pros and cons of 4 cylinder vs. 6 cylinder

[vshah]

i've been wondering about this for some time. suppose you have a 2.4 liter 4cyl, and a 2.4 liter 6cyl. what are the advantages/disadvantages of either configuration?

-Vivan

 

[Fingers]

4 cylender would be cheaper to maintain.

 

[styrafoam]

Generally more hp/torque at a lower RPM for the 6, a 4 would most likely get better gas mileage. Kind of an off kilter question because very seldom do you see "all else equal".

 

[jagec]

4-cylinder is less complicated, smaller, lighter, revs higher, and (in all cases I've seen) will get higher fuel efficiency.
6-cylinder probably has a better torque curve, the components are less stressed, and you get to slap the "V-6" emblem on the back of your car.

Frankly, I don't think I'd ever want a V-6...I think 4-bangers, I-6's, and V-8's are the best engines.

 

[Vic]

Everything being equal, the 6 would be smoother than the 4 in almost any configuration (V, flat, inline), but would be more expensive to build and maintain. The 6 would weight a bit more. More cylinders usually mean more space taken up under the hood. All things being equal, power and torque should be similar. Power comes from displacement (and/or forced induction), not the number of cylinders.

 

[Eli]

Originally posted by: Fingers
4 cylender would be cheaper to maintain.

Not enough to make a significant difference.. you're talking about what, 2 spark plugs? lol....


Well.. it totally depends on the two engines' designs. You could basically do anything you wanted with each one..

The 2.4L 6 cylinder would most likely be more torquey than the 2.4L 4cyl. It would probably also use more gas, but that is going to depend a lot on the car's gearing.. and the car itself. It could, for example, get better highway milage, but worse city milage.. it just totally depends.

I guess I don't really know why they don't make smaller but more cylinder engines. I guess it's probably pretty pointless. Why make it more complicated when you can do the same thing with only 4 cylinders? At the same displacement, the advantages to a 6cyl probably don't outweigh the added complexity and expense to design and build.

Plus I think that bigger bores are a good thing, up to a certain point.. You want as much surface area as possible to exert force against(the piston crown). That's why we don't run 2.4L V16's.

 

[TheLonelyPhoenix]

"All else equal" kinda makes it a moot point, no?

More cylinders will usually provide more torque in exchange for a lower redline and decreased mileage.

 

[jagec]

Originally posted by: Vic
All things being equal, power and torque should be similar. Power comes from displacement (and/or forced induction), not the number of cylinders.

It's never been about the peak HP/torque, it's about the curves...and that's a function of more than just displacement.

 

[vshah]

Originally posted by: Vic
Everything being equal, the 6 would be smoother than the 4 in almost any configuration (V, flat, inline), but would be more expensive to build and maintain. The 6 would weight a bit more. More cylinders usually mean more space taken up under the hood. All things being equal, power and torque should be similar. Power comes from displacement (and/or forced induction), not the number of cylinders.

basically what i was wondering about, thanks

 

[thomsbrain]

Originally posted by: jagec
4-cylinder is less complicated, smaller, lighter, revs higher, and (in all cases I've seen) will get higher fuel efficiency.
6-cylinder probably has a better torque curve, the components are less stressed, and you get to slap the "V-6" emblem on the back of your car.

Frankly, I don't think I'd ever want a V-6...I think 4-bangers, I-6's, and V-8's are the best engines.

actually, i'd guess that the 6 would rev higher, given identical displacement and internal design. the reason is the moving parts for each cylinder would weigh less and therefore not beat the crap out of themselves so badly. i'm sure there's other factors i'm not considering, but that's just what came to mind.

edit: and you can't use most common engines as your excuse to say i'm wrong, because few of them share displacements and none of them share designs... i'd love to hear if i'm wrong or right from a phsyics standpoint, but i don't want to hear any "well the S2000 revs higher than a big-block Chevy, so more cylinder MUST rev slower!!!111"

 

[cressida]

Originally posted by: jagec
4-cylinder is less complicated, smaller, lighter, revs higher, and (in all cases I've seen) will get higher fuel efficiency.
6-cylinder probably has a better torque curve, the components are less stressed, and you get to slap the "V-6" emblem on the back of your car.

