When Honda unveiled the Integra Type R in 1997, the company said the engine made more naturally aspirated horsepower per liter than anything else built on an assembly line. It said the 1.8-liter four-cylinder boasted the highest piston speed of any automotive engine in the world, faster even than those found in the company’s Formula One and IndyCar powerplants. As a result, that engine, the B18C5, cemented itself in automotive lore, a piece of engineering that helped forge the company’s reputation for high-revving, reliable power.
Engineers left nothing on the table, according to a technical guide released by Acura in-period, stretching the dual-overhead cam, four-valve architecture to its most ludicrous limits. It started with the valvetrain. The B18C5 uses lightweight valves with thinner stems than those found in the standard Integra GS-R, which help the engine spin to its 8000-rpm redline. At that speed, those feathery valves open and close nearly 67 times per second, and Honda had to turn to dual valve springs to keep up. Even the profile of the coils had to be changed on the intake side from circular to ovular, the latter offering greater strength.
Then there are the cams, each with higher lift and greater duration. The VTEC variable valve timing system increased lift by nearly a full millimeter on the intake side, and 1.1mm on the exhaust end past 5700 rpm. It also threw in an additional 10 and eight degrees of timing, respectively.
Honda needed as much air flow as possible through the head, so workers polished the intake and exhaust ports by hand to reduce turbulence. Atmosphere entered via an upsized, 62-millimeter throttle body and a lightweight cast-aluminum intake. The design uses short, single runners for each intake port, saving more than seven pounds. Engineers even reworked the fuel injector angle, aiming the nozzles directly at the intake valves to keep fuel condensation at a minimum to increase throttle response.
The block is more or less the same cast-aluminum design found elsewhere in the Honda family, though engineers added an integrated stiffener. The crank is a different story. Forged, balanced, and polished to reduce vibration and friction, it is a necessary part of the recipe that allows the engine to spin so quickly, and to do so without tearing itself apart. Same goes for the forged connecting rods. Each set were weighed, matched, and hand-assembled at the factory to help keep the engine balanced.
Even the bearings were different. In the early ‘90s, Honda’s Formula One engineers discovered that by electroplating the crank bearing surfaces of their 3.5-liter V-12 with tetramethyllead, they could create microscopic pyramids. The shapes were perfect for retaining oil at high rpm, which reduced friction. It was brilliant. Inexpensive, simple, perfectly effective-a Honda solution. The bearings showed up in several other Honda products, including the Acura Legend, but they allowed engineers to narrow the B16’s connecting rods by 2 mm to create the B18’s 17.5 mm pieces, shifting the mass to the crank webs where it could provide needed strength.
US cars produced 195 hp with a 10.6:1 compression ratio. The B18C5 can thank its fancy pistons for that. They are works of art, and Honda threw the full brunt of its racing experience at their creation. Made from high-pressure die-cast aluminum, they are strong and light, with skirts slathered in molybdenum to keep friction at bay. Engineers carved new oil paths along the piston’s underside to help lubricate the wrist pin. Knowing that heat management and lubrication are the cornerstones of longevity, Honda also threw in a set of oil jets aimed at the underside of each piston to keep the rotating assembly as cool as possible.
So much of this is common practice now, when automakers are hell-bent on squeezing every last possible bit of efficiency from their engines, but in 1997, it was wild. Honda took all of its race-winning black art and threw it at a production engine. The miracle is that the B18C5 is not some ticking time bomb because of it. It’s as reliable as the sunrise. As insane as ever, and at the heart of what turned the Type-R into collector catnip. The Integra's engine was a glimpse at the future from beneath a red valve cover.
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