The number of pistons/cylinders have NOTHING to do with the degrees of angle in which an engine uses other than the physics of counter-balancing. There are MANY factors in which manufacturers use to decide on which angle to use for a particular design of an engine. But taking the same engine and lopping off two cylinders as you stated before, would not change the angle of degree. Here's an example. You have 4 pairs of scissors, you open each pair to form a perfect 90 degree right angle and set them standing on the handles so now that 90 degree angle is turned to look like a "V". Next you set all 4 pairs of scissors in a row front to back so if you look at them straight on, it looks like there's only one pair. Now, remove one pair of scissors and you've only got 3 pairs left, however those three pairs of scissors are all still at a 90 degree angle. Removing one pair did not change the angle of the scissors. I hope that explains it better. If not, here's a pretty good one http://en.wikipedia.org/wiki/V6_engine

 

I stand corrected because the Boxer engine that Porsche designed has each piston and rod on it's own crankshaft journal unlike American V6's and V8's and maybe others as well which share a crank journal thereby forcing the firing pattern to a function of the angle of the V. 60 degree for a six and 90 degree for an eight. When Buick just cut off 2 cylinders from their V8 the resulting 90 degree V6 ran uneven and was never balanced 100%.
This is why Porsche's cost twice as much as a Corvette. It is harder and probably requires special materials to get a strong crank with lots of throws in a small space.

 

Probably any configuration can be made to work. However, certain configurations are naturally balanced and have no need for counter balancing with harmonic balancers or balance shafts. One of these internally balanced configurations is a straight 6. That's why BMW hung on to these so long and also why they are going back to them. The Buick V6 mentioned was used for a year or so and vibrated so badly that a "fix" had to be found. There are two ways to fix it: one is with a balance shaft and the other is by redesigning it to a different angle. Both were used, one after the other. Porsche had the same problem with an inline four cylinder. It required an additional crankshaft turning in the opposite direction to smooth it out or balance it.

The flat six with the alternate cylinders directly opposing each other is balanced just like the inline six is. Ninety degree V8's are balanced by the harmonic balancer on the front of the crankshaft. Ninety degree V12's are naturally balanced, as are boxer 12's. Sixty degree V12's need external balancing. It is the harmony of the firings that is throwing some configurations out of balance and an opposing "heavy spot" (my term, nothing technical) that keeps the motor from running roughly.

There may be some glossing over of technical terms by this explanation, and there may be some slight disagreements.

The move to V6's was to save space and allow for smaller cars. Some V6's were transverse and couldn't be very large (or long like a straight 6) or the car would be too wide. It is not the ideal configuration for a smooth, balanced, high-revving motor, though with some technology the "shake" can be controlled.

 

There are two different issues one has to do with how the whole system rotates the other that I have been talking about is the way the engine fires. The Buick 90 degree V6 because of the fact that opposite cylinders were tied to the same crank journal kinda fired
Boom Boom Boom Boom Boom Boom instead of
Boom Boom Boom Boom Boom Boom like a 60 Degree V6.
The uneven firing made balancing even more difficult if not impossible.
The lobes on the distributor that operated the points was just as weird to accommodate the uneven firing.

 

180 refers to degrees of the opposing cyl..

not sure why u r dividing the 180 by 8..

FYI Porsche was already racing flat-8 in 907/908 in the 60's

BTW currently all the car company are going in the direction of smaller displacement with FI for weight / fuel saving.. so i don't think we will see a 8 cyl in 991

 

Read my stand corrected post.

 

I don't think the small production units count against mileage.

ChuckJ

 

Second order vibrations would be more difficult, but probably not a show stopper.

ChuckJ

 

LOL. You're kidding, right?

 

With the way these cars are growing, I'm sure they would be able to fix an 8 cylinder boxer engine.

jk.

With all the regulations, I don't think we will be getting more cylinders anytime soon.