ESKIMO
Extreme
I am writing this without a clue as to what I am talking about, but only thinking logically.
Since a larger engine size has more torque than a smaller one, it takes less RPM's to move it forward at the same speed.
This can be attributed to the heavier clutch weights on the larger CC engine as it can keep the clutch closed at that certain ratio with a lower RPM, as compared to a smaller engine with lighter weights that need to increase the RPM to maintain that certain ratio.
This means that the larger engine burns less fuel because with the smaller RPM, the volume of fuel going through is less than a smaller engine with a higher RPM at the same speed.
Is this why most bigger engines out here burn less or same fuel than the smaller ones?
I know theres lots of other variables like lug height and how it can affect track speed vs. ground speed and things like that, but for the most part, all sleds run the same 1.25 lug heights. I guess I am also speaking very generally here.
Eskimo
Since a larger engine size has more torque than a smaller one, it takes less RPM's to move it forward at the same speed.
This can be attributed to the heavier clutch weights on the larger CC engine as it can keep the clutch closed at that certain ratio with a lower RPM, as compared to a smaller engine with lighter weights that need to increase the RPM to maintain that certain ratio.
This means that the larger engine burns less fuel because with the smaller RPM, the volume of fuel going through is less than a smaller engine with a higher RPM at the same speed.
Is this why most bigger engines out here burn less or same fuel than the smaller ones?
I know theres lots of other variables like lug height and how it can affect track speed vs. ground speed and things like that, but for the most part, all sleds run the same 1.25 lug heights. I guess I am also speaking very generally here.
Eskimo
vmaxjohn
Pro
Good questions!
Think of it this way...
a 500cc motor which runs at 100% volumetric efficiency will make the same power as a 1000cc motor running at 50%. Which one gets better milage? The 500, because there's just less fuel going in to make the same power.
Turn that around. A yamaha 500 twin gets around 11mpg at best. This is with all factory settings etc, for pure theoreticalness, hehe. Now, take a 700cc Yamaha triple. It's bigger, makes more power but gets upwards of 14mpg, again all stock settings. I've seen both of these results first hand, pay no mind if your particular sled doesn't pull these numbers...
So, since we have more power to work with in the 700, we're pushing the throttle less, we have a snappier motor which backshifts quicker, resulting in more scoot for less throttle opening.
This adds up to better milage. In this case, the 700 is less likely to have jetting problems for a given temp change, as opposed to the 500, which varies widely.
In a truck, the motor that can pull a given load at the lowest rpm possible will get the best milage. Take a low power motor and get it into OD, and it's going to suck, unable to pull. rev that motor to where the power is, and you're then using lots of throttle with lots of RPM. This means you're sucking gas.
This is why the diesels get better milage under load than gas motors, more torque, resulting in lower rpm, or the ability to carry the load there.
Make sense?
Think of it this way...
a 500cc motor which runs at 100% volumetric efficiency will make the same power as a 1000cc motor running at 50%. Which one gets better milage? The 500, because there's just less fuel going in to make the same power.
Turn that around. A yamaha 500 twin gets around 11mpg at best. This is with all factory settings etc, for pure theoreticalness, hehe. Now, take a 700cc Yamaha triple. It's bigger, makes more power but gets upwards of 14mpg, again all stock settings. I've seen both of these results first hand, pay no mind if your particular sled doesn't pull these numbers...
So, since we have more power to work with in the 700, we're pushing the throttle less, we have a snappier motor which backshifts quicker, resulting in more scoot for less throttle opening.
This adds up to better milage. In this case, the 700 is less likely to have jetting problems for a given temp change, as opposed to the 500, which varies widely.
In a truck, the motor that can pull a given load at the lowest rpm possible will get the best milage. Take a low power motor and get it into OD, and it's going to suck, unable to pull. rev that motor to where the power is, and you're then using lots of throttle with lots of RPM. This means you're sucking gas.
This is why the diesels get better milage under load than gas motors, more torque, resulting in lower rpm, or the ability to carry the load there.
Make sense?
Ski-Dog
Expert
This is a tough one. Many larger motors get better fuel milage than smaller ones particularly sleds. Some trucks are like that two some V8's do better than some V6's. But then when one compares similar engine sizes there is still large variances. Take a Yamaha 700 triple 2 stroke. Uses less fuel than any 2 stroke 700 twin. Copare 700 twins from Ski-doo Arctic Cat and Polaris. Those cats funneled fuel like no tomorrow. I had a 2000 Polaris 700 and dumped it mid season because I couldn't make it between fuel stops (after 13 trips back to the dealer as well) Poo's final answer to fix the problem was to give me a tour buddy tank - I said no thanks. In sleds there are so many variables trying to predict fuel mileage ahead of time is a shot in the dark.
Its the big reason I moved to Yamaha. I set out to buy a 04 800 REV Renegade but the deal breaker was the voracious appetite for fuel with borderline ability to make 100 miles on tank of fuel for the 800.
