Moto_Guzzi

Informative information.

I have a practical suggestion:Why not somebody with a new V6 with enough milage to witness buildup if there is going to be, take his car for an non intrusive examination via plughole, is this possible, with photos ?

Glyn M Ruck

Your self imposed myopia clearly inhibits your learning.

I could suggest some good reading but it's obvious you don't read much. You prefer being a Google parrot.

BTW - At the present time DI gasoline pistons are heavier than equivalent non DI designs. Much is being done to mitigate this.

I've been involved with my company's racing endeavours all my life - 2 & 4 stroke racing motorcycles, Motocross, Supercross, Enduro, Indycar, NASCAR, F1, DTM, Modified saloons & even some diesel racing with VW. My ear is very close to the ground. My hearing is also well maintained so that I can enjoy my audio hobby despite the excessive time spent in altitude compensated dyno rooms over many, many years.

Glyn M Ruck

A fine suggestion. I intend watching a friend's car. Unfortunately I no longer have an Olympus camera to fit my old boroscope.

MinnBobber

I am talking about the DI M276 motor/ pistons, the subject of this thread....

MBRedux

It would require removing the cowl and possibly the intake port, thus involving warranty issues. The spark plug is way too behind the intake valves to see anything significant.

MBRedux

I see the confusion. Here, please look again. This is the M276 Piston: (Please note: This M276 piston does not have a cone crown.)



This is the OM642 Diesel Piston: (This OM642 does have a coned crown.)



Not to get too complex with this, simply, the only similarities between these two pistons beside the fact that they are connected to rods via pins, contain rings, (although completely different in design, construction and composition) and have indents for valve clearances, is.... absolutely.... Nothing!

Glyn may have some of you fooled, but I stand by my comments and my 40 years of racing engine building knowledge.

2012c350

As long as you don't break anything, I don't see how it could involve any warranty issue.

2012c350

Based on your years of building race engines...when would you consider a new C350's engine being considered "broken in" enough for a dyno run? IE, how many miles?

Glyn M Ruck

Please explain the purpose of the toroidal cavity in both pistons. Toroidal cavities have been a feature of diesel pistons for years due to DI. The pre DI piston of the M272 was flat - no toroidal cavity. The gasoline piston in fact has a slight dome at the base of the toroidal cavity whereas the diesel has a more pronounced cone due to larger diesel droplet size requiring greater swirl as I've explained previously. Don't be fooled by the heavily "airbrushed" picture of the M276 piston. It's not accurate. Here is another Benz application of a similar DI piston design in which the slight dome is more clear due to chroming of the piston for display. However the main common factor in Benz DI gas & diesel engines is the toroidal cavity not present on non DI engines.



Here is the new Chrysler Pentastar engine that shares DNA with the M276 but is not DI. Note no toroidal cavity in non DI application.



For further reading on the subject I suggest publications by the likes of Sean Bennett. White papers presented to SAE etc. Do your own research. There is much written on the subject. Just make sure it's recent.

Glyn M Ruck

You can see the inlet valve tulip clearly with a 90 degree lense fitted to a steerable boroscope by going down the plug hole with the valve cranked open. A 120> deg lookback lense will give you a bad look at the porting. Unlikely to be satisfactory.

Frankly - monitoring the valve tulip will probably be adequate.

Even with port injection the fuel based cleaners like Techron could only clean where they could get. The rest of the porting got fouled.

Pic of M271 on Techron. Fouled where fuel can't get & pretty normal. Valve tulip spotless.

MBRedux

Boy for a guy who wasn't going to comment, ("There will be no further comment from me on this issue.") you sure have done your share, and by the looks of these pictures and comments, rather confused too.

Nonetheless, that picture is not of the DI M276, and if I read you correctly, is not down the "plug hole" as you indicate but a view down the intake chamber port with the manifold off, like I said earlier.

I believe you are trying to defend your reputation here rather than be truthful with the membership. So I apologize if you feel challenged, threatened or something in any way, but you have proven to me that you are simply making stuff up to save face.... playing with us by first offering to investigate, then backing off that offer (which made me think you're really a phony) which then only added to the "conspiracy" fears you accused me of but actually started instead. By refusing to contribute to the OP true concerns, you offer no information other than misimformation! How long has that been going on here? Yikes!




A = Down the intake port toward the valves. (Where your picture was taken although not of this engine.)

B = Twin Intake Valves showing location of valve seat #1 relative to the injector nozzle location with the hope that this will help with the carbon issue.

C = Piezo Direct Injector located TDC (#4 - injector tip) and forward, closer to the intake valves.

D = Spark plug located down lower than Intake Valves and between the exhaust valves. (Thus any camera probe (even with a swivel head) down the plug hole (#5) will not see the intake valves very well.)

#2 = Piston Crown showing no cone. The recess crown is typical for turbo engines including turbo diesels to reduce overall compression ratios. Now if you were to look at the other picture of the non turbo V6 DI M276, this depression is far less than this Mercedes DI turbo V8.

#3 = Piston ring depth, much less than a diesel. No full skirt seen either. No resemblance to a real diesel piston at all.... as seen here...




Sorry if this appears confusing, but this is again addressing two issues. The possible and corrective measures Mercedes took to reduce or eliminate the carbon issues in their Direct Injected engines.... and the claimed "similarities" of piston design.

Glyn M Ruck

You really are confused or not very bright. The M271 pic was to show that even with port injection - i.e. not DI into the combustion chamber the fuel can only clean where it can get to. Thus dirty inlet ports are common & thus monitoring the valve tulip for fouling on a DI engine is adequate. All engine porting gets fouled over time.

