Power = torque x RPM. Notice that the two bikes are making pretty much the same peak torque, but the Triumph peak is at quite a bit higher RPM than the Benelli. 9250 / 6500 = 1.42. At peak torque, the Triumph (at 9250 RPM) is making 1.42 times the power of the Benelli (at 6500 RPM).

 

It is not all CC; note the much higher rpm for the ratings. Horsepower is equal to torque (in lb-ft) times rpm, divided by 5252. The Triumph produces its best torque at much higher rpm, and holds on to it enough to produce more hp at even higher rpm. Doing the math, the torque at 11250 rpm is still 44.44 lb-ft, or about 60.25 Nm; it is also producing about 86hp at 9250 rpm.

 

Tq is no longer a measurement of what a single boom puts out.....it is now measured at the wheel, so the transmission wheel size final drive, all play a part in Tq and HP measurement

Basically if divide the stroke be the bore, the lower the number will tend to be the highest HP because it can run the highest RPM

Your Benelli gives .7
Triumph .64

But think.....which is more powerful

I had Kaw Voyager did 70mph @ 2500rpm, 2 cylinder, 5000 booms per min, rated under 100hp

I have Suzuki GSX-S750 69(call it 70) mph @ 5000rpm, 4 cylinder, 20000 booms per min, rated 113HP

Kaw was 900lbs Suzuki 465lbs

 

So, if you can get better performance with smaller and lighter engine, (Benelli is 45KG heavier and for sure some of it because of its engine),
what is the point to make it bigger?

I mean there must be reason or advantage of it , right?
In that example, what is advantage of Benelli ? more economic or what else?

Or what is disadvantage of Triumph?

 

So, if you can get better performance with smaller and lighter engine, (Benelli is 45KG heavier and for sure some of it because of its engine),
what is the point to make it bigger?

I mean there must be reason or advantage of it , right?
In that example, what is advantage of Benelli ? more economic or what else?

Or what is disadvantage of Triumph?

The answer is different riding styles. The Benelli has more torque at lower RPMs, which is suited for a cruising style of riding. Extreme sport bikes make most of their power at high RPMs, and as a result they make a lot of power up there. Great for racing, not so much for just cruising around town.

 

For an extreme example, check out Yamaha Star Eluder.
1854cc
76.4hp @ 4170 rpm

 

Ours is not to reason why.
They make bikes for a specific target market. There is a bike for everyone.
If you hit a nail with a hammer, each time applying 5 pounds of force. The nail will go in quicker, if you double the times it is hit. No change in force. To increase the revs of an engine introduces many engineering issues. The sudden stop the piston makes at the end of its travel. The ability of the valves springs to function properly at higher revs. The ability of extra air and gas to flow at higher revs, which means a different cam profile.

The Triumph is a sportier bike. I am sure you will find other differences, most likely with the way the bikes handles.

Larger bore is not always the answer. Beyond a certain size, the efficiency suffers due to flame travel. Rather the lack of it the further from the plug. This is why they used to let larger capacity 2 cylinder bikes, run against 4 cylinder bikes.

The horsepower is generated in the head. The piston simply just goes up and down. The camshaft profile and timing, form part of the head. So too the exhaust and intake. UK

 

You guys are getting really scientific and all that's good and stuff; but at the end of the day it's pretty simple. The Triumph is an inline 3 engine, while the Benelli is a parallel twin. The inline 3 being engineered with super torque in low to mid RPM's with speed in mind. The parallel twin is an easier engine to mount and balance on a motorcycle, and it can also be easier to work on. Simply said; one engine is designed to be an HP powerhouse, the other isn't. For this reason, comparing engine HP between two engines that were with completely different purposes is kind of obselete when it comes to motorcycles. Yes cruisers have LOTS of CC's but the compression ratio is low and the engine isn't optimized for performance, as much as it is balance and for presentation. Supersport inline engines have LOTS of HP, but they're bulky ugly gas guzzlers that require the most annoying maintenance. Single cylinders and parallel twins are compact and easy to work on, but aren't as powerful or smooth as other engines. Take this all with a grain of salt and do your own research but I find it stands up for the most part.. hope this might've solved some confusion as to why some bikes have the engines they have.

