This thing definetly was not a fluke bad piston. It has been subject to some major heat. Notice the black marks above the arrow that points to the front of the motor. The problem is, every piston had a dime sized black mark at the top edge of the piston. The machine shop that dye checked the pistons said that it was either a fuel mixture problem or timing. Now I have to figure out what the hell is going wrong in this motor.

 

Hi Charles,

I may have asked this before but do you run an Air/Fuel and EGT gauge? If so , what did your A/F mixure and engine temps look like at hard WOT runs?

I was very suprised to see that on my modified Eagle Talon that the A/F was very lean at WOT and the EGT's were almost at melt down within in minutes of high speed runs on the freeway. I would never have known. I was running a larger turbo with around 18 psi.

 

OUCH!!! I half suspected , you find the rest of them close to failing , but now you something to go with. That piston looks like a Cast piece, from the pictures of the dome. If you are sure of the fuel quality., I would look at inter cooler system. And Lets see want the fuel injector flow report shows. Call Me , I'll talk to the Wisco piston guys. I believe they supply 1 of the MB tuners with Big bore pistons?? From the looks of the hot spots on the other pistons , the Mahle pieces held up well. ___PTE___

 

If you can post a picture of the spark plug a high resolution one, i can tell you what kind of mixture you were running. The ring land that cracked is right in the region where teh hotspot is thus heat definitely was a factor.
Btw that definitely is a cast piston, as some people have suggested before you can opt to go with JE, Wiseco, Arias or CP and see if one of them will make you a forged set. Forged will be atleast 4 times more resistant to heat. Ofcourse forged pistons have a greater tendency to expand because of low silicone content so cold startup is kinda noisy as the piston slaps around a bit till it expands. Ofcourse they will be a lot cheaper than $750 a piston, you can probably get a whole set for that much. I would also have the rods checked out for straightness just for piece of mind.
If all pistons exhibit the same tendency, i think your injectors are flowing ok and consistent with each other. You might not be getting enough fuel though or timing might be too high or a combination of both. I would check the ECU to actually seee if kleeman uploaded the map, maybe there was an error, wrong map or they just forgot to put it on.
you need to have a wideband put on the car and see your ratios, by the looks the piston(unless you had them acid dipped to be cleaned up) i would guess you are running around high 13's to mid 14's on your AFR @ WOT and you should be on mid 12's for a forced induced motor at WOT. I am not too bigon merceded but by the looks of it , seems like 2 spark plugs per chamber design. Any chance that the heat range on the spark plugs might be wrong? You should have a little bit of carbon buildup on top of the piston, it is almost unavoidable on a safe burning motor as they tend to run a little bit richer. Look at your plug, if it is white, you were running tooooo lean, if it is light tan, (ok for daily driving, lean for WOT) it needs to have a little bit of dark to it. HTH. thanks

P.S Arias built us a set of 15:1 compression pistons and they worked with us quite extensively to get the design right, including mapping out domes and combustion chamber etc. Low compression pistons are a walk in the park as compared because clearance is not an issue etc.

 

Actually this is a good thing that you found out about the heat, at least you know what caused failure and can fix it now. Instead of putting a whole motor together and finding out tha hard way again. One thing that i wanted to add is that EGT's and AFR guages are great but if one cylinder is burning at a different rate than the others, it would seldom pick it up(unless you run individual eqts). So once your injectors all flow test even(ask for a report) you can eliminate that possibility.
Are the valves on your exhaust side burnt at all? One more thing to consider is (again i don't know much about mercedes) your fuel pressure. if you up boost from lets say 10 psi to 20 psi, your pressure in your fuel line needs to increase by 10 psi as well because the injector has to accomodate for the extra pressure in the line to throw the fuel in at the same rate it was doing before. Unless you have a boost dependent fpr.
I think i am throwing too many variables in, sorry for the rant. just hard to diagnose something that is not infront of someone. Good luck with everything, if you have any questions just ask. thanks

 

Valves were fine. Kleemann adds 9 psi of fuel to the rails for every 1 psi of boost.

