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The throttle has been pulled, the data has been captured, and now we know the number that many have been waiting to hear this fall, the independent dyno stats for the new 2011 Yamaha Apex.
In our early preseason dealings with the tech boys at Yamaha we were made to believe that this sled would only make 3-5 horsepower more than the 2010 Apex.
Wow, were we duped!
No reason to be blue
While Yamaha is known worldwide as the Blue Team they don’t have any reason to be feeling down after Jim Czekala at Dynotech Research put the new Apex on his dyno.
Yamaha is known for being a conservative company and often under promises, but over delivers, and that’s the case here. The particular unit we dynoed was a demo sled used for consumer test rides in the northeast - supplied by Keith Wood of Woody’s Performance in Topsham, Maine. The sled had about 1,700 miles on the odometer and we were told by Yamaha’s Marketing Manager Wade West that “at about 1,300 miles you can tell these sleds really wake up. The chassis and track finally loosen up well and the driveline is done being broken in at this point.”
This Apex was more than ready to show well on the dyno.
The final numbers showed the new Apex pulling 162.8 hp at 8,300 rpm. The exceptionally uniform and flat torque curve had a peak of 109.8 ft.-lbs. at 7,300 rpm. This sled is steady throughout its powerband, even more so than other impressive 4-stroke snowmobile engines we’ve seen from Yamaha.
Jim chimed in when we were discussing the results and said “It should be easy to clutch for those aftermarket fellows looking to get a little more performance as the 2-strokes only have a pimple of power in the powerband and 4-strokes are much better.”
For the brass at Yamaha this means that they now have a 4-stroke snowmobile that can compete with the big 2-stroke 800 twins from Cat (800 H.O. EFI), Polaris (800 CFI) and Ski-Doo (800R E-TEC) on power. The Yamaha Apex and Cat and Ski-Doo 800s have now all been independently dynoed to make roughly 163 horses while the Polaris 800 makes 143.2 ponies. (see graph)
This is good news for Yamaha guys and gals debating on buying the expensive Apex as this new, more powerful Apex engine may help them justify digging into their piggybanks to their significant other!
More thoughts from Dynotech Jim
The new EXUP variable exhaust is certainly different than the exhaust on the 2010 Apex sleds, but the small changes on the exhaust and engine certainly had a big effect on performance. Changes included the exhaust header diameter being increased from 35mm to 38mm, and the pipe from the EXUP collector to the muffler being increased in diameter.
The exhaust is made of lightweight titanium and the EXUP housing itself is made of cast titanium. The muffler flow capacity was increased as well. On the new engine the cams are unchanged, but timing WAS changed to increase overlap by 5 degrees. Finally, the intake airbox horns increased in length from 115mm to 126mm.
We did a couple extra tests on this sled including having Keith Wood help us out by locking the EXUP open while running several pulls. Interestingly, we saw a significant decline in performance when the EXUP was essentially turned off. “The EXUP surely helps in the mid-range, with no penalty on low-end and still being able to keep your top end as well,” Czekala said after the tests.
“Compared to the 150-horse earlier Apex we have an 8% increase in peak power with very minimal changes in tuning/components. Also adding 10% to “velocity stack” length, inside the stock airbox, may help peak rev tuning. A larger exhaust pipe diameter must be having a positive effect on power at peak revs and maybe the cam timing is helping here. The 5 degree added overlap is helpful for top end power too.
“One example of this was seen 15 years ago when a friend of mine Kevin Cameron (See story in Cool News) dynoed a bike to do a cam timing evaluation for Cycle magazine. We added 3-4% hp to a stock GS1150 Suzuki just by Kevin methodically “rolling” stock cams (using slotted intake and exhaust cam sprockets) around to optimize horsepower. But that added top horsepower may have cost low-end power, and that is where Yamaha’s EXUP helps!
“Finally, big exhaust pipe diameters are said to make more high rpm horsepower, but lose it on the midrange, but in this scenario EXUP makes up that difference.”