Its the big reason I moved to Yamaha. I set out to buy a 04 800 REV Renegade but the deal breaker was the voracious appetite for fuel with borderline ability to make 100 miles on tank of fuel for the 800.
jimmie d
TY 4 Stroke Master
Theory is correct must most of us would just run the larger engine just as hard, get more top end but lose mpg. The bigger the engine the faster you want to go.
Jim
Jim
vmaxjohn
Pro
Maybe true for you Jim...but I push my lil5 through the twisties as fast as a sled can and remain in control. I've got to be on the throttle in mid corner to be shifted down and going again. Granted, I'm 2 feet behind the red/green/blue 700 in front of me the whole time 
If I had 30 more hp, I could take it easy through the corners, and wack it. All that coasting means great milage! My buddy's tempaflow equipped SRX netted 20mpg on his first ride, following a wuss on a F3...
If I had 30 more hp, I could take it easy through the corners, and wack it. All that coasting means great milage! My buddy's tempaflow equipped SRX netted 20mpg on his first ride, following a wuss on a F3...
penetang guy
Veteran
- Joined
- Feb 13, 2004
- Messages
- 30
I have observed the 500 vs 700 MPG scenario with the same results - the 500 drinks gas like there is no tomorrow when it's trying to keep up with a pack of 700's and 800's averaging 60+ MPH.
I have some other amazing observations - on the snow, my preferred brand is Yamaha. On the water, I love my SeaDoo's. Running WOT (pinned) or nearly WOT, the Direct Injection 2 stroke SD's match the fuel economy of their 4 stroke. However, at anything under 80% of WOT the DI fuel economy climbs quickly. In fact, my fuel economy of my DI SeaDoo's are easily double (and then some) that of my 4 stroke SD's at half throttle. This leads me to believe that 2 stroke is the future. For now, on the snow, I stick with Yamaha because of reliability (my SD's have been in the shop far too many times for me to trust that brand to bring me home). However, I think Yamaha is sinking far too much into just 4 stroke technology because from what I've seen, the evidence is pretty clear. If you need evidence on what I'm talking about, go check out Evinrudes new line of Outboards - Engines that have no scheduled service or maintenance for the first 3 years of ownership - Engines that deliver almost double the fuel economy of comparable 4 stroke Outboards.
Another stroke against Yamaha was their oil consumption compared to SkiDoo... I tended to fill up my Ventures with a quart of oil with every tank full. Ski Doo owners usually put in a quart every 2 to 3 tanks. However, as I said, when it's minus -20 out, coming home is more important than sex appeal, fuel economy, weight etc... That makes Yamaha number one in my book because after logging almost 10,000 miles on my 4 Yamaha sleds, I've come home every single trip...in fact, I've never been left stranded on them.
I have some other amazing observations - on the snow, my preferred brand is Yamaha. On the water, I love my SeaDoo's. Running WOT (pinned) or nearly WOT, the Direct Injection 2 stroke SD's match the fuel economy of their 4 stroke. However, at anything under 80% of WOT the DI fuel economy climbs quickly. In fact, my fuel economy of my DI SeaDoo's are easily double (and then some) that of my 4 stroke SD's at half throttle. This leads me to believe that 2 stroke is the future. For now, on the snow, I stick with Yamaha because of reliability (my SD's have been in the shop far too many times for me to trust that brand to bring me home). However, I think Yamaha is sinking far too much into just 4 stroke technology because from what I've seen, the evidence is pretty clear. If you need evidence on what I'm talking about, go check out Evinrudes new line of Outboards - Engines that have no scheduled service or maintenance for the first 3 years of ownership - Engines that deliver almost double the fuel economy of comparable 4 stroke Outboards.
Another stroke against Yamaha was their oil consumption compared to SkiDoo... I tended to fill up my Ventures with a quart of oil with every tank full. Ski Doo owners usually put in a quart every 2 to 3 tanks. However, as I said, when it's minus -20 out, coming home is more important than sex appeal, fuel economy, weight etc... That makes Yamaha number one in my book because after logging almost 10,000 miles on my 4 Yamaha sleds, I've come home every single trip...in fact, I've never been left stranded on them.
vmaxjohn
Pro
Pguy...I hear ya. My 500's both drank oil at first. I went from 80mpq to 180 though, Amsoil allowed me to lean the pump past what Yamalube could do. I also put a Tempaflow on, and went from 11 to 14 reliably...same or a little better than my buddy's ZR600 EFI with power valves...I'm pretty happy with it.
Also...I tend to get pretty good milage when I'm hounding bigger sleds, that's when I pull 14mpg actually. Chalk it up to more miles per revs, since we're just hauling #*$&@.
On oil milage...there is a relationship between gas and oil consumption. I've observed sleds with great gas milage, taking more oil than sleds that suck gas. To me, it seems that a motor getting plenty of gas, requires less oil to keep it happy...Hard to do a back to back study though, hehe.
Also...I tend to get pretty good milage when I'm hounding bigger sleds, that's when I pull 14mpg actually. Chalk it up to more miles per revs, since we're just hauling #*$&@.
On oil milage...there is a relationship between gas and oil consumption. I've observed sleds with great gas milage, taking more oil than sleds that suck gas. To me, it seems that a motor getting plenty of gas, requires less oil to keep it happy...Hard to do a back to back study though, hehe.
