w204 engine line-up (c class) - petrol and diesel

[hutch789]

Hi guys

I've been looking at getting a second hand C class estate (W204 model) but I'm a little bamboozled with all the changes to the engine line-up Mercedes have made since it was first introduced.

I would appreciate anyone's input of with an overview of the different engines and the relevant changes (and when they were introduced).

From my own research, I have found out the following:

Petrol
Initially a kompressor/supercharged engine, changed to a turbo later on (I beliebe when CGI came out). CGI fuel injection system also uses uprated piezo injectors.

The facelift model has increased efficiency/power output (i.e. 1.6 engine used in c180/1.8 for 250) - not sure what the engine changes were to enable this?

Mercedes also added the eco stop/start to the blueefficiency range.

Diesel

In particular, the v6 320 cdi became the 350 cdi - but later on the output increased massively a particulate filter was added. When were these changes and what did Mercedes add to increase the power output.


I would be grateful if anyone can help by giving me an overview of the changes and when they happened, etc.

Also - wanted to know - do Merc still use the piezo injectors after all of the recalls in the c200/220/250 models when first released? And have all the issues been ironed out?

Thanks in advance.

 

[cbhp]

Hi guys

I've been looking at getting a second hand C class estate (W204 model) but I'm a little bamboozled with all the changes to the engine line-up Mercedes have made since it was first introduced.

I would appreciate anyone's input of with an overview of the different engines and the relevant changes (and when they were introduced).

From my own research, I have found out the following:

Petrol
Initially a kompressor/supercharged engine, changed to a turbo later on (I beliebe when CGI came out). CGI fuel injection system also uses uprated piezo injectors.

The facelift model has increased efficiency/power output (i.e. 1.6 engine used in c180/1.8 for 250) - not sure what the engine changes were to enable this?

Mercedes also added the eco stop/start to the blueefficiency range.

Diesel

In particular, the v6 320 cdi became the 350 cdi - but later on the output increased massively a particulate filter was added. When were these changes and what did Mercedes add to increase the power output.


I would be grateful if anyone can help by giving me an overview of the changes and when they happened, etc.

Also - wanted to know - do Merc still use the piezo injectors after all of the recalls in the c200/220/250 models when first released? And have all the issues been ironed out?

Thanks in advance.

Im going to seem lazy here however if you search for c class w204 in wikipedia it gives an exact breakdown of what I think you want in a table half way down the page.

 

[grober]

The piezo injectors used in CGI petrol engines while using the same principle will be a different design to those used in the first Diesel blue efficiency engines that gave all the trouble. For starters they run at a lower operating pressure---- this because the compression ratio on petrol cars is much lower than on compression ignition = diesel engines which rely on a high compression ratio to ignite the fuel rather than a spark plug.

 

[hutch789]

The piezo injectors used in CGI petrol engines while using the same principle will be a different design to those used in the first Diesel blue efficiency engines that gave all the trouble. For starters they run at a lower operating pressure---- this because the compression ratio on petrol cars is much lower than on compression ignition = diesel engines which rely on a high compression ratio to ignite the fuel rather than a spark plug.

Thanks grober

Is this also the reason why the injectors did/do not appear to be an issue on the 320 / 350 either - the injectors on the 2.1 diesel operate at a much higher pressure than the petrols and 3.0l diesel?

 

[grober]

Nope the V6 diesels will have similar compression ratios to the 4 cylinder diesels. There are variations across the model range however the C200cdi blue efficiency diesels always had solenoid injectors while its more powerful bretheren the C220 CDI BE and C250CDI BE had the problematic piezo injectors--- now changed to solenoid of course. Its possible the V6 diesels also had solenoid type injectors from a different manufacturer. [Bosch rather than Delphi?] There were so many variations on these injectors I can't give you a definitive answer sorry.

 

[hutch789]

Im going to seem lazy here however if you search for c class w204 in wikipedia it gives an exact breakdown of what I think you want in a table half way down the page.

Thanks cbhp - believe it or not I did go thorugh that page but I hadn't got down to the table you spoke of.

It contains a lot of relevant info - although that said, it doesn't tell me why (or what), for example, why the bhp went up for the 2011 350cdi - what engine changes caused this?

And what changed between the CGI and 180K (other than move from supercharger to turbo).

