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

 

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.

 

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.

 

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!

 

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.

 

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.

 

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".

 

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.

 

^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).

 

Ah well, yeah I suppose you are right... I dont think the FJR1300 is tuned like the traditional sportbikes :?

 

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:

 

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.

 

Well, if your looking for a bike with a torque curve that is as broad as the Pacific, and if it is going to be a bike that a beginner can feel comfortable on but even experienced riders can enjoy, I would recommend a Shadow 750. I can cruise along at 35mpr just fine in top gear, yet still accelerate smoothly from it. It does not produce a lot of power, but what torque it produces, it does so throughout 90% of it's rpm range.

If you want more, I hear good things about the 650 sized Ninja. And if your experienced enough for the big power producers, Most any liter sized bike will give you all the power you can handle on the street at reasonable rpm ranges. Some will give you way more than needed even.

More importantly, it is easier to shop around and find a bike your comfortable with, cause your very much likely to find one with plenty enough power down low for street riding. I could supply a list of good bikes for your purpose, but that would get long...

 

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)

 

From what you said above, Suzuki did it right with the M109R by putting a pair of cylinders bigger than the Hoss Boss and shorter stroke with a GSX-R motor design. Making it generate more TQ in the lower RPM and generating HP at higher RPM. And installing a wider back wheel to put all that power to the ground. I can just imagine if it has another pair of Cylinders....hmmm. J/K...

I agree with the above...except that I wouldn't compare a Hoss Boss to a GSX-R...More like a GSX-R 1000and a Ducati 1098 or a V Rod and a Roadstar. At which one has a shorter stroke and longer stroke motor design.

 

I've always wondered about how well a performance V-4 engine design would function on a Motorcycle. I know the Honda Magnas have got them, but they're not exactly performance. Harley-Davidson might be able to compete with the Japanese companies performance-wise with a V-4 configuration.

 

Honda won the AMA Superbike titles for a number of years with the first and second gen V4 Interceptors, then both the world and AMA superbike titles with both the RC30 and RC45. So the V4 can do a good job when it comes down to it. Again, it's the state of tune. I don't know exactly what if any differences there are in cams, pistons, and heads, but it would be interesting to put the VFR parts from an 80s or 90s engine in the Magna if possible.

In a side note, it was interesting to us that Honda put the 180 degree crank, which produced better lower/mid range power in the Interceptor and put the 360 degree crank which puts out better hp in the upper range in the Magna. When all things are the same the 360 crank engine will outperform the 180 for HP. The really wierd part is that the 180 crank gives the Interceptor that distinctive V8 rumble like a mini-small block Chevy where the 360 crank gives the Magna a sort of flat drone which is a bit uninspiring. That should have been reversed for the sake of sales. Imagine a Magna with a set of pipes on it... sounding like a small block Chevy. A friend had a set of pipes on his 86 VFR and it sounded incredible - no mistaking it for anything else.

If I could have made one change in the mid 80s in the Honda line up, for sales sake, that would have been it. I guarantee you we could have sold the heck out of Magnas if they'd had that rumble. The cool thing too is that the 180 crank pipes for the Interceptor were 4-2s so there could have been a pipe on each side sort of for a balanced look. I could have pulled that bike out, fired it up, blipped it several times, then gone back in and written the sales order up for the starry eyed customer! :biggrin:

Sometimes it made us wonder who was doing the market research and making the decisions...

 

Honda VFRs are V4 along with the new VFR1200. HD will have to step out of their conventional motor design like they did with the VRod with the help from Porche to deliver that kind of performance in such a smaller displacement.

 

so how does the kaw. 125 compare in this ? a 502 V8 is a big motor in the Boss Hoss.

 

There won't be any comparison. It's like comparing a grape to a large watermelon.

 

i want power all the way through the RPM range.no more then 5200 and be able to cruise 120 all day

 

With a built 1602cc Roadstar, the powerband is when you turn press the starter until turn off the key, or hit a tree, whichever comes first. I'll have dyno sheets in the spring, but it'll look something like this:

That might look a little strange to some of you non-star owners, so I'll explain it. The R* actually starts off with more power than a peterbilt, but it comes down a bit so you don't instantly destroy the clutch when you let it out, flip the bike over, or melt the rear tire. The average R* owner has owned 37 R*, typically in less than 3 weeks, because that's how long it takes to stop destroying them due to their complete awesome power. The drivers seat must have a back rest and 5 point harness, otherwise when cruising at 1mph-700mph, if you roll the throttle even a wee bit, the bike will accelerate so fast you'll fall off the back. To this date no one has owned a Roadstar and lived to tell about it.

So, I hope this has cleared up your question about power bands.

 

:coffeescreen:

 

So just to re-cap and maybe simplify things a bit... Low-end refers to torque, and top-end refers to HP/RPM. Torque is the twisting motion from the (low-end) crankshaft. Torque times RPM equal HP.

So in laymans terms:

An engine with a long stroke will have a lot of low-end. Example: V-twin.

