Polaris 800 H.O.: Interview With The Engineer

2015 Polaris 800 H.O.
A cutaway shows the three-stage variable exhaust for the new Polaris 800 H.O. engine.

Some 2015 Polaris snowmobiles will feature the all-new 800 H.O. engine that uses interesting and new technology to make it more powerful, more fun and more reliable. For the full scoop about how the new engine was developed, check out the October 2014 issue of Snow Goer magazine that’s in the mail now and will hit newsstands on August 26. Here is the word-for-word interview with Polaris Powertrain Program Lead Ricky Jaeger and Snowmobile Product Manager Jason Miller, two people who played a big role in the development of the new engine.


SNOW GOER: Polaris has been talking about how less crankshaft weight results in less inertia so the engine will react quickly. But doesn’t inertia also help get an engine moving and help create vehicle speed?

RICKY JAEGER: Inertia is basically the resistance to starting motion.If you think about spinning a top, you need some energy to get it going. By having that lower-inertia crank, it allows the engine to rev faster and react better with the clutching.


SG: Do you have any percentages or stats to back up claims about the high-flow intake and exhaust system’s efficiency?

JAEGER: A big focus as we designed this new chassis was to minimize the amount of bends and then be able to have a large, unrestricted flow of air into the main air plenum leading into the throttle bodies. If you pull the plastics off you can see how we’ve really maximized that air volume leading into the engine all the way from the intakes all the way down to the throttle body.

JASON MILLER: We used good engineering principles and common sense to make the new intake design more efficient and clean flowing, which was really a full integration effort with the chassis.


SG: With the quieter engine, was there any fear of losing or diminishing that invigorating bark that Polaris engines are known for?

MILLER: The ride is not as fatiguing. On the intake side we’ve greatly reduced the intake noise with the duct material. We’ll thrill the consumer with the performance of the machine rather than the noise.

JAEGER: The key focus was really quieting down the intake side noise and it lets the exhaust note that is there be the prominent noise. As you accelerate and get on the throttle you feel that come to life. Both from a response standpoint and then still do have nice exhaust note or tone.


SG: What is the intake duct material made from? Is it expensive? Does it have a name and how was it tested?

MILLER: It’s pretty commonly used material in the automotive world for cabin air ducting. With validation and testing we ran it through the rigor of our standard validation process. We went through off-vehicle shaker testing, [and] obviously our on-vehicle testing. That was a key technology we knew we were going to employ to kill intake noise. [It’s been] commonly used in domestic autos for five years, premium European vehicles longer than that.

JAEGER: It is more expensive than a simple blow-molded plastic that we’ve used in the past, but it basically brought several key advantages that we think is worth that added expense. Namely in quieting down that intake note and then also it does allow the engine to breathe a little bit freer, so if you do get a restriction on the intake screens you can actually pull air in through that [porous] material. It absorbs the engine’s pulses.


SG: You said the reed that was developed with Moto Tassinari exceeded your expectations for durability. What is the life expectancy?


JAEGER: Testing has shown they’ll last life of the vehicle. The rubber coated reed block gives the petal a soft landing and then we’ve integrated a much longer stop on it so that as the reed does come to full open it’s got a nice back stop. More support.


2015 Polaris 800 H.O.
If there is a problem with the variable exhaust system, a light will illuminate on the gauge.

SG: The three-stage VES’s smart electric actuator that keeps the valve in the down position is really cool. Talk more about it.

JAEGER: To help improve engine life and to protect any kind of abusive or unusual operation like extreme overheat or a bad-fuel, high-detonation scenario, what we do is we have the ability, because we have this smart actuator, is when we sense those type of conditions, to force the valve into the valve-down [position] and be able to operate the engine in that state and still give you the ability to drive home but not give you full power. [It’s] limited to about 6500 rpm. You can still cruise along pretty well, but it keeps you out of those higher throttle positions, higher RPM that can result in damage to the engine.


SG: The new variable exhaust valve system’s valves won’t need to be cleaned. Explain why the parts don’t get dirty.

