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Here we have to differ ~ The M112, M272, M276 are almost turbine smooth. Yes in the case of the 90 degree models they require a balance shaft to make them that smooth whereas the 60 degree does not but the balance shaft does exactly what it is supposed to. If they have ever seemed agricultural to you then something was wrong.
The M276 does make some typical DI noises but it is smooth.
The M272 DOHC & it's predecessor the M112 SOHC are utterly smooth & quiet. They idle without a shake as well.
None of them protest when driven hard either & are willing to be revved.
Here we have to differ ~ The M112, M272, M276 are almost turbine smooth. Yes in the case of the 90 degree models they require a balance shaft to make them that smooth whereas the 60 degree does not but the balance shaft does exactly what it is supposed to. If they have ever seemed agricultural to you then something was wrong.
The M276 does make some typical DI noises but it is smooth.
The M272 DOHC & it's predecessor the M112 SOHC are utterly smooth & quiet. They idle without a shake as well.
None of them protest when driven hard either & are willing to be revved.
We may have to agree to disagree. I found the I-6's used in the 1980s and 1990s to be quite smooth. I thought my Honda V6 had a wonderfully smooth and free-revving engine. Our family's BMW was very smooth (but not quiet).
The E320, C320, and C300's we've had never met the same standards for me, although they're def more refined than the 4-cyl engine. They were certainly not bad, but, IMO, they did feel less refined than the comparable engine from other manufacturers. While none of the newer MB engines (early 2000s) protested about being driven hard, they lacked some sort of quality (IMHO) that made them deeply PLEASANT to drive hard.
I haven't driven the C400 yet, so I can't comment on that from first-hand experience. I do think some US writer(s) stating that they were surprised by some unpleasant sounds higher in the rev range, but I vaguely recall them saying that about the engine in the E-class coupe or cab.
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
We will agree to disagree. My C240 had one of the sweetest engines ever built by Benz & the M272 quadcam 350 in my CLK is super smooth, quiet & responsive. I've always respected BMW's inline six for smoothness if not durability. A close friend has a 335i & we quite often swap cars. We both agree both cars have great engines. The 335i is of course more powerful but that's not what we are evaluating.
We will agree to disagree. My C240 had one of the sweetest engines ever built by Benz & the M272 quadcam 350 in my CLK is super smooth, quiet & responsive. I've always respected BMW's inline six for smoothness if not durability. A close friend has a 335i & we quite often swap cars. We both agree both cars have great engines. The 335i is of course more powerful but that's not what we are evaluating.
We only had the C240 briefly in the U.S, IIRC. I realize that those in the rest of the world were very enamored of the engine. I had drove it for a very brief period (i.e., a few minutes). It struck me as smooth but rather noisy (and not necessarily sweetly so) when revved. I have to admit I was rather confused by why the engine was so popular. But a few min of driving isn't a fair eval.
I very much liked the 3.5 V6 I tested in the SLK. Was never super fond of the SOHC 3.2 V6 or the DOHC 3.0 V6, although I certainly appreciated the power delivery (both much better than the Honda).
I actually found the last-gen of the I6's from BMW to be less pleasant than their predecessors (not familiar w/ BMW nomenclature, so I can't give the engine names), although I still thought that they were excellent engines. We had the NA 3.0 engine from the last gen 3-series (when they changed the name in the US from 325i to 328i). My friend had a 3-series from a generation b/f that, and that car produced a LOVELY sound when started and felt VERY smooth when revved.
For me, the truly "good" MB engines have always been the V8s. We only had one V8-engined MB in our family, but it was lovely (if rather weak.... this was a 380SL). Perhaps trying the C400 will change my mind. And, no, I'm not expecting any 6-cyl engine to deliver the NVH characteristics of a V8, in case you're wondering....
Well the 90 degree engines all shared identical configuration other than No of cylinders. V6, V8, V12 all off the same line at Bad Cannstatt.
The good old M112 SOHC was built just like a racing engine including roller rockers. The 2.6 was certainly the best version & bullet proof.
Well, then perhaps the C400 won't change my mind then.
Question for you Glyn (to any of the other very knowledgable posters).... Could the manner of "breaking in" an engine affect NVH over the long-term? The MB V6 engine cars my family had were mainly driven by my parents later in their careers.... Which means they were generally only drive for a few miles a day at very, VERY low speeds.
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Yes it can. The combination of MOS2 coated rings in Alusil bore does not appreciate too much babying. They need to be treated gently for max 1600Km's & then driven quite hard to achieve proper break in. As long as temperature remains stable you know you don't have a tight engine. Constant moderate throttle should be avoided during break in. The run-in oil should NOT be changed early.
Thereafter they thrive on fairly hard driving. They were true LEV engines at the time with
fully captive breather systems. They were designed to run on Eurograde fuels. In markets like the US & SA where the fuel is less ideal (SA is only going Euro 4 now) They fouled themseves quite badly.
The variable inlet runner tracts would foul up badly & deposits would form on the zero lash hydraulic tappet elements which could cause noise from the valve train. Enthusiastic driving tended to mitigate this somewhat. At the same time MBUSA was pushing 13,000 mile oil drain intervals with less than ideal fuel. This was later sensibly reduced to 10K miles like ROW which changed at 15,000Km's even with Euro 4 & above fuel.
Been at a Mercedes Driving Academy event and one of the nicest, sweetest engines at full pop, shrieking down the start/finish was an SLK350, and among a group of NA 6.2s I might add!