 

Way too many factors come into play, and there;'s not really any simple way to explain them all. Combustion chamber design, compression ratio and valve timing, as well as intake and exhaust system design are the major factors in determining the horsepower any given engine can produce. As has been stated, an engine that can rev higher without too great a loss in torque will produce more horsepower. If you look at a typical dyno curve, torque will peak before maximum revs, and sometimes will fall off so drastically that horsepower also drops off before maximum revs. Generally, however, maximum horsepower is reached near the upper end of the rev range and is basically flat from there to the redline.

 

The question of balance, is a result of mass changing direction. The larger the mass, the more energy involved with changing direction, which in turn creates a bigger balance problem. These days balance problems are controlled with a variety of things, but primarily balance weights, and crank timing.
Lettuce consider some engines. 500cc Norton twin, getting bigger to 650, and 750.
3 cylinder Kawasaki 2 stroke, 350 500 750.
Single cylinder Honda XL250, 350 and 600. SV650 Suzuki to SV1000.
In all cases cases the question of balance got worse as the size went up. Most noticeable example was the Norton, that they finally hung in rubber mounts. But the engine still shook. Just like a big Harley engine shakes.
It is the mass. If you do not agree with that, then you do not agree with Einstein, and he has been proven correct on this subject.
BTW. I have been on practically all of the above, with two variables. I was on a 500 Triumph not a Norton. The 650 was a BSA. The 750 Nortons were in a Reynolds Featherbed frame, and an isolastic frame. UK

 

lf displacement were the be-all/end-all (like we once thought it was), you would not have companies engineering new technologies at a frantic pace.

I had a 2004 Suzuki SV650. I currently have a Triumph Scrambler, which is an 865. The two bikes are night and day. The SV was a V-twin, fuel injected, with all kinds of high performance technology on it that is above my pay grade. The Scrambler is a very simple parallel twin. Both weigh in the 400-450lb range. The SV was responsive, quick, abrupt...if you needed to gun it to get through a sticky situation, the response was immediate. The Scrambler, not so much. EVERYTHING about it is laid back, easygoing, almost lazy, as if it were specifically built for the guy who realizes that if you go fast, the chicks never have a chance to bat their eyes at you. The SV runs at about 75hp, while the Scrambler goes about 55.

Both bike owners would look at the other and say, "Get a bike." To each their own. That's why they make a million different models.

 

I appreciate all of the technical analysis in these comments, but as a non-mechanical oriented rider I see it from another viewpoint. I'm sure I'm not alone in not liking the high pitched screaming of a motorcycle engine at high RPM, preferring the more sedate sound AND FEEL of the bike when the engine is able to meet my needs without needing the high revs. It may not make much sense but the feel and sound of a bike at high revs always seemed to tire me out, as the rider, much quicker than a larger engine that made the same speed at a lower RPM. When I was riding a Triumph America with its 865cc parallel twin engine I often felt it was underpowered, and would have to push it to close to redline all the time to get the bike to move as quickly as I wanted it to. On my current main ride, my Goldwing, I can usually accelerate from a stop quickly enough to satisfy me without ever going much over 3,000 RPM. When I want to accelerate more quickly I might push the bike to 4,500 or even 5,000 RPM which still FEELS manageable and tolerable. So for me, the big engine on the Goldwing, at 1832cc works just the way I want it to work. Once I get to really high speeds, such as 90 mph or higher, the wind noise is enough to make me not notice the higher RPM of the engine and therefore does not bother me at all. I'm sure that there are riders that feel the exact opposite of how I feel, and love the sound of their smaller and lighter engined bike when they push the RPM to 10,000 or even higher to get the power that they want.

Just recently I watched the Jay Leno video where he is taking a demo ride on the new Triumph Rocket with its 2,500cc engine. He talks about his sense that American riders generally do not make use of the higher revs that most bikes are fully capable of safely achieving, and why the Rocket may be so satisfying to many because it can accelerate really quickly without having to race the engine at all. I never thought I would see the day that a motorcycle had a 2.5 liter engine, but clearly it is just what some riders want.

