Coating Prechambers - PeachParts Mercedes-Benz Forum

libbybapa · #1 04-10-2006, 04:39 PM

What tools are necessary to remove the precombustion chamber inserts? Has anyone had them coated with thermal barrier coatings? Was there any noticeable improvement in cold starting or fuel economy?

Brian Carlton · #2 04-10-2006, 05:27 PM

There is a tool to remove the locking ring without chewing it up.

Then there is a slide hammer/puller to actually pull the prechamber from the head. They are in there pretty tight and it takes quite a few whacks to get them to release.

Don't think anyone has coated any of them recently.............

imdavid28 · #3 04-10-2006, 07:19 PM

Quote:

Originally Posted by Brian Carlton

Don't think anyone has coated any of them recently.............

Has anyone ever coated them? The guys in the engine master's competitions coat the combustion chambers, crowns and such, but they are dyno engines that are built for a few runs. I would think that if you did coat them, it would fracture and fall off before you would want it to.

#4 04-11-2006, 01:33 AM

Not really a good idea to coat them. The ball in the center needs to be clean and smooth to vaporize the fuel spray from the injector. When the engine runs, it glows a cherry red and aids in combustion like a continuous glowplug.

Ralph69220d · #5 04-11-2006, 12:32 PM

From my readings it is not unusual for old prechambers to crack, particularly wandering out from the various burn exit holes. Obviously if a prechamber broke into pieces this would wreck that cylinder, head, rods, maybe crank. I'm sure there are newer methods designed by metallurgists for coatings to make parts less vulnerable to breaking. A process called "magnafluxing" was used on the cranks of alcohol & nitromethane drag engines many years ago. I believe on the crank rod & main journals to the 'left & right' of where the bearing contacted. This was probably protection against tortional breaks more so than bending breaks. But, there are coatings that are basically one molecule thick and are highly resistive to wear, thus protecting bearing contact areas, cylinder walls, precombustion chambers, though I have no idea as to cost, but I suspect it to be prohibitive. Back to the prechamber: it sees extremely high stresses and has ideal areas for cracks to begin around the holes. I have a 220D and it is a ways down on my list of things to fix, but I should pull the prechambers at some point, as there was a greatly improved design that fits the 220D, that came out not long after 1969. Obviously any carbon deposit buildup around the holes is not a good thing; for that matter, anywhere, carboned glow plug, any hot spot that affects the geometry and temporal course of fuel burn. A coating basically one molecule thick is not going to appreciably affect exit hole geometry, so I don't think that would be a problem. I don't have any great experience to speak of what the mechanics on this site have had opportunity to see over many years. So, much of this is just my own thinking on the subject, for what that may or may not be worth. I must say I view this as a thread I'm going to watch to see what others have to say.

ConnClark · #6 04-11-2006, 12:38 PM

Coating the prechambers, pistons crowns, head chamber, and valve faces all would have some minor positive effect. However its not such an effect that the car companies are doing it yet. They are looking at it though. On another diesel forum I found one guy who was certain that this was the miracle power boost/fuel saver for indirect injection engines. He spent more than $500 having it done. The guy never reported back how it worked out.

I'm not certain you would have to keep atomizer pin from getting coated. It is not a temperature dependant thing though it does get very hot. You don't want its smooth surface to change however. Its there for the the injector jet to hit. The fuel rebounds off of it and back into the air inside the prechamber in an evenly distributed manor. This atomization towards the center burns most of the fuel away from the prechamber walls reducing heat loss.

You would however have to make sure that the orifices at the bottom of the combustion tube did not change in size. That would effect your power band. It also wouldn't be very consistant from prechamber to prechamber.

I personaly think it would be better to play with the atomizer pin ball shape to promote swirling air inside the prechamber. They did this on the OM603 atomizer pins and improved on it later.

#7 04-12-2006, 02:30 AM

I've got an itch to pull some extra prechambers from a parts yard and mess with them. Try larger orifice holes and see what happens with the powerband. I just don't want to melt the pistons (I guess waiting until AFTER I get my pyrometer is a good idea

)

Quote:

Originally Posted by http://www.circletrack.com/techarticles/139_0308_mag/index.html

You've heard the term Magnafluxed. To most, it means taking a part and checking it for cracks. Typically, the teardown guy brings a part to the "Mag" unit, wets it down with solution, presses the button a couple of times, then shines the black light on the part, checking it for cracks. The process seems simple enough, but there is much more to inspection than most racers realize.

