quote:Originally posted by George P: There's nothing like an in-line 6 or a 60°/180° V12.
But a 90° V12? I'd love to pick his brain on how he reconciled that with his love of the in-line 6.
I can see how he mechanically dealt with it ... the bitchen looking fully counter-weighted crank. Must have cost a mint.
I'll give it a try based on my conversation with the builder. There are always trades but there are a few things you don’t get to trade once you make certain choices. The crank is essentially an inline six crank with wider journals so you can hang two rods on each throw. If you are fitting it to a 90 degree V-block you’ve sort of made most of your decisions from a practical standpoint. This engine is set up as essentially two traditional inline six’s sitting next to each other 90 degrees out.
If the engine was in a car, and you were sitting in the driver’s seat, the cylinder numbering convention is just like Ford V8. Start at the front of the right (passengers for left hand drive guys) bank and go 1-6 from front to back and the left (drivers) 7-12. The throws on this crank are oriented and ordered like a Ford inline six and fire 1-5-3-6-2-4. The left bank is the follows same 7-11-9-12-8-10 cylinder across the valley only 90 degrees out of phase. So the V12 order is 1-7-5-11-3-9-6-12-2-8-4-10. Now you could have chosen to change the firing order up and down the crank between cylinders that live at TDC at the same time but that won’t change the phasing of fire in the rotation. Like I said, once you chosen 6 throws, and 90 degree V all you have is the orientation and phasing of each throw/pair of cylinders. For inline 6, the throws are 60 degrees apart with the center two in phase.
So the only way you change the timing of cylinders is change the phasing of the throws or the degree of V between cylinder banks, or try to go to 12 throws. 12 throws would be a weaker crank even if you could make it work in the confines of the Ford V8 architecture. Imagine the cam as well. You can’t change the block architecture if you’ve decided to use a Ford V8. The phasing of the throws is a fairly proven choice with regard to harmonics, crank balancing, and loading for inline 6s, he just has two of them…...so there ya-go. I think Jan basically thought it was the best of the trades given the things that couldn’t be changed. Make sense?
Now how you configure the intake manifold for even fuel distribution may require some attention. You can couple the exhaust on each back just like you would and inline six.
Best,
K