looney100

A few days ago, my wife dropped her E250 off for service. The service advisor told her that she should occasionally accelerate hard to keep the engine clean - that this was something needed for diesels.


Has anyone else heard such a thing? Is there any reliable evidence to support the need to do this?

Mud

Diesel engines (closest I've had was the 3 cyl on my Kubota DT3000 tractor) produce a lot of soot, I think that the service guy was recommending the harder driving as a means of increasing velocity in the intake/exhaust to blow out the light stuff. Any real deposits are really not able to be removed like that.


IMO opinion engine "cleanliness" is a relative term. Engine internal cleanliness, including piston rings relates to oil quality and oil/filter (and air filter) change intervals, Induction system, including valves relates to fuel quality, air filter changes, that sort of stuff. Today's engines are ECM controlled - the ECM "learns" driving habits. An engine driven with minimal throttle input sits in a slightly different control window than one that is hammered regularly, remember also that the driver reads not just engine response but shift timing as well to make subjective determinations. So if the usually slow drive engine is driven hard a few times, the ECM will change input and shift parameters a bit, giving the sensation that some sort of cleaning was done.

Maintenance is another big item - good quality fuel, oil, filters go a long way to driveability. You don't need a bunch of additives in either if the quality is good, especially no additives needed in today's oils. One overlooked item is the MAF mass airflow sensor that provides significant input to the ECM regarding throttle body airflow. Because of its location it gets dirty - I clean it with non-contact electrical cleaner whenever I do air filter changes. Not sure if the diesel has the same setup on this one, I'm more familiar with gas engines.

Remember that the ECM has operating value windows it reads from the sensors, inputs outside of these windows are what will light up the CEL indicating stored trouble codes. I can run my car connected to my scanner and see how my driving style causes changes in real time in these values.

I'm not saying that it's bad but the old style highway tuneup (blowing out the carbon) is not entirely applicable to ECM controlled vehicles. My 57 has an 850 Holley on a big block - old school - and it sits more than it is driven. Hammering it a bit does seem to blow out a few of the cobwebs from that overall crude setup compared to modern vehicles. In my MB, normal daily driving doesn't seem to be any problem relate to carbon build-up.

looney100

I thought it was a crock when I heard it. I couldn't understand how it would help.

thefisch

Doesn't sound like a reliable solution to a problem, but I'll take any excuse to put the hammer down. Add an 'Italian tune-up' to the list.

CarolinaBluetec

There are guys on the diesel forums that swear by it. At least you have a lame excuse when the cop pulls you over.

iGeorge

Goosing the system likely would do the opposite of cleaning the system; it would more likely create more particulate than it would clear. Perhaps he meant a long, sustained drive, which does help both gasoline and desiel engines.

Trancebolt

From what Ive been told by a few different dealers and diesel enthusiasts alike is as follows: Since alot of people that drive mercedes are not speed demons.... face it, a decent amount of older people who dont care how fast it can go drive these cars from time to time. In the case of any person who doesnt use a whole lot of throttle in daily driving, they say that flooring it twice a day will help. The explanation I got was this..

Since at low throttle application the manifold flaps dont open all the way, and are so often not fully opened that the buildup of carbon will prevent the flaps FROM fully opening... and thus driving your car between 2500-3500 rpms a bit more often and flooring it sometimes will more likely have the flaps open for longer....

Thats my definitely non car specialist understanding of his explanation. THats one of the reasons i was eager to try the kleemann tune box i got... The box unlocks the full range of psi from the 2056v turbo and thus makes more fuel pass through the system at lower throttle. I assume that should be a good thing for a car that has problems with cats and intake manifold flaps building up with carbon.

Maybe it will do the opposite... Dont know. Taking it off for svc b and will be doing another thorough test of it to see the stock reactions to my throttle again....and how it measures up


Also like the old gullwing, they said that the direct injection would contaminate the oil if not driven hard all the time... =D nice to hear; like anotehr member here said, even gas engines.... Any DI car in general but especially a di diesel

rediesel

I've forgotten a lot of my diesel knowledge, but on my 06 CDI an "italian tune up" was needed every so often if driven too softly. I would warm the car up and then floor the accelerator from a stop and the car would emit a cloud of soot out the tailpipe as we took off and that was it. Car would only do it once, and only if it had been coddled for a few days. I think it had to do with the EGR, butterfly valves, and carbon/oil buildup in the intake somewhere.