 

These are forged pistons, basically a cast piston put under pressure to improve metal strength. The pistons all had an even coat of carbon build up. That is why we didn't see the burn spots. It wasn't until the pistons were cleaned by the machine shop that the hot spots showed up. Thanks for the offer on the aftermarket pistons, but I will stick to the Mahle ones. These pistons are designed for this motor. They are made of a special alloy and are treated with a specific coating. I have already taked with JE and CP and they even recommend stock pistons. Kleemann also recommends stock replacements. Nobody can ensure that the pistons will be as quiet as the stock ones,

Spark plugs show no unusual signs. The plugs are the ones that Kleemann recommends.

Kleemann does not change the fuel map. The way they compensate for the boost is with a pressure regulator at the fuel rails. For every psi of boost they add 9 psi of fuel pressure at the rails.

I am having a bung welded into the ehaust for an wideband o2 sensor. I had one in my Supra. I will minimally get the car on a dyno and see if it goes lean. I still have the original MAF and will switch back and forth to see any differences. My guys still say that it is a MAF problem.

I am also going to have the fuel tested.

 

Goodluck with everything let us know how it works out. Thanks

 

Nice posts... good information/suggestions.

Nice move with the w/b o2.. You said it has a pressure regulator, is it not like an FMU?

 

He said that Kleeman increases the fuel pressure in the line by 9psi for every 1 pound of boost, it essentially is a Boost Dependent Fuel Pressure Regulator. The ratio of fuel to add is controlled by discs in the BDFPR (also known as FMU), in his case a 9:1 ratio disk.
I am sure that Kleeman knows their stuff but there is a reason tuners don't like BDFPR. Lets say your static fuel pressure in your line is 50 PSI. This is the pressure under vaccum(i.e most daily drive conditions with no boost idling,highway etc). Now if you add 10 psi of boost on top, on a 9:1 ratio disk your fuel pressure go up by 10X9 = 90 psi plus one bar(14.7psi). The one bar is unavoidable as it is the difference from vaccum to atmospheric pressure.
So all in all your total pressure goes to 50+90+14.7= 154.7 psi. now comes the question can your fuel line and pump keep up with it? are the lines too small, pump not drawing enough. Its like sucking a milkshake through a straw, if it is really narrow you have to work too hard , if the straw is an inch thick pvc pie you still have to work hard. The size of the line has to be an ideal range. Another problem is the injector disks and pintle have a hard time opening with that much pressure behind them because they are only made for stock pressure. sometimes they cannot keep up and they go static. They can go static in two conditions open or closed. If they are stuck open then fuel just drizzles instead of misting and is open all the time. If they are stuck close then you might get little to no fuel resulting in lean conditions.i hope i am not making it too difficult to understand. Thanks

 

The Kleemann kompressor will only produce 6 psi. The fuel rails will never see 154 psi, the system cannot deliver that much. I agree that boost correction is a lame way to go, but its what I have to work with. They claim they did it so third world areas like Mylasia could buy the blower and not worry about finding someone to flash the ECU without destroying it.

 

6psi should be no problem for stock lines and setup. One small thing i would suggest is before you put your pistons in, massage the edges with very fine sand paper to remove the edges and make them smooth as possible. It will remove some of the hotspots on the piston, it will help with pre-ignition.

One small question it is not related to this just for my curiosity, the second spark plug does it fire at the same time as the first or is it more like a trailing plug. What i mean is that does it just fire later to clean the unburnt mixture for better emissions? Thanks

 

Oh BTW how does Kleeman retard the timing under boost? are they using a boost dependent retarding function or is 6 psi not a lot and the stock ignition settings imply?

 

The piston has a coating on it. I do not think sanding the coating would be a good idea.

