robin wrote on 02/07/13 at 13:40:37:I think a lot of people are baffled by the 5cyl vs. 6cyl. thing. When I made mention that some sort of rationale should be forthcoming from the rules committee, I feel that it was glossed-over with no real answer other than the 'fact' that 6 cyl engines have the ability to make more power than a comparable-displacement 5 cyl.
Given the fact that a six fires typically every 120 degrees (exceptions being some 90 deg V6s derived from V8s using common crank pins and odd-firing at 90 and 150 or semi-even at 108/132)- yes there's more power stroke overlap than a five (144 degrees) - but here's the thing:
- a four cyl fires every 180 degrees and therefore has no power stroke overlap at all l
Yes, a V6 will have more power stroke overlap. But that does not actually translate into power production. Each individual stroke on a V6 will generate LESS power than a 4 or 5 cyl with the same displacement. Each cylinder on a 4-cylinder is 50% more powerful than a V6 of the same size. A little bit of power stroke overlap is not enough to make up for a 50% per cylinder power advantage.
If you look at it from a high level, on paper the number of cylinders plays absolutely no bearing on the total power output of an engine, because the pros/cons perfectly cancel each other out. It's the: "No replacement for displacement" rule coming into effect. In reality every cylinder count has a displacement range where it achieves better efficiency than any other cylinder count. And that's mostly due to difficulty of controlling the burn in a very large combustion chamber, not to do with power stroke overlap.
V6 engines under 3.0l are actually at a disadvantage to equal displacement 4 cyl, due to the increase in rotational mass/friction/etc. V6 engines do not become more efficient than 4 or 5 cyl, until you go larger than 3.0l. Otherwise we would see a ton more 1.8l V6's (à la Mazda MX3) on the market. But since 3.0l+ engines are already banned, what's the point of banning that extra cylinder?
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