Thunderheaders work just fine on M8's. I've tested them on more than a few but they are just to loud for my liking. If I were trying to do a dyno shoot out setup I would most likely be running one as they perform right at the top of the bunch. I guess I'm just getting too old to like that noise level when going for a relaxing ride.

 

Steve, thank you. Took me 6 weeks to get my pipe and I'm probably bias but it's by far the best sounding M8 I've run across. I ride with cotton in my ears, always have, old school.

 

I'm not 100% clear what i'm looking at. What is the size of the core and is it stepped? As far as the shields the profile & taper is different on the inlet side of our mufflers than the OEM mufflers so the shields do not clamp on properly, it may be possible with some modification however we have not tried that.

 

If you are running the stock cam the DNT baffles may be acceptable, however I would expect there would be low RPM gains with an insert of sorts.

 

I've heard this before, and I think I understand what you're saying. For me to compare apple to apples I need to (and I have in some cases) built a matrix of tabulated data to compare the data points of Hp/Tq at a given RPM then try to compare those numbers with what I see, hear and feel riding my current build for example if I roll on the throttle at 2000 RPM at a given gear selection and wheel speed and it bogs, I would expect the motor to be happier with bigger numbers in that rpm range in the same riding conditions. It's just more work to compare the data points. More about the data points an less about the shape of the curve!
Am I missing something?

 

This may sound stupid, but I don't care what a dyno sheet say's, if i twist the throttle and the bike immediately stands up, I'm happy with what I got.

 

That is a pic looking into my muffler from the end cap. This is magnaflows description....

The 4" Knockout with its stepped perforated core produce unmatched deep, throaty, powerful sound quality and is the ideal choice for tuned or stock engines.

 

Excellent examples of what the large core mufflers do to a torque curve once a cam with some overlap is added.

I see this all too often, a guy wants to add a cam, then doesn't understand why I suggest changing out his mufflers.

I like the Fullsac 2" cores, but that's a hassle, as to do them right and not cut the end of the can off, they have to be shipped.

The FM Outlaw mufflers with the inserts staying intact are my go to off the shelf muffler on anything using a 2-1-2 exhaust.

Inexpensive and effective.

 

Don't get me wrong they sound great for a hotrod, but a nice relaxing ride up the coast and into the canyons versus out bar hopping has me wanting something a little more quite at my age (64). The last TH I had, I used those foam ear plugs but after loosing one on several different rides over the years, cotton was the old stand by. I've been doing EFI development and tuning longer than most in this industry and when we were hired by HD factory to do EFI development and tuning for them back in ~early 1995 seems like just yesterday. Good parts will perform across the board when installed by many different shops. Look around at various installs by more than one shop to find what the average really is, would be the best advise I can give to people.

 

The only thing your missing is the understanding on how the dyno is run, can and will change the results shown on the graph. By looking for the real data at a given point and comparing that from chart to chart many times will open peoples eyes. If you preload the dyno to hold the engine at a fixed set point then release the dyno load for the run, changes the starting RPM area. This is due to the stored energy in the dyno effecting the shown output. Only problem with doing it that way is, it's not what you get in real life from the bike when you ride it. So there are plenty of ways that dyno charts can be very misleading and its just why I recommend that you look for several charts to compare to, from several different shops. This will give you a better average to expect what your bike will really perform like.