All bikes have powerbands.

[The Pastor]

Do all bikes (and cages) have powerbands?

[limbimtimwim]

Do all bikes (and cages) have powerbands?I know my mother's Peugeot is held together with rubber bands.

[curious george]

Yes, but I would like you to be more specific with your question.

[Gixxer 4 ever]

Not sure about that. I rode my sons GPX 250 and was waiting for the power band to come in. Noted the tack was at 14000 rpms and decided I must have missed it. But in all fairness to the bike it keeps up with the big bikes on the rides like the one we just had to Taupo.

[The Pastor]

Well I was having an arguement with magua about powerbands, he told me every thing has a power band, his rg150 my old zxr250c his mums car, my car indiana's fxr150....

I think that all cars/bikes do not have power bands. My car certianly doesnt. I wanted to know what you jokers thought. (yes his rg150 does have one im just saying that not everything has one... my old zxr had one but that I think was because it was a bit broken somehow...)

[SPORK]

We need a big dose of Motu in here...

[T.I.E]

two stroke engines will sometimes have a (power band) extra increase in power when hit at a certain rpm.


but all vechiles have a (power band) meaning a wave form or sign graph on what power it producers at what rpm.

so my understanding is there are two types.

[Hitcher]

Do all bikes (and cages) have powerbands?
Yes. The faster they go, the further up and down in the sleeves the pistons go. If you go too fast the piston either impacts the head or drops out the bottom into the sump. Be careful.

[mini_me]

two stroke engines will sometimes have a (power band) extra increase in power when hit at a certain rpm.


but all vechiles have a (power band) meaning a wave form or sign graph on what power it producers at what rpm.

so my understanding is there are two types.

This is my take on the whoel thing - feel free to correct me

alll vehicles have a powerband period. some are just more savage than others
and a powerband is a powerband there isn't different types just varying degrees of 'steepness' (when looking at the powercurve (hp vs Nm) on paper)
Using my v4 as an example, You lok at the dyno sheet and you see a bulge in the middle of the rpm range (AKA midrange) this is where the motor generate the most power and hence is called its powerband
but if you look at an IL4's powercurve you can see the bulge is near the upper end of the rpm range so this tells one that the powerband is near the top end of the rev-range

also powerbands are adjustable to a degree with the type of tuning that you do to your motor - you can tune in a big bottom end and nothing up the top and vice versa or you can have it somewhere in the middle or you can spread it out evenly over the whole powercurve and hence the reason some vehicles are not thought of as having a 'powerband' but in reality they just have one big powerband

m/m

[Ixion]

It depends on your definition. All bikes have a power CURVE. In some there is a section on the curve where there is a noticeable increase in steepness. In others the curve goes up at a much more steady rate.

Perceptually, if there is a sudden marked increase in the steepness of the power curve, the rider will notice it - a small increase in revs will suddenly produce a lot more power. If the curve is more gradual the increase is less noticeable.

At what point the change in the angle of the curve qualifies it to be called a "powerband" is arguable. But , in the reality, most riders will agree - the FEELING is easy to detect. But it is arguably true to say that all vehicles (even diesel trucks) have a powerband - just some are so gentle that it's hard to detect where they start.

[T.I.E]

This is my take on the whoel thing - feel free to correct me

alll vehicles have a powerband period. some are just more savage than others
and a powerband is a powerband there isn't different types just varying degrees of 'steepness' (when looking at the powercurve (hp vs Nm) on paper)
Using my v4 as an example, You lok at the dyno sheet and you see a bulge in the middle of the rpm range (AKA midrange) this is where the motor generate the most power and hence is called its powerband
but if you look at an IL4's powercurve you can see the bulge is near the upper end of the rpm range so this tells one that the powerband is near the top end of the rev-range

also powerbands are adjustable to a degree with the type of tuning that you do to your motor - you can tune in a big bottom end and nothing up the top and vice versa or you can have it somewhere in the middle or you can spread it out evenly over the whole powercurve and hence the reason some vehicles are not thought of as having a 'powerband' but in reality they just have one big powerband

m/m

might be totally right. never thought of a power band as a period of a engines power range or it's peak power.

so it's not it's peak power, but the range of a engines ability either side of it's optimum power, what is the norm for + and - from it's peak potentional?
%10, from which we measure it's power band. or is it more of a lose term.

[roger_doger]

I may be missing the mark here but I think the original debate may have stemmed from a confusion over what is correctly known as a powervalve. A powervalve is a sort of sliding plate that is attatched in front of the exhaust port of two stroke bikes (motocross and some road). The reason is that because high performance two strokes have large expansion chambers to produce high power, they would otherwise suffer greatly in low to mid rpm power because of the lack of exhaust back pressure. Different setups are operated either by cable or electronically. The "valve" is down at low rpm to create more backpressure (and power), and then opens at higher rpm so the bike can produce maximum horsepower.

