12 cylinder smoothness vs 8 cylinder cars

OK I need someone to help me understand my obsession. I have owned four Ferrari's First a 308 GT4, then a Testarossa, then a 360 Modena lastly and currently a 550 Barchetta. So Two eight cylinder cars and two twelves. I simply LOVE the twelve cylinder cars. The twelve cylinder engine with the Capristo exhaust is simply magnificant. The smooth acceleration is simply intoxicating. Soooo smooth it defies understanding. The gear ratio is so linear that its nearly like an automatic tranny in its feel. I very much like the eight cylinder cars but they seem so "not smooth" in comparison. So here is the question...Why technically speaking is the twelve cylinder experience as I have described it? I am looking for a technical/mechanical answer to this perplexing question. I dont think this is a subjective observation. Please dont be defensive in your passion for the eight cylinder cars. I have owned many very fast eight cylinder cars Ferrari and non-Ferrari and I agree they are FUN!!! But I am interested in an explanation. thanks for your time. Jon in Delaware

 

12 cylinder engine produces 50% more "power strokes" per revolution than an 8 cylinder. The pulses are closer together (every 60 degrees of rotation as opposed to every 90 degrees) so it pulls more smoothly.

 

Cool.

 

Torque

 

WOW thats an intelligent explanation. Anything else anyone would like to add? Thanks Jon in Delaware

 

To go with 2NA's explanation, here are 2 graphs that illustrate it. Im not sure if that is the exact reason for what you feel, but here ya go anyways.

From: http://www.epi-eng.com/ET-PistonExcit.htm
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My signature says it all...

 

And Enzo said it first. A Ferrari should have 12 cylinders.

 

The twelve sounds better too. V8 feels like a teenager, angry, fast & agile while the V12 like a man, composed, swift but lethal

 

All right, Ill speak a little too soon and risk it (been a risk taker all my life). The 8 cyl is supposed to be the smoothest engine by design. Dont remember where I ran across the tech info, but I will search for it , maybe today (still have no ac at work,Florida scum stole my brand new unit last Thursday). Yes, it is even smoother , in theory, than the 12......

Got nothin to do with sound or how cool a car is......

 

Also a flat 12 (TR) should be smoother that a V12

 

It is my understanding that a straight 6 is the smoothest engine design...and based on the various I-6 BMW's I have owned, I have to agree...

 

I think those "smoothest configuration" theories are only that - theory. They attempt to explain primary and secondary vibration forces. (meaning the piston and rod oscillating motions). It does not take into account such things as the valve gear, or other moving parts like for example a power steering pump or A/C compressor.

My understanding was that a straight six, or a straight eight have an inherently balanced configuration. A V8 is inherently balanced for primary and can be simply counterweighted for the secondary balance. However, this is only true for a 90 degree V8 crank, not a flat crank like Ferrari uses, which to me at least has a little kind of exciting buzz to it.

A V6 has some secondary imbalance, but is minimized at either 60 or 120 degrees bank angle, and totally balanced at 180 degrees like a Porsche 911.

V12 and V16 are inherently balanced no matter what the cylinder bank angle because they are two straight sixes or two straight eights on a common crank.

Of course, all bets are off nowadays with special counterbalance arrangements, making even V10s, etc. very smooth. Besides, none of this matters much at idle if you have too much cam overlap, or if the pressure plate or other rotating parts are way out of balance. Motor mounts and artistic specialized balance arrangements, blueprinting the engine parts, weight of the block, etc. also make about as much difference as the cylinder configuration, IMHO. Hence maybe BMW is taking a lot more care than say an old Chevy pushrod 6 motor of the past.

But a Ferrari 12 has to be the true sweet spot of all these variables, as it should be!

 

+1

Not the most powerful engine, but incredibly smooth.

 

Enzo like the 12s in his race cars as they provided instant torque out of the corners vs v8s you need to keep the revs up

 

Still lookin......heard straight 6 is actually v bad, but I need proof!!!! Gonna eat, then research some more where I ran across this tech info.......

 

That was some dinner (burp, skuze me).

Well I found it, although it is not as scholarly as I would want it to be http://www.thetruthaboutcars.com/?p=1890

This gave me a basic edjukashun, but I likewise found that Wekopedia (spelled right?) says that v12's and straight 6's are the smoothest, as Parkerfe and Bullfighter said. Which article is right?

 

I always wanted to know power to weight ratio between 12 and 8?
Seems that losing weight (and mass) is the top desire in racing and preformance?

How much is the weight penalty of the 12 cylinder, compaired to the desire for smoothness?

We've all seen those comparision videos where the Lotus Elise chases down the bigger heavyer cars with 100's more HP ??? I'm not really into track times...but do 12 cylinder take away from tossability and fun factor of driving the twisties?

 

Would be interesting to compare the performance of a 12 cylinder vs an 8 cylinder of the same displacement by the same manufacturer.

Does anyone know of such an animal?

 

Having carefully read all the entries upon this thread, I now believe that the only answer is to go to turbine power.

I think someone may be a little ahead of me on this, but it is never too late to start.

 

Not quite what you wanted, but F in the 50s (and 60s?) often would enter 12 cyl and 4 cyl cars in the same displacement class of a race. The smaller recipricating components of the 12 cyl allow higher RPM (and since HP is proportional to RPM^2) this usually gives more absolute HP at the same displacement, but less-reliabilty. If the 12 cyl blows up, then the more-reliable 4 cyl still had a shot at the win.

This difference for 12 vs 8 at the same displacement would be less. However, the 12 cyl will have a higher overall fuel consumption than something with fewer cylinders so, depending on the fuel rules of the race, this can negate the whole benefit of more, smaller cylinders (e.g., everyone in F1 going to 10 cyl rather than 12 cyl a few years ago).

The author of that article got a little over-enthusiastic:

Is a pushrod, single-cam, cross-plane 90-deg V8 an excellent compact engine design with good smoothness and power? = yes

Is a pushrod, single-cam, cross-plane 90-deg V8 the smoothest running engine = no

 

12cylinders just sound great.

 

Well, howzabout a V-12 from a 250-series car vs. a carbed Euro 308? Three liter engines both, and producing about 250 HP each in road-going tune. I looked at a couple of old R&T road tests for the 250s and found torque to be 181 pound-feet at about 5000 rpm, and the 308 to have maybe 195 at the same RPM.

 

Wonder how much the era of the design (& thus general engine technology)has to do with it?

 

Great find. Thanks.