German Car Forum

New perfect refined diesel engine:

New generation of four-cylinder diesel engines from Mercedes-Benz leads the way

Injection with the fourth generation of the common-rail principle
The new diesel unit from Mercedes-Benz ushers in the fourth generation of the tried-and-tested common-rail direct injection technology. The distinguishing characteristic of the latest generation is the increase of 400 bar in the maximum rail pressure, which now equals 2000 bar. This rise in pressure potential was of crucial importance for boosting the engine's output to 150 kW/204 hp and its torque to 500 Nm, whilst at the same time bringing about a marked improvement in the engine's untreated emissions.
Piezoelectric injectors which are a completely new development form one of the key components in the fourth-generation CDI technology. They harness the ability of piezoelectric ceramic to alter its crystalline structure with microsecond speed when an electrical voltage is applied. The actual spatial movements produced are tiny however, For this reason, the new injectors are fitted with a piezo stack, which is basically made up of piezoelectric elements connected in series. In contrast to the customary systems used to date, the movement of these elements controls the injector needle directly and enables even greater alterations in volume that are accurate to within a few thousandths of a millimetre. The benefits of this are in increase in the available injection volume as well as particularly fine and fast metering of the injection quantities. This enables the fuel injection process to be adapted to the momentary engine load and rev speed with yet greater exactness - by means of high-precision multiple injections of fuel for example - which has a positive impact on emissions, consumption and combustion noise. Plus, the engine runs even more quietly when idling than its predecessor.
As a result of the innovative actuation concept, injector operation is completely leak free. This dispenses with the need for a leak oil line to return the negligible quantities of fuel that used to accumulate unavoidably in the system on account of the operating principle. This improves the injection system’s thermal circuit to such an extent that, even at a rail pressure of 2000 bar, fuel cooling is super-fluous to requirements. Not only does this save energy, it reduces the high-pressure pump’s operating energy input by around one kilowatt at high engine loads.
In order to continue to deliver optimum injection quantities over the engine’s entire service life, an adaptive learning function is able to compensate for any tolerance deviations that may occur as a result of minimal component wear.
200 bar ignition pressure and optimised combustion chamber
The fuel is injected into a combustion chamber with a meticulously devised geometrical form that includes the precision-calculated recesses in the piston crowns. Compared to the engine it replaces, the combustion chamber has been made flatter and the diameter somewhat larger. The compression ratio was reduced from 17.5 :1 to 16. 2 : 1. This optimises the combustion process by achieving a lasting reduction in untreated emissions - NOx levels in particular have been cut drastically.
One of the determining factors for maximum power output and for fuel consumption at full throttle, from an emissions point of view, is the maximum ignition pressure. With a pressure of 200 bar, the new four-cylinder diesel from Mercedes-Benz is one of the top-ranking passenger car diesel engines in this regard. To guarantee spontaneous starting, the engine is fitted with ceramic glow plugs which attain a temperature approximately 200 degrees Celsius higher than metallic glow plugs (1250°C as opposed to 1050°C) and are virtually wear-free. Mercedes-Benz put these glow plugs into series production for the first time in the predecessor diesel engine.
Two-stage turbocharging for high torque at all engine speeds
The new diesel unit draws the air it needs to breathe from not one but two turbochargers, marking the first ever instance of two-stage turbocharging in a series-manufactured passenger car diesel engine from Mercedes-Benz. The aim of this concept is to eliminate the inherent drawbacks of a single-stage turbocharger. These include, for instance, the moment of inertia of a large turbocharger, which drivers may perceive as sluggish start-off characteristics (turbo lag). What’s more, it is virtually impossible to reconcile good start-off abilities and maximum power along with low fuel consumption even at full throttle when deploying just a single-stage turbocharger.
The compact-sized module for the new two-stage turbocharging concept consists of a small high-pressure (HP) plus a large low-pressure (LP) turbocharger. Both comprise a turbine and a turbine-driven compressor, and are connected with one another in series:

The key data

250 CDI
220 CDI
200 CDI
Number of cylinders
4
4
4
Valves per cylinder
4
4
4
Displacement, cc
2143
2143
2143
Bore/stroke, mm
83.0/99.0
83.0/99.0
83.0/99.0
Compression ratio
16.2:1
16.2:1
16.2:1
Output, kW/hp
150/204 at 4200 rpm
125/170 at 3200 -4800 rpm
100/136 at 3000 -4600 rpm
Torque, Nm
500 at 1600 - 1800 rpm
400 at 1400 - 2800 rpm
330 at 1600 - 2800 rpm

Oh.. nothing new on the actual car.... This is actually a repost

Why 3 variants though? Seems to me just 2 should do, the 170hp and 204hp variants.

Now bring the C250 to the U.S. and you'd really have something.

M

Because in Europe there are tons of people who see 170-horsepower as completely excessive. Remember, these people grew up with cars that had as much as 45- to 80-horsepower and they drove completely fine. In todays realistic driving conditions a 136-hp C200 CDI is completely adequate for these same people, if not a bit overpowered already. Most pepple won't speed or race so why would they need 170-horsepower? I've driven the current C200 CDI and it's not bad in midrange acceleration - you can overtake trucks etc. with relative ease.

This also makes sense for business fleets, where many C-Classes are C200 CDI / C220 CDI models.

The C250 CDI is gonna be a blast to drive,is it available yet to order in Germany?

Have not heard anything about it up at the dealer yet.

Cause there is a need for a low end for the A and B-class. Many car in the same price even sport less than 136hp, but the torque should do for instant thrust in such a small car. The 250CDI should toast that little sucker powering the 353d.

Are you talking about the next generation A and B. Because the way this engine is made I believe it will be too much for the A and B chassis to cope.

Really? 330Nm a little too much? Kind of right since most people driving the A-class don't need that much thrust. But the chassi should be able to handle that, no?

No, I think the power is just about right. I was leaning more towards the size and weight of the engine itself, it's based off an iron block and I think all the engines including the diesels in the A and B are aluminum based. That and the special sandwich structure of them call for are particular engine design.

I think maybe next yeap i will change my 220cdi for a 250cdi if it come to sa

The Mercedes answer to 23d engine. Donñt like when they look to the neightbour ideas.

^^ The neighbout idea? What, MB shouldn't do a motor then? MB were first to offer a diesel, BMW shouldn't have, is that right?

They are replacing the 200cdi by a 200cdi with the same power, the 220cdi by the 220cdi with the same power, and the 320cdi by a 250cdi with the same power, and then boost the 320cdi to offer 250/260hp like a 400cdi.

Where please are they looking at the neighbour? Sometimes it's just good to remove the BMW-glasses...

lol

It is an answer to the 123d from BMW but that doesn't mean Mercedes "copied" BMW. Engine and power updates are a continual feature of this industry.