v6 vs. v8

I'm wondering what is better power wise and fuel economy, a 3.0L engine that is a v6 or a v8? I know most 3.0L are a v6, but i came acorss the bmw which is a v8, just wondering which makes more power and and all that. thanks.

well, if you're looking for tourque, the six cylender will have more, bigger cylenders make more tourque. but for higher reving capacity the V8 will have more cause it has more small cylendres. but i'd go with the V6, cause if you're looking for a small engine you'll find a lot more of them than a small V8. V8's are mostly used for muscle and are made big.

All things equal, the V6 will have better fuel economy. The V8 could be made to make more power, though.

Smaller cylinders means that it has the ability to rev higher, it doesn't mean that the torque is lower. The fuelconsumption does however increase.

However, the enginedesign is much more important for fuelconsumption, torque and so on, that we can say from this.

The best design for power is a 10 cyl.
It has the best balance between valve area and parasitic loss from the valvetrain.
In your case, an 8 cyl would have more valve area, and therefore, make more power than a V6, and only have slightly less power loss.
Depending on tuning, the 8cyl could have the same, better, or worse economy, so it all depends.

V6 Hands down, More "BulletProof" You can Depend on it, gets better mileage. v6 would have more power at lower RPMS.

Depends on what you are using it for Towing, Work/School car anything you need to depend on go with the v6

The V8 well. More parts, Rev's high. Looks like a weekend toy to me

The best design for power is a 10 cyl.
It has the best balance between valve area and parasitic loss from the valvetrain.
In your case, an 8 cyl would have more valve area, and therefore, make more power than a V6, and only have slightly less power loss.
Depending on tuning, the 8cyl could have the same, better, or worse economy, so it all depends.
no a v 12 or an inline six are the best for power they have nearly perfect internal balance so almost no counter balance is used v10s are like 2 i5s put together and to the best of my knolage the audi gt didnt have the smoothest idle

well hell, if all you want is power, why not go with a stationary V20 or V24, turning a whopping 120 to 300 rpm?

no a v 12 or an inline six are the best for power they have nearly perfect internal balance so almost no counter balance is used v10s are like 2 i5s put together and to the best of my knolage the audi gt didnt have the smoothest idle
72 degree V10 engines are balanced, I5 engines as well.

However, for maximum power more and smaller cylinders are usually desirable.

Hmmmm... in terms of swept volume, you could argue a 13B rotary only displaces 1300cc - and therefore a triple rotor would be the go.

Balance is over-rated - flat plane crank V8s are far less smooth than their regular counterparts but Ferrari never had an issue with them (instead of being two banks of inline 4s they act like 4 pairs of V Twins).

There is an additional consideration to note - the more cylinders the longer the engine for packaging... it also means higher valvetrain friction and increased complexity in terms of additional valvegear, electronic control, coils etc...

There aren't many inline-6 transverse FWDs for this reason.

*V6 Hands down, More "BulletProof" You can Depend on it, gets better mileage. v6 would have more power at lower RPMS. *

Some of the worse engines duribity wize I can think of have been v-6. On top of the a v-6 is inherantly unbalanced and requirs every balancing trick in the book such as contershafts and harmonic balancers exta...

unbalanced and requirs ... harmonic balancers

here we go again... you DID know that a "harmonic balancer" doesn't help balance the engine, right?

what's wrong with balancing an engine?
be it internally or externally, I think it is inherantly better for the life of the rotating assembly.

what's wrong with balancing an engine?
be it internally or externally, I think it is inherantly better for the life of the rotating assembly.

Balancing the engine by adding another rotating assembly adds cost and complexity, and does nothing for the durability of the primary rotating assembly.

ivymike it is true that a harmonic balancer doesn't balance an engines (unless its externally balanced) how ever v-6 suffer from more torsional vibration that straight 6's hence the need for the harmonic balancer. Harmonic balancers DO! reduce torsional vibration.

Harmonic balancers DO! reduce torsional vibration.
yes, that's why they're properly called TV Dampers, or Torsional Vibration Dampers.

yes, that's why they're properly called TV Dampers, or Torsional Vibration Dampers.

hold on a second, there are examples of both v6 and v8 engines where the harmonic is ALSO part of the engine balance - i.e. any motor where enuf mass could not be put on the crank inside the pan - a perfect example is the 400 SBC. In this case the harmonic and the 'flywheel' are not neutrally balanced. On 90* v6 engines, the torsional component is rather large(especially odd firing), hence a large '400-looking' harmonic on an internally balanced motor

not sure who this is in reply to, but the inbalance of a V motor is related to the bank angle vs firing interval. 90* V6 engines were designed as an offshoot of 90* v8 engines by literally sawing off 2 cylinders. 60* v6's are far easier to calm down. fwiw, the smoothest motors used had 8 cylinders...in a row. you could run an old Straight 8 on the garage floor just sitting there and it would not move all over the place.

however the term 'balancing' an engine as I saw used is something different in itself. In this case, pistons are matched to one another and weight held to a very small difference, and whereas rods typically come from the manus in matched pairs, when a motor is balanced, the rods are matched to one another which places less stress on the thrust bearing, finally, the crank counterweights are matched to the piston/rod/ring etc load and in some cases, even on an internally balanced motor, the harmonic and flywheel have small alterations made.

fwiw, the torsional dampening is less important on larger # of cylinder motors. at each firing, the crank is sped up and actually slows down before the next firing. If we had this very long motor with 360 cylinders, there would be about zero need for the harmonic, but the smaller the engine goes in terms of cylinders, the greater the ratio of mass outside the rubber ring is to internal engine mass becomes. In any case, dont get it wrong, todays EFI motors have ign systems so precise that relative cylinder balance (a totally different term - refers to the output of the cylinder) can be measured cycle to cycle - you might have heard of the CAW and SAW (crank angle word, spark angle word) - a relative measurement of the time between firings wich is altered of course by the strength of each cylinder. A bad harmonic will really play havoc with ign timing.