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Thursday, March 17, 2011

Polaris RZR XP - The Performance Details

It doesn’t take much of a look to see the differences between a RZR and the new RZR XP! It’s taller, wider, and longer. That may be simplifying the issue a bit but it’s true. About the only place the XP is the same as the other RZRs is in the cabin. Same seats, same steering wheel, same gauges, same everything.

So let’s take a look at the differences:

Up front is a new tubular subframe designed to hold even longer a-arms. These arms are an additional 2 inches longer than the already extended arms of the RZR S so they can provide 13 ½ inches of wheel travel. That’s a lot of travel, but as Doug Roll always said, long travel doesn’t mean anything if it doesn’t work! In this department, Polaris added a set of Fox Podium 2.0 shocks. These shocks have plenty of height-pre-load adjustment as well as adjustment for compression damping.

Although the front suspension is greatly enhanced, it is the rear suspension that is the most visibly changed! Like many off-road racecars, the rear suspension now consists of a 3-point trailing arm system that provides 14 inches of travel.

The advantages of a trailing are system is multifold. First, it provides a more controlled travel and camber gain so that the tire will actually lean in at the top a bit as the travel goes up. That camber allows a longer movement with less scrub. Polaris still designed some camber in the system so that during hard cornering, the tire will lean in and keep from rolling over as much. In addition to better travel, the trailing arm set-up is also a much stronger system for off road use.

And, as on the front, the rear is equipped with long-travel Fox Podium 2.0 shocks with plenty of adjustment for preload and height and adjustment for the compression damping.

 Now for the other very big difference in the XP – the new engine! Designed from the ground up for this machine, the ProStar 900 is a work of art, looking more like something that should be in a racecar rather than a UTV. Oh wait, this is a racecar!

The 875cc twin cylinder DOHC engine now sits in a more conventional direction, with the cylinders and crankshaft running side-to-side rather than front to rear like in the other RZRs. And it’s built for performance, with the pair of 46mm throttle body injectors mounted right next to the cylinder with a very short intake manifold. Also helping to get plenty of air into the engine is a new intake system that pulls air in from the left side of the body and directly into an air box that in essence stores a mouthful of air ready for the engine to suck up when the throttle is mashed.

There’s also a new air filter that has 90%  more capacity than the old-style canister system. And it’s mounted in a box located under an easy-access panel right under the bed.

Polaris also designed a stainless steel exhaust for a freer-flowing path to extract the used air and fuel. All this helps the ProStar to produce a whopping 88hp from it’s 875cc’s.

But wait, there’s more! The ProStar is designed with a dry sump oil system. This allows the engine to sit lower and the oil to be held in a tank away from the heat of the engine’s block. It can also provide a larger oil capacity for better cooling as well. In this case, 3 ½ quarts are held in a finned plastic tank that located under an access panel on the left side of the bed. And that’s also where you check the oil level.

With an eye toward night duning and late-night racing in the desert, the engine is fitted with a large capacity stator that provides an incredible 500 watts at idle, and 750 watts at revs.

There’s also a new CVT transmission with a zero-clearance set-up and helical cut gears for faster takeoff and stronger, more reliable operation.

All of this sounds good but the prove will be in how it works. We’ll take it out for a test next.


  1. What components from this XP would you like to see incorporated into the next generation 50" RZR?

  2. Great question! And one I'd like to see Polaris do!

    I'd really like to see the engine and transmission in a RZR 50, not because we need all that power, but because it works way better - especially the transmission shifting. Maybe a detuned version.

    More importantly I'd like to see the suspension system. You could make a narrower version of the trailing arm suspension and probably still get 10 or 12 inches of travel. And by putting the front arm's rotational mounts closer together they could maybe get at least 10 on the front.

    Plus, something they didn't put on the XP (and probably didn't need) was the ADC braking system. It works really good on the Sportsmans so I don't know why they haven't incorporated it on the RZR - oh yeah, that's right it COSTS MONEY!

    And I just so would a mechanically-operated hand emergency brake.

    But I bet they paint the arms red on the next model ;-)

  3. The wheel can be a little bit bigger so that works better with the suspension system.Generally,the design is pretty amazing.