Triumpth daytona 675 3 x 74mm - 72nm

Lets develop this a bit, maybe instead of taking the size of 'a' piston, we could take the size of all pistons in the engine.

So daytona has a combined dia of 222mm and produced 72nm
the ninja 650r has a 166mm and produces 60nm
the duke 690 has 102mm and produces 67nm

the thumbrule doesnt do justice either way.

The torque output has to have core dependencies on calorific value of fuel (and the charge entering the chamber), amount of volume packed in the cylinder and thermal efficiency of the engine. Size of the combustion chamber and dimension enhances/nerfs the process with its mechanical merits / limitations.

Either way playing around with Torque figures with out mentioning the speed at which the crank is rotating is pointless.

Take a wrench of length of 500mm and exert force of 4kgs and viola you have 19nm of torque. Thats about the torque my 220 gives at the crank @ 7k revs. So when we are talking about Engines the rpm is also important.

Does it start making some sense if we add up the horizontal cross section areas of the cylinders (instead of simply adding bore lengths)? But still it won't make sense because then we ignore the stroke. And if we include stroke too, what we get is swept volume which is exactly what I mentioned in my 1st query post that engines of similar cc make similar torque regardless of bore/stroke difference.

A cylinder is a 3D object, we use bore diameter just for simplification sake. We have to include all 3 dimensions for a thumb rule to make sense.

A good comparison set would be

Pulsar 200 DTSi (17.17 Nm)
CR: 9.5:1
Bore x Stroke : 65 x 62.4

Pulsar 200 NS (18.3 Nm)
CR: ???
Bore x Stroke : 72 mm x 49 mm

Duke 200 (19 Nm)
CR: 11.3:1
Bore x Stroke : 72 mm x 49 mm

All 3 have the exact same swept volume though bore stroke is different for the DTSi.
The no. of valves at this time are immaterial to our purpose solely because the difference due to these external factors can only be seen near redline i.e. far away from peak torque RPM. Calorific value of the fuel is the exact same in all 3 cases. The only bit different that can actually affect peak torque is the Compression Ratio (CR)* .

Now since the Compression ratio for 200NS is given nowhere (that I could find), simple algebra would give us the answer as somewhere between 10.12 (for a 2 valve SOHC setup) to 10.88 (for a 4 valve DOHC setup * - since DOHC robs it of its torque somewhat) so I will safely assume it to be 10.5 (<-- can somebody better than me at googling please verify this?), i.e. exactly in the middle.

By this logic, the revised thumb rule could be, the peak torque is directly proportional to the (swept volume x compression ratio).

Please feel free to correct me if I have gone wrong somewhere.

P.S.: I am posting 1 post every 12 hours on this thread. Strange coincidence

Saerius: The point was for a single cylinder bike. (The 350/500/220)

Split it into cylinders of similar spec, and the output would vary in both a straight twin and the vTwin having same specs...

really waiting for my answers , any comments please ..

You were given this reply by satyen sir



But in the examples you gave, you compared a single cyl 690cc to a two cylinder 650cc. If that thumb rule is for single cylinder engines then i guess it can stand.

Yes there is no denying the fact that volume ∝ torque.

and yes your observation regarding c.r affecting torque is also right.

Let me explain the calorific value of the fuel issue ,If you went through my older post you would find in the fine print that i've said that calorific value of the fuel affects the torque. (i had left it vague as it was an opinion that i wanted people to reply to)

Calorific value of the Fuel plays a role, not a direct one. The fuel when mixed with air forms the charge, and this charge has potential energy i.e chemical energy, which can also be quantified under calorific value.

The calorific value of the charge is further dependent on the volume being used and the amount of compression is it subjected to.(C.R which you have rightly pointed out). If the compression is less then it results in a smaller bang, If its too high the fuel preignites, In other words the Calorific value of the fuel (octane rating) will justify how much compression can be used safely. Calorific value of the charge will also be dependent on the a/f ratio, 1:14.1 being the ratio where theoretically complete burn is achieved, which in turn will lead to piston force, which will in turn get converted to torque.

So listing the major factors that affect calorific value of the charge

1) Calorific value of the fuel
2) A/F ratio
3) Volume of the charge, (and how well it has filled)
4) Compression Ratio

This calorific value of the charge,(chemical energy) gets converted to heat (thermal energy) but losses occur, (it is understood to us as the second law of thermodynamics) and with (lets say) 24% thermal efficiency (which is : available energy (heat)/ total energy (heat) generated) the rest 76% is spent to the surrounding.

Now this 24% of energy (sorry about the generalisation, the other option would be for me to actually present an example and solve it. and i dont think many of you would be inclined to see 'that', including me), gets converted to mechanical work as 'piston force' (high gas pressure pushing away a light piece of metal) this piston force , which is a linear force, is now converted to twisting force via the help of the crank. and we have Torque.

