I have a 2002 FLHTC that has been mildly modified as listed below:

SE 203 Cams
HD Heavy Breather
Thunderslide kit in the carb
Stock exhaust header pipe
Generic (Wild Pigs?) slip-ons

It was dyno-tuned after the cams were installed (74.53 HP and 91.06 max torque) and runs great but I never liked the sound of the slip-ons. I just bought a set of used SuperTrapp slip-ons. They had closed caps and 9 discs per side to begin with washers in between the discs. It sounded good and ran okay like this but not much low-end.

I ordered more discs and was playing with it this evening and put 14 discs per side in, left the caps closed and took the washers out. It seems to have fantastic low-end power and is quieter (0 to 70 very quick by my seat o' the pants dyno).

I know I can watch the discs and read the plugs to see how it's running after a while. I'd like to see if anyone has experience with these on a setup similar to mine and if so what disc/cap setup would you recommend (disc count per side, open/closed cap, etc.) to start with?

Thanks for any help here.

Rain

 

I think the recommendation from supertrapp is like 12 discs, they told me 12-15 to start on my stage 3 build with 2:1's. You can give them a call and they are more than happy to advise you. Sounds like your butt dyno is working if you can feel the difference. If you go open end cap you will loose a lot of low end, personally S/T with open end caps sound kind of crappy IMO. Im running megashots 2:1:2 stepped headers now on a 103 stage 4 build with 22 discs on each side. Cant elaborate because I cant get the bike out of the shop

 

the open end cap ( 1.5") is equal to 10 disks in a stack- there is also a 1.4" open end cap such as on the screaming eagle fatshots = 9.


28 disks will equal the flow through the 2" core...more than 28 makes no diff.
I use 22 on my hiPo evo FXR w 2/1


on my 80" FLHTC evo stock header I ran 7 left, and 12 right- for general use when touring ( high rpm all day but for fuel stops) I add 2 disks a side.

on my 96" FLHTC stock header ( no cat), I run 9 left and 15 right.
I have not yet found an advantage to the "add 2" method for touring, maybe because the 6 speed results in lower cruising rpms, and the 96" has more tq. than the evo.


with the uneven count, I run dummy disks...so on the left side 9 disks then a solid end cap ( the thin one) then 5 disks that don't do anything...then the end cap.
the dummy disks are used so they are similarly discolored.

here's a pic, you can see the line of the thin end cap on the left side in the middle of the disk stack:



I'd guess that my 96" method may work well for you- I make about same HP, slightly less TQ. just a stage 1 for me

mike

 

I've always found more discs are better and open caps are good. Running 19 disc & open caps on my current Fatshotz. Check out the Supertrapp website and forum, it is really good.

 

Thanks to all who have replied on this, great information. I called Supertrapp today and they didn't want to say if I couldn't give them a part number on my slip-ons as different ones would have different requirements.

Of course I didn't write the number down before putting them on so slipped one off tonight and the part number doesn't match up. It's 027-7276, stamped on the inlet twice. They look just like the Fatshots and Nightsticks only are chrome and are slant cut. I'll call SuperTrapp back in the morning and see if they can identify what model they actually are. Guess they could have been old part numbers, not sure.

I bumped the disc count up to 15 on each side tonight (all I have) and it sounds healthier and now it comes on real strong at about 2800 RPM. Getting on it hard on the highway once I hit 4500 to 5000 RPM the power drops off but on the shifts it climbs right back up to the top end quick.

 

Maybe the ones you have are HD ones, I understand S/T was making the SE mufflers for HD.
Remember more discs= more noise and less low end, but better top end.