kindil

i am curous what the advantage of each kind of motor is i know some of the advantages of the flat but none of the other too if any one cares to shed some light on this topic plz do

dropkick_muppet

iTrader: (4)

inline motors were the original, and they're still the simplest. for four cylinder motors, they're fine. when you get into six and eight cylinders, they get too long and are hard to fit in engine compartments, and tend to cause all sorts of issues since they have to be run perpendicular to the cars wheelbase.

V-motors can be made shorter than inline motors with the same # of cyls. depending on the angle of the V, they can also be perfectly balanced, allowing them to make more power and feel smoother.

flat motors have the advantage of lowering the cars center of gravity, by making the motor shorter height wise then either a V or inline. they're not as balanced as 90 degree V motor, but they're significantly shorter than an inline motor.

thats the short answer...

Kostamojen

iTrader: (2)

Um, by ballancing you mean what? Because horizontally opposed cylinders are perfectly ballanced in terms of not requiring any additional means of ballancing the operation of the engine...

The Mirror

iTrader: (1)

Balancing meaning this:
Pistons pumping up and down and the corresponding crankshaft weights moving around create lots of centrifugal force. This force is transmitted into the entire engine block/assembly. With inherently balanced engines, like a flat 12 or inline 6, the force of one piston going in one direction is at any given time being countered in the opposite direction by another piston. That's grossly oversimplified, and there are other factors, but for the sake of explanation, that's the lion's share of it. Big inline four cylinders, like the 2.5, 2.7 and 3.0 Porsches from the 944/968 use belt driven balance shafts to counter these forces. Balance shafts are essentially shafts of metal with weights attached in strategic places that spin up and down with the engine through the rev range. When a piston is moving and creating a big bunch of centrifugal force, the balance shaft weight is calculated to throw a punch of force in the opposite direction......negating the big shake that would be there if there was no balance shaft. Again, a simplified explanation, but that's the basic theory. I won't get into secondary forces or harmonic vibration. There are books on that.

Inline 4's are a very good package, typically compact, lightweight or heavy duty as need be, only one cylinder head to worry about, etc. That's why they've always been around and will always be around. They are not inherently balanced though, and that's why the big ones need balance shafts, and others seem rough and buzzy. Modern design techniques have them running very smooth these days though (and improved engine mount technology plays a significant part in that).


The inline 6 is a very good passenger car application. Typically smooth (due to inherent balance), reliable, easy to service, and lots of power potential. You can build them small and lightweight (current small BMW sixes) or fat and burly (truck diesels), the I-6 configuration can handle it all. IMO, their chief advantages are balance and ease of service.
Inline 6s typically require a larger engine bay to accomodate their length. Some exceptions include Volvo's 2.9L six which is transversely mounted, as is the new Porsche developed 2.5L six in the Suzuki Verona. Both engines have small bores and long strokes, which is great for low end to mid range torque but not for high rpm performance. In extreme performance applications, inline 6 cylinder engines can potentially run into problems with those long crankshafts. In the old days of carburation, the unequal length intake manifold runners would often have some cylinders running leaner than others......a problem that's been solved by fuel injection.

The old inline 8's were heavy, very long, thirsty, and died an early death because of those issues and others.

V engines like V-6s, and V-8s are excellent packages due to balance (if designed correctly), low center of gravity, compact lengthwise, and reliable. They can also feature very light weight in relation to the number of cylinders they have. You can make a 3.0L V-6 very lightweight in comparison to a 3.0L inline six, where you would struggle to pare weight after a certain point. The short length of these engines is the reason you can stuff a V-8 Chevy into a 240Z.....a car originally designed for an inline 6. As dropkick mentioned above, tuning the angle of a V engine can balance it out. You can also play with firing orders and crankshaft configurations to give a V engine more power, more smoothness, or a combination of both. Too much to cover here. V engines can be used in a variety of ways, packaged in a variety of ways.

Flat engines like the sube, Porsche 6, or Ferrari flat 12s carry a low center of gravity, can be easily balanced (I'm almost certain the flat 12 is inherently balanced), and have nice short stiff crankshafts in relation to the number of cylinders. Virtually every piston engined light aircraft in the US has either a flat four or flat six, somewhere around 300c.i. (5.0L). They lend themselves to air cooling due to the separation of the cylinders, which make them advantagous in applications like light aircraft. Problems can arise with intake and exhaust plumbing......if intake goes in on the top, then exhaust has to come out the bottom. That can be a plumbing nightmare in tightly packaged applications like racecars. That's one of the reasons ferrari dropped the flat 12 for racing years ago, also because when they get big like that they start to weigh more than a well designed V-12.

Whew!

serrano

Standing ovation, nice clear read.

Kostamojen

iTrader: (2)

Ya, thats what I thought was being said, but it didnt come out quite like that...

Isnt all that info on the "how stuff works" website? I remember reading it ages ago.

The Mirror

iTrader: (1)

Hmmm. Not sure about that website. I'll have to have a looky.
-Mirror