What you can apply from this information: Exotic parts may not fit your budget. However, with research, you may be able to find an older configuration of your engine which had smaller main and rod journals. When properly set up, this will reduce friction (and power loss) at higher engine speeds. Carefully measure your crankshaft. If it is very straight and has consistent journal sizes, try setting up clearances at the low limit of their traditional (recommended) tolerance. This should increase oil film thickness and reduce friction. However, you must be very careful when using this strategy. If there is any error, you will experience a spun bearing.
Crankshafts In the last five years, significant developments have occurred in crank design and supply, at least at the Cup level. For example, five years ago, finished Cup cranks cost less than $3,000. Today, caused by some of the exotic materials being used, the billet of steel alone will cost this much. In fact, a finished crank can cost significantly more than $10,000. What has changed that has driven up these costs? In short, just about everything. What has been gained by using these exotic crankshafts? The improvements include reduced friction and a low moment of inertia (MOI), which helps the vehicle accelerate and improves mechanical efficiency via increased stiffness.
Most crankshafts are ground and then nitrided with a relatively thin layer of nitride. The current trend in Cup crankshafts is to have a very deep nitride layer with grinding after nitiriding. The nitride layer is very hard but brittle. A thin nitride layer provides a hard, wear-resistant surface with a ductile (flexible) core underneath. Nitriding also improves the fatigue performance of the steel. Deep nitiriding can significantly improve the fatigue performance of the crankshaft, which allows the design to optimize the section for reduced mass or MOI.
Any imperfections in the steel can cause stress and cracking, if the nitride layer surrounds them. For this reason, deep nitriding requires much "cleaner" steel. During smelting, imperfections are removed by re-melting the steel and removing the imperfections from the top layer of molten metal. The more frequently this process is repeated, the "cleaner" the steel becomes, but the smaller the yield (total metal produced). As a direct result, ultra-clean steel is very, very expensive. This explains why an ultra-clean billet may cost as much as a finished crank, five years ago.
Like most forms of heat treatment, nitriding can cause distortions in the part. Crank manufacturers go to great lengths to minimize these problems, even though they cannot be completely eliminated. Also, to improve the dimensional accuracy of a crankshaft, a deep nitride layer may be applied before removing some material by a finish-grinding process. By finish-grinding, following nitriding, significant improvements may be made in the following areas:* Concentricity of all bearing journals* Alignment of all bearing journals* Accuracy of the stroke (from cylinder to cylinder)
Improvements in the bearing journal size and alignment, when coupled with tighter bearing clearances, will reduce friction. An improvement in stroke accuracy will allow engines built closer to their compression ratio limit or to simply have more compression, if no limit exists.
Today, crankshaft designs are separated into two configurations:* Low inertia to help the engine and car accelerate* High stiffness to improve oil film thickness and reduce friction