I haven't seen Larry's exhaust, but assume it somewhat resembles mine, since he copied what I did (with my encouragement). ?The easiest exhaust to build is a simple log that runs down either side of the engine. ?The problem with that is the two cylinders on each side have consecutive exhaust strokes, so one cylinder is always pushing it's exhaust right into the pressure wave from the other cylinder. ?That kills the power. ?Unfortunately, that is what is usually supplied on most production 4 cylinder aircraft. ?That's why PowerFlow has such a successful business supplying aftermarket STC exhausts for 4 cylinder aircraft. ?
The ideal exhaust system would be a 2 into 1 cross over system, so the flow from one helps extract the other. ?You'll read that the Continentals don't have enough valve overlap to take advantage of a crossover exhaust system, but that simply is not true of the O-200 as the O-200 cam has a significantly longer duration than the other small Continental engines. ? Exhaust is all about flow, and getting the velocity of the exhaust flow right for your operating RPMs is what is going to make the engine perform. ?Bigger pipes are not necessarily the right answer either as too big of a pipe will slow down the exhaust flow making the cylinder work harder to push out the exhaust. ?I came up with an ideal length of 38" for the primary header pipe with an ideal ID of 1 3/8". ?Those numbers seemed to work pretty well for getting the exhaust out of the engine compartment and would be relatively simple to build as individual head pipes. ?Since I was welding this up to go on an already running engine, needed to fit it within the confines of my existing cowling and didn't have a jig to work with, I chose not to take on the task of trying to build a crossover 2 into 1 system. ?I went to the local cut rate muffler shop and bought 3 7' sticks of 1 1/2" OD mild steel exhaust pipe and had them put several random 90 and 45 degree bends into the pipes. ?Then I cut up the pipes and used the various bends and straight sections to tack together my exhaust pipes. ?As with building anything on an aircraft, everything is a compromise. ?I ended up with my pipes varying in length from 32 to 38 inches, which is less than ideal. ?However, there was no question that the new exhaust really gave the engine a significant boost in performance. -Jeff Scott Los Alamos, NM > ----- Original Message ----- > > : > >Why a 4 tube exhaust? > ++++++++++++++++++++++++++++++++++++++++++++ > > It lets the engine breathe a bit better and produce a bit more power > / higher RPM. If you could tune the pipes, even better. Tune, as in > match the length of the pipe to the length of the gas power > pulse. It helps extract more burnt gas from the cylinder and pull in > more air / fuel mixture. (more power) > > I had a two into one on each side on my 0-200. Easiest setup > possible but very poor for performance. > > Larry Flesner
