Only 2 Strokes have powerbands

[RangerRick]

Ok I need to prove this once and for all.My friend thinks 2 strokes are the only engines with a powerband and that it is when the rpms are as high as they could go.I always thought 2 and 4 strokes have them and its where the engine has reached its peak potenial.Who is right or are both of us wrong?

[wilkin250r]

You're both wrong. Powerbands only come on livestock, it's that thing they tie around a bulls nuts to get him to buck.

[insaneracin2003]

Originally posted by wilkin250r
You're both wrong. Powerbands only come on livestock, it's that thing they tie around a bulls nuts to get him to buck.
that is some funny chit rite ther:D

[nakomis0]

I never heard of a powerband on some nuts, but I could see how it would make you buck!

The powerband your talking about is just where it feels the power comes on the most.

[coryatver]

Your both wrong. The power band doesn't come on at the highest RPM. Depending on what exhuast you have it comes at a different point in the HP vs RPM curve. When the Pressure leaving the exhaust equals that of the pressure coming in then it creates an equilibrium condition that burns the fuel most efficient which is the power band. 4 strokes don't have a power band. They burn efficeintly the whole time because of there design.

Now powervalves keep the motor closer to the powerband the whole time by adjusting the flow of the exhuast gases therefore changing the exhuast pressure.

[300ex mxracer]

all engines have some sort of powerband, some more than others

[coryatver]

4 strokes don't have powerbands:huh

[gbcap]

A term used to describe measured torque and calculated horsepower, displayed on a graph.

powerbands are not just ONE point. it is the curve of the power in a motors rpm range. so both 2 and 4 have it.

[coryatver]

Oh really. Do you have a graph of an example of a 4-stroke powerband:confused:

[GPracer2500]

"Powerband" is a term most often used to describe the RPM range in which an engine is making the majority of its horsepower.

It is most often associated with 2-strokes because they have a very distict RPM range in which meaningful power is produced. For example, a 125 two stroke makes very little power until maybe 7000 or 8000 rpm, after which there is a sudden spike in power until maybe 11000 rpm. Many dyno charts for such engines are truncated so as not to even show the lower rpm ranges. In that hypothetical example, the "powerband" would be from 7000-11000 rpm.

On a four stroke, the term "powerband" has less meaning because they typically make usable power throughout their RPM range. However, if you built a four stroke that had very peaky power delivery characteristics (like most 2-stokes) then the trem "powerband" might again be useful in describing the rpm operating range in which useful power is produced.

To reiterate, "powerband" is just a term used to describe the RPM range in which an engine is producing meaningful power. So, in a sense the average four stroke's "powerband" covers most all of it's RPM range and the average (small bore) two stroke has a "powerband" that covers only a portion of it's RPM range.

[400exstud]

Originally posted by wilkin250r
You're both wrong. Powerbands only come on livestock, it's that thing they tie around a bulls nuts to get him to buck.

Chalk another one up for wilkin. Yet another grand technical post.

[wilkin250r]

Ok, let's be serious here for a second and answer the question.

The "powerband" of a motor is where it makes the most power. It's a simple definition. Both 2 and 4-stroke motors have them.

However, it's REALLY noticiable on a 2-stroke, due to the effects of the expansion chamber. You get that sudden burst of acceleration when the power comes on very quickly, and it drops off almost as quickly. On some engines, it's only a couple hundred RPMS wide.

A 4-stroke has a powerband as well, but it's not as obvious because it doesn't have that sharp increase. It's usually much wider than a 2-stroke, but there is definitely an RPM range at which the motor is making most of it's power.

Unfortunately, there's no set "definition" of powerband, but as a general rule, it's the RPM range at which the motor is within 15%-20% of peak horsepower.

[coryatver]

Boy I was wrong. Technically to calculate it it is the rev range between peak torque and peak power. But if you are out on the track or trails people will think you are crazy saying your 300ex has a powerband. It is just when a 2 strokes hp increases fast! I have rode a banshee and i have a 400 and I know a 400's power curve may be called a powerband but it definilty not a POWERBAND like on a banshee.

Wilkins congradulations for know how to use google and looking up stuff for everyone :p

[underpowered]

Originally posted by wilkin250r
You're both wrong. Powerbands only come on livestock, it's that thing they tie around a bulls nuts to get him to buck.

:rolleyes:

Wilkin is right, you are both wrong. What is refered to as the "powerband", is simply how the power comes on. a smooth powerband usually describes four strokes, it is a much more linear pull throughout the RPM range, not the Highest power. A 2-stroke is known to have a more violent powerband, usually has a Hit, or a stong point at which it comes on.

[nakomis0]

Originally posted by coryatver
Oh really. Do you have a graph of an example of a 4-stroke powerband:confused:

Hers my Dyno. Kinda looks like I got a little powerband st the 35-40mph marks. Cause you can see how fast the graph shoots up at that point.

Then a second one almost comes on at the 50-55mph mark.

The graph is suppose to have RPMs but the computer wasn't working right so its MPH.

http://memimage.cardomain.net/member_images/7/web/343000-343999/343319_46_full.jpg

[wilkin250r]

Originally posted by coryatver
Wilkins congradulations for know how to use google and looking up stuff for everyone :p

Oh, please. I don't need to google "powerband", that's novice stuff. Everybody should know that.

[jordan_m6]

every car, truck jets ski, any thing that goes through its rmps has a powerband.

[RangerRick]

Thats what I thought.Thanks everybody for setting this straight.

A powerband is a way to gauge what the spead of the rpm is. W hen a motor starts producing significant power referred to as "coming into the powerband" or "coming on the cam."This power production will stay at high level and keep increasing until the efficiency of the motor falls off at high rpm and as the power drops off it is referred to as "off the powerband" or "off the cam"

So that tells you that both two and four strokes have powerbands. So your right.
But a four strokes powerband is like this__,,___ and a two stroke powerband is like this ___/\/\__ way more power.