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some 09 stuff from yami site KINDA

AndersY, I may have done some snoozing... However, Acceleration is EVERY bit as important to me as top end, and all along we have been measuring equal horsepower to higher torque. Equal horsepower means top speed will be basically the same, higher torque of the 3 cylinder means better acceleration. PERIOD.
 

Word up!! I've been lurking around for a while now, but I've got to say, I love the sound of the 4 cylinder. I don't think you'll ever see a 600, 120 HP sled from Yamaha...they've already filled that void with the 120 hp triples. I love Horsepower, and would've opted for the Apex, if the 2006 Nytro, with the MCXpress Turbo hadn't been available to me. I'm a long time Yamaha fan and have been working at a couple of Yamaha Dealerships for the past 7 years. Peace!! ;)!
 
QCRider said:
AndersY, I may have done some snoozing... However, Acceleration is EVERY bit as important to me as top end, and all along we have been measuring equal horsepower to higher torque. Equal horsepower means top speed will be basically the same, higher torque of the 3 cylinder means better acceleration. PERIOD.
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No, higher torque does NOT (necessarily) mean better acceleration. Higher hp means better acceleration, PERIOD :) (things aren't really as simple as this since unfortunetly, but pretty close when we talk about snowmobiles :))

Again, take the Phazer. It's got (according to the reviews, never tried it myself) a great low'end but hardly anything on the top. Ever wondered why that is considering that it's very far from a torque monster ?
 
wow u guys..... torque is what gets u rolling..... example did anybody watch pinks with the v rod versus the big 4 cyl....... well the high torque ie larger combustion chamber so more force created everytime it fires would lunch the 4 cyl..... until the smaller pistoned 4cyl got wound up and overcame its lack of torque and come flying by........ hmmm torque does not equal horsepower
 
Laban said:
No, higher torque does NOT (necessarily) mean better acceleration. Higher hp means better acceleration, PERIOD :) (things aren't really as simple as this since unfortunetly, but pretty close when we talk about snowmobiles :))
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Try to read this ONE MORE TIME. THE ASSUMPTION IS EQUAL HORSEPOWER! That is how we started the whole discussion. A triple that makes 170 hp with more torque than a 4 holer with 170 hp WILL ACCELRATE FASTER. PERIOD. Stop trying to compare horsepower. The horsepower is assumed to be equal. The difference is that the 4 holer is using RPM to generate it whereas the triple would be using displacement. To quote an old idiom... "There is no replacement for displacement."
 
QCRider said:
Try to read this ONE MORE TIME. THE ASSUMPTION IS EQUAL HORSEPOWER! That is how we started the whole discussion.
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That's true, but then we've hade statements like "higher torque means faster acceleration". And, higher torque doesn't necessarily mean faster acceleration if they have the same hp. There's a CVT & and possibly gear-reduction between the engine and the CVT which makes torque pretty much irrelevant.

A triple that makes 170 hp with more torque than a 4 holer with 170 hp WILL ACCELRATE FASTER. PERIOD.
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And i'll say no again. PERIOD. It's still all about hp and possibly the powerband. A broader powerband might be relevant (see below) but you don't need anything close to what the new Doo produces. Such a broad powerband actually means that it's not tuned optimally for a high output.
So, same hp, both have a nice broad powerband so that the CVT easily can work within the max hp = same acceleration.

Anyway, look, the job of the CVT is to keep the engine at it's maximum hp when you accelerate. If that's at 8700 rpm (on the clutch, might be 11500 rpm on the engine) then that's where it should try to "stay". That means that the CVT will try to keep your engine at 8700 rpm when you hit full throttle. Then it'll just change "gears" as you start to go faster, while trying to keep the rpm at 8700 rpm. This is of course very noticeable when you hit full throttle on a snowmobile.

The beauty with this construction is of course that the important thing is hp. A broad powerband is still good to have since it makes it much easier to adjust the clutch (CVT). And the CVT on a snowmobile isn't perfect either.

