FWIW, this response doesn't sound like you know what you're talking about. Even if it was true that somehow you maintained the same "back pressure" (your choice of words), that would not ensure the same flow rate through a different sized opening. Pressure = force/area; the mufflers you are selling are most certainly not the same volume as the ones they replaced.

Having been doing EFI performance stuff casually for the last 18 years, I think a lot of the people who think that there needs to be some massive change to their tuning maps from exhaust or air filter changes are wrong, if for no other reason than that engineers are not foolish enough to design the fuel trims so narrow that a dirty air filter is outside of the adjustments available. In the American spirit of "optimizing" everything, I can understand the urge to edit, but I remain skeptical that any exhaust system, whether stepped drag pipes or your fancy electronic adjustable exhaust, genuinely requires a retune, but not because they aren't different as you suggest, but rather, because whatever differences are there are easily accounted for with the fuel trim ranges already built into the efi system.

I think your fancy electronic exhaust system is an interesting idea in a laboratory but I would not be installing it on my motorcycle because adding sophistication to an air cooled v twin motorcycle violates my principles when it comes to motorcycling, which is that motorcycles should be as simple as is practical. If I rode a BMW or a Ducati I may view things differently, but I don't.

 

OP -

I just got my 21 Heritage back from my builder / tuner for Stage II upgrade. I went with S&S Grand National slip on mufflers after reading a lot of reviews.

I fired the bike yesterday and it sounds perfect - like an old time Softail. I can highly recommend S&S Grand National. Pipe finish is top notch quality too.

I was just like you when I bought my 21 new - I fired it up and thought "this isn't a Harley". Lots of reading found over-regulating the emissions (exhaust and noise) was what forced them to over-civilize. I think they went too far, at least with sound. Their sound target is a "not-to-exceed" dBa pressure threshold at a specified distance under ANY engine operating condition. The bike might sound reasonable under wide open throttle from stop, but then it is whisper-quiet the rest of the time. Not acceptable to me.

As for exhaust emissions, I stayed with cats just because I remember the old days when engines stunk, and I probably breathed in too much of that **** over a lifetime. And it still sounds great.

Hope this helps.

 

Thanks for the info. I purchased and installd a set of American Custom pipes. They sound really great under throttle but otherwise are super quiet - maybe a little too quiet! I like them but wouldn't be bothered by even a little more noise actually. I do some longer rides and don't want too much volume to make the exhaust note annoying, just audible would be fine with me. I may continue the exhaust saga in the summer and experiment again!

 

I always ride with ear plugs in. So what I can hear from the exhaust is generally limited. This is exacerbated in the winter because I snap the ear muffs onto my half helmet - resulting in things getting even quieter. However, I was out yesterday and thought I was hear something weird on the bike. So, when I pulled in to get fuel, I took my ear plugs out and rode for a little bit without my ear plugs in. Good news... I heard nothing unusual going on with ear plugs out. Bonus, I got a good listen of the ACE mufflers. They indeed sound deeper and more pronounced than stock when running down the road/cruising. There is certainly a difference when rolling on the throttle. Overall I was quite pleased with them. I thought they were just about perfect for the Heritage.

 

You wear ear plugs for wind noise?

 

That is the biggest reason to wear ear plugs.
Wind Noise is vastly more damaging to your ears than a loud exhaust system. Most exhaust systems are making sound pulses behind you, especially when you're moving. The amount of energy that reaches your ears from the exhaust is decrease in intensity in the rider's seat than where you hear it from the side or behind. However the faster you ride, the more intense and unavoidable sound hitting your ears/head/helmet is.
At 65mph its equivalent to 103db, 110 at 100mph. Unprotected this will damage your hearing over time.
PLUS ontop of that, wind noise is annoying. You want to hear the exhaust, engine, and maybe even the sounds around you on the bike as well. Wind Noise makes it harder to hear these things. But Earplugs reduce the impact of wind noise significantly.
So you can hear exclusively the exhaust, and world around you. Wind Noise is irritating.
MusicSafe earplugs are great for riding a motorcycle.

 

Wow - I did not know that. Thank you.

I wear a modular full face helmet with neck seal and shell vents, but wind noise is still present.

Is "MusicSafe" a brand? Otherwise I have 3M shop ear plugs.

So much stuff I didn't know about biking. This is a great site.

 

Music Safe is a product line, Alpine is the Company.
I had a pair of these for a year before I lost them somewhere.
They were fantastic. I have a pair of MotoSafe versions and dont bother with those, they're not as good and they're super annoying to put in your ears properly.
I also use standard 10~20$ music wired earbuds when I need navigation with my phone. And I use the biggest ear tips that will fit and seal into my ears. I did a lot of testing and the largest ones you can fit into your ears will dampen the most noise.

 

Yes. Absolutely. @FranBunnyFFXII pretty much explains why.

 

Yes, you are correct. There is a difference in back pressure with the valve open and closed. The O2 sensors in the header compensate for that change and distribute fuel accordingly. There is a lot of technology inside all of our exhaust systems backed with 25 years of research and experience.
If you would like to learn more, please visit this link. https://jekillandhyde.com/us/how-it-works