2stroke triple snowmobiles comeback

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It's no secret that 2-stroke triples used to be "King of the Lake" when it came to all-out performance. They still rule when it comes to racing machines too, but you won't find ANY in the Big 4's product lines.

4-strokes can be had in both 3- and 4-cylinder versions, but all production 2-strokes all the way up to 1000cc are now 2-cylinders.

"You will never see a big triple again," said one U.S. OEM product manager confidently. "The triples with triple pipes are just too large, heavy and bulky to package in today's sleds," he continued, "and with all the new EPA requirements, the 2-cylinders are easier to work with."

Does the development of cleaner 2-strokes really mean the end to the popular triples?

Why we love them
Performance enthusiasts love the smooth, powerful triples, and through the years these machines were very successful in the marketplace. The 500 Polaris Centurion, and its large brothers the Indy 600 and 650, kept Polaris No. 1 for a long time. When customers whined about increasing weight, Polaris introduced the 580 XLT (Extra Light Triple) and later the 600 XCR, both solid hits.

Another reason these were so popular? Triples were easy to hot rod. Just replace the three-into-one exhaust with triple aftermarket pipes, and you could easily add 25 horsepower. Arctic Cat took top honors when they introduced the 162-horse 900 Thundercat with triple pipes and then upped the ante with a 172-hp 1000cc version. Performance seekers soon had the 1000cc triple producing more than 200 horses.

By the mid-1990s, all four manufacturers offered triples. Arctic had Thundercats, Polaris a new XCR, Ski-Doo the Mach Z and Yamaha the most with SX, SXR, SRX and Viper models.

Ski-Doo's smaller 600 Formula model dominated the Formula 3 oval racing class, but with snocross growing in popularity, the manufacturers switched to lighter twins in the bump wars.

Lightweight wins, sometimes
With lightweight now the new battleground, why would a manufacturer want to introduce a triple again?

The larger the twins get, the rougher they run and the harder they are on clutches. The twins hit hard and are rough on an engine. Every time a 500cc cylinder fires through a long 80mm stroke and rattles clutch components and strains belts, you are taking life off parts. You can counterbalance the piston vibrations with balancer shafts, but that doesn't dampen the torque reaction of each power stroke. More inertia through heavier flywheels will dampen torque reaction, but this means slower acceleration and increased weight.

The big twins are hitting their limit, and Ski-Doo even canceled this year's Mach Z 1000cc twin. This is understandable, as the new Ski-Doo 800R makes close to the same power in a much lighter sled.

In this industry, things go in cycles, and sometime an OEM is going to shoot for the "King of the Lake" title. A production stock triple could hit 200 hp, and still stay clean under the EPA rules. You won't do it with triple pipes, but with a light, compact three-into-one exhaust, it would be possible.

Triple emissions
When it comes to controlling emissions, the triples with single exhaust have an advantage. This system works differently than regular expansion chambers. The three-into-one manifold offers its own "plugging pulse" due to the 120-degree spacing of exhaust pulses, and it is therefore not dependent on an expansion chamber to push the extra fresh gases from scavenging flow back into the cylinder again.

The expansion chamber, part of the three-into-one system, does not resonate at engine speed like the single pipe per cylinder. Instead, this short and stubby chamber must resonate at three times the engine speed to reinforce the plugging pulses. The small chamber reinforces power at top rpm, the result being a wide power band that could compete with a 4-stroke for torque.

Since the three-into-one "log" manifold always offers a plugging pulse every 120 degrees, no matter what the engine speed, it means this system is more efficient in pushing unburned fuel into the cylinder again at lower engine speeds where an expansion chamber exhaust system is "out of tune." Emissions at lower engine speeds are therefore easier to control with a triple "log" manifold.

Ski-Doo has a jump on the competition in this area through the experience BRP has with its Evinrude outboard brand. The Evinrude E-TEC V-6 outboard motor is more powerful per pound and runs cleaner and with better fuel economy than competing 4-stroke outboards. Using E-TEC outboard technology, Ski-Doo could possibly make a compact and light 1,200cc triple that would produce 200 horses, be EPA legal, get good mileage and put a new twist into the "King of the Lake" game.

Outboard technology uses a very light and compact one-piece crank with split rod and split main bearings. Couple this with mono-block cylinders, and overall width shrinks substantially. With the mono-block cylinder castings, the exhaust ports can be angled toward each other. This shortens the flow passages in the three-into-one manifold and makes it possible to get efficient plugging pulses at higher rpm, even with a bigger bore triple. The technology is available; it's just a question if the marketplace is large enough to support the investment.

Sledders still like triples, and there are plenty of guys stuffing them into newer chassis and then asking aftermarket people like ourselves for custom pipe installations. Will we see a triple again soon?

Probably not in the near future, but who knows what may be available 5 years from now. My prediction: when the big snows return, and the manufacturers get all the new EPA and chassis technology sorted, we will likely see the triples again.