Coronavirus COVID-19: Advice on buying, owning and running a car during the outbreak | No thanks

Two new ultra-low emission petrol engines revealed at Geneva Motor Show

Published 05 March 2019

Despite a show dominated by electric cars and hybrids, an oil company is determined to prove that the internal combustion engine still has a significant future. 

Mazda developed super-efficient Spark Controlled Compression Ignition Skyactiv X gasoline engines, road tested last year here.

Now Saudi Aramco is taking a similar approach with its own ultra-lean gasoline compression ignition engine using Turbulent Jet Ignition. This enables combustion to progress in a stable manner when the fuel-air mixture has been diluted with additional air or exhaust gas.

Operating the engine under dilute conditions reduces the need to regulate air with the throttle, meaning that pumping losses are minimized and engine efficiency is increased. The more stable combustion enabled by Turbulent Jet Ignition also leads to reduced exhaust emissions. 

Saudi Aramco TJI Engine 48v Motor

It works by pre-mixing a small quantity of air and fuel in a pre-chamber. This mixture is then ignited, generating turbulent jets of hot radicals that enter the main combustion chamber, providing a wider distribution of ignition sources than a traditional spark plug. A 48v ‘mild hybrid’ electric motor/generator improves efficiency and drivability still further.

Saudi Aramco Achates Power Opposed Piston Engine 1

Additionally, Saudi Aramco has been working with Achates Power on an opposed piston engine. Not unlike the two-stroke Commer diesel engines of 1940s and 1950s, this has two pistons per cylinder instead of conventional pistons and a crankshaft. The design eliminates the need for a cylinder head and valve train, reducing friction and heat loss, making the engine more efficient, improving fuel economy and reducing emissions.

Saudi Aramco Achates Power Opposed Piston Engine 2

Operating as a two-stroke with central spark plugs combusting fuel between the two opposed piston delivers significantly greater power from a small size engine and up to 50% better fuel economy.

Saudi Aramco Achates Power Opposed Piston Engine 3

Saudi Aramco has also been working successfully on Mobile Carbon Capture that stores up to 50% of the vehicle’s CO2 emissions so they can then be used in the manufacture of plastics. This has been successfully trialed in Ford F-250 pick-ups, Toyota Camrys and in large semi-trailer trucks.

More at:





Mike Tr    on 5 March 2019

Hi John,
Just to let you know the images you show in your article correspond to the so called "1 stroke innengine", not the achates. They both use opposed piston technology but the achates engine has 2 crankshaft whereas the one you show (those blue toys) are the innengine rotative one.

Add a comment


Ask Honest John

Value my car