Japan on a big clean-up
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Tokyo's recent motor show was an important and hugely successful showpiece for Japan's automotive industries with much publicity given to greater environmental considerations.
by Bryan Jarvis • Japan has given a high priority to cleaning up the environment. It has banned the use of freon (chlorofluorocarbon) gases as a refrigerant, parts cleaner and foaming resin and there have also been numerous prototype electric, hydrogen, CNG and methanol-powered trucks.
The development of complete concept trucks and buses has taken a back seat mainly due to the industry's huge investment in low-emission lean burn" engines.
Major manufacturers such as Hino, Isuzu, Mitsubishi and Nissan have new engines to meet or exceed Japanese (and overseas) exhaust and noise emission levels. These tough measures came into force last year setting long and short-term emissions targets.
With so much traffic congestion in Japan, trucks tend to tick over for longer periods and run at much lower average road speeds than in Europe. This loads the atmosphere with exhaust gases so the new legislation lays down minimum levels aimed at correcting this condition.
The Japanese have devised their own 15-mode test cycle to reflect this type of use. On this cycle, the regulations lay down emissions limitations at maximum output of 6.0g/kWhr for nitrous oxide (NOx), 2.9 g/kWhr hydrocarbons (HC). 7.4g/kWhr carbon monoxide (CO) and 0.7 for particulates (PM).
Hino has looked at a variety of ways to cut emissions using a concept model with electronic high-pressure injection system, turbo compounding, exhaust gas recycling, ceramic coated pistons and main roller bearings.
Its latest engine for heavier models is a long stroking (122x150mm) 326hp (243k NV) P11C charge-cooled 10.5-litre straight-six fitted with cast-iron pistons and a new HSFT mixed-flow turbocharger. A new impeller design is said to give optimum air flow across the speed range.
According to an overseas divi sional head Seiichi Uchida: "We still favour our long-stroke diesel for its high torque and long in-service life characteristics. It will meet the required standards", he adds.
Hino currently fits J-series lowemission engines in its Rising Ranger middleweights. This comprises a 5.3 litre in-line four, 6.6-litre five and 8.0-litre six-cylinder models, all naturally-aspirated engines with 114 x 130mm bore and stroke.
A charged-cooled J08C(J-1A) version of the larger engine uses the same Nippondenso's common rail fuel injection system currently being evaluated by Renault. Uchida says it reduces vibrations as well as improving on NOx emissions.
The J08C develops 200hp (147kW) at 2,900rpm and 3911bft (530Nm) of torque at 1,700 while its specific fuel consumption is 211g/kWhr on full power.
A familiar four valves per cylinder design with roller rocker arms, the sump is double skinned with extra panelling below the mid-way line to cut noise. This engine becomes available in Japan from December.
Isuzu has four new low-emission engines including a chargecooled 12-litre six for its Giga range and the flagship tractor's huge 22.8-litre naturallyaspirated V-12.
Mitsubishi's new 6D40 supercharged EGR 12-litre engine uses compound turbocharging, exhaust gas recirculation and a new electronically controlled unit injection system. It is fitted with a catalyst to break down NOx and electro-conductive ceramic filters remove black smoke.
The 61)40 is claimed to be the first to use a power turbine to regenerate exhaust energy into motive power and a supercharger to boost the intake. This unit is driven by shaft output for extra torque and sharper response, whereas at medium and higher speeds regenerated exhaust power takes over improving fuel efficiency.
In addition there's a constantvelocity transmission unit with planetary gear mechanism linking the supercharger and power turbine. This regulates the boost pressure by cutting supercharger speed at low engine loads when less air is needed for combustion.
At higher speeds or loads any excess turbine power is then directed to the engine output shaft giving, says Mitsubishi, a 10% power increase and 5.0% improvement in fuel consumption.
There's still room for large naturally-aspirated engines like the 420hp (313kW) 21.2 litre V-8 in its Super Great-X concept vehicle which meets Japan's 1994 emissions standards.
Nissan too has new low emissions engines available including the new naturally-aspirated MD92TC1 beneath its ATP-4 concept cab. This is a 9.2-litre in-line six with 125x125mm bore and stroke and uses Nippondenso's common rail fuel system to deliver 220hp (164kW) at 2,700rpm.
Nissan has also developed a new 7.0 litre FE6A DI unit with exhaust gas recycling plus a mighty naturally-aspirated V-10 engine. The 493hp (368kW) 26.5-litre RH10 has four valves per cylinder and comes with Nissan's own engine retarder plus ESCOTT-11 semi-auto transmission as standard.
Japanese manufacturers still place great faith in large-capacity, long-stroking naturallyaspirated engines meeting environmental limits but more "square" charge-cooled engines are also appearing.
Whichever hi-tech path Japan's mighty moguls decide upon, they will certainly have to do so quickly and thoroughly because its strong currency problems will not go away. There are rich rewards on offer and Europe's engineering giants are on their tail.
• By 1997 vehicles up to 3.5 tonnes will hove to meet even more severe limits; NOx 4.5, HC 2.9, CO 7.4 and PM 0.25. These will apply to vehicles up to 12 tonnes a year later followed by the rest of the heavies around the end of 1999.
Euro-2 limits differ slightly with 7.0 NOx, 4.0 CO, 1.1 HC and 0.15 particulates while likely figures for our Euro-3 levels fall to 5.0, 2.5, 0.7 and 0.12. But these figures are calculated on a different test cycle.