<div class="FTQUOTE"><begin quote>Originally posted by: Redneck_giant

30.9 cc are equal to 1 Hp. So the Honda 450 has 14.6 Hp and the Grizz 660 should have 21.3 If you look at the numbers it just doesn't look right, but I work for a man that sales Chuck Wagons and they say their pumping out 340 cc or 11Hp. Things you have to consider are transmission, pipes, and any other thing that may add power.</end quote></div>

It depends on the camming of the engine for the most part. If the engine is set up like a tractor, for low rpm operation, it will get low HP numbers and require a large engine. If the engine is set up to rev out to 20,000 rpm like indy cars then it will get high HP numbers with relatively small displacement.

Another good factor in determining what an engine might put out are bore/stroke ratios. A ratio of 3:1 or 2:1 will be a high HP, high rev engine. 1:1 or less is a torque monster that doesn't rev out too well.

So, 30.9cc = 1HP only with a certain cam, bore/stroke ratio, fuel, and of course induction and exhaust system. Every other combo will have a different HP/cc ratio. Basically what I'm saying is there are no rules of thumb.

A good example of bore/stroke ratios can be seen in comparing the suzuki 250 quadsport to the honda 250x or mojave 250, all made in the mid 80's. The suzuki had a bore x stroke of 68.5x67. The honda and kawasaki had 74x57.3 and 74x58 respectively. Although displacement were all about the same (give or take a cc or 2), honda and kawasaki enjoyed higher advertised HP numbers over suzuki because they could produce more HP at higher rpm. But what nobody ever talked about was that the suzuki has more area under the HP curve up to,,, say,, 5000-7000 rpm or so. Therefore the suzuki should be a better trail quad. But in a drag race with enough distance, the suzuki should be in last place.

 

What I found crazy was the Grizzly 400 has the same Hp as the Grizz 421 I mean 450 and they both have more then the Big bear and the number's seen above are from the crank take away some at the rear...

 

The 421 might have less compression. That's 'usually' the case when models go up in size. I dont know what's up with the Bear.

 

Some of the ideas and numbers are way inflated.
There are plenty of dyno runs here
<a target=_blank class=ftalternatingbarlinklarge href="http://s182.photobucket.com/albums/x15/hetrickracing/
">http://s182.photobucket.com/al.../hetrickracing/
</a>
But for example here is the dyno pull on a stock Kawi 450

Then theres this info from highlifter, and their dynos
Make Model Size HP
Honda Foreman 450 12.20
Honda Rancher 400 13.70
Yamaha Kodiak 450 18.50
Honda Rincon 650 21.40
Suzuki Vinson 500 23.25
Yamaha Grizzly 660 28.00
Kawasaki Prarie 650 31.50
Kawasaki V-Force 700 32.75
Kawasaki Prarie 700 36.00
These are rear wheel numbers, which are th eonly numbers which matter...you cant ride or race without driveshafts or wheels. But I know the 12.2 number for a stock foreman 450 is very near correct..ive seen many charts on that motor (I have one), and even in piped and jetted form, they dont get over 15 HP.

 

Why would the AC 700 have less HP than the Suzuki 700 when they are the same engine?

 

<div class="FTQUOTE"><begin quote>Originally posted by: UGLY88

Why would the AC 700 have less HP than the Suzuki 700 when they are the same engine?</end quote></div>

Different intake and exhaust

 

Well done hondabuster! Nice chart! (link didn't work for me, but it doesn't matter, I can visualize what you mean).

The only problem I have with rear wheel numbers is it makes it hard to compare apples to apples unless I have access to a dyno. I have a lawnmower that says 14.5 on the side of it and another one that say 22HP on the side of it. That's engine HP right? The bayou 220 file I downloaded from kawasaki says 17HP @ 7500,,, that's engine HP too right? Its sorta industry standard to list HP numbers at the engine for some reason. (might be hard to dyno a chainsaw or weedeater anywhere other than the engine [img]i/expressions/face-icon-small-tongue.gif[/img] ). And all those HP numbers at the CEPA are taken at the crank too I think. Plus I have a couple of engine sim programs that only calculate HP at the crank. Now seeing RW-HP is like hearing a different language.... "Do what???"

And then I suppose also the RW-HP number will vary with time due to frictional changes in the driveline,,, also vary with driveline angle to some degree,,, also vary with tire selection and air pressure... Now guys will run around claiming a 3HP increase because they put an x-ring chain on and stiffer tires with less rolling resistance, lol. I dont know,,, but I always get excited when a see that email that says "hondabuster has posted a message entitled...." because I know you'll always throw a new spin on things. [img]i/expressions/beer.gif[/img]

 

<div class="FTQUOTE"><begin quote>Originally posted by: UGLY88

Why would the AC 700 have less HP than the Suzuki 700 when they are the same engine?</end quote></div>

Because they aren't the same engine.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Redneck_giant

30.9 cc are equal to 1 Hp. So the Honda 450 has 14.6 Hp and the Grizz 660 should have 21.3 If you look at the numbers it just doesn't look right, but I work for a man that sales Chuck Wagons and they say their pumping out 340 cc or 11Hp. Things you have to consider are transmission, pipes, and any other thing that may add power.</end quote></div>



The honda 450r has 39 horse, and the 450 foreman has 13...same size motor, way different feel and power.
If you do a search on youtube for dyno...theres some interesting stuff.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Redneck_giant

30.9 cc are equal to 1 Hp. So the Honda 450 has 14.6 Hp and the Grizz 660 should have 21.3 If you look at the numbers it just doesn't look right, but I work for a man that sales Chuck Wagons and they say their pumping out 340 cc or 11Hp. Things you have to consider are transmission, pipes, and any other thing that may add power.</end quote></div>

I'm sorry to be another guy chopping up your post but you've just given us so much wrong material to work with [img]i/expressions/face-icon-small-wink.gif[/img]


Transmissions don't add hp, actually they along with the rest of the driveline will suck power away. This decreases the hp from the value measured at the crank to the value measured at the rear wheels. Different types of transmissions have different levels of efficiency resulting in different levels of drivetrain loss.