This might be too technical a question for but I think I’ve missed something fundamental perhaps in geometry or physics so it might not be:
V6 and V12 engines often have cylinder banks at 60 degrees from one another, and V8 and V16 usually have them at 90 degrees from one another or an additional balance part is added.
Why is this? How is a V6 at 60 degrees smoother than one at 90 degrees? Is this even correct? Are there situations you’d want to use the ‘wrong’ one deliberately except to reuse a factory?
In: Engineering
Piston offset. In a straight configuration, it’s not really a problem, but doing V and other configurations makes things complicated. Each cylinder will fire every 720 degrees of crank rotation. With a 60 degree V6, it works out to where every single cylinder fires 120 degrees apart from the next, which is ideal, because 120 X 6 is 720, which maintains an even firing order and reduces vibration. This can be worked around with more complicated crank shaft pins but that drives up cost. Without a more complex crank shaft or a lot of counterbalancing adding weight and sapping power, doing a V6 at 90 degrees will have a terribly uncomfortable ride. You want exactly 120 degrees of rotation between firings.
This also why 90 is the standard on V8s. With a V8 you get a fire every 90 degrees, 90 X 8 is 720, so again it all just works out to a naturally more balanced engine.
Compare this to say a Harley Davidson,a classic V-twin. They have a lot of shake and a distinct, very much not-smooth exhaust note, because the two pistons aren’t firing exactly opposite of each other. It induces a rough feeling.
With a V6 or V12, your crankshaft has either 6 or 12 mounts, at 60 or 30 degree intervals. Those need to align with cylinders at either the same angle, or an integer multiple.
Same thing with a V4 or V8, there will be 90 or 45 degree intervals. On a V10, it’s 36 degrees, so you’ll double it up and have 72 degree offset cylinders.
There has been some successful 90 degree V6’s, the one in the first gen Acura Legend used that design, though it did require some adjustments to reduce vibration:
“The engine utilized a 90 degree V-angle to the crankshaft in preference to the taller but more common 60 degree design, with a compression ratio of 9.0:1. The crankshaft had crankpins offset 30 degrees to provide a low profile engine that fires smoothly and evenly.“
yeah engines are wild huh. so the angle affects how smooth the engine runs. 60 degrees provides better balance and less vibrations. V6 engines at that angle just shake less. V8’s at 90 degrees create more power but can feel rougher. kinda like how a skateboard rolls smoother on flat ground compared to bumpier paths. sometimes companies stick with an angle for cost or tradition. but hey every design has its charm
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