<div class="FTQUOTE"><begin quote>Originally posted by: ss97

There are also several different ways to measure HP at the crank...... net HP and brake hp (BHP) are totally different numbers...... The only ones that are "real" are what is at the rear wheels on a roller tension type dyno.



The fact that a Polaris 850 has almost 40hp at the rear wheels is probably about right. And that is a good amount of power hitting the ground for an 800 pound machine. But the number that you should really want to see on something that heavy is the torque, because it is the torque that is going to get you up and going on a machine that big.....



As the old saying goes, torque it what gets you going, HP is what keeps you pulling. Given the way that big machine moves I'd venture to guess that the torque numbers are quite impressive from a 850cc thumper.</end quote></div>


HP and TQ are related...if you know the HP at a particular RPM you can figure out TQ..that is another area where the CTV skews things..the old addage about TQ getting you moving has more truth when dealing with a conventional trans that starts at a low RPM and gains RPM to gain speed in each gear...the lower RPM the TQ peaks the more low end grunt...for instance I had a car with a twin screw superchrger that would make over 500 ftlbs of TQ at 2500 RPMs..Peak TQ was about 600ftlbs..I also had a twin turbo car that made over 800 ftlbs of tq..but the TQ didn't hit 500 until about 4500 RPM...guess which one would get out of the hole faster? Yep the twin screw..
Withe the CVT the engine will gain some RPM as the speed increases but strives to constantly keep the engine in a narrower "power band" which if set up properly can make it MORE efficient at applying power than a convientional manual of automatic tranny...if peak HP is at say 6500 RPM the longer you can keep the engine operating at that RPM the more efficient the perforance will be. For example on my 850 on WOT pull it is at 6900 at 40 mph,but it will hit 75+ without overrevving...and it doesn't change gears in reality,it just varies the raitos of the clutches to keep the RPMs in that band...

 

38.8 comes out to the old 378cc two stroke commonly known as the 400 liquid cooled,or the motor in my bike[img]i/expressions/face-icon-small-smile.gif[/img] I think the issue is the cvt,it is constantly trying to keep the engine in it's peek area of performance.

 

<div class="FTQUOTE"><begin quote>Originally posted by: scrambler400enoge

38.8 comes out to the old 378cc two stroke commonly known as the 400 liquid cooled,or the motor in my bike[img][/img] I think the issue is the cvt,it is constantly trying to keep the engine in it's peek area of performance.</end quote></div>

Except that 38.8 is at the wheels. I'm guessing the 400 2-cycle is about that at the crank.

 

But anyone I tell won't know that!I could tell them my machine has the same hp as a 850xp.But the odds of them believing me is slim to none.

 

38 is a bs. My 05 800 did 36.4 at dyno jet. The XP has at least 20 more horsepower.................My XP will kill my 800 in a side by side run. Mine was done at THE dynojet facility in Las Vegas they do all the maps for the entire country here. So that number cannot be correct. For the record, I'm not saying the poster is wrong, I'm saying that the dyno number is not accurate. There is no way the XP only has 1.6 more hp than the 800 at the rear wheels.........

 

Polaris said the 400 2-stroke had the same HP as the 500 H.O. 4-stroke, 38 HP, and yes, it was measured at the crank. I read some previous posts here that said you can't get an accurate dyno reading at the wheels on a CVT quad. Is that true or not?

 

You can get a fairly accurate horsepower rating from a dyno, however you need to use stock tires and not mud type tires.

 

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

38 is a bs. My 05 800 did 36.4 at dyno jet. The XP has at least 20 more horsepower.................My XP will kill my 800 in a side by side run. Mine was done at THE dynojet facility in Las Vegas they do all the maps for the entire country here. So that number cannot be correct. For the record, I'm not saying the poster is wrong, I'm saying that the dyno number is not accurate. There is no way the XP only has 1.6 more hp than the 800 at the rear wheels.........</end quote></div>


Well, that is what that machine made on that day on that dyno. The test was for reference only, and to get an idea of the AFR and peak readings before any mods. The next test (and tune) will be different.

 

PUT A 1000 MILES ON IT THEN DYNO IT

 

Yes that is the true use for a dyno before and after. Superflo dyno's are good dyno's but read lower than Dynojet.............but to go from 70 hp to 38 is not realistic. Let us know your "after"numbers............