MarcusF

Per the 2001 & 2002 press kits, the M113 uses forged aluminum pistons - both the 4.3 and the 5.5. According to the later press kits, the supercharged M113's use forged pistons as well. This webpage was created using the 2001 and 2002 press kits as a reference. It has information about the NA M113.

spr

Interesting so is the different compression a function of piston dome, rod length both or head CC??

MarcusF

The press kits don't say.

ProjectC55

I think it's the piston dome. Because the rod length would affect the bore and stroke if it were diff. Where the rod pins are in the 5.5L motors has not changed. Would not be a 5.5L motor anymore from what I understand. The heads on the 5.5L motors are all the same N/A and F/I. Read Vic's (Vrss)thread about the 5.5L heads in the w211 E55 forum.!

Jrocket

Rod length will not change bore and stroke.

csumt76

How much time was spent "tuning" the car? If they just flashed the ME and sent it back to you, some people would call that a bottled tune.

True what was said about examining the piston, I just meant it would be difficult to say what caused the issue... lack of fuel, poor timing, excessive heat etc.

mbenzman

Compression ratio is simply a matter of how much you squish the volume down to. 10 parts sqeezed into 1 is a 10.0-1 compression ratio.
Stroke and bore define the displacement. You generally don't touch these to adjust compression ratio. You generally use the piston and combustion chambers in the heads to determine and adjust the compression. Ie. dished pistons will lower compression if all thing remain the same.
Smaller volume at tdc=higher compression. Make more room and you will have lowered the compression ratio.

ProjectC55

Rod length would not chg the bore and stroke? Why not? Please
Explain!

spr

stroke is a function of the crank and rod length- what are you talking about

mbenzman

Stroke is a function of the crank throw only. Rod length will be determined by the piston design, installed height of that piston in the engine and the crank throw (stroke). You could adjust compression with the rod length but it's not typically the way it's done as usually you will hit the cylinder head if you went longer. That's why you have domed pistons. Shortening a rod is generally not used to lower compression either. Pistons and cylinder head combustion chambers are usually what gets adjusted for compression tweaking, higher or lower.
A little more on rods, the rule most engine builders go by is to use the longest rod you can as this allows more dwell time for combustion pressures to build. You typically shorten rods when you increase the stroke to compensate for the installed height of the piston, But you will lose some efficiency due to the higher piston speeds and thus the pressure has less time to act on them. A lot of serious builders will cheat by having the piston pins relocated higher on the (custom) piston to use a longer rod and offset the losses of an increased stroke by achieving a longer rod length.
Hope this helps before this gets too off topic.

PTE

Way Cool Rich. Can we said Rod angle ! or Offset Grudgeon pin Bore in the pistons. , God, I'm so happy That my Computer is up and running again
If you guy keep asking Questions, I'll never get my motor back together. I 'll take some picture of the pistons , In the engine block. I've got the motor part , {but not all apart} The pistons have a small Dish , no relief pockets for the valves . I will also c'c' the combustion chamber this week end also. JUST FUNNIN .I get it all to you guys. Thanks ___PTE___

c240classic

Have you checked your plugs for that particular cylinder yet? any abnormalities on it as compared to the rest of them, is the electrode tan in colour? any silver speckles? Is the gap different than the rest. Are all the plugs the same heat range? I find it difficult to imagine that your piston cracked under high boost pressure and the plug survived.
You need to post pictures up of the piston itself, did it scuff the cylinder wall? does it need to be bored or can you get away with a hone? Pistons just don't crack, if it happened once , it will happen again unless you find the root of the problem.
Maybe it is a bad tune, when you get it all rebuilt, take it to a dyno with a wideband and do a couple of full throttle runs to see that your mixture is ideal.
As somebody already suggested here that get all your injectors flow tested to see if one has gone static. If you are really worried that compression is too high, you can stack two head gaskets to effectively lower your compression or see if somebody makes a thicker head gasket.
There are a lot of good suggestions by people all throughout the thread, take your time and try to get to the root of the issue.

