Last month DynoTech Research out of Batavia, NY, got their hands on a 2017 Arctic Cat Thundercat with the new 9000 3-cylinder turbo Yamaha engine.
As an independent tester of all kinds of engines, DynoTech did their stuff. And with the mighty Thundercat belting out its best on the Super Flow dyno, the horsepower number displayed on the computer was an astounding 211!
It was the highest horsepower number ever recorded by a stock snowmobile engine. It was even 7 hp more than the Yamaha Sidewinder produced a few months earlier on the same dyno, with what was the same exact engine.
The monstrous number achieved on the DynoTech dyno comes as no surprise to the few dozen non-Cat-employed people who have ridden the various iterations of the new 9000 turbo machines, all of whom have had to come up with new superlatives to describe their insanely fast speeds.
Also not surprising was a small chorus of naysayers facebooking their certainty that this was no stock engine and that it was some publicity stunt.
So I did some digging with the engineers at Arctic Cat to find out what, exactly, occurred with this 211-hp party and how that squares with the world beyond the ol’ interwebz.
Hand-Picked “Ringer” or Truly Stock?
No, those aren’t black-ops helicopters flying overhead. And no, this was no hand-picked “ringer” sled with a modified engine. Nor was it even a (gasp!) publicity stunt. The whole scenario happened almost as a fluke were it not for the curiosity of Arctic Cat dealer Arctic Adventures, an Arctic Cat dealership in Rosendale, NY. They’d received the Thundercat (crated) for its appearance with Arctic Cat CEO Chris Metz at the Nasdaq stock market opening at the end of May, all of which went fine and dandy.
Arctic Adventures was tasked with re-crating the machine for shipment back to Cat, but with an extra day to burn before the doing so, they made the call to DynoTech inquiring if they’d be interested in test it.
“Bring it in,” was the response, and so began a day on the dyno that set the new benchmark for stock horsepower.
“This was the same sled that journalists had ridden at Snow Shoot back in February,” says Troy Halvorson, Arctic Cat Product Manager. “It was one of several such machines produced last winter in what we call our “T3” build, which utilizes all production parts. If DynoTech puts another Thundercat on their dyno later this year and tests it exactly the same way and in the same conditions, the number should be the same.”
Okay, so why is there a 30-hp difference between the “180 hp class performance” that Arctic Cat and Yamaha claim with the new engine, and the numbers these engines hit at DynoTech?
In short, it’s because Arctic Cat and Yamaha test engines one way, and DynoTech tests them a different way. Plus there is/could be a different correction made when reporting numbers.
“Reported horsepower is usually a corrected number,” says Cord Christensen, Four Stroke Principal Engineer at Arctic Cat. “The horsepower needs to be “corrected” back to a standard temperature and pressure to make tests on different days or dynos comparable. There are a number of different correction factors used when testing engines. Many companies will report horsepower in numbers corrected to the SAE J607 standards, which usually gives the biggest numbers. This standard is not considered current any longer and is not used for “official” requirements such as certification. Other factors can also have a large effect on the final horsepower number, such as sweep rate, which is how quickly an engine is run up to it’s peak power, as well as stabilization time before the sweep.”
Ultimately what’s important for any company that’s testing and comparing numbers is that they perform all such tests consistently, using the same methodology. That’s exactly what DynoTech does, so it’s truly meaningful an relevant to compare the 211 hp produced by the Cat to the 168 hp produced by the new Ski-Doo 850 Etec on the same dyno earlier this year.
As for the 7-hp advantage that the Thundercat showed when compared to the Yamaha Sidewinder, Christensen had this to say:
“Turbocharged engines can be quite difficult to test on a dyno and get consistent horsepower numbers, because the intake air temperature entering the engine is affected by the compression in the turbo and the effectiveness of the charge air cooler. From the pictures I have seen of the Thundercat test, DynoTech used the stock air-to-air charge air cooler in the sled and it would be very easy for the intake air temp to have been different enough to cause the 7 horsepower difference when the Sidewinder was tested.”
So there you have it: there’s a bit of nuance to the whole horsepower number, but when you boil it all down, you’re left with this engine producing the most horsepower of any production snowmobile. And in the real world of testing where what you feel in the seat of the pants might be different than a number on a computer, the new Thundercat remains the almighty one.
I can’t wait to see owners’ reactions when they get theirs on snow this winter. It’s going to be a fun!
Thanks to Arctic Adventures for taking the Thundercat on a detour to DynoTech, and thanks to the folks at DynoTech for the decades they’ve been testing sleds.
Thanks for reading.