The effect of all this is that in real riding conditions, it creates a sudden surge in power when the valve opens, which is a trademark of any high performance two stroke.

The confusing bit is that a powervalve is often called a powerband. But that word is also used when describing the power delivery of any motor.

But to be clear, powervalves are only present in the form described on two strokes. There is additional confusion to this saga however as Yamaha, and more recently Suzuki, have used the same principle in their four stroke sports bikes in the form of valve located in the middle of the exhaust system. This setup is used for the same purpose as a powervalve in two strokes

Just my 2c worth

[mini_me]

so it's not it's peak power, but the range of a engines ability either side of it's optimum power, what is the norm for + and - from it's peak potentional?
%10, from which we measure it's power band. or is it more of a lose term.

i've allways just thought of it as a loose term and if differs from engine to engine (or bike to bike whatever you prefer) and i dont think you can really quantify a powerband as such, and because of this there are so many different opinions about what a powerband really making it very hard to define just what it is
m/m

[Jackrat]

Do all bikes (and cages) have powerbands?

NO,at lest Kawasaki ZR750's don't.
You wann'a buy one?

[vtec]

I agree with pretty much everything said here.

I've had some serious dumbasses asking me if my bike has a powerband. And I have to help them sort out what they mean by a powerband. Most of the time, its just a term they've heard dirtbike rider's use, in terms of when the engine changes over the powervalve.

I agree that a powerband is a motorbike's effective power range or possibly, just the range where it really starts to boot you in the pants. In this case, that would mean that every vehicle has a powerband, cause all vehicles have an effective power range. Just my dad's diesel van's powerband goes from just above idle right to where you lose power, (I don't know where it is cause it ain't got no revmeter). And my little one here goes from 10,000rpm to 19,000rpm.

[MacD]

Do all bikes (and cages) have powerbands?

Not all bikes come with powerbands installed, however you can buy after-market ones (as illustrated below).

[marty]

I may be missing the mark here but I think the original debate may have stemmed from a confusion over what is correctly known as a powervalve. A powervalve is a sort of sliding plate that is attatched in front of the exhaust port of two stroke bikes (motocross and some road). The reason is that because high performance two strokes have large expansion chambers to produce high power, they would otherwise suffer greatly in low to mid rpm power because of the lack of exhaust back pressure. Different setups are operated either by cable or electronically. The "valve" is down at low rpm to create more backpressure (and power), and then opens at higher rpm so the bike can produce maximum horsepower.

The effect of all this is that in real riding conditions, it creates a sudden surge in power when the valve opens, which is a trademark of any high performance two stroke.

The confusing bit is that a powervalve is often called a powerband. But that word is also used when describing the power delivery of any motor.

But to be clear, powervalves are only present in the form described on two strokes. There is additional confusion to this saga however as Yamaha, and more recently Suzuki, have used the same principle in their four stroke sports bikes in the form of valve located in the middle of the exhaust system. This setup is used for the same purpose as a powervalve in two strokes

Just my 2c worth

i have to disagree. the powerband is created by gas flow being accelerated by the shape of the exhaust. the powervalve is only a means of allowing more gas flow. you can jam/tie the powervalves in the open position, and you will still get a noticeable powerband, especially in a performance 2 stroke (like an RS250/RGV etc). it is a result of the engine (and corresponding exhaust gas flow) reaching it's optimum tuned pipe flow rate, and the exhaust pipe literally 'sucking' the exhaust gasses out, allowing more air to come in the intake side, and correspondingly more air to go BANG.

4 stroke engines do not have a powerband in the 2 stroke sense. they have a power (torque) curve, and tend to have a much more even power delivery. this of course can be modified by cam lobe cut/valve opening duration/timing etc.

becuase they have twice the piston travel per cycle, they have a period of time when both valves are closed, so they tend to pulse more than a 2 stroke, not allowing the 'sucking' action of a 2 stroke exhaust system to be effective.

[curious george]

We need a big dose of Motu in here...
Failing that, captain sensible himself..... Ixion!
Well done that man

[thealmightytaco]

My understanding of it all is that everything has a power curve, and with 4 strokes it's pretty smooth and gradual and there's good power for much of the rev range cause the valves can close it all off so you get good compression the whole time. But with 2 strokes things need to hit some kind of rhythmic perfection before the same valve effect is working which only comes in during a certain "band" of the power curve, the rest of the curve is schlock cause things aren't humming right and you're letting things escape everywhere. Or something. So the power band is just a name for the useful part of the power curve for 2 strokes, as I have come to see it. But it's all terminology really, open to interpretation.

