carwhisperer
Mechanical
- Oct 10, 2015
- 35
My understanding is that 90 degrees is the best bank angle for a V8 while 60 degrees is best for a V6. I have studied the math that suggests that a bank angle of 90 degrees permits equating the effects of two pistons/rods sharing one crank pin to a rotating mass, which can then be counteracted with a counterweight. However, this analysis doesn't have anything to do with the total number of cylinders, just two pistons sharing one crank pin in a V configuration.
I would assume it has something to do with crank pin spacing. Two full revolutions per cycle=720 degrees of rotation per cycle. 720/8 cylinders = 90 crank pin spacing (not true for a flat plane crank V engine, which is another matter). 720/6 =120 degree crank pin spacing for a V6. I have read that a bank angle of 120 degrees is ideal for a V6 but that few are made that way because of packaging issues, and that 60 degrees, the supplement of 180 is therefor used. I realize there are many exceptions. For example, Ferrari made a 65 degree angle V6, the VW VR6 bank angle is very narrow, and Lancia, I believe, made a 14 degree bank angle V8. But I believe I am correct in saying that 60 is most common for a V6 and 90 for a V8. What is the math that leads to these two choices?
Brian
I would assume it has something to do with crank pin spacing. Two full revolutions per cycle=720 degrees of rotation per cycle. 720/8 cylinders = 90 crank pin spacing (not true for a flat plane crank V engine, which is another matter). 720/6 =120 degree crank pin spacing for a V6. I have read that a bank angle of 120 degrees is ideal for a V6 but that few are made that way because of packaging issues, and that 60 degrees, the supplement of 180 is therefor used. I realize there are many exceptions. For example, Ferrari made a 65 degree angle V6, the VW VR6 bank angle is very narrow, and Lancia, I believe, made a 14 degree bank angle V8. But I believe I am correct in saying that 60 is most common for a V6 and 90 for a V8. What is the math that leads to these two choices?
Brian