Quick reving motor verses a slow reving motor...

[gabbyduffy]

              I've ridden some bikes with motors that seem to rev a whole lot Faster then some others. What part of the equation in a motor build can you change to get a faster reving motor and what benefit will it have in a Drag race?   
              It seems like there is a whole lot more to winning a street race then who's got the better looking dyno sheet.

[No Cents]

 a very smart man told me once...you don't ride the dyno sheet!
He is known as wfolarry.
He speaka the truth!

A shorter stroke will rev faster Duffy vs a longer stroke.
A lot of things come into play, compression, intake flow, exhaust flow...just to name a few.

Ray

[jam65]

Weight hanging off of the crank and a lighter crank, but I wouldn't do the latter.

[Don D]

The highest aggregate torque motor will rev faster regardless of the stroke.

[No Cents]

 many moon ago I worked for a company called A. Hines racing engines.
He built strictly drag race and roundy round track engines for cars. Big dollar high horsepower units.
In the dyno room I quickly learned why they always said around the shop that a small block engine would rev faster than the longer stroke big block would.
  At the drag strip the small blocks would leave the line in front of the big blocks...but the big block would run him down on the big end and pass him most of the time.
I know this isn't a true comparison...but the same theory holds true I would believe.

ray

[DeneFLHR]

I can chime in with fact based builds gabby. My first mod to my bike was going from a 96" to a 103" with exhaust and SE-204 cams, (thanks Lonewolf). Fantastic. Two years later went to heads, (thanks Don Dorfman), TR590 cams and a great tune, (thanks Lonewolf). Ask me which was far more fun to ride. Case #1 103/84, case #2 123/120. My answer will surprise the hell out of you. I wish dyno sheets were made more like 4 ply toilet paper then I wouldn't have to use so much Charmin. 

[C-Cat]

many moon ago I worked for a company called A. Hines racing engines.
He built strictly drag race and roundy round track engines for cars. Big dollar high horsepower units.
In the dyno room I quickly learned why they always said around the shop that a small block engine would rev faster than the longer stroke big block would.
  At the drag strip the small blocks would leave the line in front of the big blocks...but the big block would run him down on the big end and pass him most of the time.
I know this isn't a true comparison...but the same theory holds true I would believe.

ray

TQ, suspension, traction, gearing/tire diam. width, launch rpm/tq convertor, all come into play. The Big Block setup right 60 ft. just fine, at least mine does. What I like about big engines, they can be turned down and less radical to do the same as smaller engine turned up. As fast as reving fast, lets say smaller engine has a 6500 redline and bigger engine makes more power at 5500 rpm, the small engine better rev faster. The higher revs can be an advantage or disadvantage depending on gearing. It all comes down to  setup and have everything working together. You can have a good or bad setup on either one. 

[gabbyduffy]

         how big of roll do cams play..........  a narrow LSA cam verses a wide LSA cam 

[Admiral Akbar]

A shorter stroke will rev faster Duffy vs a longer stroke.

I doubt Larry said that..
Max

[Admiral Akbar]

many moon ago I worked for a company called A. Hines racing engines.
He built strictly drag race and roundy round track engines for cars. Big dollar high horsepower units.
In the dyno room I quickly learned why they always said around the shop that a small block engine would rev faster than the longer stroke big block would.
  At the drag strip the small blocks would leave the line in front of the big blocks...but the big block would run him down on the big end and pass him most of the time.
I know this isn't a true comparison...but the same theory holds true I would believe.

ray

So a smaller motor is faster off the line.. Did the smaller more make more low end tq or was it just lighter?  What what thoery are you talking about?

Max

[Admiral Akbar]

I can chime in with fact based builds gabby. My first mod to my bike was going from a 96" to a 103" with exhaust and SE-204 cams, (thanks Lonewolf). Fantastic. Two years later went to heads, (thanks Don Dorfman), TR590 cams and a great tune, (thanks Lonewolf). Ask me which was far more fun to ride. Case #1 103/84, case #2 123/120. My answer will surprise the hell out of you. I wish dyno sheets were made more like 4 ply toilet paper then I wouldn't have to use so much Charmin. 

You like case #1?   

Max

[Admiral Akbar]

              I've ridden some bikes with motors that seem to rev a whole lot Faster then some others. What part of the equation in a motor build can you change to get a faster reving motor and what benefit will it have in a Drag race?   
              It seems like there is a whole lot more to winning a street race then who's got the better looking dyno sheet.

So are we discussing throttle blipping or racing?  Loaded or not loaded?

Max

[C-Cat]

I can chime in with fact based builds gabby. My first mod to my bike was going from a 96" to a 103" with exhaust and SE-204 cams, (thanks Lonewolf). Fantastic. Two years later went to heads, (thanks Don Dorfman), TR590 cams and a great tune, (thanks Lonewolf). Ask me which was far more fun to ride. Case #1 103/84, case #2 123/120. My answer will surprise the hell out of you. I wish dyno sheets were made more like 4 ply toilet paper then I wouldn't have to use so much Charmin. 

