Supertrapp disc starting point?

[akjeff]

My build is on a '91 XL883 converted to 1250 at 10:1 compression/Stage 2 heads. Andrews N4 cams, and S&S Super E with an extra Thunderjet fuel circuit. Pipe choice is the Supertrapp XR style 2/2 high pipes. For just good all around street performance, what would be a good starting point on the disc count and closed or open end caps? The pipes came with 12 discs per pipe, and closed end caps.

Thanks,

Jeff

[FLTRI]

The only way I know of finding the best disc count is to put it on a Dyno and measure the changes.
There may be so one here that has gone through the testing and can pass along his /her findings?
Bob

[akjeff]

Bob,

Yeah, I kinda figured that's what I'll have to do, and fortunately have access to a dyno to do just that. Will post the results when I get to that stage. Just hoped that maybe someone on here has tuned enough of them, to give me a ballpark starting point. I think I'll have some 18mm O2 bungs welded on, and just mount a permanent WB O2 gauge/datalogger on board. Kinda disappointed at the weld quality. Pretty lumpy MIG job. May have a pro dress them down and TIG them when the bungs go on. I'm sure the factory welds are functional, but to say they look like "Potty mouth", is being kind. Unfortunately, Supertrapp, is the only game in town if you want this style exhaust on a rigid mount Sporty.

Jeff

[HogBag]

I would do some homework on the supertrapp forum.

http://forums.supertrapp.com/

[HogBag]

I normally start around 14 discs and work my way up from there to 24 to 26 discs closed cap depending on the cubes. Then maybe try the open end cap from 12 to 16 on your build if your not happy with the closed cap.
Good Luck

[akjeff]

Thanks HogBag! Had no idea they had their own forum.

As an aside, I'm really disappointed in the quality of these pipes. For an $800 USA made system, I expected more. Spatter not cleaned up, just buffed over. The MIG welds on the radial seams are terrible. By contrast you look at the TIG welds on all of the joints of my Jackpot header, and they are perfect. No one else that I know of, makes an XR style 2/2 high pipe for the rigid mount XL's, so this will have to be it. Next time, it'll be Burns or Cone parts, and home made.

Jeff

[strokerjlk]

Anxious to see your results

[akjeff]

Hi Jim!

I'll work on snapping a few photos later in the week. Not much to look at yet. Got the forks(Yamaha R6), front wheel, and caliper mocked up. Working on fitting the tank and seat/tailpiece now. Have 1250 jugs on, and waiting for the heads, and powder coated engine covers, so I can get the motor together. I'm thinking it's going to be considerably lighter than stock form, and FUN! 

Jeff