One thing point that I don't think anybody has mentioned here is that a "tuned" exhaust system is very dependant on the rest of the induction system, the intake side,(Inserted by George: Oh, reaaally...
gahorn wrote:"You never answered my question if you thing a tuned exhaust works in any installation." A'contrere, my dear Bruce. I did indeed remark/imply how individually tuned exhausts are beneficial when mated to tuned intakes....gahorn
most importantly the camshaft profile, valve lift, duration, and overlap.
Unless these variables can be tailored to suit, the exhaust side of the engine has very little effect on performance. Especially in the case of our aircraft motors which are detuned to trundle along at about 2500 rpm for thousands of hours.
There's plenty more power to be had out of our 300 cubic inch six bangers, but not at 2400 rpm, not without some sort of forced induction, which in turn would probably lead to excessive heat problems. Heck they got another 30 or so ponies out of these motors just by spinning them faster and called it the GO300.
If the valve timing were changed, along with cam lobe profiles that used a significant amount of overlap then a properly "tuned" exhaust system would indeed result in more power. There is a very real science to this, but getting more power out of a motor this way involves spinning it faster, and gives up longevity for performance.
I know that a tuned exhaust
CAN help milk more power from a gas motor. However, unless it replaces a system that is just grossly inefficiant it really won't make much difference, if any. The stock exhaust on our C145 and O300 motors is actually a very efficient looking setup for the kind of rpms we spin them at.
Good discussion, enjoyed it.