DIY 2-1 question

Reply Subscribe

Thread Tools

Search this Thread

Jul 14, 2019 | 12:33 AM

handirifle

Thread Starter

Seasoned HDF Member

Joined: Sep 2018

Posts: 6,040

Likes: 1,816

From: Kalifornia

DIY 2-1 question

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.

Jul 15, 2019 | 03:20 PM

grbrown

Club Member

Joined: Jun 2007

Posts: 45,429

Likes: 2,898

From: Bedford UK

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.

Jul 16, 2019 | 01:23 AM

handirifle

Thread Starter

Seasoned HDF Member

Joined: Sep 2018

Posts: 6,040

Likes: 1,816

From: Kalifornia

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.

Jul 16, 2019 | 04:11 AM

grbrown

Club Member

Joined: Jun 2007

Posts: 45,429

Likes: 2,898

From: Bedford UK

Quote:

Originally Posted by handirifle

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!

Jul 16, 2019 | 04:58 AM

Screamin beagle

Seasoned HDF Member

Joined: Jun 2017

Posts: 5,315

Likes: 4,272

From: Granville New York

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.

Jul 16, 2019 | 05:15 AM

Slingshot383

Road Warrior

Joined: Feb 2017

Posts: 1,525

Likes: 646

From: Saint Charles, Missouri

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.

Jul 16, 2019 | 11:46 AM

handirifle

Thread Starter

Seasoned HDF Member

Joined: Sep 2018

Posts: 6,040

Likes: 1,816

From: Kalifornia

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

)