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Old 02-15-2007, 10:16 PM
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Torque? HP?

Let's test the respect thing. Hell, I haven't had an infraction since the day this place opened.

The topic is torque vs. horsepower. I understand the reasoning for wanting max torque at lower rpm's. That's where you ride mostly, and it's nice to just be able to roll it on.

I do submit that torque and horsepower have a 1 to 1 relationship at any given RPM. Carrying the torque higher into the RPM band carries the acceleration out farther.

As an extra discussion point I'm throwing out some dyno runs that really show the shift points. The hp curves are barely flattening when the run was ended, but you can see where the shifts should be made.

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Old 02-16-2007, 01:29 AM
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And your point is what?
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Old 02-16-2007, 02:09 AM
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Hi Mr. Miller.

Ok, Is what you are showing us here, your bike in different gear?

Can I ASSUME 3rd, 4th and 5th for the three runs?
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Old 02-16-2007, 06:13 AM
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I guess my point is to start a discussion of the advantages and disadvantages of early torque / later torque builds.



The chart isn't my bike they're just some charts I found. Looks like 3rd, 4th, 5th. The pulls end about 5,000 RPM so theres a little more power than what's shown.

Would you build it lower rpm higher torque or higher rpm higher horsepower or leave it alone. What would be your reason for doing so.
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Old 02-16-2007, 07:27 AM
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Quote:
Originally Posted by TerryMiller View Post
I guess my point is to start a discussion of the advantages and disadvantages of early torque / later torque builds.



The chart isn't my bike they're just some charts I found. Looks like 3rd, 4th, 5th. The pulls end about 5,000 RPM so theres a little more power than what's shown.

Would you build it lower rpm higher torque or higher rpm higher horsepower or leave it alone. What would be your reason for doing so.
I guess I'd have to say lower rpm, higher torque, since my torque peaks at 3750 and my hp at 4000. My heads leave for Big Boyz Feb 19 to try to bump the numbers, but I'm hoping my peaks don't change.
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Old 02-16-2007, 09:10 AM
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Quote:
Originally Posted by TerryMiller View Post
I guess my point is to start a discussion of the advantages and disadvantages of early torque / later torque builds.

Would you build it lower rpm higher torque or higher rpm higher horsepower or leave it alone. What would be your reason for doing so.
Me? I want TQ coming on lower, carrying my 800# bagger. With my phat azz on it, I'm moving a half a ton. The way mine is set up, it rev's like there's no tomorrow and pulls all the way to 6 grand. I'm sure a dyno reading would show that power/tq falls off before 6 G's, but it's still accelerating!!

A Lowrider or Softail, I'd want TQ coming in later, and a higher rev'ing motor to carry the lighter bike faster.
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Old 02-16-2007, 01:55 PM
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with the dyna i would tend to go high hp its a lighter bike for one and by time GG gets that 1/2 ton moving i would try to be so far i front that it would not matter.
now the ST thats a nother story try to build the motor to be used in the power band recomended. from about 3000-6200. with a mild gearing change or 6 speed.
now are thest just bolt on pieces were talking about i beleive, any thing else well it would depend on how much you want to spend.
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Old 02-16-2007, 02:10 PM
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Okay, let's start out with a basic understanding first. In a rotating engine, HP is the first derivative of Torque times N(rpm).

Torque(ft-lbs) x N(rpm)
____________________ = HP

............5252.......

It's the product of Torque times rpm divided by the constant, so bigger Torque numbers and/or higher rpm will give you increased HP.
So, you can see that the goal is to make as much Torque for as broad as a range as possible. On a side note, for actual racing, it's not just the numbers but you also want the motor to spool up as quickly as possible and pull the load in the least amount of time.

