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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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Discussion Starter #1 (Edited)
The brown box delivered a hefty brown box to my door a few minutes ago. These are aftermarket Om352 TURBO pistons.

First you will note that they only have three rings. The turbo 352 has two options, 4 ring pistons or 3 ring pistons. Non turbo 352's use either 5 ring or 4 ring pistons. I chose 3 ring for obvious reasons.

Next, you will notice the coating on the pistons. I cannot comment on what this coating is specifically. But I do know that my original N/A 352 4 ring pistons did not have this coating.

Then you will notice one of the parts that make's this a turbo piston. Around the top ring you will see that there is a different material on the top and bottom. This material addresses cooling and wear of the top compression ring. This material should be present in all modern high output turbo pistons.


Next, I chose to just bore up to 97.5MM and to hopefully reduce compression slightly.

So, where did they come from and how much? Well for the moment I will keep this fairly close to my chest as I am hoping that one or two of your favorite Mog parts dealers here in the US will have better access to these soon. And Price, well lets just say shockingly dirt cheap. I mean seriously dirt cheap.
 

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OK, why did you choose the three ring pistons? The only reason I can think of might be to try to reduce friction horsepower losses. And why would you want to lower the compression ratio? Diesels are not like spark ignition gasoline fueled engines, we don't need to worry about pre-ignition and modern design turbo diesels can run very high BMEP and engines in the displacement size (combustion chamber area and piston surface area) run 18-22 to 1 compression ratios. Best efficiency is achieved by higher compression ratio with a little less boost (if that's necessary for some reason) and higher base compression ratio will mean better starting, albeit a little more work for the battery. If you are going for max horsepower then I guess I could see dropping into the 16/1 area and boosting the heck out of the engine, but cruising efficiency will give a bit up, especially if you end up cruising with some boost because, unless you are running a variable geometry turbo, exhaust back pressure will always exceed compressor discharge pressure. Tony
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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Discussion Starter #3
First, I am not looking at building a hot rod engine. I am more or less making a hybrid of the om352, the om352A. Plus I am attempting to somewhat deindustrialize the engine.

I chose 3 ring to reduce friction as the rings are one of the larger factors. The design of the om352 doesn't allow much cooling betwen cyclinders so every little bit helps. Also, more rings work great at lower rpm in industrial engine's, but are not needed at higher rpm's and normal use truck situations.


Compression, well this is an internal loading issue. The lower compression reduces overall internal loads at cruise and Idle. And seeing as how I have the smaller crank, this will help in engine longevity. I want to run higher boost as well to help reduce power loss at higher altitude's giving me some reserve boost at cruise. ETC ETC ETC. Anyways, its a bit of a moot point because I doubt I will be able to reduce the compression at all. If anything I think it might go up slightly.
 

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mogless, except for my friends MB4-94. And a bunch of other diesel junk.
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Any chance that MB offers a thicker head gasket? I've encountered it from other manufacturers, so maybe? It would be an easy way to lower compression.
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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Discussion Starter #5
Not sure, I have seen them as well. Backcountry mech's like to double up head gaskets which is not to smart. You can also use a thin copper plate cut like a head gasket. But I really have no plan to mess with this stuff to much. If she comes out higher, I will just make adjustments in the turbo and get one of von's starters so I can actually start it.

I am still waiting on my piston jets so machine work has not begun yet. We will soon see though. I just hope she is up and running by february.
 

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mogless, except for my friends MB4-94. And a bunch of other diesel junk.
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I know you don't plan on this, but just for conversation sake..
If you were to have a copper blank water jet cut to install w the head gasket, what thickness would decrease the compression ratio how much? Would it be as simple as so much thickness alters compression x amount?
 

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in my work shop i do these copper head gaskits alot i do them 3mm tickness somw time i cut them with the waterjet and then you have to putit in the oven til it reach 220degres centigrade and the quinch in water so the copper will come more softer
regards
jekran
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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Discussion Starter #8
I know you don't plan on this, but just for conversation sake..
If you were to have a copper blank water jet cut to install w the head gasket, what thickness would decrease the compression ratio how much? Would it be as simple as so much thickness alters compression x amount?

