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Discussion Starter #1
I keep hearing the terms High end and low end power. Specifically Sport bike having a lot of high end power vs beginner bikes are tuned for more low end power. Also varying power throughout the "powerbands".

Can some one clarify the definition of these terms for me? I tried Google and kept coming up with apple computer junk :confused:
 

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Sickle Punk
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google "dyno sheet"

Also see American Muscle Car vs Japaneese sports car.

the "ends" they are referring to is the power spectrum of the engine speed. Engine speed is measured by gauge called a tachometer, sometimes just called a "rev-meter", which gauges engine speed in revolutions per minuet. Most cars as well as all real sports bikes and even some cruisers have one. The power band is a reference to the range of engine speeds a vehicle goes through. Redline reffers to the fast speed an engine is allowed to spin, or is recommended to spin at, as seen by a red line or red blocks on the tachometer. This is the upper end of the power band. The lower end is generally idle to around half way through.

Horsepower is not a set thing, as in, all engines have diffrent amounts of power corrisponding to diffrent engine speeds, and most suprisingly peak somewhere in the middle. High end power, means the engine has little power at low revs but high power once the RPMs start building. Low end power, means there is ummph right from idle, but it looses steam mid-way through.
http://www.revsearch.com/dynamometer/torque_vs_horsepower.html
 

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High end horsepower is generally the realm of racing bikes. The engine gains it's power through high RPMs.

Low end torque falls in the realm of the lower-revving V-Twins. This is the "stump-pulling" power of a high torque engine.

Think of the difference kind of like a formula 1 racer vs a monster truck. In a flat out race, the formula 1 will reach a lot higher speed. In a tug-of-war, the monster truck will pull the race car all over the place.
 

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Basically, it all boils down to this. High power bikes, such as race bikes, have inline-4 engines. These engines produce peak torque at high RPMs. Because HP is a function of torque and engine RPM, these bikes produce large amounts of horse power in the high RPM range. For race bikes such as the Suzuki GSXR-600, this can easily be in the 10,000 RPM range. The powerband is a term used to describe the optimal RPM range for a given engine. Bikes with inline-4s must be kept in their powerband in order to get the most from the bike. This is very difficult when you're not on the track, as at the speeds you'll be riding on the street you won't be in the powerband.

In contrast, twin cylinder bikes produce most of their torque in the low RPM range. V-twins in particular put out GOBS of torque. This low end torque is really much more suited to street riding as it gives you most of your power where you actually need it.

Here is a good chart showing Torque vs HP in sport bikes. Notice that torque peaks between 11k and 12k RPM:http://www.sportrider.com/bikes/046_0607_middleweights_dyno_testing/photo_02.html

At the top of this page shows how a v-twin is the polar opposite, having a peak torque at a very low RPM: http://www.mcnews.com.au/Testing/suzukivl1500intrudertest.htm

So, why exactly is a bike with low end power desirable for a beginner? Well, for starters, just getting the bike rolling is a heck of a lot easier. A sport bike will require revving quite a bit in comparison. Also, sport bikes have a very sharp increase in power. The difference between 1000 RPM on a sport bike could be 20 HP. Trying not to overdo it (maturity not being a factor here) is pretty difficult.
 

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Discussion Starter #5
So a laymans description would be:

High end power engines will be slower to start but will continue to build power to keep you accelerating.

Low end power will get you to speed quicker but will level off faster.
 

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2007 Yamaha Road Star Silverado 1700
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So a laymans description would be:

High end power engines will be slower to start but will continue to build power to keep you accelerating.

Low end power will get you to speed quicker but will level off faster.
Sorta, but not really. Once you get talking about that you have to consider the gearing of the transmission. V-twins have tall gearing to take advantage of their torque. Inline-4 bikes have shorter gearing to allow the engines to spool up faster to get into their power band.

An inline-4 will accelerate much quicker than a v-twin, but a v-twin is more suited to hauling heavier loads (heck, even the bike itself is twice as heavy as a sport bike) at low RPM for comfortable cruising.
 

