View Full Version : tuning Supermegs 95" build

06-10-2009, 02:19 PM
Hi Guys - I'll receive my new Supermegs 2:1 (#828-71454) on Friday and I have an initial tuning question for my specific build.

My bike is a 95" build on a TC88 (2006 Fatboy). I used Andrews 54 gear driven cams (.550 lift), KB pistons and had quite a bit of head work done. The CR is 10.0:1, the heads use a slightly larger 1.9" intake. They're raised port, flowing at 148CFM. Throttle body is stock and I use a Ness Big Sucker/K&N filter combo (Stage 1) for an AC. I have a PCIII installed.

I'm looking for a happy medium of adding torque and HP, with a preference to keep the noise down. - more torque is probably better. 40% of my riding is 2-up and 98+% is non-highway. How many discs should I start with and then add/subtract one or two at a time, etc.? Closed or open end cap (I read the end cap is worth 10 discs in backpressure?)

thanks - Mike

06-10-2009, 02:36 PM
The open end cap is equivelent to about 8-9 discs.
Being more 'torque' oriented, start with 18 discs, closed cap and go ride it.

06-10-2009, 04:14 PM
Will try it and report back!

06-11-2009, 08:17 AM
Keep us posted, have fun.

06-13-2009, 07:01 AM
Yahoo - the bike has more pull/is more responsinve to throttle down low for sure. The sound - a little too muted though (what a quiet pipe overall). I have an open end cap and put that on - much, much better. So what have to done to my configuration?

It seems to me an open end cap is worth 'some number' of tuning discs (vs. no end cap at all), but not as many as the closed cap (which is worth 8-9 discs), correct?

So 18 discs and a closed cap = approx 27 discs (18 + 9 for the cap). What does 18 discs and the open cap equal?

Have I increased or decreased overall flow by installing the open cap?

thanks - Mike

06-13-2009, 11:28 AM
wow - I now have 12 discs and the open cap on it - it pulls like a mother! the flat spot is gone right off of throttle and it rips up through the revs like never before. I can't beleive what a difference this pipe made over my V&H Double Barrel 16ga (2:2 with a large crossover).


06-15-2009, 07:35 AM
We're off for the weekend, but it really sounds like you answered your own question and hit the right combination.
You are correct, the open cap is equal to about 8-9 discs-increasing flow over the closed cap.
The weather is nice, go ride it.

Why dont' you send a picture in along with your comments and we'll post on the website as well as possibly use for the catalog? (good high quality hi res images).

06-16-2009, 06:49 AM
...I will take a few pics. The pipe looks great!

06-16-2009, 07:17 AM
Good deal, thank you!

07-14-2009, 09:18 AM
...I have yet to take some pics, but have another question or two.

I've been messing between 12 and 14 discs, open cap. It seems to rev a little more with the 14/open combo than with 12 with little torque difference (seat of the pants dyno). My question is am I 'outflowing the core' with the 14/open?

My static compression is 10.15 and corrected for 400' above sea level with my cam type is 9.24. Do higher compression motors like more discs?

I know that my specific config is just that - the right one for my motor/bike, but is there a general rule for taller compression builds (as far as discs used AND what happens when the core is being outflowed, lack of back pressure/torque, etc.)?

thanx again -

07-14-2009, 12:35 PM
23-24 discs and closed cap or open cap and 14-15 and your outflowing the core.
Your findings sound right, opening it up you will notice a drop in torque and increase in top end vs. fewer discs and better bottom end.
It's personal preference on what you prefer and the type of riding your doing. Most people usually prefer more torque, it's more usable.

07-23-2009, 03:26 AM
Compared to stock head pipes with 3" internal disc mufflers (15 discs L. 18 discs R.) will the Supermeg 2:1 with 16-18 discs run leaner?

how many discs in the Supermeg would be roughly the equivalent of what I had?

ps. this is on a '06 Roadking with a complete HQ 95", 9.5:1 build

07-23-2009, 07:41 AM
16-18, your going to be pretty close I think to where you were.