Magnaflux is actually the name of the company that began building magnetic particle inspection (MPI) equipment in the '30s, and is still the leading manufacturer of the equipment.

The process of magnetic particle inspection is straightforward: An inspector places a part on the bed of the unit, either clamps the part in the contact plates or places it in the coil, wets the part, magnetizes it, then looks at it under a black light. To do the job properly, you must understand the basics of the inspection process and how to find cracks or defects in parts.

imdavid28 · #8 04-12-2006, 09:09 AM

Quote:

Originally Posted by ForcedInduction

I've got an itch to pull some extra prechambers from a parts yard and mess with them. Try larger orifice holes and see what happens with the powerband. I just don't want to melt the pistons (I guess waiting until AFTER I get my pyrometer is a good idea

)

I don't think it would really increase the exhaust temps. Your still burning the same about of air/fuel, just making it easier to circulate in the combustion chamber. Would be interesting to find out what happens though. Any one have a spare engine they are willing to donate?

1983/300CD · #9 04-12-2006, 06:56 PM

A technique of supercooling metals has been developed that alignes molecules and hardens steel. Blades can be made sharper and to hold their edge longer. All you really need is a couple gallons of liquid nitrogen.

Old300D · #10 04-12-2006, 07:03 PM

Quote:

Originally Posted by Ralph69220d

...
I'm sure there are newer methods designed by metallurgists for coatings to make parts less vulnerable to breaking. A process called "magnafluxing" was used on the cranks of alcohol & nitromethane drag engines many years ago. I believe on the crank rod & main journals to the 'left & right' of where the bearing contacted. This was probably protection against tortional breaks more so than bending breaks.
...

Magnafluxing is just a process to inspect for cracks. It is not a treatment to make parts less vulnerable to breaking. A steel part is magnetized, then a compass-like instrument is passed over the part's surface. If a crack is present, you will see the field switch from N-S, as magnetic poles are formed at cracks.

imdavid28 · #11 04-12-2006, 10:52 PM

Quote:

Originally Posted by 1983/300CD

A technique of supercooling metals has been developed that alignes molecules and hardens steel. Blades can be made sharper and to hold their edge longer. All you really need is a couple gallons of liquid nitrogen.

Actually when the molecules align, the metal becomes softer.

When you quench something, you cool the molecules, and the rate at which you cool them and the starting temperature determins the dissarray (maybe the word entropy would work here) of the molecules when solid, which determines the hardness/strength.

I think you are talking about metalic glass, which is pretty experimental right now. They take a thin film of hot metal, and cool it so quick that the molecules can't for grains; the molecules are more of a ceramic or glass or liquid (depending on how you wanna look at it) arrangement. I think the only application they consider for it right now is a golf club head.

Or, you could be thinking about turbine blades that they annel forever such that they form one grain of material, which is pretty cool, but not a process that would do anygood for a already existing prechamber.

ConnClark · #12 04-13-2006, 11:20 AM

With the high temperatures and constant temperature cycling the prechamber is exposed to I doubt any annealing would do any good.

#13 04-13-2006, 11:34 AM

Maybe I'm missing something here, but wouldn't it be easier to just replace them every 2 or 300K miles and/or 20 years, whichever comes first. They're only about $100 each and could be easily done when the car needs a top end rebuild or head gasket.

ConnClark · #14 04-13-2006, 12:04 PM

Quote:

Originally Posted by Craig

Maybe I'm missing something here, but wouldn't it be easier to just replace them every 2 or 300K miles and/or 20 years, whichever comes first. They're only about $100 each and could be easily done when the car needs a top end rebuild or head gasket.

Well originally this thread was about coating them with a thermal barrier to enhance starting and fuel economy.

#15 04-13-2006, 12:41 PM

Quote:

Originally Posted by ConnClark

Well originally this thread was about coating them with a thermal barrier to enhance starting and fuel economy.

OK, I guess. But I still don't really see the point, I could think of lots of (expensive) ways to increase my mileage from 26 to 27 mpg, or I could just go adjust my valves and replace my air filter. I could also go buy a TDI and get 40 mpg if I really cared about maximum fuel mileage. These are 20 year old cars with 30 year old engine designs, trying to re-engineer these little bits and pieces just seems a little silly to me.