Mitsubishi Motor Corp. is the acknowledged world leader in gasoline direct-injection (DGI) engine development — and market penetration — but other Japanese automakers are speeding their rampup of the technology.

Toyota Motor Corp. is selling around 20,000 cars per month equipped with its ‘D-4’ direct gasoline injection engine. Introduced in December 1996, the D-4 currently finds use in the 2L Corona, Nadia and Vista and 3L Crown.

The Crown's inline 6-cyl. engine employs a ‘tumble’ swirl flow for gasoline-air stratification, conceptually similar to the approach adopted by Mitsubishi's GDI. The 2L D-4 employs a right-to-left ‘swirl’ flow.

Other Japanese carmakers with gasoline DI engines on the market or in advanced prototype stage include Nissan Motor Co. Ltd., Mazda Motor Corp., Honda Motor Co. Ltd. and Fuji Heavy Industries.

Nissan, in December 1997, began marketing its ‘Neo Di’ gasoline engine, the ‘VQ30DD,’ in the 3L Leopard sedan. Since then the company has expanded its gasoline DI lineup to include the 2.5L ‘VQ25DD’ and 1.8L ‘QG18DD.’ Newly developed 4.5L and 2L versions were on display at the Tokyo Motor Show in October.

The V-6 VQ30DD is available in the remodeled Cedric and Gloria as well as on the XVL, a concept sedan exhibited at the Tokyo Motor Show. The 4-cyl. VQ25DD also is available on the Cedric and Gloria along with the Cefiro, while the 4-cyl. QG18DD has been adopted for the Bluebird, Primera and Sunny.

Also at the Tokyo Motor Show, Mazda unveiled a prototype gasoline DI engine, the ‘DIREC-G,’ which employs a newly developed in-cylinder flow control mechanism to provide optimum air-fuel mixture. The 1.5L 4-cyl. engine, which was featured in the Neospace concept car, adopts a ‘tumble swirl’ fuel-flow concept; the engine provides 104 hp at 6,000 rpm and 111 lb.-ft. (150 Nm) of torque at 3,500 rpm.

Other system components include a sequential valve timing system to improve torque and output, internal and external exhaust gas recirculation systems to limit oxides of nitrogen (NOx) emissions and a new NOx reduction catalyst. The 16-valve engine has dual overhead cams.

Meanwhile, Honda announces development of prototype DI diesel and gasoline engines. The DI gasoline unit, employing Honda's VTEC engine with the injector facing straight down into the piston cavity, boasts a maximum air-fuel ratio of 65:1. The 1.5L engine provides 109 hp at 6,200 rpm and 98 lb.-ft. (133 Nm) of torque at 5,000 rpm. Again, no timeframe was given for its commercialization.