Simple explaination, ^ now its Clear

That's a simple and useful answer.

Curious Question: Is it possible to alter the power delivering character of engines?? like putting more low end grunt to R15 by reducing top end?? what are the general factors affecting power delivery character of a bike?

Yes, to some extent it is possible. The power delivery nature of a bike can be modified to some extent by changes made within the company/ very advanced workshop.

It has been happening for ages now, specially with the Japanese Supersports and Superbikes...

Everything that affects a bike's power delivery, may be by a tradeoff or a one sided increase/ reduction:-> Exhaust, Head, Bore-Piston, Stroke length, carb/ fuel injection system, camshaft, etc. Yes, R15's low end delivery can be minutely changed I'm sure but how exactly, I don't know. Its too complicated. Joel Joseph would be able to answer this better.

The biggest Indian example is UG2 Pulsar vs UG3 Pulsar.
UG2 Pulsars clearly had an advantage in terms of low end torque... You can feel the difference while riding them back to back. I personally rode 2-3 of them to confirm this. But rev it a bit and it won't act excited enough. On the other hand, UG3's+ have more top end in their favor.

Another good example is Unicorn's 13.3 bhp engine vs the same engine tuned to make 14.4 bhp in CBZ Xtreme/ Hunk.


But like I said in first line:- it is possible "To some extent". You can't make a present Royal Enfield rev to 9000 rpm. And you can't get Enfield-like low end torque in an R15. These are 2 extremes.

^^ use a bigger sprocket at rear wheel...

Pitching in little late..
See, within an engine, cyilinder(s) fire a given volume of charge, which propels crank and everything else connected. So, the real power produced from this is, torque. more the volume of charge "CC" more torque produce. simple. HP/PS is just the work done.

for example, if an engine can produce 100 PS at 10K rpm but there is not any torque to propel the bike/car beyond 8K rpm then 100PS output is pretty useless. Now here comes the role of gearing, almost all cars cant reach top speed in 5th/6th gear because of above reason. more PS = more speed. but without torque you cant hit max PS rev zone.

But with advancement of technology, this more CC = more torque is getting little blurry.. (but not much) with the help of ignition mapping, valve timing, compression ratio, gearing, turbo, etc. one can have similar or even higher torque, or PS or both from a lower CC engine. but in a given rev range. where as, higher CC engine will have its torque output spread more evenly in the whole rev range.



There has to be a trade off. it always has..

the easiest way to have more torque in India is to increase the length or reduce the diameter of intake runners, venturi, manifold, intake valve area and some back pressure at the exhaust end. This gives more air velocity at lower RPM. Hence better combustion or something which gives more torque.
but these things acts as restrictions at higher RPM.

I also felt the difference in Pulsar breed. Its because of different design of exhaust and intake runners, manifold and related things (thats what I have been told by a BAL rep.)

Unicorn engine is also tweaked by HH. they gave it a High lift cam, which enables the engine to squeeze little more charge into the cylinder. Hence more power. trade off here are the vibrations..

Changes in R15 is also done V1 is used to be pathetic (ok dont kill me now!) in low revs 3K to 5k and gets poke from 6k onwards but V2 is pretty stabilized at 5k rpm.. but there can not be any change which can make a R15 behave like a enfield which can start off in 2nd gear w/o throttle.

That's quite a heavy dose of info Ateesh bhai. Loved the way it is explained.

Thanks for appreciation Divya bhai. But the problem is I only know about theory & don't have any practical experience

So now I 'much more clearly' understand why the 200NS accelerates faster and hits the top speed much faster than 220 but still, the 220 *feels* more powerful. This also explains why it's harder for the NS to roll off in 1st gear just by releasing the clutch, as compared to 220. Interesting.

Cams with higher lift provide peaky powerband. Cams with lower lift provide that torquey powerband.
A shorter stroke provides peaky powerband. A long stroke provide that torquey powerband.
Straight ducting (i.e relatively vertical ducting) of inlet and exhaust ports provide peaky powerband. A relatively horizontal ducting provides torquey powerband.
Exhaust pipes of longer length and larger diameter provide peaky powerband. Exhaust pipes of smaller length and smaller diameter provide torquey powerband.

Correct me if I am wrong!

I have a query too. Consider that there are two bikes A and B. A produces 20bhp and 15nm torque. B produces same 20bhp but 18nm torque. Rest everything else, what you can think of is same in both bikes (weight, gear ratios, transmission losses, friction losses etc) and both the bikes revvlimit at, say, 8000rpm.
Which bike will reach it's top-speed earlier and why?

Agree to all but bold ones.
200NS - peaky powerband, ZMA - torquey powerband. Exhaust pipes' length - quite opposite to what you mentioned.

IMO, bike B. Due to higher torque values, it'll accelerate faster towards its theoretical top speed.

You gave the rev limit at 8K RPM. Lets assume max power is at 6k RPM and max power at 7.5k RPM.

Here, bike B will accelerate better/faster due to larger torque figures. Once you rev past 7k, you're in max power band (same values for both A and B). Once you upshift, you fall to 6k RPM or so, which is still the meaty max torque band. Hence, it'll keep pulling on and on. This way, bike B will hit its top speed faster.

@Divya Sharan - Yes 200NS has a short exhaust. But thats just one factor. It might be having high lifted cams and straight ducting which lead to peaky power band. I've read the KTM Duke 200's brochure and they have said that the head has straight ducting on the intake side. Now NS and Duke both run on similar engines so even NS must be having straight ducting on the intake side. The exhaust pipe of Hyosung GT250R is soo long compared to other bikes and it's does have a boring low-end torque. It doesn't have that Duke like pull. I've also seen the acceleration video of GT250R (Power the the Rider review of GT250R). It does 0-60kmph at around 4-4.3 secs (which IMO even the RTRs and ZMAs do it in the same time) but it does 0-100kmph at around 8-8.5 secs (which brings it in the Ninja 250R category).

Yes, that is why I was not convinced by the highlighted sentence in my last quote.
Exhaust pipe length is "not" the only factor, there are way too many factors involved.

On similar lines, Kawasaki Ninja 650 (underbelly exhaust) has loads of torque compared to 650N with an upswept pipe.

one more example for all my friends: pulsar 135 vs Yamaha SZ-R.....pulsar makes 13.5 bhp where as Yamaha makes 12.1 bhp only but yamaha's engine produces 12.8nm torque @ 4500rpm and pulsar produces only 11nm@ 7500rpm....the fact is pulsar beats Yamaha in top-end but the way SZ-R accelerates is a totally different story.....it pulls cleanly even in fifth gear from as low as 30kmph and that to without much effort....its low-end and mid range is simply superb but it starts running out of breath after 90kmph where as pulsar accelerates to 100-105 easily because its engine is tuned for better top end rather then good low end. SZ-R's roll on figures (30-70) in 4th and 5th gear are better than hunk, unicorn and pulsar 135 just due to that 12.8nm torque @ 4500rpm only where as it looses on top-end performance as it accelerates slowly after 90kmph....