The new Type−25 features a Cosworth built EJ25 (STI) short block that has gone through countless hours of dyno evaluation to determine the best combination of parts to ensure maximum reliable performance. Each EJ25 short block assembly starts with a brand new Subaru EJ257 case. The case is inspected and then the bores are honed to perfection to receive Cosworth Forged Pistons. Cosworth then balance the rotating assembly, that includes a new STI Forged crank and Cosworth Forged H−Beam Connecting Rods, to within .5 gram.
The selected parts are professionally assembled by one of Cosworth´s skilled engine builders. The same engine builders behind countless Formula 1, Indycar, Champ Car and Formula Atlantic successes. Each engine uses Cosworth’s own coated, tri−metal race spec bearings and blue-printed oil pump ensuring dependable performance in even the most demanding situations. Each short block assembly is inspected and finished off with a Cosworth serial number and build spec sheet to ensure authenticity.
The Type−25 short engine:
Each engine is given a unique build number and all measurements recorded.
For over 40 years, Cosworth has been the leader in innovative multi-valve cylinder head design. Their latest advancement is the Cosworth CNC Ported Big Valve Cylinder head. Modified from OE cylinder head castings, substantial gas flow improvements and upgraded valve train components offer superior performance for your high performance engine.
Cosworth carefully evaluated and tested both the standard STI and Spec C cylinder heads to establish the improvements required to meet the target performance level. Hours of testing and flow bench validation were used to determine the best advanced port design yielding maximum usable power and response. However, there is more to cylinder design than just maximum flow. It is critical that port velocity is maintained to ensure drivability and valve train components are matched to guarantee reliable performance.
Once all of these factors have been tested and validated, the final port contour is digitized. Using the digitized program, Cosworth then reshape both intake and exhaust ports using a 5 axis CNC mill producing an accurate and consistent port shape every time. In addition to re−shaping and enlarging the intake and exhaust ports, the cylinder heads also feature a re−shaped combustion chamber to un−shroud the valves, increasing air flow and performance (STI heads do not feature a re−shaped combustion chamber). After machining, each cylinder head is ultrasonically cleaned, serialized and then hand assembled with select high performance valve train components.
The assembled Cylinder heads are then shipped to the UK where we fit our Type−25 Cam profiles and each head is individually shimmed and modified to accept the Japanese Impreza sensors.
Type−25 Cylinder heads Features include:
