[sukheshkumar]

Given that you are not doing anything to the prime mover, that is engine,
Torque can be altered by Gearing. As a multiple of Force x Radius of the wheel, by altering the radius of the Gear wheel, torque can be changed.

It should be possible to workout the gear ratio required so that even speed need not compromised, any designer should be able to throw some light on this

[jat]

Originally Posted by Shan2nu

I didn't get what you're trying to say.

Shan2nu

BHP => TORQUE x RPM (angular velocity)

Now for any vehicle, if the gear ratios remain same, the working rpms will remain same for any given speed. That is if you are doing 120 km/hr in 3rd gear, when the tacho hits the redline, you will still be doing 120 after modifications. So working rpm range from 0 ~ 6000 or say 0~6500 will remain same. But power has increased to give you better acceleration. Which means actually torque has increased.

Now in 5th gear, the max speed is reached where the torque produced by the engine (transferred to wheels - say at 3500 rpm) is equal to the torque required to keep the car going at that speed. Hence no more acceleration. With modifications, the BHP at that rpm is increased, which means now more torque is produced at that rpm and hence higher speed for the vehicle will be attained where the torque available balanaces out the resistances.

[cbr1000f]

Originally Posted by Shan2nu

But a loaded car does the same if you look at it. You're cruising at 100kmph in 5th, you come off the acc and the car still maintains it's momentum and does not slow down as quickly as when the same car was not loaded.

By maintaining vehicle speed, it's indirectly maintaining the engine revolutions, isn't it? Same thing happens when you use heavy wheels.

But, what we're talking about here, is something else. I wanna know if using a heavy flywheel increases the max torque produced by the engine? That is the main issue here.

Shan2nu

Your not quite getting it.
Agreed the heavier flywheels would put more load on the engine compared to a lighter one .. hence getting the crank to start turning would be slightly more difficult but once in motion because of the intertia of the heavier crank turning it would be easier since it carrier more momentum or potential energy once already set in motion.

Take an example of a heavy log shaped roller and a lighter one and when both are rolled on the ground at the same rpm...which one would travel furthur

Try going thru finetunings first post again .. i think he has explained it better.

[cbr1000f]

finetuning - Its been a while since i read about the "groove technique"

But wouldnt it be ridiculously dangerous to make changes in your combustion chamber without understanding how gas/fuel flow dynamics?

[finetuning]

Originally Posted by cbr1000f

finetuning - Its been a while since i read about the "groove technique"

But wouldnt it be ridiculously dangerous to make changes in your combustion chamber without understanding how gas/fuel flow dynamics?

Dear cbr1000f,

If its that much dangerous then hundreds or perhaps thousands across the world must have cried......including me......but thats not the case.....also we are not touching anything except engine head surface....no valve lapping...& so on.....a little scratch or groove on the surface makes much difference.....you need to beleive this by experiencing the power groove produces in a stock car.........I think any such new idea or thought afffecting combustion seems so dangerous but not neccessarily they are.....

Now regarding the behaviour pattern of air fuel mixture is so complexx...till now no body can say perfectly how in real sense combustin takes place because of enclosed steel chanmbers...no enginner in the world can see whats happening inside an engine....so only assumption based on output we come to any conclusion....and if by looking at the output grooves passes on I can really say it helps in better combustion......

Enjoy.....

[Shan2nu]

It wouldn't. It would just let engine maintain the angular momentum while engine is not producing power

Thats what i'm saying. There's a diff between keeping the momentum going and increasing peak torque.

Your not quite getting it.
Agreed the heavier flywheels would put more load on the engine compared to a lighter one .. hence getting the crank to start turning would be slightly more difficult but once in motion because of the intertia of the heavier crank turning it would be easier since it carrier more momentum or potential energy once already set in motion.

Take an example of a heavy log shaped roller and a lighter one and when both are rolled on the ground at the same rpm...which one would travel furthur

Try going thru finetunings first post again .. i think he has explained it better.

Dude, your log example is the same as the car example. Take 2 cars, one heavy and one light, drive them at the same rpm/speed and let off the gas pedal, which one do you think will travel more?

In your case the log itself turns but in my case the momentum of the car causes the wheels to keep on turning.

But, if you look at the opening post, the question is not about how torque can be maintained, it's about how torque can be increased.

