Mulling over the idea of a diy 2-1 exhaust for my '07 1200L. I have been studying designs until my eyes bleed and have some questions for those that might know.

I would ASSUME that equal length pipes prior to the 2-1 collector is ideal, but am wondering how much of a difference. As many of you know the rear pipe always seems to be wrapped around the engine casing and RIGHT BESIDE YOUR LEG.
Wanting to avoid this as much as possible, it would be nice to gently blend the rear pipe into the collector without going forward first, but adding as much length as possible without interfering with my mid controls or burning my boot.

So anyone have any idea how much this shorter rear pipe would hurt performance?

Also for donor mufflers, are dyna mufflers any larger than sportsters, like inlet pipe size, body of muffler, etc?

Yes there are dozens of ready mades out there, but for huge fees, that I am not yet ready to pay. I can do the welding myself.

 

Your assumption is perfectly right, just consider the odd looking Buell pipes. They are so effective that Buells have much wilder cams and higher CR, giving much greater performance. As for making your own system, I will simply observe that IMHO making systems is a black art! Something like a SuperTrapp 2-into-1 will work wonders for your bike. Yes, I have one on my ole Glide and it is transformed.

 

Lol I see that supertrapp on there, now that you mention it. I am still considering it, partly for savings, partly for the challenge. In all likelyhood it will be more conventional in design though. I suspected the "equal length headers" applied here just like it did in hot rods of my youth.

 

Very true about equal lengths, although the Canam racing cars way back, which used big V-8s for track racing, played around with unequal length inlet trumpets, possibly pipes as well, to give a wider torque band. There is no doubt a lot of science in such things, but I suspect a fair of bit of the dark arts too!

On a more serious note there were several reasons I chose a Supertrapp for my old Glide, below, but I got benefits I didn't expect. Low/mid range torque was significantly increased, but the engine runs far more smoothly than ever before. The riding experience is greatly improved, which is why I tease ya about getting one!

 

Some exhausts use un- equal length headers but "trick" the exhaust gasses by making the headers stepped and by placing those steps in the right spots. It's not perfect and I'm sure there was alot of trial and error put into the designing of a system.

 

The unequal length stacks on the big block Chevy's that you remember was done because length of stack is from valve, not top of intake, you have to take runner length into account on those systems.

 

Yea but remember those guys were looking to gain every horse power they could. Most any "near" equal length exhaust that is a 2-1 would probably be a big help on these bike.

Grbrown
Looking at your system in the avatar, I think the toughest part would be finding the megaphone shaped muffler. Hmmm maybe something off ebay where someone has ruined the rest of the system.

I think I could get one of those kits with all the bends pre made and cut/twist/turn the pieces to get what I want. Don't get me wrong, I would love to be able to just plunk down the cash, but I kinda relate more to the early custom builders that hacked them together themselves, and learned along the way.

Hmmmm time to think now. (Sometime slow process)

 

After doing some more digging, I came across this site and it makes a lot of sense. https://www.rbracing-rsr.com/exhausttech.htm

Clears up a lot of other questions I still had, and some I never thought of.