Brings me back to my original query. How Panigale and S1000R can competitively race against each other in the same FIM class when the Panigale has 22Nm extra torque!! What will guarantee that it doesn't win all the time and the races remain competitive?

The perfect example is CBR 250 itself

1993 CBR250RR - 4 Cyl , 45.0BHP @ 15000RPM, 21.5NM @ 12000RPM
2011 CBR250R - 1 Cyl, 26.2BHP @ 8500RPM, 22.9NM @ 7000RPM

Combustion Chamber

1993 CBR250RR - 48.5mm x 33.8mm X 4Cyl
2011 CBR250R - 76.0mm x 55.0mm X 1Cyl


Due to more cylinders the engine is capable of working at higher RPMs at ease without any stress. Heat generated by 4 X 62.2CC engines will be much lesser than 1X249CC. Hence the 1993 CBR250's sprocket combination is achieved to hit the world's highest motorcycle redline at 19,000RPM generating 45BHP power output. Thus with a Single cylinder engine the 2011 CBR250R lost the RR tag (Race Replica), also there are other aspects for CBR250R to lose the RR tag like chassis etc.

Draw backs, are the cost and efficiency. A multicylinder engine like the 1993 CBR250RR has 16Valve head and the crankshaft is supported by 4 con-rods, hence the cost involved in preparing such a complex multicylinder unit is much higher when compared to a single cylinder, same as the maintenance (viz, Servicing cost, Servicemen skillset etc). Also revving the bike at higher rpms all time to be at the power band will not help the gas mileage either.





Also the above example can be applicable for Yamaha's RD350 and RE350 as well, Over 350CC the comparison goes upto to Ducati's twins vs other Inline 4Cyls. Inshort with lesser cylinders you gain more torque at minimal engine operation (low RPM) while more cylinders makes your engine stress free making more power and hit the power-band at maximum engine operation. (High RPM).

Please enlighten me why I should include another irrelevant variable (weight of vehicle) when I want to compare just the engines when there are already so many to take care of?

Also enlighten us how the drivetrain/vehicle weight affects an engine's capacity to produce up/torque. Eg. If the 250cc engine from a NINJA is bolted onto a TATA NANO (vehicle weight increased), how will the engine's torque / hp be affected ?

And that's the exact reason why we have this dedicated thread.

An injected Two stroke engine is far more powerful and less polluting than a 4 stroke engine. of similar displacement and system

Good one there Harish
Brings me back to my original query. How Panigale and S1000R can competitively race against each other in the same FIM class when the Panigale has 22Nm extra torque!! What will guarantee that it doesn't win all the time and the races remain competitive?

In a Four stroke engine there is only one power stroke for every other three strokes.In a single cylinder of 4 stroke cycle, only one power stroke is there. In a Twin cylinder engine every alternate stroke is a power stroke due to the addition of another cylinder which will fire at 180 degrees difference from each other.This is equivalent to a two stroke cycle and hence the increased traction and power...The Ninja 150R two stroker makes 30 Bhp with 120 Kgs weight.

An injected Two stroke engine is far more powerful and less polluting than a 4 stroke engine. of similar displacement and system

Being stronger on paper doesn't really means it can transform that in the racetrack. The mighty beemer hasn't been that successful n their WSBK campaign. Motorcycle usa 2012 track shootout resulted in a cbr & zx10r fastest laptime(that particular track). Many other magazines have also placed the kawi over the beemer on their track tests.

My question was, how was this formula worked out which decided that 1200cc twins and 1000cc 4cyls were 'equals'. Especially when, using its displacement advantage, the bike actually makes more torque than the 4cyl (check the graphs posted by Harish) and will probably require *at least* 3-4 less gearshifts around a 4km racetrack saving precious fractions of second in the process? How is it that manufacturers making 4cyl bikes don't protest against this *injustice*. Or is there something which levels them all up?

I read, Suzuki did some protest against this. Ducati being a main franchise in WSBK and no more producing 1000cc twins anymore and incapability or added cost in making their earlier 1000cc's race competitive, shifted to 1200cc.(there is always some internal politics). There are some restrictions for the 1200cc's to follow to make the competition fare enough!! like added weight and other technical stuffs.

with respect to the gearshifts the 4 cylinders have that extra rpm( or power band) to stay in a gear for longer time. (like that the things are somehow compensated each other!!)

Even with this displacement advantage a twin has to be super-short stroke to achieve the power output their 4cyl counterparts do. Generally 4s excels in straight line acceleration and twins comes off the corners quicker.

Well, so long as the Compression ratios are constant, #1 will have more torque because it has more displacement.

From what I learnt in my 2 years of Mechanical Engineering (2 years are still remaining), If we consider a piston, con-rod and a crankshaft arrangement, torque is the product(multiplication) of force applied on the face of the piston and the distance from the center of the crankshaft to the smaller end of the con-rod.

So the hypothetical bore x stroke dimensions provided i.e 1. 81 X 42 and 2. 61 X 55, I suppose the latter will produce more torque due to larger stroke, not the former.
Please correct me if I am wrong.

From what I learnt in my 2 years of Mechanical Engineering (2 years are still remaining), If we consider a piston, con-rod and a crankshaft arrangement, torque is the product(multiplication) of force applied on the face of the piston and the distance from the center of the crankshaft to the smaller end of the con-rod.