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Citroën Upgrades the C4

The new C4.

Citroën has upgraded its popular C4, which has sold nearly 900,000 units since its launch in 2004. In addition to styling tweaks and an interior redesign, the new C4 is now available with two new gasoline engines co-developed with BMW, and a new 2-liter HDi diesel that is the first in this engine family to comply with the future Euro 5 standard.

With low-rolling resistance tires, several versions of the C4 with the HDi 92 or HDi 110 paired with a manual or EGS6 gearbox can limit their CO 2 emissions to less than 120 g/km.

HDi diesels. The C4 range now offers the largest yet selection of Airdream engines, covering the 1.6-liter versions (HDi 92, HDi 110 DPFS with a manual gearbox and EGS6) and 2-liter versions with a manual gearbox. Airdream is Citroën’s  “eco-signature” label.

The 2-liter HDi unit has been upgraded to comply with the future Euro 5 standard. Fitted as standard with a particulate filter, the new HDi 140 DPFS develops 103 kW of power (140 bhp EEC). Fuel consumption is 5.3 L/100 km (44.4 mpg US) over a combined cycle, while CO2 emissions are down to 140 g/km.

Fuel consumption of the other diesel units—the HDi 92 (with or without DPFS) and HDi 110 DPFS—with low-rolling resistance Michelin Energy Saver tires is 4.4 L/100km (53.5 mpg US). CO2 emissions are 117 g/km, 119 g/km and 118 g/km, respectively.

Gasoline engines. The C4 is now available with two gasoline engines from the EP family co-developed with the BMW Group. It is the first Citroën to be fitted with engines from this family. The VTi 120 replaces the 1.6i 16V, and the THP 150 replaces the 2.0i 16V.

Mainly through better management of intake, the VTi (Variable valve lift and Timing Injection) 120 engine offers more power with low fuel consumption and lower CO2 emissions. The C4’s VTi 120 engine has a capacity of 1,598 cm3 and develops 88 kW EEC (120 bhp EEC) at a speed of 6,000 rpm, for maximum torque of 160 Nm (118 lb-ft) at 4,250 rpm. Ninety percent or more of maximum torque is available between 2,500 rpm and 5,750 rpm.

Mated to a five-speed manual gearbox, the engine returns 6.7 L/100 km (35 mpg US) and 159 g/km of CO2 over a combined cycle, down 6% on the old unit. The VTi 120 unit also ships with a four-speed automatic for fuel consumption of 7 L/100 km (33.6 mpg US) and CO2 emissions of 165 g/km.

Fitted with an aluminum block and cylinder head, the 16 valves of the VTi 120 are driven by intake and exhaust camshafts with continuously variable valve timing. The intake valves also benefit from a variable raising system that allows the valves’ maximum travel to be adjusted gradually depending on the force applied to the accelerator pedal. These two features boost engine efficiency, increasing the responsiveness of the vehicle through higher available torque, especially in the most frequent driving conditions (part loads).

With direct gasoline injection and a turbocharger—both technologies a first on the C4 range—the new THP (Turbo High Pressure) 150 offers both high performance and low consumption. The new unit develops maximum power of 110 kW (150 bhp EEC) at 5,800 rpm, for maximum torque of 240 Nm (177 lb-ft) from 1,400 rpm to 4,000 rpm, with 156 Nm of torque available from as low as 1,000 rpm.

Mated to the new MCM six-speed gearbox (with the same architecture as the EGS6), fuel consumption over a combined cycle is 6.9 L/100 km (34 mpg US) for 164 g/km of CO2, down 10% on the previous engine.

The C4 is also available with a four-speed automatic gearbox, for maximum power of 103 kW (140 bhp EEC). Maximum torque remains the same, at 240 Nm at 1,400 rpm. Combined-cycle fuel consumption is 7.7 L/100 km (30.5 mpg US), down 5% compared with the previous powerplant.

The THP 150 engine and the THP 140 version use the same architecture as the VTi 120. The THP engine (for Turbo High Pressure) features direct sequential injection fed by a high-pressure electronic pump mounted at the end of the intake camshaft. Maximum pressure of 120 bar allows the injectors to spray the mixture directly into the combustion chamber sideways, ensuring uniform distribution. The compression ratio is 10.5 to 1.