The second spark plug fire independently of the first. It is controlled by the ignition and the ECU. For a pretty complete review of the many features of the M113 engine check out this link. http://www.marcusfitzhugh.com/CLK/edet.html

 

are the cylinder walls in the block coated? Im gonna do a rebuild on my motor also, I believe I have the same problem as you .

Alex

 

The walls are not coated per say. The block is made of a high silicone aluminum. What is done is to the block is a process that pulls the silicone molecules to the surface and repels the metal molecules. This way the rings ride on silicone instead of metal. The silicone is actually many times harder then the metal. The block can be honed or bored, but the process that "treats" the cylinder walls must be redone. Mercedes will actually take a M113 motor with 100K miles on it that is burning oil and do nothing more then replace the rings. Never even touching the cylinder walls. If you want more info on the M113 motor read this article http://www.marcusfitzhugh.com/CLK/edet.html

 

I am quite suprised at the numerous shortcuts that Kleeman takes on their products. I have seen a couple Kleeman products first hand, and I could immediately spot numerous things that I did not like, and that could be improved. Everything that Kleeman makes works just fine, but with just a little more work/using better parts it could work even better. Now reading how Kleeman uses the fpr to adjust the fuel, I am not too surprised, but I really did expect Kleeman to go with a better route. Again, it all works, but for the prices that Kleeman charges, I'd expect them to take less shortcuts.

 

I would not recommend this setup. It is a really complete package, but for the money I think it could have been designed better. They tried to make this one kit work for everybody in the world. That usually doesn't work well.

 

sorry to hear that man.

 

Even with the broken pistons from your motor, the walls on your block were fine?! You just put new rings on new pistons with no block work? I havent taken mine apart but I know it's hurtin...I get cyl 5, 6, 8 codes, Im just preparing for the worst!

 

The cylinder walls are very durable in this motor. Like I said it is not uncommon for Mercedes to install new rings and go on a car with over 100K miles.

Be sure to get a leak down test to be sure that the cylinders are actually bad. Plus that will tell you what is bad. If the air is in the engine it is a piston or rings. If it is in the exhaust then it is exhaust valve. Intake would be intake valves. Or it could be a head gasket. Be sure to check before you tear it apart.

 

if its Malaysia you're reffering to, they recently launched a new dealer here.i haven't got any time to visit it yet the old dealer had my car sent to an independent merc service centre to have the performance kit bolted on. Basically they have this principal of "we sell but we don't mount".
i hope the new one have technicians to do the job including ECU flashing you mentioned.

 

It sounds like you're on the right track Charles. To me, the overheated pistons point to a lean condition. All of them being hot is easier to diagnose that a single slug. With all running hot, your wideband will give you the A/F numbers, and hopefully it's the MAF as suspected. The MAF is a common component, so it'll make sense it that's it.

Too bad widebands don’t live longer. If they did you could use one with an LED display. That way if the MAF is the culprit, you’d have a warning if the next MAF fails.

How long before it's back together again?

 

The engine will be assembled this week. I am hoping to get over there and clean the engine compartment and paint the blower. I am guessing by the end of the month...maybe.

 

If it is a molbdenum kind of coating, it is usually on the skirts(i.e the sides, not the tops). The coating is there to reduce friction between the cylinder walls and the sides of the piston. The tops usually don't have a coating because of combustion pressure and temperatures, they would never last. On some of our high heat applications we get the tops of the pistons, valves and the combustion chamber done in a ceramic coating but it does not last long.
Maf could definitely be a problem as it would not read the right amount of air going in and would not fuel for it. Manifold absolute pressure(MAP) i find is a lot better setup on a boosted application than MAss air flow(MAF). Ofcourse you don't have that option because running on a stock ecu M.A.P cannot be calibrated and ran.
I think you missed one of my questions about how Kleeman retards timing under boost? or do they? What exactly is in a kleeman supercharger kit?
eatons type blower
pulleys
belt, fmu
IC? what else?

how much do they charge for it if you don't mind me asking. Thanks