Shouldn't a 6 cylander engine get better gas mileage than a 4 banger?

[Accipiter22]

To achieve a certain speed, say on flat terrain, a 6 cylander would have to work less than a 4 cylander, correct? So why not get better gas mileage?

 

[theNEOone]

wow.....just wow.


=|

 

[GagHalfrunt]

And an aircraft carrier should be able to outrun a cigarette boat because the propellers are bigger.

 

[jlbenedict]

uh oh

 

[LordMorpheus]

in cars of identicle weight, both engines would have to use the same energy to reach the same speed.

If the cars also had identical aerodynamics and drivetrains, and are driven in the same manner, both vehicles should get the exact same mileage, as would a hypothetical third car in this situation with a V8.

In reality, the V6 will probably burn more gas just because every time the engine makes a revolution it'll pull more gas through it than an I4 will. Sure, the V6 won't have to work as close to it's limit as the I4 will, but it'll probably still burn more gas.

All that said, a V6 is typically in a heavier car, and a V8 in an even more heavy car, and I'd say that fuel economy is more a function of vehicle weight and driving style than of engine displacement.

 

[TomKazansky]

Originally posted by: Accipiter22
To achieve a certain speed, say on flat terrain, a 6 cylander would have to work less than a 4 cylander, correct? So why not get better gas mileage?

it's not the cylinders, but the litres. Normally a 6 cylinder would have a much larger displacement than a 4 cylinder; in THEORY, the 6 banger would use just as much gas at a lower rev as the 4 banger at a higher rev

 

[Dacalo]

Going by your concept, 12 cylinders or 16 cylinders are the most efficient.

EDIT: Oh and LOL!

 

[desy]

more moving parts means more friction mechanical loses etc.
The gas engine isn't 100% effecient to start so muliplying cylinders magnifies the loses.
Added vehicle wieght unless you remove something elsewher to keep the GVW the same and on and on

 

[TomKazansky]

Originally posted by: desy
more moving parts means more friction mechanical loses etc.
The gas engine isn't 100% effecient to start so muliplying cylinders magnifies the loses.
Added vehicle wieght unless you remove something elsewher to keep the GVW the same and on and on

actually, the most efficient internal combustion engine design is the i6 and v12. Friction counts very little in terms of efficiency (motor oil anybody?). Newer engines now usually have lighter internals, which is a big contribution to engine efficiency.

 

[iwantanewcomputer]

i don't know anything about the relationships of torque produced, cylinder number, and fuel consumption of an internal combustion engine, but i am going to post something I just made up based on my limited scientific knowledge that sounds technical.

 

[Caecus Veritas]

this is actually true in the case of the Jeep Wrangler. the 4 banger (which i owned) had way worse milage than a 6 banger's listed milage)... this, i assume, was due to the 4-cy engine having to work overtime to overcome the car's boxy aero-dynamics.

 

[Garet Jax]

Originally posted by: Accipiter22
To achieve a certain speed, say on flat terrain, a 6 cylander would have to work less than a 4 cylander, correct? So why not get better gas mileage?

Assuming all other things equals (weight, wind drag, etc...), it has to ignite more gas to operate the extra 2 cylinders so no.

 

[Thraxen]

Originally posted by: iwantanewcomputer
i don't know anything about the relationships of torque produced, cylinder number, and fuel consumption of an internal combustion engine, but i am going to post something I just made up based on my limited scientific knowledge that sounds technical.

What's funny is that despite all the snide comments people are actually having a hard time accurately explaining why.... and the people with the snide comments didn't even try to explain.

 

[desy]

Fine don't take my word on it
Internal combustion engines can contain any number of cylinders with numbers between one and twelve being common, though as many as 36 (Lycoming R-7755) have been used. Having more cylinders in an engine yields two potential benefits: First, the engine can have a larger displacement with smaller individual reciprocating masses (that is, the mass of each piston can be less) thus making a smoother running engine (since the engine tends to vibrate as a result of the pistons moving up and down). Second, with a greater displacement and more pistons, more fuel can be combusted and there can be more combustion events (that is, more power strokes) in a given period of time, meaning that such an engine can generate more torque than a similar engine with fewer cylinders. The down side to having more pistons is that, over all, the engine will tend to weigh more and tend to generate more internal friction as the greater number of pistons rub against the inside of their cylinders. This tends to decrease fuel efficiency and rob the engine of some of its power. For high performance gasoline engines using current materials and technology (such as the engines found in modern automobiles), there seems to be a break point around 10 or 12 cylinders, after which addition of cylinders becomes an overall detriment to performance and efficiency, although exceptions such as the W16 engine from Volkswagen exist.
http://en.wikipedia.org/wiki/Internal_combustion_engine#Cylinders

 

[GuitarDaddy]

There is not a 1:1 correlation between # of cylinders and fuel efficenancy. You oversimplify

 

[flxnimprtmscl]

Dude, you're right. I'm going to build the worlds first production car with a V-20 in it It's going to get 200 miles to the gallon and I'm going to be a zillionaire

 

[Ktulu]

Why is everyone jumping down the OP's throat about this. I don't think the idea is so far fetched for instance the Silverado with either the 4.3L v6 or the 5.3L v8 get the same gas mileage. According to most people here this should be impossible. But my guess is the 5.3L has to work far less than the v6. I'm not saying I'm right but it's is certainly an interesting idea.

 

[Crescent13]

OP Just got owned big time.

 

[Eeezee]

FIFTY CYLINDER ENGINE

 

[Sukhoi]

I see you failed high school physics.

 

[Sukhoi]

Originally posted by: Caecus Veritas

this is actually true in the case of the Jeep Wrangler. the 4 banger (which i owned) had way worse milage than a 6 banger's listed milage)... this, i assume, was due to the 4-cy engine having to work overtime to overcome the car's boxy aero-dynamics.

Yeah it all depends on the fuel and torque curves for the engine. A medium loaded V-6 certainly could get better mileage than a heavily loaded I-4.

 

[Sukhoi]

Originally posted by: infestedgh0st

Originally posted by: desy
more moving parts means more friction mechanical loses etc.
The gas engine isn't 100% effecient to start so muliplying cylinders magnifies the loses.
Added vehicle wieght unless you remove something elsewher to keep the GVW the same and on and on

actually, the most efficient internal combustion engine design is the i6 and v12. Friction counts very little in terms of efficiency (motor oil anybody?). Newer engines now usually have lighter internals, which is a big contribution to engine efficiency.

Piston rings anyone? Reciprocating mass?

 

[randay]

whats a cylander?

 

[Cristatus]

He was just asking a question that he was unsure of.

What if you ask a question? You guys wanna get jumped on?

The concept is interesting, and never thought about it that way, but I don't have enough knowledge to answer the question, so I'm just going to sit here and listen.

 

[Ktulu]

Originally posted by: Garet Jax

Originally posted by: Accipiter22
To achieve a certain speed, say on flat terrain, a 6 cylander would have to work less than a 4 cylander, correct? So why not get better gas mileage?

Assuming all other things equals (weight, wind drag, etc...), it has to ignite more gas to operate the extra 2 cylinders so no.

Yes, but it most likely won't have to rev as high to achieve the same amount of work thus actually using less gas.