c240classic

mbenzman is exactly right. Some people might be having a little hard time understanding i will try to make it a little simpler. There are two kinds of compression dynamic and static.
Your static compression is the ratio of air that can be squeezed into the cylinder when the piston is all the way down to the amount of air that can be squeezed in when the piston is all the way up. Ofcourse we all know that air is almost compressible. Thus if a configuration is 9:1 it means that you can squeeze 9 times more air in when the piston is at its lowest possible position in the cylinder to when it all the way to the top.
Even though you have a static compression number there are too many variables inside a variable combustion engine as in rod stroke, rod length, dwell times cam duration and lift, especially timing. You can pack air in through the intake valve but if the exhaust is bleeding before combustion occurs, you loose compression.
Rod lengths are not adjusted for increasing or lowering compression, although the dwell will affect your dynamic compression, rod lengths are adjusted to increase/decrease your rod-stroke ratio. Ofcourse you can change crank stroke too, or a combination of the two. Rod to stroke has a big effect on what rpms you can wind up your motor to and where your power band will be. HTH

Thanks

Charles Joseph

Plugs were fine. No difference from the other 14.

The injectors are going to KLEEMANN to be flow tested.

No cylinder scuffing, the block will not be honed. The piston shows no signs to any of the usual suspects (lean, detonation, or oil starvation). There are no signs of scoring (block or piston), no discoloration, no pitting, no anything. If you didn't see the cracked ringland you would swear it is a perfect piston.

As far as the tune, if it had gone lean you would have seen it in the piston. The tops of the piston, or pistons, would show the telltale signs. Mine do not. I do plan on dynoing the car once it is back together, whenever that ends up being.

KLEEMANN has no problems with the compression and neither do I. I am one of 2-3 KLEEMANN cars with any type of failure. That is less then .1%. I am still leaning towards a defective piston. I have been in contact with MAHLE, the manufacture of these pistons to get them involved. I am hoping they will inspect the piston and offer a more educated guess as to why it broke. What I am really hoping for is that they want all the pistons and will work me out some kind of deal. Unfortunate Mercedes still owns the rights to this casting number, so its not available aftermarket.

The pictures are posted at the top of this thread. https://mbworld.org/forums/clk55-amg-clk63-amg-w208-w209/188486-pics-bad-piston.html They are very low quality. I hope to have better pictures tomorrow.

Jrocket

Thank you mbenzman and c240classic,I did not have time to explain the bore,stroke and rod deal.

Many people get confused and think by changing the rods length,you are changing the stroke.You can take the rod completely out of the motor and the bore and stroke will still be the same.

mbenzman

Nice teaser Patrick!! Ok you got dished pistons to drop compression, so more boost is happening or what? I'm sure you have some coatings on the pistons as well. Is the bore and stroke untouched? It should be wicked, a modified Kleemann S4. You are making me want to play too!


Amen. You could shorten the rod until the piston barely clears crankshaft counterweights and the piston sits 2 inches down from the deck at tdc and it will still have the same bore, stroke and displacement, just a lower compression ratio. If you could lengthen the rod without the piston hitting the cylinder head, you would still have the same, only a higher compression ratio.

blackbenzz

Wow, that sucks man. I hope you get everything figured out. If you decide to sell the kinesis wheels let me know

Jrocket

If you are set on using Mahle's then yes,but if you can live with a different manufacture(which I suggest you do so)then you can have that EXACT piston copied.1 complete set of pistons(8) for the price of 1 AMG factory Mahle piston.

Charles Joseph

The problem is that they can copy the design but not the material. The pistons in this motor are not a standard run of the mill piston. They are designed so that they are very quiet on start up, and can take the abuse of pulling around a 3600 lb car at high rpms. I have talked to JE, CP and Mahle. JE and CP say that they can copy the piston, but suggest that I stick with a stock piston. That is right from them. KLEEMANN also suggests sticking with a stock piston due to the processes by with the stock piston is made. The M113 motor is a very complex motor. Mercedes spent lots of money designing every piece of it. I do not think that I can get a better piston from JE or CP.