Join Date: Dec 2001
Location: Belleville, Illinois
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Re: Streight six vs V-6
A V6 based on a V8 is a balance nightmare because, besides the reciprocating masses being oriented in a strange way, the igintion events aren't evenly spaced. That's why they will often have an auxiliary balance shaft to make up for some of that.
A V6 built to be a V6 will usually have 60 degrees between banks, although some (Ferrari, for one) have had 120 degrees between banks. They will produce equally spaced ignition events and aren't too bad to balance mechanically.
An in-line six is naturally balanced, and so is quite smooth, even with huge pistons thrashing back and forth like in a Caterpillar engine.
There is nothing inherent in any engine design that lends itself to higher torque, higher horse power or higher operating ranges, except:
Long intake and exhaust runners tend to 'tune' at lower frequency, hence in a lower RPM range. But that can be designed around by putting bends into the manifolds.
The longer the crankshaft is, the more trouble there will be controlling harmonic vibrations.
Because of those factors engine designers usually want to work with a shorter, more compact engine when they want high RPM and high horsepower. So all of the factors that truly affect the power output and RPM range where it occurs are customarily found in V engines for high power and in-line engines for high torque and lower operating range.
Those factors are bore and stroke ratio, primarily for average piston speed reasons, intake and exhaust manifold design, valve size, combustion chamber design and cam and ignition timing.
There's no reason that a V engine couldn't be designed to produce as much grunt as an in-line, and no reason that an in-line couldn't produce high RPM horsepower close to a V engine. The Jaguar in-line six was a great sports car engine, and the old GMC V6 and it's cousin, the V12, were torque monsters.
It's all in what the engine designer wants and what parameters he has to work with.