JAEGER: Typically we’ve gone through and we test to our service intervals and that’s what we recommend. We were looking at going to extended service intervals for this valve, being a little bit more complex of a system to basically try to minimize the need for the operator to pull them out and to have to clean them. And all of our testing has shown that we can run these and they don’t gum, similar to what earlier versions had done. We’ve gone through and simulated one season, two seasons, three seasons and we don’t see that buildup that would require you to service them. Now if you did get into some kind of operating mode or maybe someone was using an oil that’s not recommended that would result in more gumming, the sensor on the smart actuator actually works in conjunction with the ECU to sense that you are achieving the required position so if you do get a buildup or a gum up it would basically give you a fault, a check engine light, and set a fault code that says ‘Hey, my E-V is not working right.’ The [gauge] screen will show a code.

We have more precise fit of this valve into the cylinder. We have controlled motion of it so you actually can better control the mid-state and high throttle setting. What that means is because we know the exact position of the valve, we actually get a more consistent combustion event, which, as you get more complete combustion you have less of those deposits that can build-up. So by having a better combustion you get less of that soot on the valves and basically results in less need to clean them.

2015 Polaris 800 H.O.
An electronic oil pump ensures consistent oiling for the 800 H.O. engine. Cleanfire 600 engines in the Axys chassis will also have this pump in 2015.


SG: Reliability and durability improvements were made to many parts and systems. What, specifically, are you referring to regarding component hardware refinements?

MILLER: We validate this as a system. There are a lot of new parts and I don’t think we can understate the effect of better combustion control and with the new electronic E-Vs and precise metering of oil with the electronic oil pump.

JAEGER: It’s a lot of little improvements that overall make it better. As we’ve developed this 800, it’s grown out of a small block. It did have a couple growing pains, but year over year we’ve continued to make improvements in reliability and durability. In model year ’11 we made a pretty significant jump [for the 800 Cleanfire engine], and we think with this H.O. motor we’ve made a similar improvement in overall reliability and durability. We didn’t just change one thing to do that. We basically touched all of the systems that interact with it. We’ve done more from a cooling standpoint around the E-Vs. The new E-V system has improved the overall combustion stability of the engine. The coolant bypass system, it really provides us quicker warm-up, better control, reduced cold shock. The electronic oil pump, gives us more control over the oiling requirements for the engine. It’s really a lot of little things that add up to really making a better motor.
[In a separate email, Jaeger said, “The 800 H.O. engine runs smoother on the bottom, accelerates faster and pulls hard on the top end. While the 800 H.O. engine makes more power what will really impress the rider is the crispness, acceleration, and throttle response.”]


Here is some other interesting information supplied in an email from Ricky Jaeger about the Polaris 800 H.O. engine:

• Goals for the 800 H.O. engine were focused on reliability, drivability, acceleration and power.

• Some elements of the 800 H.O. engine have been in development for four years.  The final configuration has been in development and validation for more than two years.

• Crankcase design used Finite element analysis and data from past engine projects.  Once the design was tooled there was additional confirmation with measured data to correlate back to the Finite Element Analysis. Final tool refinements were completed before the crankcase was put through component and engine-based tests.

• A new throttle body eliminates the mechanical link to the oil pump, reduces throttle effort and weighs less. Its bore is 48 mm.

• Polaris set out working with several vendors to improve durability of the reed petal on the 800 H.O. engine. Moto Tassinari, makers of aftermarket VForce reed systems, delivered the most durable design and also had the added benefit of improved performance. The 800 H.O.’s reed is exclusive to the engine. The proprietary reed petal, rubber coated reed block and integrated reed stops are all key players in the durability and performance in the 800 H.O. engine.

• All liquid-cooled, 2015 Polaris snowmobiles will use a new extended life coolant similar to what is found in modern automobiles. Its color is yellow and can be mixed with conventional coolant, but its extended life capabilities will be reduced.

• Engineers used a monoblock cylinder design for the 800 H.O. because it makes the engine stiffer with less weight. It also provides more cooling capability between the cylinders.

One thought on “Polaris 800 H.O.: Interview With The Engineer

  • Avatar for John Hock

    I currently own a ski doo 2011 BCX. I am really disappointed that you did
    not put the new 800 motor in the switchback assault. I want to jump ship
    and get back on a poo! I am a trail and off trail rider. I hope you can easily
    remove the hood for a muffpot cooker. I would purchase the assault but
    will wait till 2017 model year now. How does the suspension do on the
    trails???? How does it handle turning in corners??? My BCX doesn’t turn
    real well in trails but the suspension is really good on beat up trails. The new ski doo BCX is too mountainized for me with the t motion etc. Please
    email me back—–Thanks—jh


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