I know, If they'd put more theory in my applied thermodynamics paper, i would pass.

But
Honestly i dont think we should generalise the torque output on volume and CR alone, because if you look at it 17.17nm 18.3nm and 19nm..
the difference is quite a lot, number wise it might look similar, but when you are speaking in terms of force they are quite apart. and not to mention the 'paper numbers' will vary depending on the life and upkeep of the engine.
There are quite a lot of factors (factors out of the scope of this post, due to the limited knowledge of the poster and more importantly the size of the information.) which affect the torque output , enough to prevent us form generalising it.?

At the top speed, most of the power is not being used to make the vehicle accelerate more, it is being used to overcome aerodynamic drag.

The opposing Force caused due to aerodynamic drag is given by:



Where

FD is the force of drag, which is by definition the force component in the direction of the flow velocity,
ρ is the mass density of the fluid, (in this case, air)
v is the velocity of the object relative to the fluid, (without any wind, this would be your actual Speed on GPS)
A is the reference area, and
CD is the drag coefficient — a dimensionless constant related to the object's geometry and taking into account both skin friction and form drag.

When motion of a motorcycle inside air is involved, ρ, A & CD remain constants so their multiplication will also remain constant. For the sake of simplicity, lets replace it by K.

Force Formula can be simplified as

FD = K * V^2 .

This simply means, the drag caused by increase in speed increases exponentially, or in simple language,

Consider a Classic 350, with its top speed of 115 kmph. At 115kmph, all the power is used to overcome Force of aerodynamic drag FD(since at top speed bike is no longer accelerating).

Lets consider this power to be a certain x.

For an identically shaped Classic 500, with its top speed of 132-133 kmph, same situation occurs as above. But the FD in this case is much higher at

FD = 1.34x . i.e., to raise the speed by 15%, 34% more power was needed just to overcome the extra aerodynamic drag. And we haven't even considered the fact that Classic 500 will have higher rolling friction to overcome due to its higher weight.

I hope this explains your query 'where' the extra power disappears.

Just to give you an extreme example, a 1001 bhp Bugatti Veyron has a top speed of 407 kmph.

Its ligher and more powerful version, which is identical in shape, the 1201 bhp Veyron Super Sport has a top speed of 431 kmph.

Which means, the additional 200 bhp (20% more power) could take the new, lighter car just 24 kmph more (<6% more speed). By comparison, a 181 bhp India spec. Honda Accord has a top speed of 220kmph.

Edit: @Saerius I have used simple algebra (Cross multiplication) But I wanted to get it verified just to check how flawed or accurate my simplistic logic was.

P.S.: Seems like I am late by 2 hours today .

I was not even thought, that i will get all this huge information at the time of posting this query..

Thanks guys, Don't know how much time I will have read each post to understand it completely...

In retrospect i feel snobbish for not answering your question. anant sir has hit the nail in the head regarding your query about the lost horses.

Just adding two cents.

For the sake of practicality ρ (density of fluid) can be taken as constant. But it has a noticeably big effect on the top speed of the vehicle, and in real time it is never constant. (altitude, ambiance temperature) More on this in later.

If you've seen the TopGear video of James May giving the beans to the SS, you will remember him as saying that the Bugatti people choose the afternoon to test the top speed, because the air is less dense and it will help the vehicle cut through the air better.

It is also the reason for vehicles accelerating better when under slipstream of the leading vehicle, (pressure and density have a husband wife relation)

The more on this part, there is a specific stretch of road where i do my top speed test, it is a wind sheltered piece of road with a downward incline, the incline is to help reduce the distance required to touch the 140s. i used to do 145, 147, 148 (separate instance in a span of 18 months) But in the last week i was able to do 150 and 151 respectively.
The difference between the two set of speeds is time of day. cool mornings vs hot summer afternoon.

The effect is very noticeable because during the runs, the ones done in cool weather, the engine used to crawl past 140, digit after digit.
But the hot afternoon runs, the engine is pulling past 140 and touched 150 with considerable ease, (riding gear and shoulder bag overloaded with engineering books and all)

The earlier attempts were me trying to actively get big number on the speedo, and these two recent attempts were with me not being so committed at the start of the stretch.

thanks for answering my questions with such huge infos
helped a lot
thanks

One of the best threads which has made me understand a little bit of technicality....not sure how much has gone in.

i appreciate you guys for having these kind of knowledge & information.

Just somebody clarify me on a very basis doubt, dont take me wrong

1. why would a CI 535 struggle to catch up with a 350 UCE?