Finding the optimum shift points for the best acceleration you have to think of the transmission as a torque multiplier that changes delivered rear wheel values for every gear you are in. Right away you can intuitively guess that the best shift points are different for each upshift. You also have to keep in mind that as V increases, acceleration decreases. If you recall, Power=Force*Velocity. From this you can solve for Acceleration and substitute terms to get: a=P/(m*v). Simply put, the higher the velocity, acceleration diminishes proportionately. The math gets complicated after this but essentially you need to solve for what the power curve looks like in every gear. Remembering that the transmission is a torque multiplier, the peak torque transmitted happens at different rpms for all the different gears. Fundamentally, you want the current gear transmission torque to be equal to the next gear tranny torque when you shift. Generally speaking, this will appear to be shifting after the HP peak and the next gear will be before the HP peak. The old rule of thumb is..... peak HP rpm + 10%

Check out the attachment I threw together this morning. You'll have to plug in your transmission gearing numbers and dyno torque numbers for it to calculate your torque table.
Attached Files
File Type: zip Calculating shift_pts.zip (4.3 KB, 9 views)
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Old 02-16-2007, 02:22 PM
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I don't think there's anything wrong with my stock torque curve, but I'm going by what I feel in the saddle. I think HD got it right, at least for me. Riding solo, the acceleration all the way to cruising speed is adequate but I'm no jack rabbit or speed junkie, not in the States anyhow. A sixth gear would be nice for interstate riding. If I needed more acceleration or more speed, rather than re-inventing the wheel I think I'd try duplicating the curve while increasing torque across the band.

Edited .. yeah, what Tote said (I love reading his stuff).

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Old 02-16-2007, 08:02 PM
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Terry, are you second guessing your build or are you doing another?
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Old 02-16-2007, 11:37 PM
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I believe Mr. Miller has a Softail Deuce. The one pictured here.....
(I hope you don't mind, i borrowed it from your Profile picture on the Vtwin forum)


Nice Ride Mr. Miller.

Anyway, to bring up the torque, the first thing i would suggest would be a good 2 into 1 exhaust, like the Thunderheader.
Also a air cleaner with a directed flow, like the K&N air filter system(It have a velocity stack built in.
I know they are cosmetically challenged, but they really do work.
Horsepower and torque do work hand in hand...to a point, what you need to do to get more SPEED is to increase horsepower, what you need for pulling off the line is Torque.
For torque, you need air speed and fill in the cylinder at low rpm's, overreporting the ports will hurt this, low compression, too much cam lift and overlap, and low manifold pressure will kill it too.

Without knowing your build, It will be hard to advise you farther, but these two Item will help it run quicker.
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Old 02-16-2007, 11:57 PM
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Quote:
Originally Posted by Big Tom View Post
Terry, are you second guessing your build or are you doing another?
Neither, my next bike will be a '57 tourer (because it's the year I was born) or a new EG. Either of them would not require any more than stock. This build on the deuce wasn't what I thought I wanted when I started talking about it, but even without the final dyno tune is just what the bike needed.

The point of this point was to get the 2400-4000 rpm high torque guys to state their reasoning to the best of their ability. The same for the 3600-6000 rpm guys.

A popularity poll wasn't what I was looking for, but the reasons behind it. Future readers would then have a basis for deciding which camp they fell into. The shift point calculator was kind of a nice adder to the topic because it needs to be discussed.

Here's what I know based on education and training.

Power = Acceleration (thanks again Tote)
Higher torque = higher power at any given rpm.
There's no substitute for displacement and any big bore kit will give you more torque off idle than stock regardless of the (within reasson) cam selection.

Here's what I don't know (based on experience with riding different builds)

Why the light bike heavy bike talk? They're 570 to 800 lbs. Rider weight varies more than the weight between the bikes.

What are the upsides / downsides of having a bike that shifts at 6200-5000 vs a bike that shifts at 4300-3500?

I don't know that there's a firm answer, but I know there's firm beliefs. If I could get the knowledgeable guys to state the reasoning behind their preference then that would be helpful to future readers.
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Old 02-17-2007, 12:21 AM
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Well,

I know the build, I also know it is a light Deuce. If you like the HP build cool. You know I am have a preference for low end torque and ride a heavyweight. Often two up.

Now I forget what I was going to type. Started with XO and now down to Presidente.

Oh well.
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Old 02-17-2007, 01:16 AM
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Hi Mr. Miller.

Torque, the force the engine make in twisting power.
Horse Power is how fast it will push the vehicle.

I.E. torque gives you wheelies, and horse power pushes you past the speed limit.

I think to start this discussion, were most rookies mess up is not having a plan when they start a build, change direction half way through, and miss-match items that kill the potential these item would give to the build if they had the other right components.

