May well have been asked or discussed previously, but why are the inside diameter of my mufflers different?? The rear cylinder muffler has a bigger inside diameter than the front cylinder... and why is the "active exhaust" butterfly only on the rear cylinder header pipe???... and are these 2 things connected, apart from literally???? I'm talking about a 2011 Heritage Softail, thanks in advance.

Ok, but by looking at the system, with the active exhaust butterfly closed all or most of the exhaust gas will go through the smaller inside diameter muffler..... that does not make sense to a "pre EFI" mechanic like me???

Is there a real benefit in the "balance pipe" between the 2 exhausts? I had the whole system off today and there is so much shit hanging off the exhaust that I could throw a lot of it away and not worry about putting myself on a diet for a while...

The balance pipe is there to up the low end torque.

Exhaust scavenging the "official" reasoning. All market bikes have this from the factory. It's a good thing !

We here in Oz get the Euro 4 spec exhausts. In town at low speed the bike runs as a restricted 2:1. Runs shit but passes European noise regs.

As soon as you fit any aftermarket muffler set they are then both the same diameter outflow. Much better.

Stock downpipes, freeflow mufflers, exhaust valve permanently open and you're all good to go.

In my experience ( which is LOTS !) the balance pipe is a good thing . I ALWAYS retain it on my own bikes , and reccomend it to others.

Bikes that run "True Duals" I find harder to EFI tune . That is bikes with 2 completely seperate downpipes, one for each cylinder.

Some V&H complete systems have a "Power Chamber" ( their term !) which is in effect a 2:1:2 or a "balance pipe".

True dual V&H pipe systems are the hardest to stop the decel popping ( "backfiring" if you like )

Even after 3 hours of Dyno time Frasers will not guarantee to totally negate the decel popping !!

In terms of "best bang for the buck" stock HD factory downpipes with tapered freeflow mufflers are the easiest to "tune" for and give the best return performance wise for the least dollars spent. I can tune the bikes to have no "decel pop" at all with tapered mufflers.

2:1 systems are noted for power output , but most are FUGLY as, and most all are too noisy for the fuzz.

Bizarrely I use "touring" Calibrations ( AKA MAPS) for 2:1 bikes as the touring factory stock exhaust is in effect a 2:1:2 system.

Got that tip from the Yank forum YEARS ago , before this forum existed !!

Thanks Retro, I am currently running a stock system with the active exhaust disabled and dare I say the "welsh plugs" knocked out of the stock tapered mufflers. Yes I know that the cat no longer works particularly well..... I am going to stick with this system, just modify it a little more and as soon as a TTS is available for my model, I'll be jumping on that bandwagon. Thanks again for your comments.
Cheers,

Stock "Aussie" mufflers modded is still restrictive

Stock yank spec mufflers can be modded and quite well too ( no cat y'see ! ) Buy them off US ebay no worries

Khrome werks look the "most stock" if that's what you like, S&S have a big embossed logo that the fuzz spot right away

Rollies in Qld used to stock the Khrome Werks, maybe still do , or get them ex-US , ebay or direct from Khrome Werks

Check out the Suppertrapp internal disc mufflers for your heritage. There adjustable for torque or HP with a very deep exhaust note. If the cops put a EPA noise defect on the bike its easy to remove a few discs to get it back under 82 decibel compliance. There not loud and don't attract unwanted attention. I had a set on my old 88 cube 06 dyna and she was putting out 76 HP with 74 torque.