ORIGINAL: Barry Cazier
bodywerks...
I'm hoping, that maybe the RPM will pick up a bit. I'm running both engines very close to the proper lean out. I've heard you don't really have to run the gasser overly rich. So I'm peaked and backed off an 1/8 or maybe a little more.
I'm running the Slimline on the DA and the EVO pitts style on the EVO. The Slimline is still too loud I feel. The EVO muffler is nice and quiet. About 96 DBAs at 10'. I think that's what the AMA has for a noise limitation. I know our field is starting to monitor noise levels. They are trying to be proacitve and catch the restriction before it is mandated. Last year it was 92 DBA but they increased it to 96. The EVO passed, right on the number. I haven't measured the DA yet. But, I'm fearful it won't pass, even with the Slimline. I don't think DA should make an engine and muffler that doesn't meet the AMA standard. With a little good design work they could keep the power and go to quieter mufflers. I wonder if they ever heard of tuned muffers. ALA motorcycle industry. Of course I wouldn't want them to look at NASCAR who is an absolute disgrace in this area. I went to a race in Pheonix a few years ago. You couldn't even hear yourself think. Ruined the experience for me. And as stupid as this sounds, they use restrictor plates to slow the cars down yet allow them to go unmuffled. I hope with all my heart we never get any NASCAR nerds involved with our RC industry. It would surely ruin it. Noise will be the next hurdle, like it or not. I think DA ought to take that to heart as a leader in the RC engine industry and quiet their motors down. Of course I don't want them to lose power in the process, I want it both ways. The motorcycle industry has proved it can be done.
For now, I feel I must accept the 200 RPM loss for the sake of noise control. I am pretty pleased with the performance with both my gas engines but I'm worried I won't be able to fly the DA at my perferred field.
Thanks
Barry
Barry,
A HUGE part of noise is it the prop, not the exhaust. For what it's worth, I have stock mufflers on my BME 110 and a CF prop and it is almost too quiet for me, and that's even on asphault ground. In the air it might as well be electric. The point behind pitts-style mufflers is not to quiet the engine even more over a stock muffler, they are just to have a more scale appearance and to add weight.
Also, tuned mufflers pretty much won't help 2-strokes - they are an entirely different animal than any 4-stroke NASCAR or motorcyle engine. At the very best, they would be called cannisters - we already have them, and they may restrict less than stock mufflers and some have been known to improve RPM, but they are by no means considered a tuned muffler.
Also, you are right about gassers not needing to be run overly rich to break in. The richer oil mixture which is usually a more abrasive oil is what breaks in the engine. With that said, 1/8 turn might actually be too rich. I tune for max RPM and back it off by about 100-150 RPM, which is usually only about 1/16-turn.