So when one should start a build is first asking the question, What do I want?
How much power, how much speed, and how much are you ready in invest to get there?
The second question should be, What Bike is this in?
A Sportster is a very light bike, so is a Dyna, these bike don't need all the torque in off the line, so you can move the rpm window up to get more top end Horse power.
On the other hand, a Heritage or Touring bike needs that torque down low to get it a movin', high speed running is not what most heavyweight bike owners want or need, so moving the rpm window down lower will give great returns in this set up.

Riding habits and solo vs. two up have to be considered, then and how much weight will the bike NORMALLY carry.

Once you get this sorted out, you can now sit down and start the planning.

Volumetric efficiency, this is the heart of any engine build.
In simple trems, how well air/fuel gets in and exhaust gets out, sounds simple, right?
You have to consider everything from the air into the filter to out the back of the pipes, everything will positive or negative effect on the outcome.

A good starting point on any build will be to start with the heads.
Valve heads are the most important and most restrictive part of the Harley Engine.
If you are not going to port the heads, then I suggest you use a Harley SE203 and a 95 kit and be done with it, any thing bigger, and the heads will not be able to flow the cam at potential.

Large valves and Big ports with a mild cam is a waist of money.
Stock ports with a large high lift cam is the same, a waist of money.
Large ports on a torque engine will kill the torque off.
And stock ports will run out of steam at the upper rpm range.
So you need to talk with the tech that will be doing your port job, and discuss what you want the engine to do.
At this point they will make recommendations to cams and what compression and pistons to run to match there port work.
Do ask them what exhaust and Intake system you are planning on using, Carb or Throttle body size should also be talked over, they may have some better suggestions for you to look at.(Steve at GMR is very good at this)

Last part of any build, Ignition and tuning. The stock Ignition(Carburated) or stock ECM program just won't do anymore, A performance Ignition or SE Race tuner needs to be included, the wrong timing or fuel curve, and you can do major damage to the inside of your engine.
There are two type of tuning, basic, a quick flash programing of adding a performance ignition and throwing jets in to the carb, it is crude, but will get you a fair running bike. You need to do this right after a build to get the bike to run well enough to get through the break-in period.
Then there is dyno tuning.
This is far more expensive to do, but will get the engine running at efficacy, getting all the power you paid for out of your build. Be sure to ask around to who is the best in the area, in the Notherwest, Mike Stegmen at Latus is one.
Many people skip this step, it is expensive, usually 3-5 hours on the dyno to get it right on the money.
But it is were you will get all the power you paid for, so please, budget it in.
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Old 02-17-2007, 08:41 AM
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Quote:
Originally Posted by TerryMiller View Post
The point of this point was to get the 2400-4000 rpm high torque guys to state their reasoning to the best of their ability. The same for the 3600-6000 rpm guys.

Power = Acceleration (thanks again Tote)
Higher torque = higher power at any given rpm.

Why the light bike heavy bike talk? They're 570 to 800 lbs. Rider weight varies more than the weight between the bikes.

What are the upsides / downsides of having a bike that shifts at 6200-5000 vs a bike that shifts at 4300-3500?

I don't know that there's a firm answer, but I know there's firm beliefs. If I could get the knowledgeable guys to state the reasoning behind their preference then that would be helpful to future readers.
As I see it (in non-techie speak) -

Power = acceleration ... yes, if it's available in the time which you want to accelerate and with the right gearing, a lot of people build up from stock but ignore gears, diesel load-haulers have a lot of power and so do Formula 1 cars

Higher torque = higher power at any given rpm, exactly right, torque is the force that can do work, HP (horse Power) is the measurement of the work being done by the force as it's applied .. having torque or power available and using it are two different things

Light bike / heavy bike .. everything from the engine through to the tires being equal, the lighter bike can accelerate faster and fuel use can be lower with light. The engines in both have the same torque and HP available and can do the same work but the lighter bike doesn't have to. If the light bike has to, it can do its work more efficiently or faster.

Upsides / downsides 6200-5000 vs a bike that shifts at 4300-3500 ... heat (or energy) management is one thing to consider, wear on moving parts is another

Why build an engine that revs higher when you can build one that doesn't? an engine that revs higher has a larger percentage of the range to work with: in a 0 - 5,000 rpm engine, 20% of the range is 1,000 rpms; in a 0 - 20,000 rpm engine, 20 % is 4,000 rpms .. spreading usable torque across 20% of the rpm range means the higher revving engine has more flexibility
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