Your help is much appreciated.

 

[grober]

The torque and fuel efficiency increase on the turbo from kompressor petrols stems directly I believe from the move from indirect [ manifold] to direct [cylinder head] fuel injection and associated cylinder head modifications? Just to confuse things there was a shorted lived earlier CGI [direct injection] version of this M271 engine but it was never imported to the UK and stopped production in 2005.

 

[markjay]

Supercharger provides extra power all the way up from idle, while turbocharger only kicks in when the revs are high enough.

The compression ratio on turbocharged engine is deliberatly reduced to accommodate for the higher induction pressure when the turbo is on, hence the comparatively low-power feel of a turbocharged engine when in low rev.

I am aware that we all know that, and my point is this - could it be that the turbocharger helps reduce the car's official emission figures and increase official mpg figures because the car is being driven sedately during the test and off the turbocharger? If so this might explain a thing or two regarding MB's engine lineup...

 

[cbhp]

Thanks cbhp - believe it or not I did go thorugh that page but I hadn't got down to the table you spoke of.

It contains a lot of relevant info - although that said, it doesn't tell me why (or what), for example, why the bhp went up for the 2011 350cdi - what engine changes caused this?

And what changed between the CGI and 180K (other than move from supercharger to turbo).

Your help is much appreciated.

It's all very complicated, there was a c180K 1.8, C180K Bluefficiency 1.6 and then the c180 cgi 1.8. As far as I know the engine is different between the K and CGI. However im not sure. From reports I have heard the K seems to have little lag but is less efficient. The move to turbos was for fuel efficiency but seems to have introduced slightly more lag. I have also heard that the CGI engines are more refined and have direct injection. I am not sure about the diesel models but it has a lot to do with direct injection and a larger turbo or different turbo combination.

 

[grober]

Supercharger provides extra power all the way up from idle, while turbocharger only kicks in when the revs are high enough.

The compression ratio on turbocharged engine is deliberatly reduced to accommodate for the higher induction pressure when the turbo is on, hence the comparatively low-power feel of a turbocharged engine when in low rev.

I am aware that we all know that, and my point is this - could it be that the turbocharger helps reduce the car's official emission figures and increase official mpg figures because the car is being driven sedately during the test and off the turbocharger? If so this might explain a thing or two regarding MB's engine lineup...

Don't think so. For best fuel consumption you want the car to be developing maximum torque- this would not be achieved " off boost" These variable vane turbo-charged petrol engines develop a very flat max plateau to their torque curve at extremely low rpm-- starting at 1,500 rpm irrc? They derive their better fuel consumption from the inherently better thermal efficiency of the turbocharged engine where waste heat in the exhaust is reconverted to useful energy to compress the air charge to the engine whereas the kompressor is essentially "parasitic" requiring engine power to drive it. In practical terms the difference is slight but was the reason "allegedly" that Mercedes changed from supercharging to turbocharging.

 

[hutch789]

So, in sum...

The injector issues affected only the c220/250 cdi models, pre-facelift? The petrol CGI and C350 cdi were not affected?

The turbo is more fuel efficient but causes lag.

That sound about right?

 

[hutch789]

sorry - did the injector issue affect the c200 cdi at all?

 

[grober]

sorry - did the injector issue affect the c200 cdi at all?

No always had solenoid injectors--- ironic the cheapest lowest power single turbo version of the OM 651 was the most reliable till the present injector upgrade.

 

[grober]

So, in sum...

The injector issues affected only the c220/250 cdi models, pre-facelift? The petrol CGI and C350 cdi were not affected?

The turbo is more fuel efficient but causes lag.

That sound about right?

The latest direct injection turbo petrol engines have negligible lag.Certainly nothing you would notice in day to day motoring particularly with an auto box.

 

[misfire84]

thats good to know I am picking up a 250 CGI tomorrow !

 

[hutch789]

No always had solenoid injectors--- ironic the cheapest lowest power single turbo version of the OM 651 was the most reliable till the present injector upgrade.

When did Merc upgrade the C200 CDI injectors - on the 2011 facelift?

Thanks again for your very informed advice, grober

 

[grober]

The single turbo C200 OM651 had solenoid injectors from its release. All the earlier OM 646 engines were solenoid injected.