Originally Posted by
Cat 1
It would just be nice to substitute the air pump for muffler pressure and compare both "in Air". I will try and fly both for comparison..
That REALLY would be educational. Especially comparing the "tunability" of the pump versus the "natural stability" of muffler pressure.
Originally Posted by
Cat 1
One thing I know is I can run a less restrictive Exhaust with the air pump - Best case with muffler pressure would require chambers like you run I think - I could not get the pressure my carb "likes" with the straight pipes unless I restricted the ends.
Unrestricting exhausts IMHO is not desirable. At least, NOT when that means "wider than standard". Restricted headers also are not desirable: Not enough volume and length. Ideally one wants the inertia in the exhaust tract to provide the backpressure, not the cross section. And for that you need volume and length.
I never have tested side by side to make sure, but I have the distinct impression engines run better with an exhaust "system" (a header, a muffler volume and a tailpipe). Not so much in absolute power, but more in "behaviour throughout the throttle range". Something to do with valve overlap and the inertia in the gas stream. Now that might be just me and my imagination (although some effects noticed with the Wankel seem to confirm that simply adding length to the exhaust system, regardless of "tuning that length" significantly improves that Wankel's performance), but at least my clubmates agree that those mufflers really do a nice job on the engine.
Mind you, the ones I used are the "baffled mufflers" as JustEngines from England sold them (I think they still do, by the way), but I am 100% sure that with your machining skills, you'll be able to turn out a set within a single afternoon, not even breaking a sweat...
What JustEngines did, was make two muffler halves, leaving the external diameter a bit wider than final dimension, TIG-weld the two halves together with the baffle inbetween, then turn down to final diameter, with that last cut removing all visible traces of the weld and making the mufflers appear as being made out of one solid piece of barstock.