Frankly, I don't think I'd ever want a V-6...I think 4-bangers, I-6's, and V-8's are the best engines.

hail the I-6

 

[otispunkmeyer]

v6 is smoother.......becuase of the "V" the engine in more balanced....the pistons are basically pushing against them selves.....in a 4 pot, the pistons move straight up n down and the all they push on is the crank shaft....even what happens is crank gets bit misaligned and u get a knocking noise

4 pots are generally rougher....or at least will become rougher with time much quicker than a V

 

[Eli]

Originally posted by: vshah

Originally posted by: Vic
Everything being equal, the 6 would be smoother than the 4 in almost any configuration (V, flat, inline), but would be more expensive to build and maintain. The 6 would weight a bit more. More cylinders usually mean more space taken up under the hood. All things being equal, power and torque should be similar. Power comes from displacement (and/or forced induction), not the number of cylinders.

basically what i was wondering about, thanks

As jagec mentioned, though.. that isn't entirely true. Like I said, you could do anything you wanted with the two engines as far as power output goes.

A well designed 6cyl could easily trump a poorly designed 4cyl in every aspect, and vice versa..

 

[TheLonelyPhoenix]

Nm, I need sleep.

 

[vshah]

Originally posted by: Eli

Originally posted by: vshah

Originally posted by: Vic
Everything being equal, the 6 would be smoother than the 4 in almost any configuration (V, flat, inline), but would be more expensive to build and maintain. The 6 would weight a bit more. More cylinders usually mean more space taken up under the hood. All things being equal, power and torque should be similar. Power comes from displacement (and/or forced induction), not the number of cylinders.

basically what i was wondering about, thanks

As jagec mentioned, though.. that isn't entirely true. Like I said, you could do anything you wanted with the two engines as far as power output goes.

A well designed 6cyl could easily trump a poorly designed 4cyl in every aspect, and vice versa..

yeah agreed. but i was more wondering about the theoretical limits of each design. so i guess jagec and vic are both true. note Vic said similar, not exact.

 

[Nebor]

All things being equal, a 2.4l 4 cylinder generates less power than a 2.4l 5-cylinder. This isn't theory, it's been proven by the Volvo guys, who have both 2.4l n\a 4 cylinders and 2.4l n\a 5 cylinders.

 

[OS]

Originally posted by: jagec

Originally posted by: Vic
All things being equal, power and torque should be similar. Power comes from displacement (and/or forced induction), not the number of cylinders.

It's never been about the peak HP/torque, it's about the curves...and that's a function of more than just displacement.

Well, notice his initial qualifier, "all things being equal". If you kept the bore/stroke ratio same, timing/ignition, fuel grade, cam profiles/timing setup, flow rate of heads/manifolds, whatever else i didn't think of, blah blah blah, all the same, it pretty quickly boils down to displacement.

 

[jagec]

Originally posted by: otispunkmeyer
v6 is smoother.......becuase of the "V" the engine in more balanced....the pistons are basically pushing against them selves.....in a 4 pot, the pistons move straight up n down and the all they push on is the crank shaft....even what happens is crank gets bit misaligned and u get a knocking noise

4 pots are generally rougher....or at least will become rougher with time much quicker than a V

actually, an I-6 engine is considered "perfectly" balanced. A V-6 is not.

 

[0roo0roo]

err its all based on design.. bleh. but if you only have X(small amount of money) its much easier to make a 4 banger that is deecent then a 6 obviously.. less parts and stuff. other then that its really not easy to compare. look at stuff like the evo and wrx, those are 4bangers that can wipe out most v6's.

