In the new issue of ATV sport magazine, They test 22 sport quads on the Dyno and The banshee peak HP is 40.5hp The scrambler 400 doesn't say It's Horsepower, but I thought the banshee was supposed to be about 36hp? Whats the deal? It was at the rear wheels too.

 

There are several uncontrolable variables that can alter chassis dyno readings, altitude, ambient tempreture, jetting, dyno manufacturer, ect. Additionally a chassis dyno is an inaccurate tool to use in measuring RWHP on a CVT equipped machine, because there are even more variables with clutching to factor in.

Thats why HPD uses a crank dyno to show their numbers, as inheirantly a certain percentage of power is lost through "transfere". You can spend the time to dial a CVT in on a chassis dyno and produce a given amount, however if you were to take that machine and go directly to the trail its "real world" performance would be poor.

I just ran my bike on a dyno in early October, at Othon Racing, and produced a RWHP reading of 56 (@83MPH). However the RPM readings of where I was making that power was way off due to the CVT working as it should. This is with a full blown HPD race mod motor, which is said to make 72+ at the crank. Should I be concerned, NO! A nicely tuned CVT should account for approximately a 20-25% loss of power from crank to the rear wheels which puts me in that range, actually at about 21% which is good. Im uncertain of the power loss ratio for a manual but estimate it to be near 15-20%. This is the realm of Polaris power most often neglected... clutching efficeincy!!

As stated earlier I could've spent hours messing with my clutching to acheive a higher number like 60+, but that set up would not be practical on the trail/dunes.

So, the deal is don't be fooled by numbers. HP is power, but where in the powerband your bike makes that power is what matters. Take a well built Shee and my 400 and put them on a dragstrip. If my bike makes its peak HP at say 7800RPMs and my clutching is dialed in right, I can be there in 2-3 seconds, whereas that Shee has to shift through 5 gears, all the while their RPMs rising and falling as they shift. Know any Shee riders who can get to 5th gear in less that 3 seconds, even starting in 2nd? I dont, unless they are running a tranny override, and those are only on the fastest Shees out there.

Not to say that the CVT is better, but when dialed in, it can be more "efficeint".

 

Strappin' a Polaris on a chassis dyno is just a gee-wiz fun time. Strap your a$$ on the seat, and then let the machine talk. Don't get me wrong, it's fun on the dyno, but it's a lot more fun to see who's ahead after the sand settles.

Ken

 

Guys,

Besides that fact, they compare the horsepower and RPM on the Banshee graph and horsepower and speed on the Polaris graph. I'm no whiz kid, but that seems like comparing apples and oranges to me. Both show the horsepower, but they take them at different readings. One for RPM and the other for speed.

This might explain why the dyno numbers on Ken's machine weren't all that great. Do they mean to tell me that at 60 mph you're making less horsepower than at 50 mph? I don't think so. Same RPMs + different speed = same horsepower on CVT machines. The clutching may change, but what about wind resistance? I guess you can't measure that on a dyno. No the only way to compare the two machines would have to be crank to crank. I'm a firm believer in this.

 

Quoted from a previous discussion on this topic...

"Keep in mind that one of the functions of the cvt is to keep the motor in it's power band. Polaris has no rev limiter. The cvt operates on torque feedback from the rear wheels. As the load from the dyno changes; the cvt will sense it and continuously shift. A standard trannied quad such as a Banshee will be placed in fourth gear and revved out on a dyno for consistant readings. The tranny is locked in and no shifting occurs.
If I have this correctly; a dyno measures how fast the inertia roller is accellerated within a given time. Depending how much engagement that you have dialed into the cvt; you can change this accelleration figure and fool the dyno. For example; I install a light primary spring and heavy weights. The bike will accellerate slowly due to the heavier weights and lower engagement speed. This will give poor dyno readings due to the lackluster accelleration. Now; take the same motor and install a heavy spring with the same weights. The bike revs to a higher r.p.m. before engagement and engages violently. This in turn accellerates the dyno drum much quicker than the previous setup with the same motor. What's the dyno going to read? More h.p.
If you talk to some of the biggest names in sled clutching, such as Bartell or Redline; they'll laugh at the mention of a track dyno. If you go to a sled drag event; you'll see how these cvt's are really tuned. They use timing lights, onboard computers and tachs. AEEN has developed a $150,000.00 water brake dyno to measure the h.p. It is believed to be one of the most accurate dynos built. Guess what he uses for clutching? Timed runs on the track. Sled manufacturers dyno at the crank as well. CPI; well known for their sled pipes; dyno at the crank. HPD; who built mine and AZ400L's engines; has the world land speed record in a 600' run on a sled. 190 m.p.h.!!! This record is old and has never been beaten. Was the dyno used for clutching? Nope. Too many variables in the cvt.
AEEN, PSI,Hot Seat, HPD, CPI all show the Polaris 400 atv engine making peak h.p. in the area of 6300 r.p.m. up to 7500 r.p.m. Are all these aftermarket vendors wrong compared to Ohton's dyno readings? I don't think so; or they'd all be out of business. Charlies dyno shows Jerry's bike making peak h.p. at 4800 r.p.m. Anybody who's worked with large bore two strokes knows that this is grossly incorrect. The tach on the dyno showed Jerry making peak h.p. at 8000 r.p.m. repeatedly. The dyno printout showed peak h.p. at 4800 r.p.m. Figure that one out. If I clutched Jerry's bike for 4800 r.p.m., following the dyno chart; it would be a complete dog in the sand. Hell; I and others set our engagement r.p.m.'s well over 3500.
I'm not trying to make this out to be a big controversy. Basically; i'm trying to give a better explanation of the dynos effects on the cvt. Until we can determine what's going on between the cvt and dyno; we can't rely on it's readings for tuning. Hopefully; Charlie will soon grasp the cvt and determine what changes could be made in the dyno process. He's a great guy and very smart. I have a feeling he'll come up with something. Hope this helps and look forward to your response."
Fasterthangas.

 

Aaen Performance has one of if not the nicest dynos of anyone in the business . I read about it somewhere in a sled magazine . If I remember correctly it was worth more than my house .

 

Rick, you need a nicer house!! [img]i/expressions/face-icon-small-smile.gif[/img]

Here is something I wish someone with access to a dyno would do.
Honda has made it easy for us with the Rubicon. Hook it up to a Dyno, and see how much HP it makes in manual shift mode. Then try the D1 mode. Now run the test in D2. I am willing to bet it will show that the same engine suddenly puts out less HP. The CVT is at fault for these low readings. On a load test, they see how much 'pull' the machine has at certain speed/RPMs. If you leave it in one gear, you can completely max out the engine output, less mechanical loss. With a CVT, as load increases, speed decreases, whether or not RPMs lose much. This confuses the Dyno into low readings. It would be like a gear drive machine with a slipping clutch. Went through all that in school, at the Tractor Test lab. A Hydrostatic tractor would move a pulling sled farther than a gear drive one would (farm tractor, not a pulling tractor). However, on a rear-wheel dyno test, it showed it pulled less. Explain that??

 

As Darrell always says, you almost have to effectively "pin out" the clutches. Mike, as far as wind resistance goes, ATV Sport told me during my radar runs, that a Raptor they had tested actually had gained 4mph by trimming plastic alone. Then there's the issue of Ken's "Root Beer Belly" hockey season is hear, so I'm workin' on that. Rick, you just need a bigger kennel for more Beagles!

Ken