. Try Daves Discount Motors for the scooter offerings.

AV8TOR

earlwb

I would like to think that the turns would have some effect on the exhaust gasses, but maybe it doesn't really have much if any effect. In looking at some of the engine tuned exhaust systems with complicated turns and twists the turns don't seem to affect the engines much, or they wouldn't be doing it. I think that the length, entry cone and exit convergent cone as well as the stinger and its length are the main critical components of a tuned pipe setup.

av8tor1977

My Feedback: (6)

That is correct. If the dimensions remain true and proper, a tuned pipe can be turned and twisted all over the place with no ill effects. It does seem strange, but it's true. It's not about "flow" per se with a tuned pipe, it's all about sonic waves that aren't affected by turns ironically.

AV8TOR

aspeed

I think the first couple of inches from the piston are critical, and after that, you could go as tight as you have the capability of making. K&B made a tuned muffler/box which was CNC milled in a zig zag fashion for the whole length. Granted, it had no converging cone like a real pipe, but it did increase performance. It was the 100 Aero rear exhaust. Kind of an interesting design which doubled as a motor mount. It looks like it is still available.