Does the sportsman 700 twin have more power because it's a twin that fires at parallel times?

I'm talking about the 700 that has the two pistons in the same position, but one fires whiel the other one doesn't, and then vice versa. If this was a single, would there be less power?

 

I'm not precisely sure what you're asking...so I'll throw around a few answers and hope one sticks. I'm not an Engine builder, but just have a good understanding.

The fact the pistons fire in opposite (one is up/the other is down) wouldn't/shouldn't matter all that much for Hp...but more to torque. The other reason is balance...it will run alot smoother.

As for twin/single. 600 cc's is 600 cc's, whether it's two or one. Once again, torque would be the main difference in the two with some HP gain. Someone can jump in and totally tell me I'm wrong, and I won't be pissed....but a single should have lower torque, whereas the twin would have torque at higher rpm. The reason I say this...is the single will have a larger piston (obviously), with a lot less moving parts....for the same 600cc.

I think the ratio goes something like this.

1 pound lost on non-moving parts is 1 times return on HP
1 pound lost on moving, wheel related is a 5 times return on HP
1 pound lost on moving, engine parts is a 15 times return on HP

So..you can see pretty quickly why the NASCAR/NHRA guys send all the time in the engine shop shaving weight off the engine parts. Save just a few ounces, and you've got 3 or 4 more hp...which could be the difference in passing someone.


I'm sure...700cc's is not the end of the line on power...I'm sure we'll see 1000cc ATV at some point....it's inevitable.

 

Does the twin, by nature of being a twin give it more power:

Not necessarily. There are soooo many other variables, it is hard to compare. For example, think Raptor. It is a single-cylinder machine, of smaller displacement than the Sportsman, and it can make quite a bit of power.
What the twin-cylinder brings is (arguably) more torque, and definately smoother power output, especially at higher RPMs. As a piston gets larger and heavier, you have more and more mass to start & stop every piston stroke, which can add up to quite a bit of vibration.

Twin cylinder engines have smaller pistons, which allow higher RPMs, all else being the same (think how fast the little chain saw engine spins with it's tiny piston compared to, say a big truck engine), and with lower vibration. Also, by having twice as many smaller 'power' strokes, there is also less strain on the driveline, the flywheel can be lighter (making the engine faster revving). The biggest downside to the twins is more complexity & moving parts.

The paralell inline twin of the Sportsman has a few other advantages as well, when compared to a V-twin. By having the cylinders inline, and the intake strokes evenly spaced, Polaris can get by with one carbureter, and one set of valve gear (pushrods, rockers, etc). The V-twins need 2 carbs, and a set of valve gear on each head, pointing different directions. Don't get me wrong, the inline twin needs as many rocker arms & such, but they are all together, so to speak, so it has a slightly simpler design.

The biggest dis-advantage I can see to the paralell twins is that they will be a little wider than a comparably sized V-twin due to the fact that you can 'stagger' the cylinders of the V style engine. The paralell twin needs room between the pistons to still have a water jacket. A V-twin, with its pistons offset, only needs to be enough wider for 2 connecting rods on the crankshaft.

Farmr

 

A little off topic here.

if one piston is firing and the other is on the ehaust stroke but both are @ tdc @ the same time would you not in theroy have a 2 stoke type of power delivery? (a powerstroke every time pistions are @ TDC). Also would you get more torque?
( 2 pistons on same crank positions acting like one big piston)

I must agree with Ken and Frmr. less vibration, lighter rotating mass and more simple engine design.

Maybe I'm blowing sunshine up my own skirt but i just have been thinking about this engine design and the diffrent exhaust sound intriged me. (Been a little slow here in the office).

Rider

 

One other to consider. The Sportsman 600/700 use 2 valves per cylinder... now excluding all the other factors mentioned (cam profile, compression, ignition curve, bore / stroke. intake tract length, port size, etc) ... 2 valves heads typically cater to better low rpm /' torque. And considering most people with utility quads want power and torque at low RPMS, this engine design is perfect. If you were trying to build an engine that made tons of power high in the RPM range, 4 valves would definitely be more appropriate.

 

Just to add more confusion, what is the difference between a twin cylinder engine, with 2 valves per cylinder, and a single cylinder engine, with 4 valves per cylinder, and equal displacement?