Yes, it is that simple if you have all the correct numbers to calculate the compression ratio. And diesel's such as ours are very easy to calculate the compression since the combustion chamber is in the top of the piston.
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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Discussion Starter #9
in my work shop i do these copper head gaskits alot i do them 3mm tickness somw time i cut them with the waterjet and then you have to putit in the oven til it reach 220degres centigrade and the quinch in water so the copper will come more softer
regards
jekran
I love your attitude toward this stuff. It's very similar to my own. I would much rather machine or fab out all my own parts. To bad I do not have a machine shop available for personal use. You hiring!?! The wife would be more inclined to move to Malta than Colorado or Alaska where I belong.
 

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OK, you have your three ring pistons, so you can't change now, but be aware that rings are one of the major heat transfer pathways that cool the piston. Three rings will reduce friction horsepower losses, but they will likely cause higher crown temps on your piston. It's not really the friction that puts heat into the liner and cooling system, but the exposure of the liner during the combustion stroke to the hot combustion gasses as the piston moves toward BDC. Less rings will mean less heat transfer from the piston into the liner, but you should carefully monitor your EGT when you set this engine up and do your initial tuning. Oil squirters will help alot. And don't be in a hurry to lower your compression ratio, especially for use at altitude where the air charge is less dense to start with. Tony
 

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Discussion Starter #11 (Edited)
OK, you have your three ring pistons, so you can't change now, but be aware that rings are one of the major heat transfer pathways that cool the piston. Three rings will reduce friction horsepower losses, but they will likely cause higher crown temps on your piston. It's not really the friction that puts heat into the liner and cooling system, but the exposure of the liner during the combustion stroke to the hot combustion gasses as the piston moves toward BDC. Less rings will mean less heat transfer from the piston into the liner, but you should carefully monitor your EGT when you set this engine up and do your initial tuning. Oil squirters will help alot. And don't be in a hurry to lower your compression ratio, especially for use at altitude where the air charge is less dense to start with. Tony
Well, I understand where you are coming from. But these pistons have so many benifits to reducing heat plus my oil jets, I am not worried even a little bit. Also, keep in mind these are OM352A pistons. I did not have these custom built they are what you will find in many OM352A's and even in the OM366. So I am not doing anything radical here. Its simply updating to what mercedes felt best.

Piston rings can contribute to as much or more than 30% of total friction in an engine. Reducing this can seriously reduce overall heat. And the addition of cooling jets adresses piston temps.

Also, most if not all modern diesels such as the cummins found in a dodge truck will run 3 ring pistons.


And just another clarification: THESE ARE DIRECT REPLACEMENTS FOR AN OM352A and would be considered comparable to the same mercedes part.
 

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Then you will notice one of the parts that make's this a turbo piston. Around the top ring you will see that there is a different material on the top and bottom. This material addresses cooling and wear of the top compression ring. This material should be present in all modern high output turbo pistons.

So, where did they come from and how much? Well for the moment I will keep this fairly close to my chest as I am hoping that one or two of your favorite Mog parts dealers here in the US will have better access to these soon. And Price, well lets just say shockingly dirt cheap. I mean seriously dirt cheap.

Protect the MB vendor relationship?" Hey...If you really want to help the Mog world out bring competition to the UNIMOG market. We all know parts are expensive as is...but really who really cares except one or a few wanting to protect their interest/vendor/MB interest. If you want to sell the above pistons at a profit...Go for it. Let the vendors come to you or is this not something you want to do?
 

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Question....since we all know Mercedes knows how to make pistons...How do you know that the "Aftermarket Tubo Pistons" are as good or better than MB pistons? Why would a Unimog enthusiast take a chance on putting aftermarket pistons in his power plant? Does the company offer a replacement warranty to remove the skepticism that many people may have at trying a aftermarket turbo piston? Apparently your willing to take the risk but it seems to me that if your wanting to bait the MB dealerships with parts from a 3rd party which for all we know could be from Harbor Freight/Schucks/O'Reillys ect.. other than MB parts then I'd think calling them would be better than this?...Could this infuriate MB directly thus causing all MB owners higher prices? It just seems counter productive.
 

