why are fans cooled sleds so differnt in power than liquid cooled sleds. is it just they cant cool as fast or what.


what are some hop ups fer fan cooled sleds if any??? the sled is a formula sl 500

Have you riden an A/C 570 or 440 Sno-Pro Fan?
They're not as slow as you might think. I'm sure Pol, Doo and Yami's are good too.
But, yes.... the reason is air cooling is not as efficient as liquid, so you can't reliably produce the same HP.

I too had noticed the hp difference,,,but never knew the exact reason,,,

what r some hop ups

Someone may be able to explain this better than me but here is my interpretation.

A liquid motor has a cooler running cylinder and more consistant cylinder shape than a fan or free air motor - as the cylinder heats up the jug shape and size changes.
A liquid motor cylinder reaches a small temperature window once at operating temp and the shape stays the same (or close).
A fan motor cylinder is constantly shrinking and swelling depending on the cylinder heat and air flow (and outside temp)
The more consistant the cylinder shape, the tighter the piston clearances possible.
This allows for a motor with higher compression - compresson = power.
The cooler cylinder also allows for more timing advance without the risk of detonation - adds even more power.
Add to the fact that if the cylinder is cooler - the air bieng compressed in the cylinder is cooler and is thus denser also adds power.

This is why a fan motor runs so much faster once the temps drop - or are doggy in warm temps.
This is also why it is so critical to allow a liquid sled (especially a big bore) to reach operating temp before beating the snot out of it (cold sieze).

As far as mods for a fan I'm afraid that there arent many - make sure it is clutched properly (good clutch kit), jetted for your alt and temp, and perhaps gut air box (Not sure on a Ski-doo)
Maybe a Ski-doo guy (or gal) could offer more insight but I have never seen pipes , etc for a fan motor.

Hope this helps,
Vman

Great interpretation V man!!!!

:withstupid: Very well done V man

VMan you said it all basically.

Fan cool sleds are handy to have when it's real cold out since they produce so much hot air it's nice to warm up helmets and gloves after they fog or get icy from the snow.

The Fan cool is lighter than the LC so you have that going for you.

Things to make sure are good and setup properly are:
Fan belt (Won't run too long without it)
Debris in the shroud pre winter check should include removing the shroud over the head to check for mice debris.
Check for fan damage. (we had a belt break and it cracked a blade and at 6500 RMP the cracked blades don't stay on too long.)
Clutch it to run in the current conditions. Wet snow, fluffy snow etc...

There is not a whole lot that you can do to increase power since the cooling is limited. It is not worth the risk unless your just lake racing or don't mind the walk back to the hotel. The LC sleds run higher compression and can run leaner since the cooling of the cylinder bores and heads is much more even.

Enjoy the ride. There are things that you can do that a heavier sled can't. A good friend of mine has the 340 version of that sled and it does everything I would want of a sled excpet the 90+ MPH thing. It is a much better hill climber than I thought it would have been and get's decent mileage.

Chris

Yep liquids can rev much higher rpm than a fanner, but a fanner will still go 70 fast enuff to cause some serious pain if ya fall off

Vman hit it right on the head. this is why cars are water cooled too....
as far as hop ups... just get a new snowmobile. its not worth it to "hop up" a 500 fan, as it will never be as fast as its liquid counterpart. probably not even as fast as a 440 liquid. Its kind of like trying to hop up a kia... theres no point. just spent the money and get something that is designed to go fast, not to just go.

I will say, however, my old 88 polaris sport 340 fan was/is one of the most fun snowmobiles i have ever ridden. it wasn't fast, but it was small, nimble, and i could throw it around like nothing.

- Jason

Ya you can get pipes for them give ya 10 more hp , you can trail port it , you could put in some reeds ... Mind you all this will add more heat to the mix ... but then you just jet it up some .

hi, i have an 88 fan cooled yamaha phazer, and it is a blast, dont listen to these guys telling you it aint worth modding your fan motor. i have jetted, piped and clutched my phazer and have taken plenty of liquid cooled sleds on and won. just keep an eye on your plugs and have fun. I have had this setup for 2 years now and no problems whatsoever with also 1600 hundred miles on the setup. Have fun modding :D :p

I had a 96 Formula Sl 500 for a coulpe seasons and what a ride. This sled could easily lift the ski's and could move along pretty good too. The best part was how well it cornered, racing in a oval in a snow covered field, I couldn't be beat by any of the liquid sleds because of the cornering ability. Had to eventually upgrade to more h.p., but always enjoyed the lightness of the fan sled. :thumbsup: :christmas:

versatileman,,,,,have you by chance had to explain that before,,,you act as if youve done it a time or two,,,,

thanks I have a better understanding now!!

Uh, yeah - I kind of teach this sort of stuff.

Originally posted by versatileman@Dec 4 2003, 01:30 AM
Uh, yeah - I kind of teach this sort of stuff.
High school shop teacher??? Mechanic??? What do you do?

Alright, I don't normally do this.
I teach advanced automotive systems at a great technical college.
I routinely teach all automotive areas except for transmissions (we have a specialist) but my primary areas are advanced electrical systems, advanced fuel and emissions systems and ABS - traction control -- body control electronics.
We are now also teaching hybrid fuel systems and alternative fuels vehicles.
I have 12 years experience as an automotive technician for various independant shops and Chevrolet dealers (mostly driveability and Corvette work)
I am GM master certified as well as ASE master certified.

I have worked several winter seasons at a local Ski-doo / Polaris dealer in our programs lean years (we have really grown in the last 5 years).
In those lean years we ran alot of 2 and 4 week seminar type classes.One of my favorites (and my baby) was a two-stroke performance class.
One of my cohorts taught a 4 stoke street bike performance class.
-Man, I miss those days -
In my spare time (not much) I do odd hop ups and service to family, friends, and club members sleds, bikes, boats, etc. at my home shop.
Maintaining MY toys takes most the shop time - I'll try to post a pic.
Anyway, that is me.

Vman