Snowmobile Fanatics banner
1 - 20 of 21 Posts

·
Registered
Joined
·
193 Posts
Discussion Starter · #1 ·
Have heard that warmer temps make a sled run richer.

1st ? just to satisfy my curiousity is why?

2nd question - Have heard that running hotter plugs (8's vs 9's for example)is good when it's warm to burn off the extra, true or false?

3rd Question - If the answer to 2nd question is true, at what point do you switch? ie. what is considered warm? 10? 20? 30? 40?

4th ? - At what point should you change jetting because of temperature? Not for ideal optimal performance, just for the average joe rider not wanting to melt down his pistons...

5th question - do tempaflows work well and solve both of these issues automatically? Are they hard to install? Is there noticable performance gains when using one or just piece of mind knowing you won't lean out or something?

Thanks for your answers.
 

·
Registered
Joined
·
247 Posts
Originally posted by krappana
[br]Have heard that warmer temps make a sled run richer.

1st ? just to satisfy my curiousity is why?

2nd question - Have heard that running hotter plugs (8's vs 9's for example)is good when it's warm to burn off the extra, true or false?

3rd Question - If the answer to 2nd question is true, at what point do you switch? ie. what is considered warm? 10? 20? 30? 40?

4th ? - At what point should you change jetting because of temperature? Not for ideal optimal performance, just for the average joe rider not wanting to melt down his pistons...

5th question - do tempaflows work well and solve both of these issues automatically? Are they hard to install? Is there noticable performance gains when using one or just piece of mind knowing you won't lean out or something?

Thanks for your answers.
i think that the answer for number 1 is that the air is less dense when it is warm, and doesn't need as much fuel mixed in with it. on a cold night, it will run better, because the air is denser. all an inter cooler does is make the air more dense, giving more power.

don't know the answer to numbers 2-5 though, sorry[V]
 

·
Registered
Joined
·
3,258 Posts
I had the same engine, I always ran the ngk 9's and ran it at stock jetting the whole time I owned it. I would notice it running rich in temps over 32+. Tempa flow is a great add on, I didn't have one but when riding with darkstar who also had a 600 ves with tempa flow i burned at leat a gallon more fuel in warm temps.
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #4 ·
Didn't think about the mileage but that would be a bonus to the tempaflow as well...
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #5 ·
Anyone else want to take a stab at this?
 

·
Registered
Joined
·
6,424 Posts
I ran a 6. I will NEVER do that again. So hot it'll burn your pistons up
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #7 ·
How about the other questions extreme?
 

·
Registered
Joined
·
2,518 Posts
Originally posted by krappana
[br]Have heard that warmer temps make a sled run richer.

1st ? just to satisfy my curiousity is why?
An engine runs richer at warmer temps because the air is more dense. Because the air is more dense, not as much of it can flow into the engine.

2nd question - Have heard that running hotter plugs (8's vs 9's for example)is good when it's warm to burn off the extra, true or false?
False. You can run hotter plugs if all of your riding is slow-speed putt-putting around, but you should not put in hotter plugs to compensate for richer jetting.

4th ? - At what point should you change jetting because of temperature? Not for ideal optimal performance, just for the average joe rider not wanting to melt down his pistons...
Typically jets have a 30 degree temperature swing. The best way to tell where you jetting is at is to merely check your plugs. You want the electrodes to be a nice golden brown or chocolate color. If the electrode is black its too rich and if its white its too lean. I like to err on the side of rich because it gives me a margin of safety should it get really cold for a few days. Im willing to give up a little throttle response and fuel economy for that added peace of mind of richer jetting.
 

·
Registered
Joined
·
4,322 Posts
Originally posted by Octane
[br]
Originally posted by krappana
[br]Have heard that warmer temps make a sled run richer.

1st ? just to satisfy my curiousity is why?
An engine runs richer at warmer temps because the air is more dense. Because the air is more dense, not as much of it can flow into the engine.
wrong cold air is more dense then warm air.
 

·
Registered
Joined
·
33 Posts
Cold air is more dense than warm air (That's why heat rises). Dense cold air causes a much hotter burn condition than warm air which can cause a meltdown if not compensated for. Compensate with jett changes, not plug heat range. I have dial a jetts that work well for me. I have never used Tempa flows but have always heard good things about them. I've run the dial a jetts for 11 years is the reason I've never tried Tempa's.
 

