Steve Dinan has been building high performance and racing engines for BMW’s since 1977, winning 11 racing championships including 3 prototype championships and two 24 Hours of Daytona. The same engine shop that builds the racing engines also builds the street car engines; these talented engineers, machinists, and builders have built hundreds of engines from OEM street rebuilds to full-blown racing engines.
The S55 engine is not designed to take a large increase in boost beyond the OEM spec. Due to the design of the crankshaft, it is known to have the timing chain sprocket spin on the end of the crankshaft, causing the cams to go out of time. In extreme cases, the valves can hit the pistons, causing catastrophic damage. Furthermore, the S55 only has half of a normal crankshaft thrust bearing.
If you are planning a large power increase with bigger turbos, CARBAHN Autoworks has designed a high-performance engine to handle very high outputs by pinning the cam sprocket to the crankshaft. To ensure durability we also machine the block to accommodate a full circle thrust main.
In addition, we utilize higher quality racing Carrillo connecting rods. If you have not yet experienced an engine failure, your stock pistons can be reused. In case of previous failure, or simply as an option, we offer forged CP pistons as well.
This rebuild kit is based on the durability upgrades of pinning the crankshaft and adding the full thrust main bearing. If you would like to rebuild your own engine, the pistons and rods can be purchased separately.
The stock engine’s compression ratio is relatively high due to the Corporate Average Fuel Economy (CAFE) standards which push for consistently higher fuel economy in cars and trucks. However, this increased compression limits engine performance with higher boost settings by decreasing the size of the fuel-air charge in the combustion chamber, forcing the ignition timing to retard far below MBT (Maximum Brake Torque, the theoretical optimal ignition timing). Therefore, the CARBAHN Autoworks S55 engine has 0.5 less compression to optimize the engine for the increased boost. In an emissions-legal street car, the lowered compression has the added benefit of reducing catalyst inlet temperatures and improved drive-ability on pump gas.