Polaris 850 PRO-RMK 155 2.6" QD 2021, Manual

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9850060 R02 - 2020-2021 850 AXYS™ Long Track Snowmobile Service Manual
© Copyright Polaris Inc.
3.105
ELECTRONIC VARIABLE EXHAUST
VALVES (E-VES-II)
E-VES-II OVERVIEW
IMPORTANT
Never tamper with or modify the function of the E-VES
actuator or push / pull cable to set the valves to a fixed
position. Doing so may cause severe engine, E-VES
actuator, or push / pull cable damage.
IMPORTANT
Do not replace the E-VES actuator motor / cable
bracket assembly rubber bulkhead mounts with
washers or similar parts. Replacing the rubber
bulkhead mounts will transmit chassis vibration into the
actuator motor, which may damage internal electrical
circuits.
The assembly is designed to move during vehicle
operation, and movement has no effect on E-VES
performance because the actuator arm and push / pull
cable mount are part of the same assembly.
The Re-Learn Procedure must be performed using
Digital Wrench when the following occurs:
• EV actuator motor is replaced
• Push / pull cable is replaced or disconnected from the
tie bar
• Any exhaust valve (upper or lower) is replaced
• Cylinder is replaced
• E-VES valve assembly is moved to a different engine
NOTICE
Polaris recommends using Polaris VES or VES
Extreme Synthetic Two-Stroke engine oil.
Never mix different brands of engine oil.
Main components of the Polaris Electronic Variable
Exhaust System (E-VES) are:
• EV Actuator Servo Motor
• Push / Pull Cable
• Exhaust Valve Assembly
• ECU
The E-VES system controls the effective exhaust port
height in each cylinder to provide maximum engine
horsepower at high RPM without sacrificing fuel
economy and engine torque at low to mid-range throttle
settings.
In order to understand the operation and function of the
E-VES, we must first consider the characteristics of a two
stroke engine. The height of the exhaust port in a two
stroke engine cylinder has an effect on the total power
output of an engine, as well as the RPM at which the
power occurs. Exhaust systems are “tuned” by design to
match engine exhaust port configuration and desired
power delivery characteristics. Engines with relatively
“high” exhaust ports (and exhaust pipe to match)
produce more horsepower at high RPM, but only at the
expense of low to midrange fuel economy and torque.
On the other hand, “low” port engines provide good fuel
economy in the mid-range and make their power at
relatively lower RPM, but will not produce as much peak
horsepower for a given displacement range. In general,
an engine designed for a high performance snowmobile
will have a relatively high exhaust port compared to an
engine of the same displacement range designed for
touring. Although the E-VES does not in itself increase
horsepower, it does allow an engine to be designed for
maximum horsepower without the inherent
disadvantages of a high exhaust port.
With E-VES, effective exhaust port height for each
cylinder is controlled by an upper
q
and lower exhaust
valve
w
. The lower exhaust valves are secured to a tie
bar
r
. The tie bar ensures each cylinder’s lower valves
are synchronized with each other.
A non-adjustable push / pull cable
e
links the tie bar with
the EV actuator servo motor. The EV actuator servo
motor pushes and pulls the cable to set the valves in one
of three stages (closed, mid, and open).
Upper exhaust valves sit on top of the lower valves.
These valves feature exhaust boost port fingers and are
each held in place with two tensioner springs. The upper
valves also feature steps to control how far each valve
protrudes into the exhaust ports and when the lower
valves engage the upper valves.
The E-VES system operates in three stages:
ENGINE / COOLING / EXHAUST