A car producing 500nm will still produce 500nm with a heavier flywheel, but it'l be able to sustain it for a longer period of time.

Shan2nu

[jat]

Originally Posted by cbr1000f

Your not quite getting it.
Agreed the heavier flywheels would put more load on the engine compared to a lighter one .. hence getting the crank to start turning would be slightly more difficult but once in motion because of the intertia of the heavier crank turning it would be easier since it carrier more momentum or potential energy once already set in motion.

Take an example of a heavy log shaped roller and a lighter one and when both are rolled on the ground at the same rpm...which one would travel furthur

Try going thru finetunings first post again .. i think he has explained it better.

The purpose of the flywheel is to smoothen out the ripples of torque. It is not adding anything to engine, it just takes something from the engine and give back the same thing to the engine (on paper a little less and will decrease the power). Therefore it can not increase mean torque and that is what, i think, people here are talking about - how to increase mean torque? From your description, it looks like you are talking about increasing the minimum torque over a cycle of engine and not the mean torque. The minimum torque will increase, but the max torque will consequently decrease.

[Shan2nu]

BHP => TORQUE x RPM (angular velocity)

Now for any vehicle, if the gear ratios remain same, the working rpms will remain same for any given speed. That is if you are doing 120 km/hr in 3rd gear, when the tacho hits the redline, you will still be doing 120 after modifications. So working rpm range from 0 ~ 6000 or say 0~6500 will remain same. But power has increased to give you better acceleration. Which means actually torque has increased.

Now in 5th gear, the max speed is reached where the torque produced by the engine (transferred to wheels - say at 3500 rpm) is equal to the torque required to keep the car going at that speed. Hence no more acceleration. With modifications, the BHP at that rpm is increased, which means now more torque is produced at that rpm and hence higher speed for the vehicle will be attained where the torque available balanaces out the resistances.

Yup thats true, for power to increase, torque has to increase. Not necessarily peak torque but the torque at which rpm the power is being calculated.

If a car produces 100bhp@6000rpm, the torque fig at that point would be 118.69nm@6000rpm. But to produce 110bhp from the same engine at the same rpm, the torque curve will have to be modified in such a way that it produces around 130.56nm@6000rpm. But to use 118.69nm and still be able to produce 110bhp, the curve will have to be modified such that 118.69nm is being produced at 6601rpm.

In short :
118.56nm@6000rpm = 100bhp
130.56nm@6000rpm = 110bhp
118.69nm@6601rpm = 110bhp.

Shan2nu

[finetuning]

Hi shan2nu,

Very good discussion going on.....One thing I must say that we must not consider Torque as some fixed quantity in any given car with certain bore & stroke.......what car makers publish torque figure at certain rpm is not the final one....there is so much scope to generate more torque at same rpm..........after all torque is the outcome of combustion process......if combustion is made wild either by NOS or by other method car output is increased.....we dont know that what we call as efficient combustion has so much scope for improvement......the more a bang inside cylinder more power is produced....all car makers have different methods for this BANG.......this is essentially turbulance creating methods.....

Enjoy....

[Shan2nu]

Hi shan2nu,

Very good discussion going on.....One thing I must say that we must not consider Torque as some fixed quantity in any given car with certain bore & stroke.......what car makers publish torque figure at certain rpm is not the final one....there is so much scope to generate more torque at same rpm..........after all torque is the outcome of combustion process......if combustion is made wild either by NOS or by other method car output is increased.....we dont know that what we call as efficient combustion has so much scope for improvement......the more a bang inside cylinder more power is produced....all car makers have different methods for this BANG.......this is essentially turbulance creating methods.....

Thats true, there's always scope for improvement as far as torque and power curves are concerned. Nobody denies that.

Shan2nu

[dr fate]

I guess like others have said there is no replacement to displacement!!bigger the better,everything not just one or two,but one way to go if we need to invoke torque is like suresh kumar said is to go for differerent gearing e.g:baleno try replacing the std gearing with say 76 or 77 you do not loose much rpm between shifts i think thats torque at play,

where as the top end is curtailed a bit here there is a display of torque here,and as far as flywheel is concerned i think what also needs to be observed is the gears connecting have a fight going about as to who is the boss if heavier both keep each other running without loosing momentum if lighter the latter will overwhelm the former so they have to be matched.

