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The Cosworth VR38 connecting rods have also just been released. These rods were designed for 200 hp EACH. The rods are made from EN40B (similar to SAE4340). The pin end bushes are a high quality bronze material superior to most stock shelf rods and all Chinese rods. Cosworth rod bolts are made of H11 tool steel. Also notice the lightening pockets on the big end to the sides of the big end bore. This is another detail added to further reduce rotational mass without sacrificing strength.
Another A feature designed to reduce reciprocating mass is the radial truss feature on all Cosworth rods. The trusses allow weight reduction without sacrifice in strength. It also reduces flex and twisting of the pin end which further reduces stress on the piston’s pin bosses. The entire Cosworth connecting rod program was optimized with FEA to produce a rod that is optimal for the specific application.
The OE Nissan door stop weighs in at 722 grams. 6 rods = 4332 grams or 4.33 kg (9.546 lbs.).
A set of Cosworth rods = 3.72kg. That’s a weight savings of 0.61kg (1.34 lbs.) over the stock door stoppers. Couple the weight savings with a set of Cosworth pistons and you’ll save another .384 kg (.847 lbs) for a total reduction in your rotating assembly of 0.994kg (2.19 lbs.). All while making everything significantly stronger and increasing reliability at higher RPMs.
What does this all mean to a VR38 @ 8000rpm? Quick calculations reveal a reduction of 1178.74 pound-force per cylinder every time the piston and rod assembly goes up and down. If a GT-R were on a road course and was on track for a 30 minute session with an average RPM of say 7000 rpm (you gotta love the twin clutch transmission), the crankshaft would have had to deal with 378,075,600 less pound-force (7000 rpm * 30 minutes * 2 reciprocating accelerations * 900.18 pound-force per acceleration event) per cylinder for that 30 minute session. How’s that for increasing reliability and decreasing the chances of a failure occuring? We are talking a huge reduction in the requirement for oil film strength and a massive reduction of stress on both the rod bearings, crankshaft, and main bearings. Keep in mind this is just a quick calculation to illustrate how component weight reduction can reduce stresses within an engine over time without taking into account details such as infinite life of steel (of the crank), force at different crank angles, etc.
Coming soon from Cosworth are 4.0L stroker engines and components, camshafts, cams, more big bore and different thickness head gaskets, H-11 tool steel head studs, etc. We’ve had discussions of inlet plenums and cylinder heads in product development meetings as well. Stay tuned for more news and details on Cosworth VR38 components. For now, visit the Cosworth USA website by clicking the link below for more information.
