World’s Smallest Diesel
The DaimlerChrysler Smart FourTwo features the world’s smallest direct
injection diesel engine. The 800c turbo 3-cylinder develops 33kW at just 3800
Over the European fuel test cycle, the FourTwo diesel engine gives fuel
economy of 3.3 litres/100km and emits just 88 grams of CO2 per kilometre.
Fuel injection pressure is 1600 Bar and 7-hole injectors are used. A large
amount of exhaust gas is recirculated – as much as 60 per cent of exhaust gases
are cooled and then returned to the combustion chambers.
As is the case with other current direct injection engines, the
electronically-controlled diesel uses a pilot injection squirt that ignites and
preheats the cylinder, reducing noise emissions.
A tiny turbo is fitted. The compressor has a diameter of only 33mm but it
rotates at up to 280,000 rpm. A maximum boost pressure of 1.2 Bar is used. The
small turbo and diesel configuration allows for low-rpm torque development –
85Nm is available at just 1500 rpm!
However, the 770kg car is abysmally slow – 100 km/h comes up in a fraction
under 20 seconds and top speed is only 135 km/h.
Most Economical 5-Seater
Volkswagen claims their Polo BlueMotion is the most economical 5-seater in
The 59kW 1.4 litre 3 cylinder develops maximum torque of 195Nm at 1800 rpm.
As with other VW diesels, the BlueMotion doesn’t use common rail injection but
instead pump nozzle injection that’s electronically controlled. A turbo with
variable geometry turbine is used.
Over the standard Polo TDi, the BlueMotion features exhaust gas recirculation
(EGR) with a more powerful cooler and electronically controlled flow valve.
Taller gear ratios are used for gears 3, 4 and 5 in the 5-speed manual
Low rolling resistance 165/70 14 tyres are fitted and the Polo body feature
aero tweaks to get its drag coefficient down to 0.30.
Fuel consumption is listed as 3.8 litres/100km, corresponding to a CO2 output
of 99 grams/kilometre. Performance is also quite respectable – the Polo
BlueMotion can accelerate to 100 km/h in 12.8 seconds and reach 176 km/h.
The Fun Bubble
Not a tiny car like the original, nonetheless the new Fiat 500 can still
claim to be amongst the most economical of cars in its class. It uses in one
model a 16-valve, 1.3 litre (closer to 1200cc – it’s actually 1248cc) common rail
diesel that develops 55kW at 4000 rpm and 145Nm at 1500 rpm.
A fixed geometry turbo is used in conjunction with a wastegate and
Fuel consumption of the 980kg car is 5.3 l/100 km in the urban cycle, 3.6
l/100 km out of town and 4.2 l/100 km in the combined cycle, and CO2 emissions
are 111 g/km. The engine weighs only 130kg and is 50cm long and 65cm tall. As
with the other cars covered here, a particulate trap is used in the catalysed
exhaust and recirculated exhaust gas is cooled.
Performance includes a 0-100 km/h time of 12.5 seconds (measured two-up with
an additional 20kg!) and a top speed of 165 km/h.
But where’s Japan?
With their love of big brawn, you might expect that the US is not going to
have a super economical diesel-powered entry – but where is Japan in the
development of tiny car diesels?
In anyone’s terms, Japanese engineers have long been masters of superbly
built and engineered small engines. But diesels, while manufactured in large
numbers for export cars (and export and domestic commercials) are almost
invisible in Japanese car sales. Recent numbers show annual sales of a little
over 2000 diesel cars in a market of just under 6 million!
So the jewel-like turbo 660cc and 1 litre cutting-edge diesels that you might
expect to see being produced in Japan, powered in development by local demand,