I had to do some digging, but I found my original post on the subject of those dual exhaust things sold on ebay, and it was on another forum, but here's what I wrote:
Ok, I used to fly alot, and most of my planes had pipes. I wondered how they worked, so I did some reasearch on the subject. I can't find my book, but I'm pretty sure it was Clarence Lee's nitro engine book put out by RCM. This guy has been into nitro engines for ever and knows his stuff about them.
Anyway, the reason they're called tuned pipes is that (on aircraft) you have to tune them to the engine. This involves putting the thing on, taching the highend, and cutting off about 1/4 inch from the header side of the pipe and putting it back on. This will result in an increase in performance, up to a point. You keep trimming off the header side until you see a drop in RPM and you stop. The system is now tuned. Since planes are basically long, pipes and their headers have all the room they need to take. Nitro cars don't, so I guess the headers are the length they need to be and the pipe geometry is varied to get the proper tuning.
Take a look at an aircraft pipe, and look at a car pipe. Both are essentially a long cone joined to a short cone. It's not gas flow that matters, it's the shockwave. The shockwave slows down as it enters the pipe (due to an increase in the diameter of the cone), then it gets reflected by the short cone and heads back toward the header. As the diameter decreases, the velocity of the shockwave increases and causes a ramming effect that is greater than the exhaust/fuel air mix comming the other way. This shoves the FA mix and a bit of exhaust to be shove back in and increases the compression ratio, and thus increases HP.
Now to the point. The plumbers pipe dreams are complete BS because there is no tuning or thought to the physics of exhaust systems, even the one with the chamber. That POS should be used only to capture spent oil in case someone wants to use it later to mix their own *beep*. Also, those "pipes" will be ear shatteringly loud. Loud is cool, but ice picks in my ears are not (ever blow a header gasket and run for a while?).
Someone on this thread made mention of the "home depot" cost of the parts for one of these POS's, probably around $10. The roll bar I welded cost about that for my savage. I might try making one of these wonder pipes and see what it really does, probably not much but WTF. Another stupid mod I tried was a silencer for the savage. Worked really well, but screwed up the tuning. Pix comming soon.
yadda yadda whatever, thanks for reading.
Whitt.
here's the link to the thread that this came from incase you want to get it in context.
http://forums.rcinfo.co.uk/viewtopi...order=asc&highlight=savage+tuned+pipe&start=0
hope this helps.
