I’ve been wanting to write an article about the venerable Japanese twincam engines for a while now. I was initially attracted to the Japanese car scene through magazine features of large turbo-charged behemoths such as the R32 Skyline and the JZ-series Supras. As I delved deeper however, it was the smaller engined cars that really grabbed my attention. In popular culture these small-but mighty vehicles enjoy a reverence on a par with their substantially more powerful brethren. More often than not, the engines behind these cars were 1.6 litres, twin overhead cammed with only 4 cylinders. Three such engines really stand out, the 4-AGE from Toyota, and the ZC and B16A from Honda.
The 4-AGE was first launched in 1983 and was a joint collaboration between Yamaha (who designed the cylinder head) and Toyota. It was one of the first 4-cylinder engines to combine fuel-injection with the 4-valves per cylinder layout and dual camshafts (one operating the intake valves, the other the exhaust). The engine was immortalised through its usage in the legendary AE86-chassis Sprinter/Levin RWD hatchbacks. Initially it only produced a lowly 120hp and lacked the later sophisticated variable valve timing of the Honda VTEC engines. It did however feature the innovative T-VIS system, which had secondary butterfly valves in the intake manifold that opened at 4200rpm, and helped low down torque without sacrificing the need for greater air volume at higher RPM’s. There were numerous incarnations, including the ‘Red-top’ version, the most powerful of the 16 valve 4-AGE’s. For this version, produced in 1989, Toyota bumped the compression ratio to 10.3:1 and ditched the T-VIS system. In this guise the engine was rated at 140hp. These early engines were not only used in a wide-variety of Toyota production vehicles, the AW11 Mr2 and the N-series Corolla Gti’s but also retro-swapped into a whole host of other cars, such as the older KE70 Corolla, the KP61 Starlet and even non-Toyota’s, in particular the ’74 to ’87 Daihatsu Charmant. The 4-AGE survived until 1998, by which time it had evolved into a 165hp heavyweight. Toyota increased the number of valves per cylinder to 5 (20 valves in total), introduced VVTi (Variable Valve Timing) technology and even went so far as to use 4 individual throttle bodies on the intake side. This highest spec 4-AGE is colloquially known as the ‘Silver-Top’, due to its silver camshaft/head cover.
Honda introduced its own 1.6 litre Twincam engine in 1984 and shared very similar specifications with Toyota’s 4-AGE. The ZC engine, again, had a 4-cylinder layout with 4 valves per cylinder with twin overhead camshafts. It was rated at slightly more power (130hp) but there were many variations both in Japan and Europe/USA (where it bore a D- series stamp). It initially featured in the AT Civic and AS CRX Ballade models with the ‘Brown-top’ designation but later also featured in the EF3/7, Civic/Crx and the DA Integra as the ‘Black-top’. The engine was effectively shelved in 1991 after the resounding success of the more powerful B16A engine. It was however, reintroduced for a brief factory run on the limited edition EG5 Civic Si which commemorated both Honda’s 20th Anniversary and the fact that the new EG-series Civic won Japans ‘Car of the Year’ award for 1991-92.
This is not the 1.6 engine for which Honda became famous for though, instead that accolade goes to the B16A. This engine was the first of-its kind to feature the pioneering VTEC system. VTEC operates by switching the camshaft profile at a pre-defined point (often at around 5600rpm) to a much more aggressive one. This means that it negates the poor low-rpm characteristics of high-lift camshafts and effectively creates a dual-engined vehicle; one that is happy to run at 1500rpm through town, with enough power to satisfy the humble commuter, whilst offering lightning-quick performance at higher rpm. In its initial incarnation in the DA6 Integra Xsi the engine produced 160hp (1st Generation), whilst later models such as the EG6 Civic SiR and Ek4 Civic SiR had power bumped to 170hp. I have detailed the differences between the two generations in my EG6 Guide. The first generation engine is more commonly associated with the EF8 CRX and the Civic equivalent, the EF9. This is because of the DA6 not being released in Europe, and America’s lack of enthusiasm for small sports cars preventing many of the more powerful engines being released there. In its 2nd generation guise, the B16A produced an astonishing 106hp per litre, unmatched by many of its contemporaries, and still impressive nearly 20 years on. Indeed, if we compare it to the Ferrari F355 of the same time period, its 3.5 V8 only produced marginally more @ 109 hp per litre. It goes to show what an important breakthrough the B16A was when Honda decided to use the VTEC system on its NSX supercar in 1991, and that 20 years on, nearly all small engine vehicles use some form of variable valve timing.