It won’t save the planet, but Peugeot/Citroen’s new diesel micro-hybrid system is still worth having

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.

On a Citroen C5 or Peugeot 508, it’ll save more like 10g/km of CO2 – but that’s still not a great deal. It also encourages you to coast along out of gear in town, which we wouldn’t recommend as a driving technique.

As a cheap and unobtrusive way to make PSA cars a little more efficient, however, we approve of e-HDi. On a typical new Peugeot or Citroen, the system should cost you a few hundred pounds as of later this year, save you 15 per cent on urban fuel consumption, and deliver savings on VED road tax too.

If it proves reliable, it would be among the first options we’d choose.

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Matt Saunders

Matt Saunders Autocar
Title: Road test editor

As Autocar’s chief car tester and reviewer, it’s Matt’s job to ensure the quality, objectivity, relevance and rigour of the entirety of Autocar’s reviews output, as well contributing a great many detailed road tests, group tests and drive reviews himself.

Matt has been an Autocar staffer since the autumn of 2003, and has been lucky enough to work alongside some of the magazine’s best-known writers and contributors over that time. He served as staff writer, features editor, assistant editor and digital editor, before joining the road test desk in 2011.

Since then he’s driven, measured, lap-timed, figured, and reported on cars as varied as the Bugatti Veyron, Rolls-Royce PhantomTesla RoadsterAriel Hipercar, Tata Nano, McLaren SennaRenault Twizy and Toyota Mirai. Among his wider personal highlights of the job have been covering Sebastien Loeb’s record-breaking run at Pikes Peak in 2013; doing 190mph on derestricted German autobahn in a Brabus Rocket; and driving McLaren’s legendary ‘XP5’ F1 prototype. His own car is a trusty Mazda CX-5.

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Add a comment…
artill 10 June 2010

Re: Citroen C3 1.6 e-HDi

Uncle Mellow wrote:
BMW diesels have stop-start and "efficient dynamics" but they don't call them hybrids because they cannot be driven on battery power alone. Why are |Autocar not telling us how far this hybrid Citroen can be driven on battery power alone ? Pretty poor article.

The point of destinction is the combined starter/alternator which these have and BMW dont (as far as i am aware). But i agree to me and everyone else that doesnt make it a Hybrid, even of the Micro type.

Of course it cant be driven anywhere on battery power only, but then neither can the Honda Hybrids, which are proper hybrids

Uncle Mellow 10 June 2010

Re: Citroen C3 1.6 e-HDi

It must be battery powered , or it wouldn't be a hybrid. BMW diesels have stop-start and "efficient dynamics" but they don't call them hybrids because they cannot be driven on battery power alone. Why are |Autocar not telling us how far this hybrid Citroen can be driven on battery power alone ? Pretty poor article.

catnip 10 June 2010

Re: Citroen C3 1.6 e-HDi

beachland2 wrote:

there are lots of cars with stops starts, but they are not classified as hybrids, why is this a hybrid? its not powered by a battery is it.

That must be why they call this a micro-hybrid rather than a hybrid.

Whatever next......