JDKRXW
TY 4 Stroke Junkie
penetang guy said:
PG; respectfully, what you're saying goes against everything I have read about the advantages of using 4 strokes in marine applications. I would be interested in knowing the models numbers of the Sea-Doo's you are referring to in your post.
Here's a direct comparison for you
http://www.iboats.com/sites/trailerboat ... e_243.html
Suzuki 90 F.I. 4 stroke -5.9 mpg at best fuel economy.
Evenrude E tec 90 -6.6 mpg at best fuel economy.
Above test done on the same boat, same load, same day.
Better, yes...... but double the fuel economy is pushing the credibilty limit in Bombardier's advertising.
Like they say........ there's no magic bullet. If there was everyone would be using it.
penetang guy
Veteran
- Joined
- Feb 13, 2004
- Messages
- 30
Bombardier doesn't promote double the fuel economy. I have this run I like to do on my SeaDoo's which is 51 miles each way on the marine map...a 102 mile round trip. The SeaDoo's that I own and have driven on this loop (many times) are:
2001 GTXDI 2 stroke 3 seater 950cc 130 HP
2001 RXDI 2 stroke 2 seater 950cc 130 HP
2002 RXDI 2 stroke 2 seater 950cc 130 HP
2002 4 TEC 4 stroke 3 seater 1.5liter 155 HP
2003 4 TEC SC 4 stroke 3 seater Super Charged 1.5 liter 185 HP
All of the above machines have the same fuel tank - 56 liters. The range on my 2001 DI's was 115 to 125 miles per tank The 2002 had improvements in the DI system and the range I found on that unit was about 135 miles per tank. My observed mileage was typical from the SD message boards - about 8 - 9 MPG of 35 to 45 mph driving. However, when one starts driving them at WOT, the fuel economy plummets and oil consumption goes through the roof (I'll use a 1 quart per tank at WOT).
Not so with the new 4 stroke SeaDoo's. I got at best 80 miles per tank with the 155 HP - maybe 72 miles per tank at WOT with the SC. Take at most 10 percent off the numbers for slower cruising speeds of 40 mph.
My experience shows that on the water, if you are are hard driving WOT dude like me, you are better off with a 4 stroke (unless you plan on going on long "cruises" and then the only choice is DI).
On the snow, one rarely runs pinned for any length of time. So from what I've seen, the DI injected 2 strokes are going to be the future. That's my opinion. In stating so, you might think I'm a SD fanatic. I'm not. The reliability of my SD's above has been horrific. My SC died twice last year. My 02 RXDI required an engine rebuild. My RXDI developed a bad leak. I'll stick with Yamaha in the winter, but in the summer, they are going to have to come out with something a little more exciting to get me interested. 215 HP SD RXP vs the 160 HP Yamaha HO. uh uh. No competition. The GPR is a gas guzzling oil burner. Not for me, although I'm sure the testosterone crowd loves it. But...the RXP sounds exciting.
Come on Yamaha, get the turbo out for your 4 stroke PWC, call up the style artists and get in the god damned game so I can have the PWC I want with relibability.
2001 GTXDI 2 stroke 3 seater 950cc 130 HP
2001 RXDI 2 stroke 2 seater 950cc 130 HP
2002 RXDI 2 stroke 2 seater 950cc 130 HP
2002 4 TEC 4 stroke 3 seater 1.5liter 155 HP
2003 4 TEC SC 4 stroke 3 seater Super Charged 1.5 liter 185 HP
All of the above machines have the same fuel tank - 56 liters. The range on my 2001 DI's was 115 to 125 miles per tank The 2002 had improvements in the DI system and the range I found on that unit was about 135 miles per tank. My observed mileage was typical from the SD message boards - about 8 - 9 MPG of 35 to 45 mph driving. However, when one starts driving them at WOT, the fuel economy plummets and oil consumption goes through the roof (I'll use a 1 quart per tank at WOT).
Not so with the new 4 stroke SeaDoo's. I got at best 80 miles per tank with the 155 HP - maybe 72 miles per tank at WOT with the SC. Take at most 10 percent off the numbers for slower cruising speeds of 40 mph.
My experience shows that on the water, if you are are hard driving WOT dude like me, you are better off with a 4 stroke (unless you plan on going on long "cruises" and then the only choice is DI).
On the snow, one rarely runs pinned for any length of time. So from what I've seen, the DI injected 2 strokes are going to be the future. That's my opinion. In stating so, you might think I'm a SD fanatic. I'm not. The reliability of my SD's above has been horrific. My SC died twice last year. My 02 RXDI required an engine rebuild. My RXDI developed a bad leak. I'll stick with Yamaha in the winter, but in the summer, they are going to have to come out with something a little more exciting to get me interested. 215 HP SD RXP vs the 160 HP Yamaha HO. uh uh. No competition. The GPR is a gas guzzling oil burner. Not for me, although I'm sure the testosterone crowd loves it. But...the RXP sounds exciting.
Come on Yamaha, get the turbo out for your 4 stroke PWC, call up the style artists and get in the god damned game so I can have the PWC I want with relibability.
