The twin vs triple debate. time to bring back the trip---or not?

[cs5]

I am not talking about bringing back any old triple I am talking about a specific purpose built engine you need to clear your mind of the past and think future here. Supercharger would eliminate the need for triple pipes so that is not an issue. I would give up some flickability for a 200hp sewing machine that would sound like a dream. Port timing is less issue with direct injection and supercharging as well, as long as the engine is designed as a package. You could include a sealed crankcase with oil bath but that would be adding some weight. I am just dreaming out loud here but hey the technology is hear to do this and be very reliable, COST are you joking, have you seen what we are paying for our sleds already if they build it you will see a lot of them on the snow? Cooling may be the only issue I can think of with this set-up.

 

[jpgmtech]

I am not talking about bringing back any old triple I am talking about a specific purpose built engine you need to clear your mind of the past and think future here. Supercharger would eliminate the need for triple pipes so that is not an issue. I would give up some flickability for a 200hp sewing machine that would sound like a dream. Port timing is less issue with direct injection and supercharging as well, as long as the engine is designed as a package. You could include a sealed crankcase with oil bath but that would be adding some weight. I am just dreaming out loud here but hey the technology is hear to do this and be very reliable, COST are you joking, have you seen what we are paying for our sleds already if they build it you will see a lot of them on the snow? Cooling may be the only issue I can think of with this set-up.

What you are talking about is probably the direction 2-strokes will go for emissions. To make a triple like that, you are getting pretty close to the overall weight of a 4-stroke anyway. Even so, a twin may be more economical for the manufacturers to produce. And it's more about their cost than what we pay, LOL!

 

[cs5]

What you are talking about is probably the direction 2-strokes will go for emissions. To make a triple like that, you are getting pretty close to the overall weight of a 4-stroke anyway. Even so, a twin may be more economical for the manufacturers to produce. And it's more about their cost than what we pay, LOL!

Overall weight will not be the same because it will not need 1200cc's to make 200 hp and it will not need the valve train that comes with a 4 stroke, there is a reason they let the 1000cc 4 stroke run in the 600cc class. I cant argue about the cost issue but this thread is about what we want not what we will get.

 

[Modman]

Modman you are correct on a few accounts however the only engine (triple ) I know that ran the counterbalance was cats 1000 triple and the big watercraft. As far as ignition goes there's one box and a extra coil? The oil pump had a extra line running to case hardly anything hi tec. As far as stroke goes the 809 had a 68 mm the new 800 is 75 mm so not a big stretch ! The 120 degree firing had smoother pulsing that allowed the piston speed to exist. Those engines were very realiable other than stator issues. Some 809's had a oil feed hole that was not drilled from factory and caused premature crank bearing failure. Once corrected they were quite reliable. Quite abit better than these twin bangers out now!!

You are right, the big Cats did have balance shafts (900 as well as the 1000), but all triples over 800 ccs should have been built with one IMO. I'm not saying they weren't reliable, the watercraft triples have demonstrated that they are quite reliable over the years, albeit in a somewhat de-tuned state. The firing order and pulses make it possible on the triple, but there is more than just an extra coil and plug. There is an entire extra cylinder that has to be machined, as well as machining of the case. More oil passages to machine, more bearing races, more ports. Fueling (carbs/injectors), more RAVE valves, larger hi flow fuel pumps, reeds, bearings, cooling passages etc. Some of the earlier triples had issues with the heat in the center cylinder due to the reduced cooling (which is why the jetting is usually staggered in the center hole). Fueling and syncronization were issues on the triples as well, and setting up 3 cylinders is 33% more effort than a twin.

The 7 mm of stroke is not that close for the 809 and 800 if you consider that 7mm of stroke is 10% of the total stroke length. At 7500 RPM, the piston speed of the 809 and 800 engines is close, but a triple will rev to 8500 rpm easily to make the same power as HP as a similar sized twin, and that horsepower is simply a function of torque x RPM (compared to 7500 RPM of the twin). The smaller piston does not generate as much torque on the bottom end of the RPM range, so in order to make equivalent power you need to move the torque up in the RPM on the triple (which is why it was not uncommon to rev a triple to 9000 RPM). So if you compare piston speeds at similar horsepower outputs (not RPM levels), the piston speeds for the triple are actually much higher.