A twin-scroll turbocharger groups the gas ducts by pair (cylinders 1-4 and 2-3) in the exhaust manifold. The optimal gas flow combination this provides makes the turbine extremely fast-acting and considerably cuts down on lag time. The turbine can rotate at up to 200,000 rpm, developing pressure limited electronically by the discharge valve to 0.8 bars. Turbocharging is noticeable from 1,000 rpm.

The intake camshaft benefits from continuous variable timing, which provides more torque at low engine speeds while reducing fuel consumption and CO2 emissions.

An oil pump with throughput regulation supplies the right amount of lubrication for optimal functioning and reduces fuel consumption by 1%. This system also features an oil intercooler, fitted in the filter and regulated by a thermostat, for faster heating and better temperature management, even during rough handling.

The new C4 will have its world premiere at the Moscow International Motor Show, which opens on 26 August 2008.



As always, the diesels impress... but seeing that the USA is not yet embracing diesel technology (due to numerous factors- higher diesel fuel tax being just one) let's take a closer look at their gasoline powerplants.

The gasoline direct-injection turbocharged TH140/150 are quite impressive.

A high 10.5 compression ratio allows 177ft-lb torque while returning 34mpg- this is quite good for gasser ICEs! Perhaps these engines might find their way into a US Nissan product?


DH, you have your French car companies confused. Renault and Nissan are working together. Citroen is owned by Peugeot. Apparently these guys are working with BMW, but they've got nothing to do with Renault or Nissan.


I'd like to see an updated version of the THP 150 in a BMW e92 body. Sweet functional ride...

"Fuel consumption of the other diesel units—the HDi 92 (with or without DPFS) and HDi 110 DPFS—with low-rolling resistance Michelin Energy Saver tires is 4.4 L/100km (53.5 mpg US). CO2 emissions are 117 g/km, 119 g/km and 118 g/km, respectively."

It really begs the question as to why anyone would look at paying the extra for a hybrid doesn't it?


Nice to see a well organized article with so many facts and so little hype.

It was a little jarring to see this:

"Mated to the new MCM six-speed gearbox ..... fuel consumption ...... is 6.9 L/100 km (34 mpg US) for 164 g/km of CO2, down 10% on the previous engine."

For a moment I wondered if CO2 was down or mpg was down. (The usage is correct, 'mpg' is in parenthesis.)


117 g CO2/km from a car of this size!
and 149 from the C5 !
In the meantime Fiat have taken the lowest European CO2 average away from PSA (Peugeot-Citroen) who held this record for 2006.

You're not going to see these kind of figures on a BMW.
Together with Mercedes they hold the worst averages in Europe.
Even if you did (which ain't going to happen any time soon), the quality/price ratio simply wouldn't be there.....


@anon (please provide a name!):

It really begs the question as to why anyone would look at paying the extra for a hybrid doesn't it?

A few things to bear in mind:

A diesel carries a price premium too. I believe for the C4 it is around 2000 euro's (in Germany).

The reason for people buying a more expensive hybrid instead of a diesel can be financial. In Europe you generally pay more tax for a diesel. So the money you save for a diesel, you lose in higher road tax.

A hybrid based on a downsized THP engine could probably get even lower CO2 emissions.


"You're not going to see these kind of figures on a BMW."

...except for the Mini which is made by BMW, sold in the US, has the same engine and gets similar mileage.

Bear in mind that the European combined cycle is much more generous than the EPA test. Just about everybody who comments on this site mentions that they beat the EPA mileage figures (I know I do, and by quite a bit).

Henry Gibson

Since the US government refuses to do anything about the speculation in the non free market of crude oil, The US government might as well make extra money and put a tax on imported crude just like europe does. The high efficiency of these diesel engines should scare the supporters of fuel cells. It is amusing that CO2 per mile has become important, but larger engines on cars are still sold. What happened to the CV-2(two horsepower) type cars? India? Now is the time to import more French nuclear power into Germany so that the French can build more nuclear power plants, and Germany can use plug-in-hybrids that use mostly electricity. The Netherlands now buys much hydro power from Norway at greatly reduced prices over the new cables. Electric plug-in-hybrids might even pay for themselves. ..HG..

Carter Lee

High static compression ratios increase cylinder pressures and return better efficiency until somewhere around 16:1 on gasoline. Detonation can be avoided by light throttle input. On these engines direct injection is the Chevron combustion Pattern. In 1950 this was patented. It shoots a gasoline spray at and near the spark plug. It works like a stratified charge lean burn where drastic leanness exists everywhere in the cylinder except by the spark plug. Pumping losses and radiant heat losses However, are the bain of IC engines.

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