[TwoSeven]

i have to disagree. the powerband is created by gas flow being accelerated by the shape of the exhaust. the powervalve is only a means of allowing more gas flow. you can jam/tie the powervalves in the open position, and you will still get a noticeable powerband, especially in a performance 2 stroke (like an RS250/RGV etc). it is a result of the engine (and corresponding exhaust gas flow) reaching it's optimum tuned pipe flow rate, and the exhaust pipe literally 'sucking' the exhaust gasses out, allowing more air to come in the intake side, and correspondingly more air to go BANG.

4 stroke engines do not have a powerband in the 2 stroke sense. they have a power (torque) curve, and tend to have a much more even power delivery. this of course can be modified by cam lobe cut/valve opening duration/timing etc.

becuase they have twice the piston travel per cycle, they have a period of time when both valves are closed, so they tend to pulse more than a 2 stroke, not allowing the 'sucking' action of a 2 stroke exhaust system to be effective.

I think these two posts are talking about similar things. While I dont know much about two-smoke tuning. I would suggest that the expansion chamber shape is used for both gas expansion/slowing (start of the expansion chamber) and for resonance [not sure if thats the correct word] tuning of the power wave (the closing part of the expansion chamber). If thats the case, then the rebounding power wave will require something to cause it to rebound back off the exhaust port and either build pressure for extra combustion or scavange the port - which ever affect is desired.

This is the same as in four-smokes and is a part of header/megaphone design. To get the effect occuring at two different RPMs (usually mid-range and high end), you insert a valve at the end of the attenuator (primary pipe) which as the effect of changing its length - thus changing the period (I think thats the correct word) of the rebounding wave.

Hopefully I got it right.

[Motu]

Modern bikes don't have noticable powerbands these days - 2 strokes now have powervalves and are sorta 2 motors in one,with the powervalve in the lowspeed position (shut) the exhaust port has timing suitable for low speed power,although the other ports are unchanged.With the powervalve open the bike makes high speed power,they also have reed valves and crankcase induction.Two strokes make strong hard horsepower everywhere these days - it's seamless....and still scary.Strongest hitting powerband I've ever come across was on a mid 80s Husky 250 MXer,it was the proverbial lightswitch and I was never able to keep the front down when it hit,even on the road where there were no other obsticals to run into.

As for 4 stroke, a by product of car makers having to meet emission controls,there have been huge advances in combustion chamber design and camshaft profiles.There are even motors with variable cam timing,so sorta like a 2 stroke powervalve - so a street 4 stroke now makes much more HP than a ropey almost unriderble motor did 25 yrs ago,but idles around town like a Morris Minor.The race tuned singles and twins from the 50s and 60s had rather narrow powerbands and were quite hard to ride with close ratio 4 speed boxes - they had megaphonitis when the dropped ''off the cam'' and would 8 stroke and splutter,you'd have to slip the clutch into the powerband and get the speed back up.

Powerbands are a thing of the past...for old fart to reminiss about.

[gav]

Rather than the term "powerband" think of it more as a a "sweetspot", that rpm range that your engine is working at its best, you know how sometimes you may need to shift down one or two gears to pass something, or how you know you should change up a gear when you feel the power start to flatten out after hitting peak pwer. "Powerband" is more a two stroke term as a tuned two stroke will barely function outside its sweetspot or powerband, so you tend to ride them on the track just knowing where that maximum hit or rush of power is going to come in, ie you'd prefer it just as your exiting the corner rather than entering normally, or just as youre about to pull out to pass that car or ya mate! Equally a two stroke will almost feel like it hits a wall when you over rev them. Look at the hp curves in magazines, look to see if the power has a "kick" at a certain revs and also how the power drops away quickly after hitting maximum hp. Four strokes tend to have a flatter curve and more of an over rev ability, see how the power curve slowly drops, you've got a wider power curve to use, hence a wider "powerband" or "sweetspot".
Hope this helps!

[Jamiepo]

Yes. The faster they go, the further up and down in the sleeves the pistons go. If you go too fast the piston either impacts the head or drops out the bottom into the sump. Be careful.


I have been pondering this staement for a wee while and am wondering how much truth there is is its?? I just can't see how unless the metal stretches it would do this, I know that in a 4 stroke the piston can sometimes hit the overhead valves at high RPM especially with sticky valves but going higher and lower in the sleeves at a high RPM, I just can't fathome how that works. Or was hitcher just being sarcastic??

[avgas]

everything has a 'powerband', not everything has powervalves.
Of course in some machines the powerband is all over the rev range.