At 8500-9000 RPM, the piston speed is way up on the triple at 4200 ft/min (over 15%) compared to 3600 ft/min on the twin. More bore and less stroke would not live at 8500+ RPM in the twin, too much piston at that rotation speed - it would blow up. But it is happy at 7250 all day long, right where it makes peak torque. and Its all about the torque.

The bore/stroke oversquare on the 800 is 1.10, compared to 1.03 on the triple. The twin is going to make more torque at lower RPM in that CC displacement. Twins have a broader torque curve typically for a comparable displacement (piston diameter and port timing specifics). The broader the torque curve for more RPM means that the sled accelerates quicker and is less susceptible to falling out of its peak power curve. Add this to the CVT style of the snowmobile that works more efficiently at lower RPMs and this makes the sled easier to clutch (or at least more forgiving to not being uber-precise with the clutch set up out of the box).

The triples were far more acceptable as an eastern sled IMO where you could get the sled revved up and stay in the powerband once you hit peak power (still why they are popular with drag racers). Pound per pound, a triple will run away from a twin on the top end. However for mountain riding, its the torque curve of the twin to be able to respond better to on/off throttle style of riding. I never found my triple to be harder to lay over than a twin, and I think the big watercraft triple guys would say the same. I would I suspect it might have been the chassis designs of the day but that being said some guys might have noticed it. I'm definitely not going to calculate it but I'd be interested to know the inertia force/gyroscopic effect on a big triple running at lower RPM compared to a twin running at higher RPM (i.e. 1200 triple at 6300 rpm vs 1000 twin at 7500 rpm) making same power. Gyroscopic difference might not be that much?

In the end I think it came down ultimately to manufacturing/production costs though, twins are just cheaper to make and allowed chassis development to advance to rider forward designs as the overall packages could be more compact.

Best thread we have had in a long time!

 

[popcorn popper]

You are right, the big Cats did have balance shafts (900 as well as the 1000), but all triples over 800 ccs should have been built with one IMO. I'm not saying they weren't reliable, the watercraft triples have demonstrated that they are quite reliable over the years, albeit in a somewhat de-tuned state. The firing order and pulses make it possible on the triple, but there is more than just an extra coil and plug. There is an entire extra cylinder that has to be machined, as well as machining of the case. More oil passages to machine, more bearing races, more ports. Fueling (carbs/injectors), more RAVE valves, larger hi flow fuel pumps, reeds, bearings, cooling passages etc. Some of the earlier triples had issues with the heat in the center cylinder due to the reduced cooling (which is why the jetting is usually staggered in the center hole). Fueling and syncronization were issues on the triples as well, and setting up 3 cylinders is 33% more effort than a twin.

The 7 mm of stroke is not that close for the 809 and 800 if you consider that 7mm of stroke is 10% of the total stroke length. At 7500 RPM, the piston speed of the 809 and 800 engines is close, but a triple will rev to 8500 rpm easily to make the same power as HP as a similar sized twin, and that horsepower is simply a function of torque x RPM (compared to 7500 RPM of the twin). The smaller piston does not generate as much torque on the bottom end of the RPM range, so in order to make equivalent power you need to move the torque up in the RPM on the triple (which is why it was not uncommon to rev a triple to 9000 RPM). So if you compare piston speeds at similar horsepower outputs (not RPM levels), the piston speeds for the triple are actually much higher.

At 8500-9000 RPM, the piston speed is way up on the triple at 4200 ft/min (over 15%) compared to 3600 ft/min on the twin. More bore and less stroke would not live at 8500+ RPM in the twin, too much piston at that rotation speed - it would blow up. But it is happy at 7250 all day long, right where it makes peak torque. and Its all about the torque.

The bore/stroke oversquare on the 800 is 1.10, compared to 1.03 on the triple. The twin is going to make more torque at lower RPM in that CC displacement. Twins have a broader torque curve typically for a comparable displacement (piston diameter and port timing specifics). The broader the torque curve for more RPM means that the sled accelerates quicker and is less susceptible to falling out of its peak power curve. Add this to the CVT style of the snowmobile that works more efficiently at lower RPMs and this makes the sled easier to clutch (or at least more forgiving to not being uber-precise with the clutch set up out of the box).

