: Speed And Gas Mileage
01-21-2004, 11:20 PM
My son is doing a science project for school to see if the speed of a snowmobile affects the gas milelage assuming that the trail and weather condition is the same. His question is: Will the speed of a snowmobile change the amount of gas it uses over the same distance?
Please let us know what you think and why.
We're using this forum as research and then we will test it with a controlled experiment.
01-22-2004, 12:01 AM
The faster any object travels, the more energy required, or in a sleds case, fuel.
A snowmobile generates more friction and more wind resistance the faster it travels.
This added wind and ground friction require more fuel. (no, covering more ground in less time will not makeup for ad addiional fuel use)
Somewhere in my archives I have a simple formula for horse power addition required for every mile per hour increase given a certain friction load for an automobile. I imagine it could be converted to be used on sleds, the friction of a sled is so much higher than that of a car, but none the less, I'll try to find it.
01-22-2004, 01:22 AM
I don't have anything to back this up but I don't think it is that simple. I think efficiency of the engine has to be considered. The engine will be most efficient at a certain rpm and that would translate to the most efficient speed.
I used to receive several boating magazines and they would always point out the most efficient rpm/speed. It was usually around 3/4 top speed.
In general, higher speeds will require more fuel.
01-22-2004, 06:06 AM
i thought i seen an experiment on something like this before, I believe the result was you still covered more ground with going faster on the same amount of fuel. But i also think this was over car's ??
whil out riding on saturday with my f6 and our sabrecat 600 i found that over the same distance the sabrecat was using less gas. not much though, my f6 took 20 litres and the sabrecat took 18. its hard to compare 2 sledds becaus ethey are all different. But i ride my f6 a lot harder than my mom does with her sabrecat 600. i am not sure how much more gas i would save if i didnt ride hard. I do know what sucks the fuel up is running them wide open. when the trials are perfect with a hard base i would bet that it would matter if you drove 40 of 70 mph the fuel ussage would be very close. jetting also playsa big part. somesleds are jetted to high or low in mid range so that can affect the mpg as well.
01-22-2004, 07:13 AM
I agree, dawg. Running wide open uses a lot more gas, but I think that the difference between say running at 50kph ( trail speed in ontario) - 80 kph wouldn't be that much, but it would still be a little higher comsumption at 80. Yes you would cover more ground going faster, but comsumption has to go up.
yeh its so hard to tell. i wonder if if there is a certian speed where you would get the best gas mileage and cover the most ground. Its like driving a car, u get great gas mileage on the highway at like 100- 110 kms an hour. Now drive in the city and u get really bad gas mileage. i guess it all has to do with gear ratio. if your vehicle runs at 3000 rpm in a certian lower gear and is only doing 40 kph u may not use anymore gas driving at 130 kph riding in a higher gear also reving at 3000 rpm. This would mean u would use the same gas but coevr a lot more ground. not sure if this would apply to sleds but they do shift so it might i dont really know.
01-22-2004, 08:52 AM
Both of my Polaris machines get terrible gas mileage wide open, but also get bad gas mileage at low speeds (25 mph or less). When I'm trying to stretch how far I can go before running out, I tend to run around 30-40 mph. Especially on the Storm, the mileage get's pretty good at that speed range.
01-22-2004, 09:14 AM
Wait a minute here guys nobody said "Do you use more gas when running wide open?" it said at a faster speed.Its just like highway driving with your car you use less gas with the clutching changed up to high gear as long as your not going full out.If your cruising on good trail at around half throttle you will use much less than crawling along at say less than 1/4 throttle.I have proved this theory on a week long trip from Sudbury to Cochrane and back.Also my wife's 583 got a little better mileage than my 670 as long as we stayed below or around 70-80KM/PH.Any faster than that up to 100-110 and the 670 actually got better mileage than the 583.There's more to it than just overcoming friction.Clutching and gearing and the proper cruising rpm for the specific engine make all the difference.
01-22-2004, 10:23 AM
One thing that I have not seen mentioned here regarding this topic is power valves or RAVE's. What is the purpose of these. To decrease noise, increase fuel economy and increase low end power as well as top end depending on the engine. If 2 identicle sleds travelled the same distance on the same stretch of trail at the same time but sled A's rpms were kept just below the opening rpm of the exhaust valves and sled B's rpms were above the opening rpm of the valve one would find that sled A used less fuel over the same distance. But this really does come down to just how fast these sleds are going. If both are below this valve opening rpm the difference could be near zero. One thing we do know is we fight friction right from the get go. Anyone care to hazard a guess about at which rpm the CV transmission is more effiecent ? Certainly with bigger lugged tracks the faster you go the more air the track will "pump" and therefore require more power to turn and use more fuel. Most 2 stroke exhaust systems are tuned to a certain rpm as well. There are a lot of variables here. Your findings will be interesting.
01-22-2004, 12:39 PM
A big issue is how hard to you accelerate to that speed. WOT will use lots of gas but running at a contant speed can use the same MPG even though you are going faster, you are using more gas, but you are also covering more distance in the same time.
I have a Chevy Avalanche which has a fuel mileage computer on it including instant fuel mileage. If you go 40 mph or 75 mph the actual MPG is very close as long as you are at constant throttle on even ground. You use more gas at 75 mph, but cover more distance.
There are tonnes of variables like acceleration, engine load, etc. I would say in some situations you would be able to have the same MPG at higher speeds.
01-22-2004, 04:19 PM
Any of the big sleds I've had got 8-10 mpg,didn't matter how you rode them or how fast.I tried the slow and easy throttle just didn't help.Yamaha triples were the only sleds I ever got more than 10mpg,they all got in the teens 13-15mpg running them hard and fast.I would have to say there's not more than 10% difference in the way you run them,they are VERY inefficient.
01-23-2004, 08:55 AM
Oddly enough on the same conditions my XLT seems to be getting the same fuel mileage regardless of speed. (Exception WOT, which I don't ride for long distances)
Last Monday I ran the same trails up and back. Total 106 miles.
I put in just over 24 liters at the far end and drove back the same direction. I filled it again and it took again just over 24 liters. (plus or minus .1-.9). I always fill to the bottom of the neck not by dollars or liters.
On the way up we took 2.5 hours, returning we took 1.75 hours. Obviously we picked up the pace and there was marginal difference in fuel, 10ths of a liter.
I can always count on my sled to run the exact same fuel mileage on groomed similar conditions.
Now braking trail or powder that's a different story. Last year I ran a tank in 45 minutes in powder braking trail.
Can't explain it but for my sled this is true. I think it is due to the clutching keeping the RPM in the power band through varying loads. A car mind you does not cruise anywhere near its max HP number.
Now my 69, the fuel mileage is directly proportionate to the speed and distance. I putt 50 mph, it will get around 9-10 mpg, hammer down and I can darn near see the guage move.