[cbr1000f]

Originally Posted by Shan2nu

Thats what i'm saying. There's a diff between keeping the momentum going and increasing peak torque.



Dude, your log example is the same as the car example. Take 2 cars, one heavy and one light, drive them at the same rpm/speed and let off the gas pedal, which one do you think will travel more?

In your case the log itself turns but in my case the momentum of the car causes the wheels to keep on turning.

Dude i think your mixing up your fundas man.
Obviously the lighter car would travel more man
HEavier car would put load on the complete engine .. it wouldnt work like potential energy would .. as the ppl arent moving in anyway.While in the case of the heavy crank it turns itself causing the weight to be converted into energy.

Yes Jat.. Peak torque would decrease (i think not sure here)but the torque curve would be higher.

[finetuning]

Do read this link for flywheel comparisons.............

Naturally lighter flywheel has difficulty especially climbing a hill......where as a heavier one makes much difference..........

http://www.torquecars.co.uk/Tuning/f...lightening.php

Enjoy........

[shazikon]

Heres my bits..
Torque is the angular energy(force) required to perform action..Torque is what you feel when you are pushed back to your seat. In an ICE, torque is to move the crank and ultimately the wheels. Talking about the torque at the crank, keeping the combustion area constant, torque can be increased by increasing the quantity of fuel : air mixture in the combustion area, more dense the mixture nearing TDC the more BANG you will get and more twisting force (torque) on the crank. More Bang can be createed by adding Bang creating substance like NOS to the normal mixture. Another way is to introduce a dense mixture. dense mixture can be created in a cylinder by two ways of forced induction : turbo charging or supercharging. Now to make peak BHP for a car, it matters at what RPM do you want this peak BHP cos at 4000 RPM, you will generate twice the amount of peak HP as compared to 2000 RPM with the same amount of Torque. It is beneficial to generate peak torque at lower RPMS for drivability but if you are looking at a drag performance car, it matters how long or how wide (range of RPM) is your car producing torque..car which can "pull" with peak torque through a wide RPM range makes a car faster/quick compared to a car which has a huge torque at one RPM and the torque dies off soon..horsepower increases with MAX torque for a wider torque curve your car will be able to pull longer and harder with out changing gear.. now comming to gearing, this is what puts the effective torque(rotational motion) on the crank to forword motion on the drive wheels.
So How you utilize the torque in the torque curve is left to the gear ratios. If a car makes peak torque at 4000 RPM in a gear thats the max torque you can get in that gear, if you can change gear ratios to rev up to 6000 RPM in the same gear, you will be able to deliver more torque to the wheels and thus more BHP. So taller the gear ratio the more torque can be delivered to the wheels. Comming to the flywheel stuff..a lighter flywheel helps in accelerating the car faster (with the same force) because the force required to move the engine components would be less but a heavier wheel stores more energy compared to a lighter wheel and this energy will be released when you are not pushing your accelerator. A lighter fly wheel doesnt affect MAX power of an engine but it will sure help in drivability and accelaration. a heavier fly wheel takes a few more secs to reach peak power than a lighter flywheel. Hope this helps...

[Shan2nu]

Dude i think your mixing up your fundas man.
Obviously the lighter car would travel more man
HEavier car would put load on the complete engine .. it wouldnt work like potential energy would .. as the ppl arent moving in anyway.While in the case of the heavy crank it turns itself causing the weight to be converted into energy.

Nope, the heavier car will travel furthur. Due the weight of the vehicle the engine braking wouldn't be sufficient enuf to slow down the car as fast as it would with a light one.

Now don't tell me a heavy car can stop faster than a light car when you hit the brakes, just bcos it's putting down more drag. The car maynot be turning, but the car sits on wheels that turn.

Yes Jat.. Peak torque would decrease (i think not sure here)but the torque curve would be higher.

When you use a heavy flywheel, you sacrifice the torque curve at higher rpms. So technically, you're only improving low end torque (and not the entire torque curve). Lightning the flywheel lets the engine produce better torque at higher rpm and that gives you better bhp figures.

So, whether you increase or reduce flywheel weight, you're losing out on either top end or low end torque. Bottom line.....peak torque wont increase in both cases.

Shan2nu