The newly introduced 4B11 DOHC 16V turbo MIVEC engine is the latest talk of the town as engineers and performance tuners have lined up to get their hands on the new powerplant in hopes of unlocking the hidden mysteries that have shrouded the Mitsubishi powerplant. When we left off, the Tomei Powered engineers had gone into extensive details on the 4B11 T/C upper cylinder head. As we continue our second and final analysis, we should point out that the 4B11 found in the milder version Mitsubishi Lancer rated at 152 hp and 146 lb-ft of torque, while the 4B11 T/C inline-four turbo found within the Lancer Evolution and '08 Lancer Ralliart sold in North America delivers a factory rating of 295 hp and 300 lb-ft of torque. Both engines sport the same 2.0-liter displacement but were designed and built by Mitsubishi engineers to handle two completely different power levels. The 4B11 T/C was designed by Mitsubishi with a lower compression ratio (9:1) to handle boost and consists of numerous reinforcements to withstand a higher generated horsepower. The most significant change from the 4G63 engine to the new 4B11T was the change in material used in the block design. The 4B11 block, the first engine in the Lancer Evolution series that uses a die-cast aluminum cylinder block, is comprised of a lighter aluminum construction, which is considered a huge change compared to the previous cast-iron 4G63. Mitsubishi managed to save 27 pounds using the lighter aluminum from its previous cast-iron setup. But has the cost of shedding a few pounds and a new block design jeopardized the legendary Mitsubishi Lancers reputation for a nearly bulletproof bottom end? Before you jump to any conclusions, read on as Tomei Powered completes their analysis of the 4B11.
Four-Bolt Crank Cap Increases Block Strength
For each journal, four bolts clamp down each of the crank caps to increase the block strength and rigidity. This design is widely seen in V-style engines and not much so in inline or straight-style engines. Four bolts provide more strength than the conventional two-bolt style and is a step in the right direction for Mitsubishi engineers.
Cylinder Block That Endures High-Power Output
The newly engineered aluminum die-cast block features a half-skirt design, which was incorporated to decrease the overall length of the engine. The bore pitch measured in at 96mm compared to the popular SR- 20DET engine that measures 97mm. The crank caps are equipped with four bolts and the two-structure ribbed oil pan is designed to provide rigidity and strength to the aluminum block. The deck areas are reinforced at the necessary areas and provide plenty of strength and support. The rear section of the four-cylinder didn't receive strengthening, which raises concern if the unit will be affected by the transmission. The emphasis on stress dispersion can be seen on the internals of the block. A smooth design (no rough edges) at the blow-by tunnels/ oil pan entrance and exit, and the connecting portion between the crank journal to the inside of the block shows that this engine is not affected by applied stress.
Semi-Closed Deck Design For Longevity And Endurance
The 4B11 is equipped with a semi-closed deck design with cast sleeves, which promotes longevity while cooling the engine significantly. The water jacket is designed so that it isn't affected by the bore structure, especially when installing the head bolts. This design makes changing the sleeves an easy task.