The triples were far more acceptable as an eastern sled IMO where you could get the sled revved up and stay in the powerband once you hit peak power (still why they are popular with drag racers). Pound per pound, a triple will run away from a twin on the top end. However for mountain riding, its the torque curve of the twin to be able to respond better to on/off throttle style of riding. I never found my triple to be harder to lay over than a twin, and I think the big watercraft triple guys would say the same. I would I suspect it might have been the chassis designs of the day but that being said some guys might have noticed it. I'm definitely not going to calculate it but I'd be interested to know the inertia force/gyroscopic effect on a big triple running at lower RPM compared to a twin running at higher RPM (i.e. 1200 triple at 6300 rpm vs 1000 twin at 7500 rpm) making same power. Gyroscopic difference might not be that much?

In the end I think it came down ultimately to manufacturing/production costs though, twins are just cheaper to make and allowed chassis development to advance to rider forward designs as the overall packages could be more compact.

Best thread we have had in a long time!

Read this the 809 made peak at around 8700 and the 800 twin around 7900 rpm so only a difference of 800 rpm.look at the stage tuning and see where you can get now think if it was etec??

 

[cs5]

I don't care who builds it, if someone comes out with a DI 2stroke triple, one will be on order. I miss the triples and I don't think I'm alone.

 

[Longhairfreak]

I don't care who builds it, if someone comes out with a DI 2stroke triple, one will be on order. I miss the triples and I don't think I'm alone.

Im out. Im a torque guy. Torque is what gets you up the hill.

 

[CUSO]

AAAAAAAAAAAnnnnd STAY OUT!!!!!

Im out. Im a torque guy. Torque is what gets you up the hill.

 

[Longhairfreak]

AAAAAAAAAAAnnnnd STAY OUT!!!!!

I get it you must think cc for cc the triple will make more torque. You need to do more research before you post a thread.

 

[CUSO]

Another thread wrecked.

I get it you must think cc for cc the triple will make more torque. You need to do more research before you post a thread.

 

[popcorn popper]

I get it you must think cc for cc the triple will make more torque. You need to do more research before you post a thread.

The etec 800 makes 160.9 at 8000 rpm on the dot peak tq was at 7950 at 105 ft lb. the stock 800 triple wasn't that far off at we're talking 12 year old technology ?? I don't buy the 800 twin makes more tq!!if you look at Dyno charts the triple made peak tq at 7700??? Hmmmmmmm seems lower in rpm range? Also when they added vforce reeds the tq almost equals etec at lower rpm. I guess the twins aren't as torquey as one would think.http://www.hardcoresledder.com/forums/409-xp-xr-new-style-mxz/595693-2012-etec-800-dyno-results.html

 

[Longhairfreak]

The etec 800 makes 160.9 at 8000 rpm on the dot peak tq was at 7950 at 105 ft lb. the stock 800 triple wasn't that far off at we're talking 12 year old technology ?? I don't buy the 800 twin makes more tq!!if you look at Dyno charts the triple made peak tq at 7700??? Hmmmmmmm seems lower in rpm range? Also when they added vforce reeds the tq almost equals etec at lower rpm. I guess the twins aren't as torquey as one would think.

At 7700 RPM the 809 made 99.3 ft lbs torque

 

[popcorn popper]

At 7700 RPM the 809 made 99.3 ft lbs torque

If you look at the triple at 7000 it makes 98.9 and the etec makes 92?Stock to stock the etec does make more tq at peak by 6ftlbs but just adding reeds it nearly equals twin but at lower rpm?

 

[Longhairfreak]

If you look at the triple at 7000 it makes 98.9 and the etec makes 92?Stock to stock the etec does make more tq at peak by 6ftlbs but just adding reeds it nearly equals twin but at lower rpm?

A big twin makes over 100 ft lbs torque at 6000 rpm. What is it your trying to say and where are you getting your numbers?

 

[popcorn popper]

Link is above longhair and your twin is not 800cc!!HAHA

 

[Longhairfreak]

Link is above longhair and your twin is not 800cc!!HAHA

Im talkin your 809 numbers.

 

[popcorn popper]

Im talkin your 809 numbers.

They also posted above!

 

[Clode]

I think the OEM's pushed twins only because they are cheaper to build, if triples had continued to be developed I am sure the power they would make with today's tech would be impressive. A few bad triple designs gave all triples a bad name, but its strange how todays twins are proving to be not much better. I would like to see a modern triple.

 

[Longhairfreak]

They also posted above!

Not seeing them.

 

[popcorn popper]

Not seeing them.

Look past the twin jugs grasshopper !!