The crankshaft is the center of any engine. It converts the reciprocating motion of the piston and connecting rod into rotational motion. It is the main rotating component to an engine. A crankshaft contains integrated counterweights. These integrally cast counterweights partially balance the forces of the reciprocating piston and reduce the load on crankshaft bearing journals. Commuter friendly vehicles are designed with large counterweights, to stabilize and slow the RPM response. This slow and safe stability offers RPM comfort while working through traffic, or cruising in a steady RPM range down the highway. When quicker RPM response is desired, the heavy factory counterweight hinders the need for a quicker RPM transition. That is where Steve's Lightened and Knife-edged crankshafts are far superior to the factory unit. With common weight reductions in the range of 15-20% of total weight, improved windage, better oil drag profile, and dynamic balance our lightened crankshafts offer crisp and prompt RPM response with minimal parasitic drag.
It is our philosophy to maintain the structural integrity of the factory unit, and focus on excess parasitic weight removal. We will not trade weight for structure, here at Steve's. We pride ourselves on maintaining the strength of the factory crankshaft, while adding the benefits of a more responsive unit.
Performance characteristics of a lightened crankshaft:
1. The engine will accelerate much quicker under load. "Stoplight to stoplight" times are improved.
2. The engine will decelerate much quicker under load and engine braking.
3. You find lightened crankshafts in oval and time attack track cars because their RPM range is so wide(3000-9000) and they must slow down in the turns(less stress on brakes/improved engine braking time). The "quick on" and "quick off" response leads to faster lap times.
Disadvantages of a lightened crankshaft:
1. Because a lightweight crank doesn't have as much inertia, it is easier for an engine to "stumble" at launch on a drag strip. This is especially true in turbo applications with compression drops. They require the consistency of heavy inertia to overcome the turbo lag and launch consistently. Lightened flywheels and crankshafts are usually not recommended for low to moderate boosted engines running low compression. Only extreme performance turbo engines running aggressive anti-lag will realize the benefits of lightened rotating masses. Adversely, naturally aspirated engines and high compression builds traditionally respond very well to lightened rotating masses.
2. If you are hard launching a small engine in a very heavy car, a lightweight crank is probably something you don't want.
3. Some light highway speed "flutter". Since RPM response is maximized, small changes in acceleration offer instantaneous response. Especially when paired to a lightened flywheel, some minimal RPM flutter may be noticed at steady RPM highway speeds. If long distance commuting is more the desired vehicle use, heavy factory units may be more appropriate. Crankshaft lightening is purposed for the high performance/ aggressive driver.