Had my bike in for Supertrapp 2:1 exhaust installation last week and had it dyno tuned. With 18 discs and end cap on the muffler the results are as follows:
RPMs HP Torque
2.5 20 40
2.7 35 65
3.0 38 68
3.5 47 71
4.0 55 70
4.5 60 69
5.0 65 67
5.5 70 66
6.0 72 64

They replaced my 45 pilot with a 42, and the 185 main with a 175. Throttle response feels a little quicker with the Supertrapp exhaust, no carb farts and it sounds great!

Good numbers for a Stage 1 :)

Looks to max at: 72 rwhp @ 6,000 / 71 ft. lb @ 3,500

My bike dyno'd at: 69 rwhp @ 6,000 / 74 ft. lb @ 4,100 when it was a Stage 1.

Looks to me that SuperTrapp 2-1 puts out a few ponies more than the SE IIs I had on my bike back then.

Good numbers for a Stage 1 :)

Looks to max at: 72 rwhp @ 6,000 / 71 ft. lb @ 3,500

My bike dyno'd at: 69 rwhp @ 6,000 / 74 ft. lb @ 4,100 when it was a Stage 1.

Looks to me that SuperTrapp 2-1 puts out a few ponies more than the SE IIs I had on my bike back then.

Doesn't it feel like a new bike with the stage 1.


My Stage 1 posted: 74.51 rwhp @ 6000 / 77.04 ft. lb @ 4300

That was with a SE a/c kit and D&D slip-ons.

It seems like your torque peeks early. It falls off after theat. Did they dyno tune the bike or did you just have it pulled for numbers. With a trapp your torque #'s should not fall off so quickly.

I do most of my riding in the 2,400 to 3,500 rpm range and requested the max. torque in that range. Because the Supertrapp exhaust system is tuneable, I could push the torque peak higher by adding a few discs to the muffler. I think that raising the torque peak also increases the HP. Anyone know? The exact #'s are Max. power 72.15, max. torque 71.44.

I think that raising the torque peak also increases the HP. Anyone know? The exact #'s are Max. power 72.15, max. torque 71.44.

Hp and Tq are mathamatically dependent on each other. The formula is;

TQ= HP x 5252 div by RPM
HP= TQ div by 5252 x RPM

If one goes up the other goes down. It also depends on what you mean by "Raise the TQ peak".
If you mean you had 71 lbft @ 3100 rpm and made the Tq go up 4 lbft to
75 lbft @ 3100 rpm, then yes, HP goes up to.
But if you mean you moved it up the rpm scale as in, 71 lbft @ 3100 rpm to
71 lbft @ 3600 rpm then there is no HP increase.

Maddog,
I meant moving the torque peak up the rpm scale. Supertrapp says "fewer discs will tend to increase low end torque.......more discs move the power band up". Over on the NHRS Performance page there is a post that shows dyno runs on a Supertrapp equiped bike from 12 discs @ 77.5 HP, in increments of 2 discs up to 26 discs @ 83.3 HP. If this is true, adding discs to the 18 already in my ST muffler should move the torque peak up the rpm scale and increase the HP. What am I missing?

Here's the torque curves for the aforementioned Supertrapp test.

Basically, adding discs up to 24 did nothing to hurt the bottom end at all, and gave progressively better results through the midrange and on top. Only at 26 discs do we start to see just a slight impact on the very bottom end. I'm even hesitant to make that claim, just because we could still be within the repeatability of the measurement, especially at a really low rpm like that where the motor is lugging and the result is heavily influenced by how quickly I opened the throttle. Bottom line, I wouldn't worry about losing anything on the bottom up to 26 discs at least, if your bike is like mine that is.

On this whole Hp/TQ discussuion ... Horsepower = (torque x rpm) / 5252 ... but conceptually, you can ignore the divide-by-5252 part, that just scales the number down to what Watt's horse could do. Think of power as torque times rpm, i.e. the combination of torque (how hard you're pushing) and rpm (how fast you're pushing). More torque at any given rpm = more power and likewise more rpm at any given torque = more power.

What most people want from a street motor is a torque curve that's broad, so they have good power everywhere. In a race motor, we don't worry about such nonsense, we instead try to make as much torque as we can at as high of an rpm as we can, even if it costs us torque elsewhere, because that's how you get the most power. To see what I'm talking about, see the 82 inch dyno sheet elsewhere in the dyno section.

Pipes have a huge influence on the placement of the torque because they can radically affect intake flow on the front end of the intake cycle, while both valves are still open (overlap). The best motors get the pipe working in harmony with the port sizes and cam timing.

I have a much more thorough description of torque & power here:

http://www.nrhsperformance.com/tech_power.shtml

aswracing,
Thanks for the info. Very informative. It's always nice to know "why" it feels good when you roll on the throttle.

Phil,

I wouldn't say that your TQ falls off very fast at all. You're curves sound exactly like mine, though I think my peak TQ is a little higher than yours. We discussed our difference in numbers before, but conceptually the only thing I noticed as that you're HP is a higher figure than your TQ and mine is the oppposite.

XL1200R,
I suspect that dyno testing is an inexact science due to the existence of so many variables. I find that my bike idles better, responds quicker to throttle input across the rpm range, and in general feels "smoother" than before the Supertrapp exhaust was installed and the bike dyno tuned. I've noticed that my average rpms during normal riding have gone up by about 200 since the work was done. I think that the exhaust sound is more pleasing to my ear and I'm stretching my gears a bit more than before. Gas mileage has not changed. I'm still getting 50 mpg+/-. I will likely not be able to resist adding a few dics and subtracting a few now and then just for fun. Spitzies man had to drill a 3/8" hole in the center of the closed end cap for dyno testing. I'm going to swap it for a new one that Supertrapp is sending to me at no charge. I must say that I'm supremely happy with my bike and it only gets better!

Maddog,
I meant moving the torque peak up the rpm scale. Supertrapp says "fewer discs will tend to increase low end torque.......more discs move the power band up". Over on the NHRS Performance page there is a post that shows dyno runs on a Supertrapp equiped bike from 12 discs @ 77.5 HP, in increments of 2 discs up to 26 discs @ 83.3 HP. If this is true, adding discs to the 18 already in my ST muffler should move the torque peak up the rpm scale and increase the HP. What am I missing?

You're right Phil..I misunderstood the earlier post..You're packing everything into the upper rpm range.

I would like to post my dyno graph and don't have a scanner, so I had a friend email it to me so it is saved in my email filing cabinet. How do I get it from my email file to this thread?