A supplied crank is cut to customer's requirements, balanced, and polished. This modification is suitable for all 4-cylinder engines except those running substantial boost. Benefits are especially helpful (and even critical for sustained operation) at high rpms.
Cranks are reprofiled to improve reduce aero/fluid dynamic drag and overall mass. This is done via carefully profiling the counter weights to cut vs. bash their way through the air and oil that's in the pan. This should follow the first step of using a windage tray and possibly a crank scraper setup. The less oil drags on the crank, the more free it can rev and transmit power to propel the car.
Tech note: Anybody that's revved a sportbike knows that the throttle response is spectacular. They pick up rpms so quickly because the ratio of engine output to engine mass is much higher. There is literally less engine weight for the engine to have to move around. The heaviest moving item in any engine is the crankshaft. So, strategically removing some mass means that more power gets to the wheels sooner and faster. With that said, lighter pistons and rods should be implemented before or at the same time the crank mass is reduced. A light crank with full weight rods/pistons will shake.
Tech note2: The improvement is not quite "VTEC" but is lots better up top than a normal configuration. Instead of a 7200 RPM redline, you may safely rev to 7800, etc. Keep in mind that such rotational speeds are not commonly used on BIG boosted engines. The charger forces the air in vs. the engine spinning faster and faster to move more air. There's just no need to rev like mad. So, given that the benefits are not usually enjoyed and the costs are what they are... Most casual boost enthusiasts do not get involved with knife edging. Hardcore racers will, however.
Tech note3: This service is rendered upon a customer-supplied crank that may either be used or brand new. Given the number of heat cycles that a used crank has been through, there may be tensions built up within the crank due to metallurgical changes. This causes unavoidable warpage about 1.5% of the time according to our statistics. In such case, the crank must be reground and used with oversized main bearings. This service costs $150.
Lead time: 3 - 4 weeks