Watch your fingers

"It's a "Porch-uh"" (ikazuchi)
08/30/2013 at 17:11 • Filed to: 944

Knife-edged crank. Unfortunately not going in my motor (would be cheating... if I got caught).

DISCUSSION (8)

pdthedeuce > It's a "Porch-uh"
08/30/2013 at 17:15

...and I know no one here would EVER cheat...

DocWalt > It's a "Porch-uh"
08/30/2013 at 17:22

mmm... I myself have a knife edged crank sitting around, but I can't decide if it's worth it or not. damn spun bearings ruining my plans!

desertdog5051 > It's a "Porch-uh"
08/30/2013 at 17:30

Nice directional chamfer on the oil holes.

matthewklein220 > It's a "Porch-uh"
08/31/2013 at 04:26

This is new to me, I assume this means less reciprocating mass? And in what series/why would it be cheating?

It's a "Porch-uh" > matthewklein220
08/31/2013 at 23:24

Yes, less weight for quicker revs (both up and down). To really reap the benefits, you also need to run lighter pistons and conrods.

The do have some downsides (which is why you manufactures don't just make them all this way). Not a good idea for high HP/torque motors since you're actually making the crank less structurally sound - in the 944, you're not getting close to the limit. The lack of inertia mass makes it easier to stall the motor in launch conditions - so not a good idea for a drag car (or even a street car).

matthewklein220 > It's a "Porch-uh"
09/01/2013 at 04:47

So is it the quicker throttle response that makes them illegal?

It's a "Porch-uh" > matthewklein220
09/01/2013 at 11:32

And better engine braking.

The main issue in a spec class like this is the increased cost. They want to keep the motor completely stock for parity.

matthewklein220 > It's a "Porch-uh"
09/02/2013 at 17:58

Ah, makes sense.