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American Snowmobiler is the first to give you a third party dyno report on Yamaha's highly anticipated 2008 Nytro, spawned from its Snocross racer... and the news is good!
The power-makerSnocross blood runs through the veins of this 1049cc 3-cylinder, open loop fuel injected, liquid Genesis 130 engine. And this fire-breather is designed to run best on 87-octane fuel, good news for riders who often find themselves out in the sticks where higher octane is sometimes unavailable.
It weighs 10.2 lbs. less than the Genesis 120 engine found in the Vector and Venture sleds. Bore and stroke on the Nytro are 82 and 66.2 respectively.
Initial snow testing of this powerplant provided us a chance to feel first hand the incredibly strong, and long, pull the Nytro's engine has out of the hole right up through the top end. No wonder Robbie Malinoski was able to rocket out of the corners on the WPSA Snocross tracks this past season and won the Brainerd, Minn., race. Some of the throttle response is due to a new lighter, responsive and durable crankshaft. The shaft is 1.7 lbs lighter than the Vector's, which makes a difference when we're talking about reducing rotating mass.
A big radiator sits above the engine and rearward of the headlight with channels constantly directing fresh airflow through the radiator for high cooling capacity. This 4-stroke stays cool in all conditions. Unlike the 120 and 150 engines from Yamaha, the Nytro uses a straight exhaust pipe design that exits as a single out the sled's tail. The exhaust maximizes horsepower, dissipates heat and helps centralize the sled's mass.
ShockingOur Nytro engine test was conducted by
AmSnow's Technical Editor, Olav Aaen, owner of Aaen Performance in Racine, Wis., on the same day he dyno-tested the Yamaha Genesis 120 engine, which helps provide us a good side-by-side comparison.
The Nytro's power outperformed our expectations and quantifies the strong pull we talked about after riding the first prototypes in January. The numbers tell the story of a 138.6 hp brute that packs a ton of torque. Peak horsepower was made at 8,500 rpm and a top torque number of 94 foot-pounds was recorded near the bottom end at 7,100 rpm.
Compare those numbers to the Genesis 120 engine that showed a high horsepower number of 122.6 at 8,400 rpm, and a top torque number of 83.4 ft.-lbs. at 7,500 rpm. That's a full 16 horsepower gain! Not to mention that these 4-strokes hit harder off the line - which is where you want most of the torque - and it should make them easier to clutch too.
To get the best feel of these numbers, we looked at comparable 800cc and 700cc sleds that we've had Rich Daly at Dynoport test for us. The Arctic Cat F8 showed 143.7 hp at 7,700 rpm and 99.9 ft.-lbs. of torque at 7,500 rpm. The Ski-Doo 800 PowerTEK delivered 140 hp and 94 ft.-lbs. of torque. While the F8 and Doo 800 have higher horsepower numbers and the Cat posts better torque figures, it's important to keep in mind that the Nytro has a much broader power band. The Yamaha 4-strokes simply have long legs and keep winding out.
Comparing the Nytro to recent 700s including Cat's former F7 - which was a stunner in its day as far as engine performance - and we see it dialed up 140.1 horses. Polaris' Dragon 700 is pushing just under 140 hp at peak rpm. While both of these 700s hold a higher horsepower rank, neither has Nytro's put-you-in-the-backseat torque.
Final thoughtPower-to-weight has been the talk of the town this year, and with the high horsepower super-lightweight 800 race engine from Ski-Doo and a new huge horsepower 800 from Polaris, you can understand why.
To give you a glimpse, when you do the dry weight math, the Nytro has .26 hp per pound. Last year's 2007 Cat F8 had .28 hp per pound, which was still less than the 2007 Polaris Dragon at .285 hp per pound, which was trumped by the 2007 Ski-Doo Blizzard with .29 hp per pound. None of these 2007s could match the old F7 at .30 hp per pound. To add more fuel to the fire, none of the aforementioned sleds will even come close to the new Ski-Doo 800 REV XP, or Polaris Dragon 800, for power-to-weight.
Here's something for you to ponder though: with all this talk about lightweight and huge horsepower being the No. 1 priority, how was Robbie Malinoski able to win the national Snocross race at Brainerd, or place as well as he did throughout his first race year on a Nytro?
Shouldn't he have been dead last? Food for thought.