Leave off the weight of the bike for a minute

2. Why would the vibration be higher on a CI than a UCE?

Heavier the bike, vibration to be lesser

Not sure if there are already answers, dint get much about this in my layman brain, if you can give with examples it would help me

I am no field guy (yet) so take my answers with a pinch of salt/lemon

To answer Query 1, i guess we should look at the query 2 first.

The CI ones had what a 1~2lts/min plunger type oil pump? and pushrod actuated OHV?
The UCE ones have a 14ltr/min rotary type oil pump? and hydraulic lifters (not hydraulic tappets) OHV?

also isnt the CI ones notorious for having leaky valve guides?

So low oil circulation rate would mean oil starvation beyond a certain rpm threshold, that means friction, and vibs, also means that the internals expand more than what the tappets are set for, which gives off some more vibs. To complicate things further the oldschool style pushrod valvetrain (Q:is the complete valvetrain made of the same material?), has quite a bit of mass, which is a source of additional vibs when you think of revving the motor harder. And when tappet clearance goes bleh, they just get worse.

The UCE engine has better lubrication, alloy head on alloy block (same rate of thermal expansion) and the hydraulic lifters have comparatively less inertia and heat doesnt throw the tappet setting out of the window.

Also Cast Iron has the resonance and thermal ability of a temple bell. aluminum alloys is much more malleable, is softer and close to 3 times better at conducting heat. So the flute vibration from the cooling fins are of a lower frequency (compared to the CI), and is easier ignore by the subconscious. And better thermal conductivity means less heat in the block to mess up the delicate tappet clearances.

Now the query 1, above reasons (thermal expansion throws valve timing off, blah blah blah) +, dunno how the 535 is setup, (doubt) could be the result of lack of detailing done on the engine internals/the minor engineering bits which has been signed off as 'chalta hai'?

But like I stated, I am a novice regarding the bullets. If you could give me 'the' 535 and help me with the de-building re-building of the engine (repeating, novice here), then maybe we could unlock more knowledge about the mysterious bull.

@the Enfield veterans, *waves white flag* do not shoot me, if i am wrong then please guide me, you would have no clue as to how ill i am with bull fever, and how words of the ages would help enlighten me more about this creature.

PS: Let there be light ^^

EDIT: and a heavier bike needn't necessarily mean less vibrations, its a game of materials and design. Weight in some instances help, like a heavier balanced flywheel (counter weighted crank to be diplomatically correct in this scenario) will smoothen out the torque pulses, though

Oh and a query(s), doesnt the CI and avl engine's non unit construction design cause the primary to be a source of vibs (chain,bearings,sprocket wear) too due to insufficient cooling and lubrication? (avls had some improvements done in the primary too right?) when compared to the uce ones? (the uce primaries are spoilt sods with a tub for themselves, right?)

Finally a thread that has more info,rather than the usual bashing we are seeing off late.About the CI UCE comparo,i totally agree with saerius,material does play an important role.Why are you comparing the CI and UCE,do a comparo between the ol gen(read of the 60s or 70s) CI and the CI of the last lot,theres a world of difference.CI has excellent sound and vibe damping property as compared to Aluminium,cant comment on the high speed vibes.

Hi Guys...thanks for the info, but still for a dull headed like me, dont understand all the technical terms

fine, let me see if i can read through again to understand better

@Kishor, for a change, even I didn't understand a word .

@Ramesh Madhavan: From what I understand, the Lightning has a 4 speed 'box so I guess the tall 5th gear is something that is missing. From what I am told, all CI engines revved even lower than what the UCEs do, with a missing tall/overdrive ratio, the engine is bound to stress more as the speeds climb.

I am sorry I couldn't fish out the other specs from google but from my experience till now, I think it will answer your query without even getting into engine internals by just looking at the specs. We can answer better if we at least get peak torque / power RPMs and gear ratios. As far as I have seen, you can always predict behavior by just looking at the numbers.

P.S.: I am a total RE Noob. My only experience with riding REs is 200km of riding my best friend's RE TBCI 350. During those 200km,
1. First, the bike started behaving as if it had no fuel (10 seconds), followed by *no problems* (20 seconds) after working perfectly well for 25odd km. This kept on happening for over 10km.
2. Then I lost the key and the chrome coated plastic side panel (which fell off due to vibes).
3. Had no idea about its FE so had to abandon my ride midway and return, the FE of the bike turned out to be ~25-26kmpl even though I was sticking between 80-90kmph.
4. Eventually ran out of fuel (because I couldn't open the tank because I lost the key ), finally had to pust the thing for the last 500 meters to reach back home safely.

This experience has left an indelible mark on my mind and has made me completely biased against REs and needless to say, I never had any more courage left to trust an RE over the P220 for any more rides *out of city*.

The specs that we see on paper-is it whats available on crank or on wheel.