What is it?
A Citroen C3 powered by Peugeot-Citroen’s EU emissions legislation trump card: a micro-hybrid diesel powertrain called e-HDi.
By 2012, PSA is aiming to sell a million cars in Europe every year that emit less than 120g/km of CO2, and most of them will be powered by this engine.
Diesel-sipping ‘stop-starts’ are much less common than petrols because, since diesel engines have higher compression ratios, heavier crankshafts, flywheels and balancer shafts and greater internal friction, they take more re-starting. Those diesel micro-hybrids that do exist use beefed-up starter motors and gearing systems that, claims PSA, are unsuited to fast, smooth hot starts.
So the French automaker has developed a stop-start system driven not by the car’s starter motor but off its alternator. Backed up by two ultracapacitors as well as a conventional battery, the alternator motor can supply 50 per cent more torque to the crankshaft than a conventional ‘ISG’.
That means its gearing can be higher and its engine restart performance faster. And because the stop-start system has a separate belt drive, it restarts the engine more quietly and smoothly than others too.
What’s it like?
The e-HDi system will appear on PSA diesels ranging from 1.4- up to 2.0-litres. In a 1.6-litre Citroen C3, it’s smoothness and speed of operation was very impressive indeed.
Here’s how it works. In a manual, the car must be in neutral and your foot off the clutch before the system will cut in. You don’t have to be stationary: below 13mph it’ll kill the engine if it thinks you don’t need it, but can restart it within 400 miliseconds.
Faster than you can dip the clutch and re-engage a gear, in other words.
Should I buy one?
Perhaps not if you’re looking to make an environmental statement. Despite its low rolling resistance tyres, taller gear ratios, low viscosity gearbox oils and intelligent ancilliaries, e-HDi is only worth five grams per kilometre on a car like the C3.