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Have you ever heard, when talking about HP, that a bike or a car will produce 150hp @ 15000RPM? basically when you red that a bike has 150HP it means that the engine generates 150HP at the optimum RPM. For example an inline 4cyl as it has been said before, will produce it's maximum output of power at higher engine speeds i.e 15000RPM a V twin will most likely generate its max power around 5000rpm.

When we say power we also mean torque, which is basically how powerful your engine is at a specified speed. So power and torque go hand in hand, it's a little complicated but you got the basic concept kinda right: Vtwins generate maximum performance at around 5-6000rpm so cruising speeds, In line 4cyl @ 15000rpm, you aint cruising at 15000, your hauling as$.

Some times you can feel it even in your car, at least with a manual I dunno with an automatic, I had a honda accord v4 2006 coupe and I noticed that if I accelerated keeping the foot at the same spot on the gas in 3rd without shifting, going from 1500 to 2000 felt smooth, but once It hit 2500 it felt like the car got a boost of energy and picked up power... so 2500-3000 was probably where my car produced the most torque and power, because if you think about it, if you go past 3500 4000 you are not accelerating normally, you are racing ah ah, and since the car was not meant for racing, but for city use, they tuned the engine to give power at medium rpms in order to use all its available power... same concept applies to bikes more or less.
 

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Well I think the only way to truely understand is to take a ride on an in line 4 and a twin. They are very different and the in-line-4 runs much differently than I thought it would. The 4cyl has so much more HP that I can be in top gear (5) going 40 and the motor wont lug (unless you crank the throttle) where as a twin hates anything below 3.5k Rpms (6 gears).. I dunno I can run the 4cyl at 2500 and its smooth.. do that on a twin and your bike will not be happy and you will know. When you got enough experience I honestly dont think it matters other than preference. Dyno charts mean nothing IMO its just something you have to "feel".
 

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Oh and the "powerband" Is where the RPMS create the greatest amount of torque/HP depending on the bike the "powerband" can be like 4-6kRPMS on a twin or say... 6-12k on an in-line 4 cyl depending on bike. I have a FJR1300 and the torque punts off around 8k but I can ring to 9k If I want. My twin is happy around 4-6k and wont give much torque after that. But as someone mentioned, they seem to typically have higher gearing to even that out.
 

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^You've got it backwards... a v-twin you can ride around town in top gear all day and not know the difference. An I4 might be rough and luggy below 4k depending on how the engine is tuned (the I4 in my concours is tuned very differently from the I4 in ZX-10R).
 

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Basically, it all boils down to this. High power bikes, such as race bikes, have inline-4 engines. These engines produce peak torque at high RPMs. Because HP is a function of torque and engine RPM, these bikes produce large amounts of horse power in the high RPM range. For race bikes such as the Suzuki GSXR-600, this can easily be in the 10,000 RPM range. The powerband is a term used to describe the optimal RPM range for a given engine. Bikes with inline-4s must be kept in their powerband in order to get the most from the bike. This is very difficult when you're not on the track, as at the speeds you'll be riding on the street you won't be in the powerband.

In contrast, twin cylinder bikes produce most of their torque in the low RPM range. V-twins in particular put out GOBS of torque. This low end torque is really much more suited to street riding as it gives you most of your power where you actually need it.

Here is a good chart showing Torque vs HP in sport bikes. Notice that torque peaks between 11k and 12k RPM [link removed since i am a newbie]

At the top of this page shows how a v-twin is the polar opposite, having a peak torque at a very low RPM: [link removed since i am a newbie]

So, why exactly is a bike with low end power desirable for a beginner? Well, for starters, just getting the bike rolling is a heck of a lot easier. A sport bike will require revving quite a bit in comparison. Also, sport bikes have a very sharp increase in power. The difference between 1000 RPM on a sport bike could be 20 HP. Trying not to overdo it (maturity not being a factor here) is pretty difficult.
Thank you for the informative response. I have a followup question to the original poster. I am hoping that someone here can provide a suitable response that might be able to help me, short of just simply trading in my Honda 2009 CBR 600 RR for a v-twin or the new Triumph Daytona 675 triple.

I am curious as to how I can best improve the lower range power of my CBR ? What kind of modifications can be implemented in order to achieve a decrease in the powerband for optimal within-the-city riding?

