4 stoke vs 2 Stoke -- Cold weather question

[chrishall]

On a really cold day (-32 to -45) with a 2 stoke you have to worry about blowing your engine running a river WOT for a long period of time. With my new 05 RX-1 ER, is it the same? Are 4 stokes different?

 

[Mighty]

Let er rip. At -45 I'd worry more about myself...........
4 stokes don't lean out like a 2-smoke does. At least not to the extent

 

[LazyBastard]

If you've got your 2-stroke jetted correctly for the temperature, you don't have to worry about blowing it.

The issue is with oxygen density... lower temperature = higher oxygen density = more oxygen per intake cycle. If the jetting can't keep up with the oxygen going in, kaboom!

4-strokes will do the same thing as 2-strokes, just not as fast and not as bad. Doesnt matter what engine type you have, you should ALWAYS be jetted for what you're riding in.

Note; 4-stroke HUGE advantage in these conditions is that they LIKE to run rich, unlike 2-strokes that are very sensitive and like to run on the line. Result is that typically, a 2-stroke will be jetted much closer to the kaboom line than a 4-stroke, which gives the 4-stroke more slack to mess around in.

 

[PACMAN]

If you've got your 2-stroke jetted correctly for the temperature, you don't have to worry about blowing it.

The issue is with oxygen density... lower temperature = higher oxygen density = more oxygen per intake cycle. If the jetting can't keep up with the oxygen going in, kaboom!

4-strokes will do the same thing as 2-strokes, just not as fast and not as bad. Doesnt matter what engine type you have, you should ALWAYS be jetted for what you're riding in.

Note; 4-stroke HUGE advantage in these conditions is that they LIKE to run rich, unlike 2-strokes that are very sensitive and like to run on the line. Result is that typically, a 2-stroke will be jetted much closer to the kaboom line than a 4-stroke, which gives the 4-stroke more slack to mess around in.

Lazybastard...

I really enjoy reading your replies!!!

You seem to be a very knowledgeful type of person!

Keep the good work!

 

[BOUNTYHUNTER]

Just one thing to add to LB's post;

It is advisable to run a lighter weight oil in your 4 stroke under those conditions. As you do build up a little more crankcase pressure than normal, even more so with the ECP Kit.

I agree for a youngster The L.B. Mizester knows his #*$&@.

 

[chrishall]

So with my stock jetting and newly changed oil to 0-w30, I am or am not OK to run WOT for the length of a long lake? Normally I blieve, Yamaha puts jetting in which is on the big side any way.

 

[Bob Miller]

Actually from what blackjohn tells me, the stock 135 main jets are slightly on the lean side from plug readings that he has taken
He has switched to 137.5 mains and raised his needles one step!
He states that the sled performs better and has better top end, and the plugs are burning a nice tan color now!

 

[Mighty]

So with my stock jetting and newly changed oil to 0-w30, I am or am not OK to run WOT for the length of a long lake? Normally I blieve, Yamaha puts jetting in which is on the big side any way.

You are fine
If not, that's what the warranty is for. I have yet to read of any jetting related meltdown of the Genesis Extreme :ORC

 

[LazyBastard]

I like to run 137.5's in mine, I run at ~700 feet elevation. Castrol synthetic 5w50 seems to work good at very cold temps, so 0w30 will be fine.

 

[Bakemono]

You can pretty much treat your sled just like a car. You dont need let it warm up like you do with a 2-stroke, but you dont want to start it up and run it WOT right away.
As long as you let the engine get warm (Id say once its been running for 5 mins) before you run it hard you should be just fine.
Hebi

 

[NOS2stage]

You can pretty much treat your sled just like a car. You dont need let it warm up like you do with a 2-stroke, but you dont want to start it up and run it WOT right away.
As long as you let the engine get warm (Id say once its been running for 5 mins) before you run it hard you should be just fine.
Hebi

what??????? a four strock will cold seize a piston just as fast as a 2 stroke..... before u say anything else u better understand how a motor works....a piston will expand faster than a steel or plated cylender..so go rite a head a run a 4 stroke hard before it has time to warm up!!

 

[impalapower]

I'll second that, let them warm up. Whats the hurry?

 

[SuperStroker!]

Density refers to the mass contained within a unit volume under specified conditions.

Mass is defined as the property of a body that causes it to have weight in a gravitational field.

Volume is the amount of space an object occupies.

Air Density is defined as the mass density of a parcel of air expressed in units of mass per volume. Air density is further defined as the total mass of air per given volume, the weight of a given volume of air. Air is denser at lower altitude, at lower temperature, and lower humidity.

The composition of air:
Nitrogen N2 78.084% 99.998%
Oxygen O2 20.947%
Argon Ar 0.934%
Carbon Dioxide CO2 0.033%
Neon Ne 18.2 parts per million
Helium He 5.2 parts per million
Krypton Kr 1.1 parts per million
Sulfur dioxide SO2 1.0 parts per million
Methane CH4 2.0 parts per million
Hydrogen H2 0.5 parts per million
Nitrous Oxide N2O 0.5 parts per million
Xenon Xe 0.09 parts per million
Ozone O3 0.07 parts per million
Nitrogen dioxide NO2 0.02 parts per million
Iodine I2 0.01 parts per million
Carbon monoxide CO trace
Ammonia NH3 trace

Air is mostly nitrogen. Air is not oxygen! Air is a composite of all the above, mixed together. The ideal situation would be to increase the level of oxygen in air and decrease the level of nitrogen, in order to make more HP. This is part of what Nitrous Oxide does…it boosts the level of oxygen. Nitrous Oxide is in air but in a very small amount. Nitrous has a significant fraction of oxygen hanging from its molecular structure…it essentially brings a high level of oxygen as part of its molecular structure and that makes HP.

Nitrous also creates a cold environment in and around your intake and engine, cooling the intake charge and boosting charge (air density) density, which allow more molecules of gas (air) per unit volume (fixed by displacement).

More air in the same volume means more HP, but you also need more fuel to make more HP, EVEN ON A 4-STROKE ENGINE!

If your 4-stroke Yamaha engine finds its best ratio of fuel to air at 10 degrees F and you run the engine at -40 F, your engine will be lean and will make less HP. However, a 4-stroke is very forgiving to lean conditions with regard to burning pistons, only because there is more time for the piston crown to cool (4-strokes to combustion vs. 2 strokes to combustion).

Make no mistake, A 4-STROKE ENGINE THAT IS LEAN, WILL MAKE LESS HP and GO SLOWER than a correctly jetted 4-stroke for the present ambient temperature. If your 4-Stroke is faster at -40F then your probably rich at +40F. The good thing is 4-strokes tolerate a wider F/A ratio difference than 2 strokes and the power is affected less.

THAT’S WHY WE NEED FUEL INJECTION as soon as possible…so your sled is significantly faster in colder conditions, consistently!

 

[cgwiz]

SuperStroker, nice post! just one point, the concentration of ozone will vary based on location, season, and amount of sunlight. Ozone at ground level is formed by the effects of UV rays on hydrocarbons (pollution), so the "dirtier" the air, & the more sunlight, the higher the ozone concentration.

 

[yamadoo]

MAN I love this site, I get to review physics and Chemistry in the context of something I really care about. Thanks LB and SuperStroker if you are ever wondering if anybody really cares to know what is going on on the molecular or physics level of mechanical understanding the answer is YES.
I and I suspect it is a big WE love it.
THanks
YamaPoo aka yamadoo