Megaphones
 

I was cleaning up my old car magazines on the weekend and I came accross my old RX7 Performance book by Jim Downing and Dave Emanuel and I was really interested in how they did the exhaust back then. They were really firm on the ID's of pipes and length of pipes, but what I thought was really interesting and something that I had forgotten, was the use of an exhaust extraction megaphone on the end of the exhaust pipe.

Anybody still use them and any reason why they have dropped out of favour? I can really understand the concept and how it works and it may be something to try on my setup, though they go from a 2"id to a 4" id. That looks like a 100% expansion rate. Seeing as my outlet pipe is 3", I would need to expand to a 6" pipe. Tuner city here I come, LOL.

Thoughts, idea's on megaphone exhausts?

Eric

My father used it years and years N/a Bridgeport application just loud as shit ...

purely conjecture on my part, but I would imagine noise restrictions at tracks have only gotten more strict (and will trend further in that direction for the future), and particularly with our cars, cars are too bloody loud with megaphones.

i don't really know, i haven't gotten that far yet. i'm thinking i'll have a short one, but i'm letting the engine decide what it wants

maybe once could get the benefit of a megaphone (I dont see or know or have verified there is one) and make a certain volume after the mephone, and then use a reverse con or bellmount to a muffler. much like a 2 stroke exhaust

So at the end of the day, do they create power or just noise?

I believe Racing Beat sells or used to sell megaphones...

I've only seen megaphones used after the collector, not on the tailpipe...

In the old Mazdaspeed build charts, they show a megaphone on their IMSA motor setup charts and even give the dimensions and how to build one. They are at the very end of the exhaust. I may try to build one and see what happens.

Eric

can you post that up?

lately, I've been kicking around the idea of playing with a megaphone ... but possibly placing it midstream - leading to an expansion chamber.

not sure if you prefer to build or not, but if you don't necessarily want to try building one, if you check out Burns Stainless, they have some. maybe see if they have what you're looking for.

should work fine, the long systems use the universe as the expansion chamber, but really its just because 90" headers on a 95" wheel base car do not leave much room for anything else :)

it's funny how the simplest metaphors can become a powerful moment of insight. you know, i never thought about the long systems that way.