Toyota unveils new diesels with advanced thermal insulation combustion; 15% more fuel efficient, 25% more torque; 44% thermal efficiency

2.8-liter 1GD-FTV direct-injection turbo diesel engine. Click to enlarge.

Toyota has introduced a new line of turbodiesel engines with more torque, greater efficiency and lower emissions. The new GD engines feature Toyota’s next-generation advanced thermal insulation diesel combustion to reduce cooling loss significantly.

The use of Thermo Swing Wall Insulation Technology (TSWIN) helps make the 2.8-liter 1GD-FTV engine one of the most thermally efficient, with a maximum thermal efficiency of 44% (measured in-house). Despite smaller engine displacement in comparison to the current KD engine, maximum torque is improved by 25% and low speed torque improved by 11%, while fuel efficiency has received a 15% boost.

Toyota will gradually phase out the current globally deployed KD diesel engines and replace them with GD engines. By 2016, production will reach approximately 700,000 units a year with introduction in approximately 90 markets, set to expand to at least 150 markets by 2020.

The newly developed 1GD-FTV is currently available in the new Hilux small pickup truck launched in Thailand in May 2015, and in the partially redesigned Land Cruiser Prado launched in Japan on 17 June. The same engine lineup includes the 2GD-FTV 2.4-liter direct-injection turbo diesel engine.

GD engines main specifications
	1GD-FTV	2GD-FTV
Displacement	2,754 cc	2,393 cc
Bore/stroke ratio	92×103.6 mm	92×90 mm
Compression ratio	15.6	15.6
Maximum output	130 kw (177 PS) @ 3,400 rpm	110 kw (150 PS) @ 3,400 rpm
Maximum torque	450 N･m (332 lb-ft) @ 1,600-2,400 rpm	400 N･m (295 lb-ft) @ 1,600-2,000 rpm
Low speed torque	370 N･m (273 lb-ft) @ 1,200 rpm	330 N･m (243 lb-ft) @ 1,200 rpm

Advanced thermal insulation diesel combustion. Toyota’s new advanced diesel combustion system features a number of elements. A port shape more conducive to air intake significantly increases the amount of air flow into the cylinders—some 11% greater with the new GD port than with the port used on the previous generation KD diesels.

Precise pilot injection matching the state of the ambient air occurs before the main injection to shorten ignition delay, achieving stable combustion even in the world’s harshest environments, while ensuring quiet operation and high thermal efficiency.

A newly developed piston combustion chamber shape and a common-rail fuel injection system that achieves higher pressure and more advanced control of fuel injection pressure are used to optimize the injection of fuel into the combustion chamber. This maximizes air consumption, enabling higher thermal efficiency and lower emissions.

Due to the world-first use of Thermo Swing Wall Insulation Technology and the use of silica-reinforced porous anodized aluminum (SiRPA) on the pistons, cooling loss during combustion is reduced by approximately 30%. SiRPA is a high insulation and dissipation material that is easy to heat and easy to cool.

In a 2013 paper describing the Thermal Swing concept, Toyota engineers noted that the surface temperature of the commonly-used metals for combustion chambers—i.e., iron or aluminum—have almost constant surface temperatures udring the whole engine cycle. As a result, the difference of temperature between the working gas and the wall surface during the combustion period is large. This is the main cause of heat loss in the combustion chamber.

Traditional adiabatic engines, including the engines with ceramic thermal barrier coatings, cause almost invariably high temperature on the wall surface during the whole cycle including the intake stroke…and result in decrease in the volumetric efficiency, increase in working gas temperature, and facilitate the occurrence of engine knock.

On the other hand, using a “Temperature Swing” coat, which is a low-heat-conductivity and low-heat-capacity material, on the combustion chamber walls, leads to a large change in surface temperature. … the surface temperature with the insulation coat follows the transient gas temperature, which decreases heat loss without heating intake air.

—Kosaka et al.

In that 2013 paper, the Toyota engineers also noted that the effect of the “Temperature Swing” coast is larger in a turbocharged diesel engine than in a naturally-aspirated diesel engine. They attributed this to two factors:

• The larger temperature fluctuation of the wall due to large heat transfer coefficient based on both higher cylinder pressure and higher gas flow speed in diesel engines.
• The larger reduction rate of the temperature difference between the working gas and the combustion wall surface resulting form the lower peak of gas temperature.
• Another factor is that the exhaust energy increased by heat insulation is recovered with a turbocharger.

Turbocharger. The new compact high-efficiency variable geometry turbocharger (produced in-house by Toyota) used by the GD engines is 30% smaller than its current equivalent, and features a newly developed turbine that improves efficiency, and a newly developed impeller that provides instantaneous acceleration response and produces maximum torque over a wide range of RPM.

By reducing size and increasing efficiency, the newly developed turbocharger with the GD engine delivers approximately a 50% faster response in the rate of boost pressure increase.

Toyota-first urea selective catalyst reduction (SCR) system. Use of Toyota’s proprietary, compact, high-dispersion urea selective catalyst reduction (SCR) system eliminates up to 99% of emissions of NO_x. This will help vehicles conform to Euro 6 and the 2010 emissions standards set by Japan’s Ministry of Land, Infrastructure and Transport.

Resources

• Kosaka, H., Wakisaka, Y., Nomura, Y., Hotta, Y. et al. (2013) “Concept of “Temperature Swing Heat Insulation” in Combustion Chamber Walls, and Appropriate Thermo-Physical Properties for Heat Insulation Coat,” SAE Int. J. Engines 6(1):142-149 doi: 10.4271/2013-01-0274