An engine with a higher RPM limiter will have more top-end. Example: in-line 4

 

Unless it's a short stroke big bore V twin like the Aprilias and the 4 is a longer stroke smaller bore like some of the older 80s models...

We had similar misconceptions when the Yamaha 4 stroke MX bikes came out. Guys were telling other guys that the 4 strokes were "easier to ride than a two stroke, so buy the big Yamaha", basing that "knowledge" on past experience with the old longer stroke milder tuned Honda XR series. Our first customer who came in with that line, bought the YZF425 on a Saturday and was sitting at the door of the shop Monday, after riding it about 50 feet with no wear on the front tire, but a fold marks on the rear fender... he traded it in on a 4 wheeler.

In other words, research the bike being considered for purchase before jumping in. You could find things aren't always what they seem to be. You can expect a lot of grunt from a Harley, but if you carry that thought over to an Aprilia or a KTM V-twin you might be in for a GIANT surprise.

 

I don't know if this will help or hurt the info that has been shown/discused here
but, if you examine this dyno chart, you can basically see how this engine was designed
to have a very broad and usable power-band.
This engine, will pull like a tank from 3-9,000 with a very flat torque "curve".
So, just off of idle, it is very near it's torque peak.
The "sweet spot" is were the TQ. and HP peaks intersect. From that point , the HP takes over.
This engine was designed with very little camshaft lift and duration.
It would also be considered a "square" engine.
The bore and stroke are nearly identical. 72 mm bore X 66 mm stroke.
A square engine, makes a flat torque curve. It is an inline 4-cylinder.

Eric

 

Here is another example of a square engine. This time a V-8.
3.54" Bore X 3.5" stroke. This engine, suffered from an exhaust restriction
at 5,500. You can see where the HP and TQ just STOPPED!
This engine, was just coming alive at 5,000.
Again, notice the long flat torque "curve." Just off of idle.

Eric

 

67fire,

That first dyno chart does show a very good power spread, with a minimum of about 75% max torque available from 3000 rpm through the peak of 8000. That was what sold me on leaving my 550 drive line alone, the torque held at over 80% from about 3500 rpm through 10,000 rpm. The dyno chart that Cycle ran in it's 1990 test of the Zephyr 550 pretty much looked like that, but didn't sign off as quickly and wasn't quite as high of numbers probably due to displacement and the state of tune required to get that sort of power delivery. I figured if I messed with a pipe or cams it'd just screw up a good thing... if I wanted faster I should buy faster.

The problem for most riders is the psychological barrier of running the engine into the good power. Most riders seem to want to lug along about a thousand under the start of the power, thinking it's the best thing to do. The reality is an engine should be run in the range for which it was designed. I seldom drop below 3500 on either the KLX or the Zephyr and spend a whole lot of time over 4000 on the Zephyr.

I learned of the engine design reality when selling Hondas and dealing with the complaints about gas mileage and poor engine performance by the 1100/1200 Gold Wing riders who thought their bike engines were made by John Deere. They'd lug them around at 2000-2500 rpm and expect them to run smooth. Of course they didn't and we'd get the complaints. Honda told them and us the engine was designed for best performance when run above 3000 rpm and best mpg came in when kept between 3000-4000 rpm, downshifting if necessary. I can tell you from riding my 1100 Wing, back when, they were right.

In other words that bike in your dyno chart should not be run under 3500 rpm under any significant load. It should be worked in the range from 3500-6000 on a regular basis for optimum mpg and performance. Essentially that's the range it was designed to use. Very similar to my under square (58/52.4 bore/stroke) Kawasaki 550 in-line four.

Proving it still has a whole lot to do with more than just bore/stroke or cylinder layout. There seems to be a whole lot of relationship to cam lift/duration/timing and ignition timing/advance. On a Nighthawk S, a simple backing off of the 133 degree cam advance to around 105 will boost midrange noticably while losing around 3 hp... nothing in the bore and stroke changed.

For a more radical example, just consider how streetable the Vance-Hines pro-stock "Harley" engine is...

For a more common example, some engines have drastic reaction to removal of airboxes or changing exhausts. Usually those in a higher state of tune can have major issues due to flow dynamics and jetting. It's like sharpening a knife, when the edge is near razor sharp it's hard to get better, but when the edge is virtually blunt any sharpening is a help. The current supersports fit the former, some of the cruisers and dual sports fit the latter. Unstuffing my KLX boosted performance both in "seat of the pants" and side by side performance of it compared to another "control bike" (I'm not blowing money on dyno runs for a 40 hp single) and oddly enough in MPG, going from 50 mpg to 60 mpg.

It's not so simple as to involve an engine configuration of cylinders or of bore and stroke. Some time dealing with a variety of engines will demonstrate that. Also realizing how the power comes in helps too. If the power comes in higher, the rider just needs to stay in a lower gear. Any Ninja 250 rider can tell you about that. :thumbsup:

 

I just read a good article on torque vs hp:

http://www.vettenet.org/torquehp.html

 

Tigz, it was meant as a humorous post lol