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Originally Posted by coladin
Been at a Mercedes Driving Academy event and one of the nicest, sweetest engines at full pop, shrieking down the start/finish was an SLK350, and among a group of NA.2s I might add!
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Originally Posted by Glyn M Ruck
Yes it can. The combination of MOS2 coated rings in Alusil bore does not appreciate too much babying. They need to be treated gently for max 1600Km's & then driven quite hard to achieve proper break in. As long as temperature remains stable you know you don't have a tight engine. Constant moderate throttle should be avoided during break in. The run-in oil should NOT be changed early.
Thereafter they thrive on fairly hard driving. They were true LEV engines at the time with
fully captive breather systems. They were designed to run on Eurograde fuels. In markets like the US & SA where the fuel is less ideal (SA is only going Euro 4 now) They fouled themseves quite badly.
The variable inlet runner tracts would foul up badly & deposits would form on the zero lash hydraulic tappet elements which could cause noise from the valve train. Enthusiastic driving tended to mitigate this somewhat. At the same time MBUSA was pushing 13,000 mile oil drain intervals with less than ideal fuel. This was later sensibly reduced to 10K miles like ROW which changed at 15,000Km's even with Euro 4 & above fuel.
Alsyli. Another consideration we all have to accept is that as we move forward to leaner & leaner burn engines so they become more "brittle" feeling from a driveability perspective. The latest Benz stratified charge DI engines are getting into that area. They early pulse the injector to allow higher CR without knock & then multipulse thereafter to ameliorate the effect.
An engine running well below stoichiometric will always be smoother & more driveable across the rev range at the expense of fuel consumption.
As we progress in making the internal combustion engine more efficient we will likely see a progression to more ratios in the auto box or CVT's with ultra lean burn engines operating in a narrower rev range to optimise output while maintaining driveability. They will probably be uninspiring things to listen to.
Benz Diesotto engine might yet get into production as well to obviate pumping losses.
Last edited by Glyn M Ruck; Dec 5, 2014 at 08:49 PM.
Alsyli. Another consideration we all have to accept is that as we move forward to leaner & leaner burn engines so they become more "brittle" feeling from a driveability perspective.
(snip)
Benz Diesotto engine might yet get into production as well to obviate pumping losses.
::sigh:: I can only comment on my subjective experience since I'm not an engineer (and have nowhere near that level of understanding). Hearing a BMW I6's and V8's firing up in a small garage from several yrs was a wonderful experience. I suppose I shouldn't expect more modern engines to sound that way. And hearing that BMW may be moving to V6 is... sad. But, as you say, at least the more modern engines have other benefits.
I also have to say that our MB I6's and the Honda V6 didn't feel super smooth until we had driven them for tens of thousands of miles. WITH lease deals being so good here in the US, we generally don't keep our car for more than a few yrs.
Do you know when Diesotto (or the GM equivalent) will be introduced? Didn't MB put it in a concept nearly 10 yrs ago??? I'm ready for the next revolution in combustion engines. =)
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
The Diesotto 1800cc was shown in reliable running form in 2007. I had the good fortune to be allowed to drive one in an S Class mule on a race track in Spain. IIRC it produced just on 400Nm of torque. It's acceleration was amazing.
Bottom line ~ building a variable compression engine is too expensive for series production at present.
The internal combustion engine is likely with us for a long time to come. One good thing is Benz is learning a lot about hybrids from the F1 programme.
I still think that Hydrogen fuel cell has a lot to offer. The problem being a distribution network. Petroleum & electricity networks are in place.
There is a very good white paper out from the ExxonMobil Corp on why IC still makes sense.
Last edited by Glyn M Ruck; Dec 7, 2014 at 11:08 AM.
Just to close the loop on this, I test drove both the c300 and c400, and decided to go with the c400. My observations (clearly layman):
the 400's engine was very smooth for me, it provided more than enough power, while never feeling any lurch or vibrations.
the 300's engine was powerful enough as well, but I noticed that the turbo took a second to engage, and I could feel the vibrations in the cabin a bit more at rest than the 300.
Just to close the loop on this, I test drove both the c300 and c400, and decided to go with the c400. My observations (clearly layman):
the 400's engine was very smooth for me, it provided more than enough power, while never feeling any lurch or vibrations.
the 300's engine was powerful enough as well, but I noticed that the turbo took a second to engage, and I could feel the vibrations in the cabin a bit more at rest than the 300.
Indeed. Most of it is just down to the engine configurations (cylinder layout, firing order, etc.) and the noise and vibration they each produce. In general, I4s produce more NVH than V6 and are harder to isolate and again with V6 versus V8. I never liked the way I4s performed (and sounded) so have had V6s most of my life and have enjoyed them. Now in the last few years of finally getting into some V8s, its again another level above V6s in terms of power delivery and NVH performance.
I would have bought the C400 if I had driven it earlier before buying my C300, but either way it's all good...The c400 has a crazy experience and makes you have such form of bravado while driving it, 😁👍🏻.. Quality over quantity always speaks best, you may feel like the quantity of fuel that will be saved by the C300 is the reason to get one of it, but it won't really give you such feeling !
The M276 is enough of a reason to get the 400 over the 300
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I found the I-6's used in the 1980s and 1990s to be quite smooth. I thought my Honda V6 had a wonderfully smooth and free-revving engine. Our family's BMW was very smooth (but not quiet). 