·
Registered
Joined
·
1,969 Posts
yeah, the last two posts are right about the air. cold air is more dense specifically because the molecules shrink. there is more oxygen in the same volume of air compared to warm air. more oxygen = hotter combustion. don't compensate with plug range. just use the factory recommended plugs and adjust main jets if you need to.

according to my manual stock jets for a 2001 600xcsp are 430s and that's for a temperature range of -20f to +10f if that what you have now, and you're running in warmer temperatures, you can go down in jets.
 

·
Registered
Joined
·
764 Posts
I've always heard that every ten degrees colder is comparable to a jet size leaner, whether or not its true, i dont know, but looking at the plugs when riding in 37 degrees weather compared to 17 at night i'd say it sounds about right
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #13 ·
^ SO I have this straight, you INCREASE jet size (bigger number jet) the COLDER it gets to get more fuel to mix with the denser air... and conversely decrease jet size the warmer it gets to lean it out? and this is only done on the main jets right?
 

·
Registered
Joined
·
2,378 Posts
Increase your jet size if the tempature is colder than what your manual says, correct. There are main jets, and pilot jets, but I'd only worry about the mains because mains are 3/4 throttle and more.
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #15 ·
OK... just wantd to be sure... thanks.

Also, I'm sure there is an explanation on the site somewhere, but is changing jets difficult? Do you have to remove carbs from sled?
 

·
Registered
Joined
·
1,969 Posts
depends on the sled. but in the case of your 01 600, i'd say yeah. i personally can't fit my hands under there to do it. it's relatively easy to take the carbs out though.
 

·
Registered
Joined
·
282 Posts
Have heard that warmer temps make a sled run richer.
only because warmer air will carry less oxygen than cooler air for the same cubic foot
2nd question - Have heard that running hotter plugs (8's vs 9's for example)is good when it's warm to burn off the extra, true or false?
unless you got a serious problem fouling plugs at low speeds dont even think of running a hotter plug,Ive seen people switch to a cooler plug to run the mountain machine with high compression at lower altitude,it lowers the egt by over 100*
4th ? - At what point should you change jetting because of temperature? Not for ideal optimal performance, just for the average joe rider not wanting to melt down his pistons...
follow your jetting chart,you can find a happy medium in there usually that will let you ride without jetting,when you climb in altitude your sled gets richer and richer,the colder it gets you get leaner,vari flow and tempa flows do work good for altitude and temp changes and will keep you on the performance for sure
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #18 ·
Thanks 900geek and everyone else for their insight... appreciate it!
 

·
Registered
Joined
·
404 Posts
1) Air, though it is made up of many constituent gases is considered an ideal gas. That means that it follows the relation:
PV=mRT. P is the pressure, V is the volume it takes up, m is its mass, R is the gas constant, and T is temperature. If you decrease T but leave the rest constant V will decrease a corresponding amount. This means that the air has become more dense and that there is more air in the same amount of space or alternatively the same amount of air in less volume. This means that there is also more oxygen as well. The additional oxygen causes the mixture to lean out in the same way that a carburetor air screw would. The increased oxygen requires additional fuel to keep the proper fuel air ratio, so you need larger jets to flow more fuel. Barometric pressure also has an effect on the amount of air that goes in the engine as well, it doesn't very as much as temperature though, so it is less of an issue.

2) I wouldn't recommend it. Plug heat ranges are really far apart and could lead to your melting a piston. Changing plugs usually only occurs when you have modified an engine from stock. If the compression is increased, for instance, you need to run a colder plug to prevent a meltdown.

4)Depends on the sled. Each sled has a chart in the owners manual that shows you which set of jets to run to be safe at different elevations and temperatures. They are usually pretty conservative, so you can run a little leaner and still be safe, but your margin for error will decrease a little too. Generally, richer is better than lean (can lead to melted pistons) but too rich has its own detriments (poor fuel economy, carbon buildup, plug fouling).

5) Can't really answer that one, as I have never used one.
 

·
Registered
Joined
·
2,518 Posts
Yeah, youre right. Cold air is more dense. Thats what I get for posting late at night instead of going to bed like I should.
 
1 - 20 of 21 Posts
Top