 

[Vic]

Originally posted by: otispunkmeyer
v6 is smoother.......becuase of the "V" the engine in more balanced....the pistons are basically pushing against them selves.....in a 4 pot, the pistons move straight up n down and the all they push on is the crank shaft....even what happens is crank gets bit misaligned and u get a knocking noise

4 pots are generally rougher....or at least will become rougher with time much quicker than a V

Not entirely correct. A V6 is not a very balanced engine, scarcely more balanced than an I4 and less balanced than a H4. What makes the 6 feel smoother is that extra fire every revolution. Now the I6 is perfectly balanced.... and the pistons all move straight up and down. What makes knock in a well-maintained engine is usually poor fuel grade and/or overly lean AF mixture.

Originally posted by: OS
Well, notice his initial qualifier, "all things being equal". If you kept the bore/stroke ratio same, timing/ignition, fuel grade, cam profiles/timing setup, flow rate of heads/manifolds, whatever else i didn't think of, blah blah blah, all the same, it pretty quickly boils down to displacement.

Correct. Torque curve and redline have much more to do with bore/stroke, compression, cam profiles, and flow rates than with the number of cylinders.
The 2.5L H4 in my GF's Subaru is smooth and torquey, with an almost perfectly flat torque curve, and a redline at 6250rpm.

Originally posted by: Nebor
All things being equal, a 2.4l 4 cylinder generates less power than a 2.4l 5-cylinder. This isn't theory, it's been proven by the Volvo guys, who have both 2.4l n\a 4 cylinders and 2.4l n\a 5 cylinders.

All things are not equal between those two engines. Volvo designs more power into the 5cyl because a high output I4 tends to be rough and buzzy, while the I5 design is relatively smoother.

 

[MikeMike]

Originally posted by: jagec

Originally posted by: otispunkmeyer
v6 is smoother.......becuase of the "V" the engine in more balanced....the pistons are basically pushing against them selves.....in a 4 pot, the pistons move straight up n down and the all they push on is the crank shaft....even what happens is crank gets bit misaligned and u get a knocking noise

4 pots are generally rougher....or at least will become rougher with time much quicker than a V

actually, an I-6 engine is considered "perfectly" balanced. A V-6 is not.

why not an I-5? i know its not balanced etc, but its supposed to offer best of both worlds in theory.

then we could go on to the rotary engine.

MIKE

 

[MercenaryForHire]

Originally posted by: 0roo0roo
look at stuff like the evo and wrx, those are 4bangers that can wipe out most v6's.

I'm going to club you with an intercooler if you don't understand that comparing a turbo I4 to an NA V6 is a dumb thing to do.

And Vic's right - I6 = balanced engine. IIRC, V12s are also balanced.

- M4H

 

[tweakmm]

Originally posted by: thomsbrain

Originally posted by: jagec
4-cylinder is less complicated, smaller, lighter, revs higher, and (in all cases I've seen) will get higher fuel efficiency.
6-cylinder probably has a better torque curve, the components are less stressed, and you get to slap the "V-6" emblem on the back of your car.

Frankly, I don't think I'd ever want a V-6...I think 4-bangers, I-6's, and V-8's are the best engines.

actually, i'd guess that the 6 would rev higher, given identical displacement and internal design. the reason is the moving parts for each cylinder would weigh less and therefore not beat the crap out of themselves so badly. i'm sure there's other factors i'm not considering, but that's just what came to mind.

edit: and you can't use most common engines as your excuse to say i'm wrong, because few of them share displacements and none of them share designs... i'd love to hear if i'm wrong or right from a phsyics standpoint, but i don't want to hear any "well the S2000 revs higher than a big-block Chevy, so more cylinder MUST rev slower!!!111"

I think that you are basically right, F1 engines have lots of cylinders, but a low displacement and rev to crazy speeds.

 

[freebee]

Always pick the 6. Each cylinder actually fires less, meaning less wear over the life of the car. Engine will last longer. Makes sense?

 

[GTaudiophile]

Originally posted by: freebee
Always pick the 6. Each cylinder actually fires less, meaning less wear over the life of the car. Engine will last longer. Makes sense?

Tell that to Miata owners who love to rev their engines to 6500rpm every day and yet successfully put 250,000 miles on the engine.