Cams with overlap will make that reversion worse. That's up there in the rpm range too. When it has a dip on a stock engine it's not a good sign. My experience, tho not with these, has never been good with mufflers like that. Short 2in1s with it are even worse.
There may be exceptions but there's way better slip ons to take that chance imo.
​​​​​​Being a carbed bike makes dealing with reversion a lot harder.

 

What do you think is the main difference between these mufflers and a better set of slip ons? Smaller size or the conical shape?

 

These are too short and yes, the megaphone shape. I have never seen them NOT suck. They look dumb as fk too.

 

Aesthetics is always a matter of personal taste, I think they look quite cool.

I'm more interested in the technical aspects of exhaust design. I do understand that the volume of the muffler will impact the sound, you tend to get a deeper and fuller sound from bigger mufflers, baggers always sound wonderful with the grand dual mufflers.

When it comes to the length, I was under the impression that the most important is the total length of the pipe, it will impact wave harmonics and decide what rpm range reversion will cause issues. And from that point of view I think my pipes are a bit too short (around 40" is a classic rule of thumb I think), but really not much worse than any other 2-1 exhaust, except pipes like Thunderheader that might be slightly longer.

But as to the impact of the length and shape of the actual muffler bodies I really have no clue. A perforated inner tube tightly wrapped in fiberglass packing will have very little impact on flow, does the shape of the outer shell of the muffler really have a significant impact?

Thanks for your input, its much appreciated.

 

Entirely different engine so not 100% relevant to you but sharing for the hell of it. I remembered seeing these on GMR’s FB page. 114” M8 Softails with TTS 175 cams. Not much to dislike here.

How they will work on a smaller cube motor with 2 valve heads and more overlap, that I don’t know.

 

Thank you, Im not sure either how relevant it is, but still nice to see them perform well in one configuration

 

Muffler design on a motorcycle is restricted because they are out there for everyone to see. There has been much research on muffler design in the automotive racing community over the years. with shape placement in regards to exhaust port (length), and diameters. A correctly shaped expansion chamber canceles soundwaves without hindering total exhaust flow, but has to be sized for each engines total airflow at max rpm/ max load. On a motorcycle this would be an ugly muffler that you wouldn't want unless it could be hidden somewhere.

 

any one run these on 114 or larger M8'

what's the torque curve like ?

i like the look of them , remind me of old hurricanes dad had