You like case #1?   

Max

Bigger cam, same pipe and gearing add 750-1000 per shift. Along with that comes more mph and less shifing to cover the same distance. Now at your backroad test track you're only getting into 3rd instead of 4 gears. Short bursts where most street use is at, the short 5500 rpm cams are fun, especially when the hit hard and rev fast to redline. When they don't seem as fun is when you're along side the high rever that doesn't seem as fun to ride, but is putting lenghts on you. My 124 with 2.97 gears uses a lot of real estate in each gear going to 6400 rpm. Kind of hard to do the street light to street light and shut down.

[DeneFLHR]

I can chime in with fact based builds gabby. My first mod to my bike was going from a 96" to a 103" with exhaust and SE-204 cams, (thanks Lonewolf). Fantastic. Two years later went to heads, (thanks Don Dorfman), TR590 cams and a great tune, (thanks Lonewolf). Ask me which was far more fun to ride. Case #1 103/84, case #2 123/120. My answer will surprise the hell out of you. I wish dyno sheets were made more like 4 ply toilet paper then I wouldn't have to use so much Charmin. 

You like case #1?   

Max

Yes, case#2 was a right hand build with more top end than most would want / need.

[Admiral Akbar]

I can chime in with fact based builds gabby. My first mod to my bike was going from a 96" to a 103" with exhaust and SE-204 cams, (thanks Lonewolf). Fantastic. Two years later went to heads, (thanks Don Dorfman), TR590 cams and a great tune, (thanks Lonewolf). Ask me which was far more fun to ride. Case #1 103/84, case #2 123/120. My answer will surprise the hell out of you. I wish dyno sheets were made more like 4 ply toilet paper then I wouldn't have to use so much Charmin. 

You like case #1?   

Max

Yes, case#2 was a right hand build with more top end than most would want / need.

It would be interesting to look at the dyno runs.. I like flat power bands and suspect that if you used the same exhaust you got a flatland tq curve in both cases.. The issue is that going to the higher performance version made the bike less enjoyable.. Humps are no fun in the twisties.. You might want to give up the hump curve for something flatter. It will make the ride much more enjoyable..

Assuming this is a road glide, I'd agree to a point on the power.. I've got an FLHTC that is currently a 103 that has a real nice power band.. I've got a set of 107 cylinders on the bench that will boost the cr to about 10.5 from 9.9 and probably pick up a bit of power.. Still the bike runs so damned good there ain't any reason to take the bike apart until something breaks or wears out.. Might be a while for that..

Max

[FlaHeatWave]

The highest aggregate torque motor will rev faster regardless of the stroke.

+Compression, Cams, Gearing, rear tire/rim size (inertia), Hp/Tq to weight ratio (more inertia), all come into play...

Either all of the above, or the guy's clutch is slipping  

[strokerjlk]

The highest aggregate torque motor will rev faster regardless of the stroke.

I agree . Only I would have said Hp .
Given the same gearing , the only thing that decreases spool time is Hp .

[rbabos]

Over square motors rock.
Ron

[Admiral Akbar]

The highest aggregate torque motor will rev faster regardless of the stroke.

I agree . Only I would have said Hp .
Given the same gearing , the only thing that decreases spool time is Hp .

  hp is the key..

Max

[Templer]

Just to clear my thoughts: A higher Hp then Tq or Higher Tq then Hp is quicker to spool up?

[gordonr]

What part of the equation in a motor build can you change to get a faster reving motor and what benefit will it have in a Drag race?   


Its "all the equations" not just one. When I'm working on a project I will focus on BMEP pressures more than hp and tq trying to find the best combination.

[2006FXDCI]

Ron , I agree over square motors rock ! I have an all bore 107" in my 06 super glide . I dont believe I will ever change the stroke on it .

[aswracing]

              I've ridden some bikes with motors that seem to rev a whole lot Faster then some others. What part of the equation in a motor build can you change to get a faster reving motor and what benefit will it have in a Drag race?   
              It seems like there is a whole lot more to winning a street race then who's got the better looking dyno sheet.

f=ma, or in this case, it's rotational equivalent which is τ = mr^2α, where:

τ is torque
mr^2 is the mass moment of inertia (mass times the square of the radius, reflecting that mass placed at a larger radius is more significant)
α is angular acceleration

So from a physics point of view, it's simply how much torque is generated vs. how much mass moment you have. Forget all this crap about a longer or shorter stroke does this or that, it boils down to torque and how much mass it has to spin, or more accurately mass moment of inertia.

But we're talking purely about the acceleration of the motor, not the acceleration of the bike, which adds a whole 'nother dimension to the problem.

[strokerjlk]

Forget all this crap about a longer or shorter stroke does this or that

[Templer]

Solution: Ya want Faster and Quicker? LOSE weight and width!!! A lighter total bike weight and less wind resistance means BOTH!!!! Start with the pilot!!!!