I'm kind of curious about something in a technical way especiallyt since I'm not a gearhead. When you compare the Sporty and Dyna models in terms of acceleration, the Sportster is supposed to be the faster bike, although the Dyna presumably has a higher top end speed.

Why, though, would the Sporty be signifigantly faster? Consider:

Running Weight:
Sportster: 589 lbs.
Dyna: 676 lbs.

Torque (Stock):
Sportster: 79.0 ft. lbs. @ 4000 rpm
Dyna: 91.0 ft. lbs. @ 3125 rpm

The difference in weight is less than 100 lbs, and the Dyna pulls 12 ft. lbs. more torque at a lower RPM. Just from that alone, I wouldn't expect the Sportster to be signifigantly faster.

The gear ratios are different for the two models, but look pretty close in the first three gears.

Sportster:
1st 9.315 / 2nd 6.653 / 3rd 4.948
Dyna:
1st 9.312 / 2nd 6.421 / 3rd 4.774
The gear ratios on the Dyna are certainly lower. Is that what accounts for the acceleration difference?

 

My 03 sportster is 491 lbs...It aint stock either, I will eat up a new stock dyna. I guess if a skinny guy was on a new dyna and a fat guy was on a new sporty, it would be on. Besides Sportys aint considered the fastest Harley anymore, things change.....[quote]ORIGINAL: Dale Franks

I'm kind of curious about something in a technical way especiallyt since I'm not a gearhead. When you compare the Sporty and Dyna models in terms of acceleration, the Sportster is supposed to be the faster bike, although the Dyna presumably has a higher top end speed.

Why, though, would the Sporty be signifigantly faster? Consider:

Running Weight:
Sportster: 589 lbs.
Dyna: 676 lbs.

Torque (Stock):
Sportster: 79.0 ft. lbs. @ 4000 rpm
Dyna: 91.0 ft. lbs. @ 3125 rpm

The difference in weight is less than 100 lbs, and the Dyna pulls 12 ft. lbs. more torque at a lower RPM. Just from that alone, I wouldn't expect the Sportster to be signifigantly faster.

The gear ratios are different for the two models, but look pretty close in the first three gears.

Sportster:
1st 9.315 2nd 6.653 3rd 4.948
Dyna:
1st 9.312 2nd 6.421 [IMG]

 

there really isnt that much difference and in reality it would depend more on the rider than anything else

 

I don't know, and I actually don't care which is faster. If fast is what I wanted I'd have a Kawasaki ZX14, simple as that! Now, what are the differences among the ZX14, a Sportster, and a Dyna? Aw heck, throw in a V-Rod also.

 

I think the old thinking of the sporty being faster than a Dyna was based on the dyna having a 88 in it. With a 96 in it, it is going to have better pull on the top endwith the larger cubes.

 

My '07 1200L feels quite a bit faster than my '08 Softail Custom. That's one of the things that makes the Sportster more fun to ride. The Sportster does have a Stage 1, slip-ons, and Power Commander, though. And my Softail is bone stock (Well, until I pick it up from the dealer later this week. ). Now I understand why the 1200 was too much bike for my wife, and why she's scared of it now. After riding it more myself, I can see that it was simply too fast for her. It's a little harder to ride than the Softail because of the power. Now she just wants to be a passenger again. That's fine with me, though. She'll still ride with me, and now I have two bikes.

 

I thought HD detuned the DYNA alot to make it more of a slug.Women friendly type bike...Guessing thats why more beginner womenbuy a DYNA.But what do I know,I ride a sportster!

 

The sportys short stroke enables it to rev faster which in turn makes it a fast bike on the low end. The dyna or other bt is a long stroke engine which in turn makes it a slower reving engine but because of that it will pull long after the short stroke spoty. Because of this and the wieght differnce the sporty can get moving alot faster. The same priniple applies to car engines as well. You have two cars that are the same,lets say a Chevelle, one has a big block one is a small block, both rated at the same hp. The small block will almost always get off the line faster but the big block will overtake it in the long haul. This type of thing has been tested and retsted a gazillion time. Also has some to do with the final drive ratio, as in the pulley arrangment.

 

25 words or less: Hp to weight ratio.

The Dyna (and probably it's rider) is much heavier than the Sporty with about the same horsepower.

Torque, cubes and chrome don't matter when the light turns green; horsepower ALWAYS wins...

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[IMG]local://upfiles/32069/29C9B5CD05D0499FA66A7A86D08C3BE5.jpg[/IMG]

 

Torque gets you movin, horsepower maintains it. Build it for torque and let the horsepower end up what it is.

Dave