Mahle Pistons

[Caithness]

Detail on 2.0 6-bolt piston
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I've searched and found two (2) threads. What's the scoop on these pistons? I found a discussion on the local .org that said Mahle recommends a .002 wall clearance, which is incredibly small if true. The things are more than 50 grams lighter than any other piston I've found full info on, which is huge and could make a big difference in high-rpm reliability. That and they're not much more than most other mainstream pistons on the market. They look like a very attractive package. So why is nobody using them yet?

 

[treebonker]

Maybe because it is generally known that the 4032 alloy is best suited for N/A applications. The alloy used also explains the lighter weight(although 250g is surprising) and tight clearance you can use with mahle's. Not considering the rods, in a 150mm rod and 350gram piston setup 40g less reciprotating mass will give around 12% less(500lbs) inertia force at TDC at 9500rpm and around 11%(300lbs) in 7500rpm, while heavier I'd still opt for pistons using 2618 which is known to be more suited for boosted/nitrous application d/t it's better tmp/str characteristics. Also when a failure occurs the results will be less dramatic where as the high silicone content in the 4032 alloy makes it porous in effect and turns into shrapnel.

-treebonker

 

[94awdcoupe]

I am building my 2.3 for my evo 1 with these pistons. The quality is exceptional. Wiseco pistons are 4032 and people have very good results with them. I choose this piston because I dont want piston noise on start-up. And I don't plan on running more than 25psi with them. My experience with 2618 is if you dont here them when cold you set the clearance too tight and they will pinch when trying to run high boost. Mahle has a patented skirt design that flexes at the surface. this is why they can be run at very close tolerance. I wouldn't go .002 though. Maybe .0035. I am going to run em at .004. I wouldn't go lower than .0055 for a 2618 forging. My advice with piston to wall clearance is better be safe than sorry. If they scuff the block has to come back out for rebore.

And the reason they are light is because they are a strutted skirt design. The skirt is shaped like a bathtub and not a circle. This is how the evo8 pistons are designed. Light but strong.

 

[treebonker]

Wiseco pistons are 4032

No. They use low-silicone 2618 forgings for the 4g63t

My experience with 2618 is if you dont here them when cold you set the clearance too tight......I wouldn't go lower than .0055 for a 2618 forging

You have just lost all of your credibility.

-treebonker

 

[insanewayne]

Hey Tree bonker, I really need more informationg on this. I read what your saying, and you seem to know your shit, but has anyone tried them on high boost, my stuff on it's way tot the machine shop, and my machinist said that the ross's I was planning on using are race pistons, which aren't all the great for a DD street/strip car, even though you can't hear it, they are slapping, and there designed to witht he looser tolerances they run. He said he saw some mahle the other day and they looked like a great peice, and that there using them in F1 and Nascar....but, I don't care abuot N/A . I'm going to bring up your first post with him and see what he has to say. I will be running 25psi on the street, and 30-35 on race gas, with all the mods to back it up. So you would say definately no to the Mahle's for that then eh?

Thanks a bunch,

Wayne

 

[drivemusicnow]

Any more information on these?

They look like a decent piston, And I know that Mahle is used in OEM Porsche turbo motors, as well as BMW and others. I guess I just wanted to know whether anyone was running them, and if there is any more tech available on this topic.

 

[GTM]

They look like a decent piston, And I know that Mahle is used in OEM Porsche turbo motors, as well as BMW and others. I guess I just wanted to know whether anyone was running them, and if there is any more tech available on this topic.

I've used them since the late '60s for both Porsche and VW big bore kits with no problems. However tremendous piston and metal improvements since then have reduced clearances mostly for emission reasons.

Speaking of fitting clearances of .002" vs .005" is the difference between race and DD. Mfgs as a general rule consider the smaller clearances light duity and the .005" for heavy duty applications. They include pulling trailers, fully loaded car, long grade pulls, automatic tranny all generate sustained heat with greater piston expansion over longer periods. Playing stop light grand prix isn't going to present the problem unless it's wide open road and WOT.

I seriously doubt that at .005" you are going to hear piston slap unless you are lugging the engine.

Cheers,
GTM

 

[Turbo Shogun]

Anyone know what compression these pistons are running? It seems my block needs an overbore and I was looking into a set of Wiseco's. For a little more buck, I've been considering these as well.

 

[alex]

I found a discussion on the local .org that said Mahle recommends a .002 wall clearance

You won't have to worry about the clearance, the Headgakset should make up for it.....typical heagasket is around 0.032" (approx.)

 

[drivemusicnow]

You won't have to worry about the clearance, the Headgakset should make up for it.....typical heagasket is around 0.032" (approx.)

He is talking about piston to cylinder wall clearance.

I think no matter what piston I use, I'd be putting at least .0045" in there. Most likely more.

I'm just curious as to how these compare as far as strength. Is this Mahle 4032 alloy more likely to fracture when detonation occurs?

This month's Race Engine Tech mentions Mahle with respect to their Le Mans 2006 preview article. It mentions that Mahle recommends 4032 due to its high silicon content making it more wear-resistant, as compared to 2618, "the normal choice for sprint races." Goes on to say the 4032 is hard enough to not require hard anodizing on the ring lands. Hard ano hurts the ring seal.

My other question is about CP pistons. In every other boosted and N/A application I've seen, CP and Mahle are typically considered "top of the line" pistons. CP now makes both 2.0 and 2.3 liter pistons for us, and I guess I'm trying to figure out if it would be worth it to go with something that is new, but has a better reputation elsewhere, or just go with what is known to work in the DSM community.

 

[alex]

My bad, I should have read a little bit closer. Sorry about that.

 

[GVR4592]

And the typical headgasket for our cars isn't .032". Stock is .042" compressed, Cometic is.051" and the Mitsubish MLS .067".

 

[94awdcoupe]

Treebonker, wiseco uses both alloys for their pistons. The shelf stock pistons that can be bought for around 450 are the 4032 alloy. These have been successfully run on 600hp setups with .035-004 wall clearance. You CANNOT run .0035 wall clearance on a 2618 forging. They will pinch running 25 psi. Wiseco does have 2618 alloy pistons. They are called 1400hd extreme duty pistons. They cost 520 and they don't come with rings. You can check them out at the link below. My recommendations come form building 50 plus 4g63 motors. I have my own torque plate that I had made. I have used just about every piston out there for the 4g63. I have seen another shop locally bore an engine .0135 piston to wall. Yes thats 13.5 thousands. They mismeasured the piston and bored .030 overbore for .020 pistons. This engine surprisingly ran very well for about three months. The excess piston slap was noticable but not real loud like you would think. I will stand by my recommendations as good advice. I have seen 5 out of 5 sets of JE pistons (2618) pinch from trying to run them at .0035. And these were all 450hp or less setups.

http://www.importperformanceparts.net/

 

[herostar]

My JE's slapped really bad on an .020" overbore and 0.004 clearance.