Question:
Hello,
I wanna know how much torque the Yamaha Apex, and Yamaha Attack have.
You all always talk about how much torque is in the four strokes, but never put a number down that I’ve seen. How about the Polaris classic turbo also?
Thanks, from a guy who has nver ridden a four stroke sled.
Tim
Response:
Excellent question, Tim.
We have had difficulty getting the torque numbers for 4-strokes, too. The OEMs are a bit reluctant to give them because the impression of a 4-stroke is that it generates way more torque than a 2-stroke.
At the end of the day the numbers are actually quite similar, but here’s where the difference lies.
Take for example a 1000cc 2-stroke: We know that Cat’s 1000 makes a claimed 120ft-lbs. Although we don’t have the numbers for a Yamaha’s 1000 4-stroke Apex we suspect the actual torque peak is somewhere close, perhaps even less.
The difference is where the peak torque comes in on the RPM scale. 4-strokes tend to make the highest percentage of their torque at lower RPM than 2-strokes.
For instance, although a 1000 Cat may produce 120 ft-lbs, it may not show up until 7500 RPM. The 4-stroke may make 110 ft-lbs but it peaks at a lower 4500 RPM. This gives the impression of a way torquier power delivery, even though the peak number may be lower.
If you’ve spent any time with a 4-stroke you know those engines have a feeling of disproportionate grunt down low but sign off quicker than a 2-stroke.
The other difference is that the torque curve on a 4-stroke is flatter, perhaps reaching its peak at 4500 and maintaining over 100 ft lbs up to 8500. 2-strokes tend to need more RPM to generate a more peaky torque curve that may be over 100 ft-lbs for a narrower span – say, 6000 to 8000 (I’m just guessing at these numbers, but you get my drift).
Turbo 4-strokes are similar. Always remember, a turbocharger is a torque generating device. It makes the engine think it’s bigger than it actually is. If the boost is set for low RPM, you’ll get a huge increase in torque at a lower point in the power scale.
Depending on how they’re set up (say if the boost continues beyond the peak horsepower point), you’ll be building torque all the way. You get that feeling of enormous grunt from boost until sign-off – one of the reasons I, personally, love turbochargers.
We’ll try to get some actual numbers for next season – hasn’t been easy so far.
Kent Lester