[MisterD]

I have been pondering this staement for a wee while and am wondering how much truth there is is its?? I just can't see how unless the metal stretches it would do this, I know that in a 4 stroke the piston can sometimes hit the overhead valves at high RPM especially with sticky valves but going higher and lower in the sleeves at a high RPM, I just can't fathome how that works. Or was hitcher just being sarcastic??

I think it's called exaggerating for comic effect....it certainly is possible for the piston to hit the cylinder head at high revs, especially with 2-strokes where the shape of the head and the squish band is important. If your piston is too heavy then it certainly is possible for the crank to stretch enough to cause an expensive problem.

[*sic]

Vt@k Y0...

[Lou Girardin]

The Rocket has a power band, starts at 800 rpm and goes till the limiter stops play.

[Motu]

I think it's called exaggerating for comic effect....it certainly is possible for the piston to hit the cylinder head at high revs, especially with 2-strokes where the shape of the head and the squish band is important. If your piston is too heavy then it certainly is possible for the crank to stretch enough to cause an expensive problem.

Back in the 60s when 2 stroke design was being pushed to the limits,they were getting some astounding rpm,it would still considered doing pretty well these days.Because a 2 stroke fires everytime the piston is at TDC,there is a resistance to the pistons desire to reach for the sky - this was taken into account in the design,everything as light as possible....but if the engine just misfired the piston could fly apart from the forces.So in a way Hitcher is right....but you knew he couldn't be wrong eh?

[MisterD]

Back in the 60s when 2 stroke design was being pushed to the limits,they were getting some astounding rpm,it would still considered doing pretty well these days.Because a 2 stroke fires everytime the piston is at TDC,there is a resistance to the pistons desire to reach for the sky - this was taken into account in the design,everything as light as possible....but if the engine just misfired the piston could fly apart from the forces.So in a way Hitcher is right....but you knew he couldn't be wrong eh?

I was actually wondering if he knew how right he was! I've seen some real horror-show pictures of what happens when you over-do your 2-stroke tuning.

I have a grand total of 2mm clearance between my piston and cylinder head squish band on my Lambretta, which is fine with the alloy piston I run but would be dodgy with heavier jap motorbike pistons....

I had noticed that no-one seems to be recommending up-rating your piston-return springs, what's with that?:wacko:

[TwoSeven]

I think it's called exaggerating for comic effect....it certainly is possible for the piston to hit the cylinder head at high revs, especially with 2-strokes where the shape of the head and the squish band is important. If your piston is too heavy then it certainly is possible for the crank to stretch enough to cause an expensive problem.

Actually, con-rods are known to stretch. How much so these days I havn't bothered to check what with forged titanium being used in high end applications its probably almost zero, but it is an amount thats big enough to require taking it into account when tuning engine.

From memory, its to do with having the weight of the piston on top thats accelerating from stop to x-miles an hour in half a nats whisker of a second and then trying to stop again.

I think there is a special engineering formula around thats used to calculate it all. But I dont know what it is.

[Brian d marge]

have fun ..click here (http://www.slowgt.com/Calc2.htm#PistSpeed) for some easy engine calculators

Stephen

[T.I.E]

and there is no other thread i have enjoyed, or more so have i accquired a bloody head ache.
lmao.
hell sweet spot sounds better to me. "sweet spot" when the bloody engine is producing the most approiate amount of power for what the rider can handle.
then its each to their own.

so how do you like to eat your cabury cream egg?

[ducatilover]

Well I was having an arguement with magua about powerbands, he told me every thing has a power band, his rg150 my old zxr250c his mums car, my car indiana's fxrpersonally i dont know shit but i want to say my 1c worth.....i would call a power band an area in the engines operating range where there is a significant amount more power in an instantaneous kind of way, some engines do not have a powerband of sorts as its more of a linear gathering/increase of power output with most cages and four strokes.....my old man had an xs1100 and fitted a "special" 4 into one system on it, he found this created two areas where there were huge amounts of power and being an 1100 thats the kinda power that throws you off or causes extreme speed wobbles or power slides and the sort......welll i just lost myself and forgot where i was so i hope you enjoy my pointless input:yes:

[avgas]

4 stroke engines do not have a powerband in the 2 stroke sense. they have a power (torque) curve, and tend to have a much more even power delivery. this of course can be modified by cam lobe cut/valve opening duration/timing etc.

So wouldnt that dictate a 'power band' - when the valves and cams reach harmonics over a bandwidth?

[avgas]

The Rocket has a power band, starts at 800 rpm and goes till the limiter stops play.
LOL sounds like my old David Brown 885 (International)