 

I appreciate all of the technical analysis in these comments, but as a non-mechanical oriented rider I see it from another viewpoint. I'm sure I'm not alone in not liking the high pitched screaming of a motorcycle engine at high RPM, preferring the more sedate sound AND FEEL of the bike when the engine is able to meet my needs without needing the high revs. It may not make much sense but the feel and sound of a bike at high revs always seemed to tire me out, as the rider, much quicker than a larger engine that made the same speed at a lower RPM. When I was riding a Triumph America with its 865cc parallel twin engine I often felt it was underpowered, and would have to push it to close to redline all the time to get the bike to move as quickly as I wanted it to. On my current main ride, my Goldwing, I can usually accelerate from a stop quickly enough to satisfy me without ever going much over 3,000 RPM. When I want to accelerate more quickly I might push the bike to 4,500 or even 5,000 RPM which still FEELS manageable and tolerable. So for me, the big engine on the Goldwing, at 1832cc works just the way I want it to work. Once I get to really high speeds, such as 90 mph or higher, the wind noise is enough to make me not notice the higher RPM of the engine and therefore does not bother me at all. I'm sure that there are riders that feel the exact opposite of how I feel, and love the sound of their smaller and lighter engined bike when they push the RPM to 10,000 or even higher to get the power that they want.

Just recently I watched the Jay Leno video where he is taking a demo ride on the new Triumph Rocket with its 2,500cc engine. He talks about his sense that American riders generally do not make use of the higher revs that most bikes are fully capable of safely achieving, and why the Rocket may be so satisfying to many because it can accelerate really quickly without having to race the engine at all. I never thought I would see the day that a motorcycle had a 2.5 liter engine, but clearly it is just what some riders want.

That's exactly how l feel when l ride my T-Bird. l occasionally romp on it to pass someone but for the most part my riding is below 4k rpm

 

I have a Benelli 752 and have covered 1000miles on it. Suits the road, Lovely steady suspension especially when pushed. Great brakes. Engine sounds good with enough for a gusty over-take. It's like an XSR700 with slightly more steadiness at speed. An XSR700 would out accelerate it and maybe the top speed but in the corners the Benelli gives more confidence.

 

Cool!
but you maybe should have posted that in new introductions and not on an old thread

 

"Bigger engine but less horsepower, how?"
Answer was too easy: bigger valves = better breathing was always a good start to making more horses.
tiny valves = tiny horsepower unless it's so you can put more of them in there, now you are making it breath better a different way.

Put a blower on it, now you made the tiny engine out perform the bigger non aspired engine even more.

 

'...better breathing was always a good start to making more horses.'

Yes but not the tiny valves doing it. Or, the idea of the 4 valve head cannot work. Smaller valves there but they flow more than bigger ones.

Basic physics, smaller engines make more power than bigger per inch of size, because air has weight and is harder to control in larger amounts. In short, smaller engines are more 'air active' to do something with that air. Why the 4 cylinder makes more power than the twin, the four smaller 'engines' add together to make more power thn the two larger ones. Why hp. per cu.in. is always higher on smaller motors. You do well to get 1 on a big car motor but you can get 3 on a small motorcycle engine. You get much higher volumetric efficiency on smaller engines.

 

Dude, if you put 4 tiny valves into a cylinder head you can make it move more air, it's a well proven fact 4-valve engines out perform 2 valve engines, it's a matter of how big and how many circles you can fit into a bigger circle to begin with.

 

You mischaracterize my post, read it again........I insinuated the same thing. So why all the drama in post #20?

I'm OK with the 8 valve chamber of the Honda NR500.

 

Must have been because I could not make head nor tails sense out of your post #19
... the theory of heavy air.

 

That's OK, look at the dichotomy between (it's coming)........

(had to go back and look at it!).........my first sentence and the words 'yes but', I now clearly missed something myself. My bad.

Heavy air? Not heavier, same weight per unit but in more or less accumulated mass. two close sounding but not the same things. All bigger engines handle air differently than smaller ones, you cannot escape it.

 

Two small intake valves can move as much or more air than one larger intake valve. Plus, the smaller (and lighter) valves can move faster. That's part of the equation for making an engine with a higher redline, and therefore more power.

 

Yep, on my zetec Fords the cams have valve springs so soft the cams will look new at 200K miles yet the engines rev to 6500+ rpm easily. You can push the valvesprings down by hand to open a valve on an assembled head.

There IS a difference in the way flow comes through the two valve types, inertia flow works a lot better on a bigger single valve to swirl and the twins tumble into the chamber instead, it forms much of the porting regimen you use on either. How flat the valves are in the head have a lot to do with flow changes too.