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Fully lightened and knifed the crank in my 2.5, and the 3L. Of course you need to send it to the balance shop. IMO better throttle response, maybe a little quicker spool. Makes the clutch just a little touchy but not bad at all.
I would spend the $ on a crankshaft scraper over a knife edge crankshaft. My 2.5 with just an aluminum flywheel will stall at stop signs. With the knife edge it's worse. You have to bring the curb idle up from stock because of the loss of centrifugal weight. That being said it won't pass California smog because it won't meet their curb idle low RPM specs while performing the smog test, for those if us in Cali. Here is a link that you may be interested in for your biuld. http://www.crank-scrapers.com/Porsch...20failure.html http://www.crank-scrapers.com/Porsche_944.html
I have a knife edged crank in my 968 engined race car. Many seasons of use with no problems. I run it up to 7000RPM regularly. I did have it balanced with the whole rotating assembly. Not sure if there are any other considerations with a boosted engine.
My last lartmobile had a Kep stage I pp and spec lightened fw with a knifed and edged crank, compared to my other lartmobiles and the 100's of 951's that I had the pleasure to drive, this is my assessment; The car does rev very quick and acceleration is also faster, the downside is that torque is a little bit less than usual. I wouldn't mine driving a car with a knifed and edged crank if you get the proper clutch pp and fw setup. Ideally the kep stage I, steel lightened FW and a 930 clutch will be good for about 400rwhp.
I would spend the $ on a crankshaft scraper over a knife edge crankshaft. My 2.5 with just an aluminum flywheel will stall at stop signs. With the knife edge it's worse. You have to bring the curb idle up from stock because of the loss of centrifugal weight. That being said it won't pass California smog because it won't meet their curb idle low RPM specs while performing the smog test, for those if us in Cali. Here is a link that you may be interested in for your biuld. http://www.crank-scrapers.com/Porsch...20failure.html http://www.crank-scrapers.com/Porsche_944.html
How about explaining instead of the +1s. My car came with a knife edged crank and I put it back in when I rebuilt it. It makes sense to me to have the counterweight lightened in combination with lighter pistons and rods and then the whole rotating assembly balanced. The windage tray may not be perfect anymore on the late oil pans that have that.
11-25-2015, 10:21 AM