Thanks in advance!
 

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I am curious as to how I can best improve the lower range power of my CBR ? What kind of modifications can be implemented in order to achieve a decrease in the powerband for optimal within-the-city riding?

Thanks in advance!
The bike could be geared lower. Having a larger rear sprocket or a smaller front or a combination of both will change the characteristics of RPM vs speed. There are repercussions in making changes to the gearing. Lowering the gear ratio will lower potential top speed and run at a higher RPM for a given speed. The front wheel will be more likely to raise and the rear wheel more likely to slip at lower traction if care is not given with the throttle.
 

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Ideally, in order for you to change how your bike deliver it's power, you'll have to mess or change the internal components(cams, sprocket, gears). All bikes are geared differently thus all differ in power delivery. Simply changing a rear sprocket on your Cbr will give you more low end torque but less top end speed.
 

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The bike could be geared lower. Having a larger rear sprocket or a smaller front or a combination of both will change the characteristics of RPM vs speed. There are repercussions in making changes to the gearing. Lowering the gear ratio will lower potential top speed and run at a higher RPM for a given speed. The front wheel will be more likely to raise and the rear wheel more likely to slip at lower traction if care is not given with the throttle.
Thanks to you and Tigz for the quick responses.

Given that these alterations will have their consequences (especially the rear wheel slippage, which i would not particularly enjoy) in conjunction with the fact that if/when I want to sell the bike, the next rider would be stuck with these modifications -- I suppose the best thing to do is just leave it as it is and trade it in for something already engineered for lower end power..

Once again, thanks for the advice and info.
 

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Basically, it all boils down to this. High power bikes, such as race bikes, have inline-4 engines. These engines produce peak torque at high RPMs. Because HP is a function of torque and engine RPM, these bikes produce large amounts of horse power in the high RPM range. For race bikes such as the Suzuki GSXR-600, this can easily be in the 10,000 RPM range. The powerband is a term used to describe the optimal RPM range for a given engine. Bikes with inline-4s must be kept in their powerband in order to get the most from the bike. This is very difficult when you're not on the track, as at the speeds you'll be riding on the street you won't be in the powerband.

In contrast, twin cylinder bikes produce most of their torque in the low RPM range. V-twins in particular put out GOBS of torque. This low end torque is really much more suited to street riding as it gives you most of your power where you actually need it.


Not true. Close, but no cigar. Any layout of engine can be designed for any specific powerband. An in-line 4 cylinder four stroke tractor engine has massive low end power (torque) with very little top end horsepower. An Aprilia SXV550 V-twin has minimal low end power but some serious top end horsepower. It all depends on design.

My in-line four 550 only has 43 HP, but the available power is broad, with 82% of the peak torque available from 3000 rpm to about 8000 rpm. Perfect street power and the reason I am not modifying the engine, carbs or exhaust. It is easier to ride fast on winding roads than it is on a peakier 600, not as fast on straights, but way easier to ride faster in corners based on power delivery. I've ridden an Aprilia SXV550 supermoto and can tell you it is a serious hand full, especially when compared to my 550.

The GoldWing 1800 flat 6 is a powerhouse down low, on par with most comparable V twins of similar size. So cylinder count and layout mean less than what is done with it.

I just want to clarify that it is less to do with the layout and more to do with the state of tune designed into the engine. Since the advent of the Honda CB750 and Kawasaki 900 the in-line 4s have become synonymous with higher horsepower and with the extreme horsepower of the current crop of in-line 4 supersports of both 600cc and 1000+cc peakiness has also become synonymous too. The low end power output of the Harley Davidsons since the first twins they made, has the V Twin synonymous with low end power and tractability. Both incorrect, it's how the power delivery is engineered, as any 4 cylinder tractor and any supersport V twin may demonstrate.
 

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Thank you for the informative response. I have a followup question to the original poster. I am hoping that someone here can provide a suitable response that might be able to help me, short of just simply trading in my Honda 2009 CBR 600 RR for a v-twin or the new Triumph Daytona 675 triple.

