Junon

so a buddy of mine is building his motor, and his crank needs to go to the machine shop. i've heard of knife edged cranks, but what kind of benefits are there to gain? are there any downsides (ie, short life span) blah blah. any info is appreciated.

Jarrod

What kind of car? Boosted, NA?

NEO_WRX

from my understanding, a knife edged crank is utilized in a very high revving N/A set up. When the crank will be turning well past 9K a "knife edge" will literally help it "cut through" fluids achieving the desired rotational speed with less difficulty.

...i think

gear

pretty much summed it up. there is a myst of oil in the engine, and the knife edge helps to cut/rotate faster. Alot of NA guys swear by it.

eng

Unless you plan on running really RPMs getting that done to a crankshaft is kind of a waste of money as it doesn't really do much for power until the higher revs. My guess would be 10-15HP at 9000 RPM.

I hope that's not the only thing that's getting lightened in the rotating mass. Granted I doubt knife edging the crank really takes the weight down all that much, so it might be all right.

However, why spend money on something if you're just half-assing it anyway? There's better things to spend money on before resorting to knife edging the crank.

Junon

good info, thanks for the help. saved us some money =P

eng

Maybe saved money is the wrong word, more like postponed

Junon

true.. anyway you look at it, building a motor is a moneypit :\

Enigma

N/A apps need all they can get, dropping 2 lbs. or so at the crank while lightening the flywheel will not net any gains, only free up power that was already there that was turning those lbs. This will help the motor rev quicker and help it turn faster (higher RPM's).

Boosted apps might actaully see more problems with this than gains.