Polaris CFI-2 Engine and why you may NOT want to warm it up
I have been holding
on writing about this for some time because it is going to be very
But, I believe it is
time to discuss this..
What I am talking
about is this whole "idea" that letting your sled warm up until it hits "X"
degrees before taking off on it is a GOOD IDEA!
pertains to the Polaris CFI engines.
We all have heard and read
about how the sled owner lets the sled warm up to 120+ degrees before ever
getting on it and how this is a "good" thing..
I am going tell you
that this is NOT a good thing and actually can be very bad for your engine.
not telling you to pull the sled off of the trailer and PIN IT!..
Hopefully, this article will clarify what I am
trying to relate.
1) Without getting
into Physics and the laws of thermodynamics (not the intent here), let's
touch on the FACT that HEAT ALWAYS travels to COLD.. Hot "anything"
will not seek out something that is hotter..
This is very
important to remember when reading this article.
2) Your coolant temp is not ALWAYS a good indication of how "hot" the rest of
your engine components are (see #1 above)..
Hotter coolant temps
tell you that it has removed HEAT from your engine and
transferred it to the cooling system.
It does NOT tell you
that your engine is SAFE to run at high loads!
AGAIN… we are not trying to dive into ALL of the aspects to what is
happening internally.. That would be far too vast and boring to capture
This article will be
kept VERY SIMPLISTIC in its nature and, YES, any good physicist will, most
likely, be able to find “holes” or “exceptions” within the content.
It appears that
it is very common to pull into the
unloading zone, start your sled, then proceed to get dressed while your
sled is running.
Once dressed, you go
to your RUNNING sled , check the coolant temp, see that it is at or above
120 degrees F, then jump on the sled and floor it out of the loading area.
With this particular
engine design, this, IMO, is a very bad idea!!!
WHY??? OK, let’s try
and break it down in very simplistic terms
1) See #1 and #2
2) With this engine,
AT IDLE, the oil pump is supplying little to NO OIL to the engine. So, all
the time your engine is “warming up” it is near starved of oil.
NEVER A GOOD THING… EVER!
3) The engine is
heating up, the pistons are expanding, the internal temps are ,somewhat,
stabilizing (trying to obtain a state of equilibrium with its surroundings)
and the engine is transferring some of its heat energy to the cooling
Any oil that was present on the cylinder walls and the
piston itself (to provide the NECESSARY oil film barrier needed for a 2
stroke engine to survive) has been completely removed or reduced to an
un-safe amount to provide an adequate film protection layer/barrier.
In other words… your
engine’s piston and crank-shaft are heated to a high level that is not
desired for the amount of oil that is present.
NOTE--> The ONLY way ANY piston can seize in an
engine is to have the oil barrier removed.
As long as the oil barrier
remains fully intact, you can not seize an engine.
OK, back to the
subject at hand…
4) The rider,
“eye-balls” the temp reading, sees an acceptable number and “feels” that the
engine is now in a “SAFE” state for WOT running…
With this confidence in
mind, he/she grabs a handful of throttle and “peels out” of the loading zone
heading to the “good stuff”
THIS IS WHERE THE
5) The engine has
just been subjected to HIGH RPM and possible pro-longed running with a
cylinder and crank that have little to no oil barrier/film on themselves or the
This is the same scenario when new pistons are
installed and the owner decides to let the engine do SEVERAL “Heat Cycles”
in the garage after prolonged idling ... Not a good idea either! But that is
a whole other topic!
Let’s break it down
a bit further….
5a) The engine’s oil
barrier is near depletion, the piston and crank are very hot . The
cooling system is also at a high temp reducing its ability to
successfully REMOVE heat from the engine.
The piston relies on this oil barrier to form a “coating” on itself and the
cylinder wall. This oil barrier MUST be present to avoid Metal to Metal
contact between the piston and the cylinder wall.
It may be good to
note that the cooling system OFFERS the engine cooler running temps SOLEY
by giving the engine an outlet to REMOVE its heat.
Many think that the
cooling system is actually “COOLING” the engine by surrounding it with cold
temps. This is not the case … The engine is removing some of its heat energy via the cooling
system... see #1
OK, on with the
5b) The throttle is
“cracked” and the piston is immediately accelerated. Internal temps and
pressures begin to elevate VERY quickly! With these higher pressures and
temps (not coolant temps but engine temps), the oil’s function is of extreme
5c) But wait… we are,
severely, lacking in this oil dept!... NOT GOOD!!
5d) Due to the
throttle lever being open past idle, the oil pump is supplying a higher
volume of oil to the LOWER END ONLY! There is no direct oil supply path, in
this engine, to the cylinder walls!!
This is another issue with this
5e) Oil supply is
increased but, keep in mind, at 8000RPM the piston is making 133 revolutions
PER SECOND!! And it takes time for this newly supplied oil to reach the
cylinder wall and adequately coat it with the REQUIRED barrier (more than a
few seconds worth of time).
So, the piston ,in say 3 seconds, has made near
400 revolutions with little to no oil between it and the cylinder wall.
5f) During this short
time, the piston has grown even more because the heat of the piston has
The piston is relying on the oil film
and fuel to help cool it back to a
better level and protect it from making aluminum to NikaSil direct contact.
BUT, the oil film is lacking and the hotter piston begins contacting the
cylinder wall at small “points” along the cylinder wall TRYING
to fuse itself to the cylinder wall.
This process continues until
the oil can get in there to do its job.
The oil barrier is
not able to form as easy on the intake side of the cylinder or piston… WHY?
Because the piston and cylinder,at BDC, is such that the oil is
scraped off the piston skirt via the cylinder skirt (another design
OK… What is the end
result of all this??
The end result is
that the intake side of the piston will become lightly scored due to its
prolonged attempts (sometimes successful) to fuse itself to the cylinder
This intake scoring does not affect HP or reliability in any way, providing
there is NO material transfer, ring stiction, or “scrapers” produced on the piston skirt
from this experience.
OK, I know what you
are going to ask... “Why is the stock piston not as prone to this intake
That is a very good
Here is the answer:
The Stock Polaris pistons suffer from skirt collapse VERY quickly. The
intake skirts will collapse inward as much a .006” over a very short period
of time. With this added piston to cylinder wall clearance, it is much more
difficult to make contact to the cylinder wall for reasons that are
With this excessive
clearance, the piston will develop “rock” and “lever” itself against the
cylinder wall. This has been a known problem with the OEM pistons. This
causes the cylinder to eventually crack and break causing catastrophic
engine failure!!! It has also been shown to crack the lower intake CYLINDER
This is the main reason why Polaris thickened the cylinder skirt on
the 2013 and newer cylinders.
Polaris decided to
keep the same problematic piston design and they WILL still break causing severe
OK.., How do you
Here is what we
1) Run about a 200:1
premix of oil in every tank of fuel.
2) Install a better
vented oil cap to assure a steady flow of oil to the pump.
3) Turn up the oil
pump lever screw a couple of turns.
4) When you arrive at
the loading area, start your engine, let it idle for about 2-3 minutes MAX.
Your coolant temp will vary depending on the day. But, hopefully, it will be
in the 80-90 F range after this.
5) Pull it off the
trailer and SHUT IT OFF!!
6) Get dressed or do
what you have to do before leaving for the day.
7) When ready to
start the day’s ride, start the engine, let it idle for about 1 minute. Get
on the sled and leave the area using VARYING throttle (NO Pro longed WOT
running or hill pulls) until you get about 1 to 2 miles out of the loading
8) After #7--> Ride
it as you see fit!!
Using the above
method will make for a longer lasting engine.