Quote:
Originally Posted by The Atomic Ass
This is entirely theory, but I think it's a good one.
Given a fixed displacement, say, 2.0L, we have 3 engines. First is an I-4. Second is a V-8. Third is a W-12 (for compactness).
I theorize that the V-8 will produce more usable torque at lower RPM's than the I-4, and the W-12 will likewise "lower" the bar over the V-8.
I imagine a small displacement V-12 spinning at 1,100-1,200 RPM, or even less, on the highway.
It's giving me thoughts about building an engine from scratch.
My theory comes from reading the charts in the following page: Torsional Characteristics of Piston Engine Output, by EPI Inc. |
Lets assume that all three engines have a Stroke to Bore ratio of unity. The Stroke for the three engines would be as follows
4 cyl - 86mm
8 cyl - 68.2mm
12 cyl - 59.6mm
As short stroke engines do not produce as much torque at low speeds as longer stroke engines, the four cylinder engine will produce more torque than the eight and twelve cylinder engines.
Another disadvantage of the 12 cylinder engine is the greater surface area to volume ratio of the combustion chamber compared to the four cylinder engine. This will result in larger heat losses and thus inferior fuel economy compared to the four cylinder engine.
The twelve cylinder will certainly be smooth running but low speed torque and fuel economy will be inferior!