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Discussion Starter #15
No, I am not selling these. And they have been around for some time now. In fact, they have been used to rebuild a couple mog engine's here in the US already.

There were some major changes in the distribution chain of these recently that cuts delivery time from several months to a couple of weeks. As well as delivery time, the retail price has been slashed because of the change in how they are brought into the states from Germany.

The reason I am being quiet is that a certain mog vendor made me aware of these and was going to suplly me with them. I however did a little research and study which lead me to helping pro bono two companies start a relationship that will streamline the availability of many OM352 parts.

Ultimatly, the price I paid may in fact turn out to be the retail price, but I am letting these new relationships simmer for a little to see how it turns out for them.

But What I can say is that once, the OM352 was not really worth rebuilding as you could buy a low time unit from ATK VOS for less than just the parts required. But now, rebuilding the OM352 and even the OM366 will be about the same as rebuilding a chevy/ford V8.

And if anyone is in need of pistons valves and other hard parts for any Merc diesel, I will be more than happy to get them connected to the right party.


Rest assured, there will be some good friendly competition for these parts in the future.
 

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Discussion Starter #16
Question....since we all know Mercedes knows how to make pistons...How do you know that the "Aftermarket Tubo Pistons" are as good or better than MB pistons? Why would a Unimog enthusiast take a chance on putting aftermarket pistons in his power plant? Does the company offer a replacement warranty to remove the skepticism that many people may have at trying a aftermarket turbo piston? Apparently your willing to take the risk but it seems to me that if your wanting to bait the MB dealerships with parts from a 3rd party other than MB parts then I'd think calling them would be better than this?????thus infuriating MB directly over the MB Benzworld site and causing unneeded price hikes ect...ect...It just seems counter productive.
Really, I mean Really did you think about this before you posted it.

Well, first is price, call around and price out a set of 6 OM352 pistons. You will be looking at over $600 a piece retail.

Next, the company is a very large reputable engine parts manufacturer.

And who cares about MB dealerships here in the US

You know what, I don't even have the patience to finish responding to this. You are way way off in another world right now and are looking into it way to hard.

I'm just trying to help out some well known Unimog parts shops here in the US, stop trying to turn this into an international incident.

PS. they have OM617 parts to so it will help you out if you ever need to rebuild so relax and enjoy the cheaper parts........
 

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No, I am not selling these. And they have been around for some time now. In fact, they have been used to rebuild a couple mog engine's here in the US already.

There were some major changes in the distribution chain of these recently that cuts delivery time from several months to a couple of weeks. As well as delivery time, the retail price has been slashed because of the change in how they are brought into the states from Germany.

The reason I am being quiet is that a certain mog vendor made me aware of these and was going to suplly me with them. I however did a little research and study which lead me to helping pro bono two companies start a relationship that will streamline the availability of many OM352 parts.

Ultimatly, the price I paid may in fact turn out to be the retail price, but I am letting these new relationships simmer for a little to see how it turns out for them.

But What I can say is that once, the OM352 was not really worth rebuilding as you could buy a low time unit from ATK VOS for less than just the parts required. But now, rebuilding the OM352 and even the OM366 will be about the same as rebuilding a chevy/ford V8.

And if anyone is in need of pistons valves and other hard parts for any Merc diesel, I will be more than happy to get them connected to the right party.


Rest assured, there will be some good friendly competition for these parts in the future.
Sounds promising...I've actually seen some pistons on Ebay. I take it there is good feedback that will be coming from the rebuilt engines ect. Thanks for sharing and don't worry...Tarazan and Jane are in my back-yard!
 

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Discussion Starter #18
Rest assured, these are not Ebay pistons. They are made in germany as well. they even make parts for the gasoline version of the om352. I will check to see if they make m180 parts
 

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Discussion Starter #19
well, in fact they do offer "some" parts for the m180 and they are even listed as being used in the 404. Could have saved myself many hundreds of dollars on building my HC head for my 404 had I known back then.

Also, just FYI. All parts can be looked up by specific engine build numbers. So its not just one size fits all.
 
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