A good low-end (call it torque if you will) might be preferable for utility type of snowmobiles though. That's actually a part where the Ski Doo marketing is correct about the benefit of "torquey" engines. That is, "lower sound where most of the driving is done". Dunno about the "fun performance" part :)
 
Laban said:
higher torque doesn't necessarily mean faster acceleration if they have the same hp. There's a CVT & and possibly gear-reduction between the engine and the CVT which makes torque pretty much irrelevant.
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You watch too much F1. Ask any engine designer if they would prefer high torque or high RPM as their means of generating HP. The answer will NOT be RPM. :o|

Anyway, I'm done. Your argument is completely based on what you WANT in a sled versus what would make a faster sled. I prefer the sound of the 4 holer too, but I could give up that sound for something that pulled like the proverbial freight train. (which by the way have a lot of torque...)
 
QCRider said:
You watch too much F1. Ask any engine designer if they would prefer high torque or high RPM as their means of generating HP. The answer will NOT be RPM. :o|
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You're making this way to simple in this case. The benefit of having a smaller engine and generate hp at higher rpm's is that you get a smaller and lighter engine. I would think that this is one of the primary goals when making a snowmobile engine. And as i said, a snowmobile uses a CVT so this happens to be a perfect match, well, not really perfect since you need the gear reduction above ~9000 rpm but close :)

Anyway, I'm done. Your argument is completely based on what you WANT in a sled versus what would make a faster sled.
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No it's not. May i ask if you agree with me on how a CVT works ?
And if that's the case, why would a 120hp@8500 rpm engine accelerate faster then a 120hp@12000 rpm engine ?

And another thing that you seriously need to think about is that the gear reduction does something afa torque goes. Torque applied at the primary clutch in this case. Perhaps this will explain a thing or two:

http://teamdavinci.com/understanding_gear_reduction.htm

What are the advantages and disadvantages of gear reduction?

And third, along those lines, the torque produced by the output is inversely proportional to the amount of reduction in the gear box. Say what? Basically, if you have a 4:1 gear box then the bot moves 1/4 as fast but has 4 times the torque! So you can have a 120 pound robot with the right gearing that will push a 400 pound load across the floor!
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What do you think this means when comparing 120hp@8500rpm vs 120hp@12000 -> 8500 (gear reduction) rpm afa torque applied at the primary clutch ?
 
I was hoping that you would say "the torque on the clutch will be exactly the same, now i understand. And of course there won't be a difference in acceleration between a 120hp@8500 rpm and a 120hp@12000 rpm engine, all else being equal" :)

Perhaps you could explain what you're disagreeing with

How the CVT works ?
gear-reduction -> torque on the clutch ?

None of the above but you still think that higher torque = faster acceleration ?
 
Laban said:
You're making this way to simple in this case. The benefit of having a smaller engine and generate hp at higher rpm's is that you get a smaller and lighter engine. I would think that this is one of the primary goals when making a snowmobile engine. And as i said, a snowmobile uses a CVT so this happens to be a perfect match,
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My way of looking at the logic is more in line with Laban. These are air pumps, in a 4 cylinder you can have 33% more valves. Yes you could use bigger valves in the 3 holer, but that would limit RPM.

You cant dismiss F1 either, 300HP of displacement per liter, some 19,000 RPM. F1 cars need to be fast yes, but they need to be amazingly fast at accel and decel and cornering. Of course those are great qualities to have for a snowmobile as well.

In the real world, look at the fastest production vehicles you can buy.
Motorcycles where 4 cylinders are the way to go, if the faster bike would be the 3 cylinders, then you would see a bunch of them from ALL the manufacturers.

Nothing wrong with gear reduction either (my guess would be 4-5 lbs at most) allows the higher RPM which makes power, to be used with fly weight CVT in a simple elegant manner.

Spine tingling thrill to the senses........
don't get me wrong, the 3 cylinder Yamaha motors are great, but to me the 4 cylinder is a symphony of delight that thrills the senses. Most boring, actually no thrill at all (in my humble opinion) are the 2 cylinder 2 strokes.
 
I kinda like the fourbanger sound myself. Doesn't mean that i think they should put a 4cyl motor in the snocross sled though.

You need to balance the nr of cylinders depending on the hp you want. I'm thinking that what Yamaha is doing today is pretty optimal afa weight/hp goes:

500cc twin = 80 hp

1000cc quad = 150 hp (probably 160 very soon)

All that's missing is a 120-130 hp triple at 750-800cc instead of the Nytro engine (i'm guessing something like 15-20 lbs lighter) and perhaps a detuned version at around 100 hp too :)
 
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