What is a powerband?

[Tri-ZNate]

I always hear talk about people taking them out of dirtbikes to make them road legal. I also heard there were power bands in some trikes. So what are they?

[Huffa]

The engine's character in terms of power
production is often termed the "powerband." Where does the engine begin to make power? Where does the engine begin to fall off in power production? Is the power delivery flat and consistent or aggressive and peaky? These questions are answered in the description and understanding of the engine's powerband. Some powerbands are narrow, while other are deemed broad. Some are peaky, some are flat. An engine that makes appreciable power from only 6000 to 8000 rpm (a range of 2000 rpm) would be considered to have a narrow powerband. A comparable-sized engine that makes power from 3000 to 7000rpm (a range of 4000 rpm) might be considered to have a broad powerband. More so than any other internal components of the engine, the camshaft and its complimentary valvetrain components will establish the powerband of the engine

[TimSr]

The "power band" is the RPM range in which your engine can deliver the fastest rate of acceleration. In 4 strokes it tends to be somewhat linear throughout the middle of the RPM range. In two strokes, it tends to be a lot sharper, more sudden, and mostly in the top part of the RPM range. The idea of different pipe designs is to shift the powerband more in the direction that best suits the type of riding a person does. If you trail ride or hillcimb with a two stroke you may want more of a low end or midrange powerband, so you get a pipe designed to accomplish that. If you are MX racing a 4 stroke, you may want more of a top end powerband and change to a pipe or other modification for that. The powerband is not a part. Its the RPM range in which you engine delivers the most power.

[Tri-ZNate]

Oh ok. Its starting to make sense now.

[Rex Karz]

Powervalves, hovever, are used in some designs of 2-stroke engines. They open and close ports at different rpm's to control the engines output. They also, incendentally have direct influence on the *Powerband*. Engineers who are trying to optimise engines for emissions can use powervalves. It's funny, how the 2 stroke makes so much power, but the waste is just too big a factor. Think about it - for every 30 tanks of gas you use, you are throwing a tank full of oil out on the ground.

[250rAL]

Powervalves, hovever, are used in some designs of 2-stroke engines. They open and close ports at different rpm's to control the engines output. They also, incendentally have direct influence on the *Powerband*. Engineers who are trying to optimise engines for emissions can use powervalves. It's funny, how the 2 stroke makes so much power, but the waste is just too big a factor. Think about it - for every 30 tanks of gas you use, you are throwing a tank full of oil out on the ground.

Every 50 tanks for me

Would you run 30 tanks of gas through a 4 stroke before "dumping the oil on the ground"?

If you think of it that way, a 2 stroke actually uses LESS oil

[Mr. Sandman]

It's funny, how the 2 stroke makes so much power, but the waste is just too big a factor. Think about it - for every 30 tanks of gas you use, you are throwing a tank full of oil out on the ground.

If you really think about it all gasoline powered vehicles, 2 or 4 stroke, are dumping oil onto the ground or into the air since gas is made from oil. I'll also add that there are cars that leak more oil in one month than my 2 stroke will ever dump onto the ground for as long as I own it.

[Rex Karz]

I don't understand the logic here, please explain:

Would you run 30 tanks of gas through a 4 stroke before "dumping the oil on the ground"?

If you think of it that way, a 2 stroke actually uses LESS oil

And Sandman, you're ingoring scale. Your 280 lb ATC uses less oil than a 3000 lb car? By that argument, my weed wacker pollutes less than a bulldozer so does that mean I can throw my yard clippings on the freeway? LOL

We're talking degrees here. The main point (for Me) is "how can engineers get a higher power/pollution ratio from the 2 stroke engine?"



Actually, I think the main source of 2-stroke emissions comes from unburned fuel scavenged through the pipe.

[Oldshell4481]

ever rode a two stroke dirbike and held the throttle and you got the trailprotrailprotrailprotrailprotrailpro scared out of you when it all the sudden accelerated greatly?? thats powerband

[Tri-ZNate]

ever rode a two stroke dirbike and held the throttle and you got the trailprotrailprotrailprotrailprotrailpro scared out of you when it all the sudden accelerated greatly?? thats powerband

Nope I have never had the priveledge of riding a two stroke or a dirtbike.

[edog]

I can't wait to get my 1988 125 kx going,they have a scary powerband.

[Mr. Sandman]

I don't understand the logic here, please explain:
And Sandman, you're ingoring scale. Your 280 lb ATC uses less oil than a 3000 lb car? By that argument, my weed wacker pollutes less than a bulldozer so does that mean I can throw my yard clippings on the freeway? LOL. We're talking degrees here. The main point (for Me) is "how can engineers get a higher power/pollution ratio from the 2 stroke engine?" Actually, I think the main source of 2-stroke emissions comes from unburned fuel scavenged through the pipe.

I'm saying my 2 stroke will burn less oil than all the cars, trucks, atv's and everything else out there that are so poorly maintanined or worn out that they either leak/drip oil all day long everywhere they're parked or they burn a quart of oil or more a month. Take a look at any parking lot in the country, you could scrape up enough wasted/polluting oil start your own refinery.

As for the power/pollution aspect of two strokes, I agree there's always room for improvement, but that will never happpen since it's easier for our jerk ass legislators to ban them (like CA has and it'll eventually be nationwide) and force the manufacturers to go the 4 stroke route.

Granted the two strokes of old needed to run 20:1 mixture, but with todays synthetic oils there is no need to mix that rich. I run my 250R at 100:1 and have never had a problem. Smoke is almost non-existant and performace and reliability are 100%.

And 250sxwheeliepop, didn't mean to hijack your powerband thread.

[TimSr]

They both burn oil, it just takes a differnet path getting there. The pollution aspect is easy to address for two strokes, though, but your right in thats its easier to just ban them. There are some super good non-petrolium based oils out there that are completely biodegradeable. Ive never had emmisions analyzed, but I know that my two stroke put out less smoke than any of the adult sized 4 strokes at the race track yesterday, and Im running one of those environmentally friendly oils I mentioned.

[Mr. Sandman]

Don't be shy, sales pitch it! It's Blue Marble and I use it too.

[TimSr]

Don't be shy, sales pitch it! It's Blue Marble and I use it too.

LOL! Thanks Sandam! Its a lot more believeable when pitched by someone besides the salesman!