My boroscope with a 90 degree lens attached to the tip & inserted down the plug hole will easily see the entire inlet valve tulips with the valves cranked open. Our additive company sells 50% of the fuel detergents/detergent components dosed into fuel globally. I'm more than accustomed to examining inlet systems on some very difficult designs. The very reason that decent boroscopes have many different angle optics available is so they can look around 90 deg corners 120 deg corners etc. Known as prism lenses for your edification. This is how non destructive examination of aircraft turbines is achieved etc. The way that a medical endoscope can examine the whole of your colon.

Here is a 90 degree tip as an example. My prism tips are approx .6 of a cm long & in a range of 10 angles.



You of course always shirt the toroidal cavity question. As I have previously stated & you have difficulty understanding. Gasoline DI pistons have taken on diesel characteristics but are more lightly built than diesel ones but more strongly built than non DI designs.

They have longer skirts than non DI but not as long as diesel to prevent thrust side scuffing.

They have a stronger crown than non DI gasoline pistons due to early cracking problems experienced - go do your homework. There is a whole SAE paper on the subject

They are at present heavier than non DI designs although a lot of work is being done to mitigate this.

They have adopted diesel type toroidal cavities to operate in desired swirl, low turbulence conditions ideal for DI but with a different fuel.

Yes - they are lighter in construction than diesel pistons because they don't have to contend with diesel compression ratios & knock. They have, however, by design taken on diesel piston characteristics. As injection improves DI diesel & gasoline pistons will look more like one another but diesel will always be stronger. I stated this up front.

I strongly suggest you go and do some reading & learn. Kevin - who is the OP of this thread will have no trouble grasping what I'm saying.

If you don't then tough!

I'm not violating my company embargo. That will not happen.

My original statement was "See how the piston design is adopting diesel characteristics - obviously of far lighter construction." I'm sure a whole SAE conference would agree with me. I did not say the pistons were identical.

MDMercedesGuy

I'm reasonably concerned that this thread has been hijacked into a 1 sided pissing match that has since lost any sense of the original intent.

MBRedux

Well said... and fully agree. I'll apologize for my half, no matter how on earth this happened.

I've got several back in our shop, but not this old. Our's is made by Olympus Optical, has several different bendable, rotatable and detachable heads, (via joy-stick) with WiFi high def video capable (720p) etc.

Glyn M Ruck

Indeed. Mine is the older, much older Olympus. But nevertheless steerable 10 head & still film camera bayonet compatible. Obviously our research labs have the latest. Mine is more than good enough for home use & was given to me by the company after I ran a fuel clean up program for them many years back. A nice gesture at the time because it cost a bomb. A lot more than they are now. The pic is of a fixed 90 deg head. Not my unit.

We will agree to disagree.

Thanks to all of those who flooded my PM box with support.

MBRedux

I am still standing by until someone either gets to the bottom of it or the fat lady sings.

kevink2

Great minds think alike .... earlier, post 82, 2-16-12 :

"There might be a special thin rod borescope that can be past down the spark plug hole when the intake valve is wide open, to view build-up on the back side of the valve head."

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kevink2

This was stated by MBRedux in post 127, for the mixed mode operation. Also shown in in my Bosch video:

Post for Bosch DI Fuel Control Video

.

Glyn M Ruck

Indeed!~

MBRedux

Even when the valves are opened fully. But there could be something on the manifold like a sensor, vacuum point, or some other hose that when removed will give you access point to the intake valves through "A".

kevink2

That's an excellent graphic illustration you posted, with the arrows, but it's still a bit difficult for me to visualize how scoping won't work. It worked up my butt

I like the bookeds you showed, from a piston trophy. I have a twin row 80mm spherical roller bearing that failed and got so hot it welded the rollers to the inner race (outer race removed). It came to me at the office, in a box with others for analysis. it was too good to toss, so I cleaned it up and useded it as a paper weight.

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kevink2

As OP here, I have several unenumerated powers, and I am using one now to suggest civil sanity. Glen and MBRedux are well known powerhouses of knowledge for this forum, and it's below each of them to tussle via keyboard, as it is too easy to do.

As a yahoo in LA (who won the top $3.8E6 award for playing a race card) once said about 30 years ago, "can we all get along?" .

nuuf said, can I hear an Amen?

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Glyn M Ruck

Amen!

Gavin Baker

I had a 2007 Mini Cooper S, which had to be disassembled and dipped to get all the buildup off, at 47k. I bought my 2008 C350 because its a strong engine without DI....back to the drawing board like VW has done.

leehotung

As a new owner of a E260L using the M271EVO (the Chinese long version coded V212, it is not called 250L just because 250 means stupid person in Beijing slang), I experienced some engine knocking in the first few months of ownership (the car has just 1600km now). I bring back to the dealer to check and the technician blame it on the poor fuel quality. I started searching on the Chinese internet and apparently it affects both C and E class commonly. And import version seems more affected but local assembled version like mine has problem as well.

Unfortunately we don't have independent Mercedes specialists to go to so the only option is the authorised dealer but the general feeling is they do not have a clue (or maybe MB is unable to really solve the issue).

My questions are if there is anything I can do to minimise the knocking / delay the carbon build up. Obviously I can do nothing about the fuel quality, but e.g. can I change my driving habit (I am now using manual change to keep a higher rpm when hard acceleration is needed), or put fuel additive (the dealer recommend Keropur from BASF), or can I ask the dealer to change some ECU parameters (and what are they??? fuel requirement? emission?). Thanks.