number of cylinders

imported_guy

whats the performance difference between a 4l v8 and a 4l v12? is there an advantage in having smaller, but more cylinders?

while looking this up, i found ferrari used to have a 1.5l v12 engine

wouldnt that be REALLY heavy compared to a 4 cyl 1.5l? was there a reasoning behind having more cylinders here?

mandrake04

No in fact it should be lighter because the rotating parts could be made lighter, also a V12 would be smoother and more responsive.

imported_guy

mandrake04 wrote: »

No in fact it should be lighter because the rotating parts could be made lighter, also a V12 would be smoother and more responsive.

i would have thought the 12 cylinders would take up more space, more metal and hence be heavier, no?

mandrake04

Probably would, but I think a V12 requires a smaller flywheel.

But I reckon you still get more power from a V12 for its weight compared to a 4.

old_aussie

Smaller bore and stroke per cylinder delivers higher horsepower, but usually not much more torque.

imported_guy

mandrake04 wrote: »

Probably would, but I think a V12 requires a smaller flywheel.

But I reckon you still get more power from a V12 for its weight compared to a 4.

thanks!

is it easier to balance vibrations with more cylinders?

old_aussie wrote: »

Smaller bore and stroke per cylinder delivers higher horsepower, but usually not much more torque.

that explains a little bit, thanks!

lomb

V12s have less power Id say all things being equal. Much higher frictional losses although Id say torque would be up?
Anyway manufacturers are going to less cylinders now eg vw golf due to better fuel economy.
Having said all that a V12 old s600 passed me and it sounded fantastic....

Mikros

imported_guy wrote: »

thanks!

is it easier to balance vibrations with more cylinders?


that explains a little bit, thanks!

I'm sure someone can explain this better -

Certain engine configurations are inherently balanced because of their set-up, for example the straight-6. The front and rear trio of cylinders are mirror images, and the pistons move in pairs. That is, piston #1 balances #6, #2 balances #5, and #3 balances #4, eliminating the rocking motion that occurs in other configurations.

Each cylinder bank in a V12 is essentially a straight 6 so it also has perfect balance. This means it doesn't need any balance shafts or counter weights and can be lighter than other configurations. Because there are more cylinders the power is delivered twice as often as straight-6 leading to smoother delivery/more refinement. This also reduces the need for a large flywheel to smooth out the power delivery.

The extra complexity of the V12 adds cost which is why we are not all driving them.

peasant

To understand why bigger isn't always better, you have to look at extremes.

15 liter single cylinder engine

https://www.youtube.com/watch?v=-b2R0ImvaZ0

Note the size of the flywheel, rods, etc and all it puts out is 25 PS at a leisurely 350 rpm.

The principle translates down to modern engines. The bigger you make the cc per cylinder, the beefier you have to make pistons, rods, camshaft, flywheels, the lot and your rpm is limited so that you don't shake the whole thing to bits.

A bigger cc per cylinder gives you more grunt (torque); higher rpm gives you a better power band and as always the most useable compromise lies somewhere in the middle.

A 1.5l V12 might work in a screaming racecar but would be useless for a hillstart in commuter traffic.

imported_guy

Mikros wrote: »

I'm sure someone can explain this better -

Certain engine configurations are inherently balanced because of their set-up, for example the straight-6. The front and rear trio of cylinders are mirror images, and the pistons move in pairs. That is, piston #1 balances #6, #2 balances #5, and #3 balances #4, eliminating the rocking motion that occurs in other configurations.

Each cylinder bank in a V12 is essentially a straight 6 so it also has perfect balance. This means it doesn't need any balance shafts or counter weights and can be lighter than other configurations. Because there are more cylinders the power is delivered twice as often as straight-6 leading to smoother delivery/more refinement. This also reduces the need for a large flywheel to smooth out the power delivery.

The extra complexity of the V12 adds cost which is why we are not all driving them.

peasant wrote: »

To understand why bigger isn't always better, you have to look at extremes.

15 liter single cylinder engine

https://www.youtube.com/watch?v=-b2R0ImvaZ0

Note the size of the flywheel, rods, etc and all it puts out is 25 PS at a leisurely 350 rpm.

The principle translates down to modern engines. The bigger you make the cc per cylinder, the beefier you have to make pistons, rods, camshaft, flywheels, the lot and your rpm is limited so that you don't shake the whole thing to bits.

A bigger cc per cylinder gives you more grunt (torque); higher rpm gives you a better power band and as always the most useable compromise lies somewhere in the middle.

A 1.5l V12 might work in a screaming racecar but would be useless for a hillstart in commuter traffic.

these explain alot! thanks