I am curious as to how I can best improve the lower range power of my CBR ? What kind of modifications can be implemented in order to achieve a decrease in the powerband for optimal within-the-city riding?

Thanks in advance!
I agree with your assessment of it when you consider switching bikes.

If you like the sport bike layout, but want the low end consider one of the Harley engined Buells. My brother has a Ulysses and it pulls like a tractor down low, yet puts out some resonably serious horsepower. Ducatis may do the same as will Aprilias. The Daytona is really interesting in that it wasn't made to compete head on with the 600s on the track, but rather on the street, making better usable power in the lower range.

Unfortunately I also see where you hate to trade and lose the depreciation right now.

Like someone said, the best trick for easier around town on the CBR is to drop the gearing with either a smaller countershaft sprocket or larger rear sprocket. Saves you any loss on trade in. Also avoid putting a header on it. They get more horsepower sometimes, but usually at the expense of power in the lower midrange - that around town range of rpm you use.

You might also be able to pull more midrange with some electronic trickery through a Dyno Jet Power Commander or the like. You can call some of these places and ask them about it they can tell you if they can help. I would, sometimes simple ignition timing changes can alter power significantly. Consider that some bikes are now coming with switch mechanisms to soften power for wet weather, stronger for regular dry, and finally a hotter set up for track days, at the touch of a switch. You might find an answer that will suit you.
 

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Ideally, in order for you to change how your bike deliver it's power, you'll have to mess or change the internal components(cams, sprocket, gears). All bikes are geared differently thus all differ in power delivery. Simply changing a rear sprocket on your Cbr will give you more low end torque but less top end speed.
Yeah! like, these guys here who belong to a "stunt" team and go around giving "wheelie" demonstrations. The can pop it up and wheelie almost effortlessly at extreamly slow speeds, but their back sproket is like, 12 in. dia. maybe more. :icon_cool:
 

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While we're at it, what's a good bike that makes lots of torque and HP throughout the entire powerband? Would make a pretty **** good streetbike.
 

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Well look at it this way.

The huge torque factor coming from engines produced by Harley-Davidson, Boss Hoss, old American muscle and powerful Pickups are long-stroking, big bore engines. That's not just a phrase you can use to turn on your lady. (It works though, trust me ;) ) These engines have got pistons the size of garbage cans and huge, long connecting rods. Off the line, a Boss Hoss will ALWAYS beat a GSX-R, but in a quarter mile drag, the sportbike will take the race 10 times out of 10. The American engines put high torque at the back wheel while the Japanese... don't.


Take a look at the GSX-R 1000. In the 09-10 model, the cylinder has got an oversquare 2.93 inch (74.5 mm) wide cylinder and a 2.26 inch (57.3 mm) stroke. This gives it a relatively low torque factor at high RPMs (80 ft·lb (110 N·m) at 8,000 rpm).

Now compare to a V8 Boss Hoss. The 502 ci engine belts out 567 ft/lbs @ 4200RPM. The garbage can sized cylinders have a whopping 4.470 inch bore and a 4.000 inch stroke. As you can see, the Stroke Ratio (Bore/Stroke) is 1.1175. FAR closer to square (1.00) than the 1.296 ratio of the GSX-R.

Another slightly more applicable example would be the 88 ci Harley-Davidson Twin-Cam engine. It has got a 3.75 inch bore with a 4 inch stroke. The Evo engine is actually under-square! (.9375)

(one more, I promise)
Compare this to the smaller H-D Revolution engine used in the VSRC V-Rod. This has a 3.94 inch bore and a 2.83 inch stroke. A massive shift by Harley-Davidson from its under-square Evo's to a 1.39 Stroke Ratio! This allows the engine to rev up to 9,000 RPM's with a respectable 74 ft. lbs. of torque @ 7000 rpm.



Moral of the story: You want low-end torque? Get big pistons and big crankshafts, and keep their measurements as close to equal (square) as possible. If you're modifying an engine, increase your stroke length, and you can bring down your stroke ratio dramatically.



(If ya'll don't understand the 'square's and 'undersquares' then go HERE:
http://en.wikipedia.org/wiki/Stroke_ratio)
 
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