Mahle vs JE

[Tippy]

Wow, had no idea

[Trackrash]

Yea, that is what I was thinking. The Chinese could be supplying who knows what to Mahle.

[tom1394racing]

In my former life, I worked for a large jet engine company. We had several joint ventures in China who manufactured critical aerospace parts for our commercial engines. Once the quality requirements were clearly understood, these ventures produced reliable, quality parts that were as good as any other supplier domestic or international. Only federal export restrictions prevented us from manufacturing parts for military engines there.

[sp_cs]

Just wanted to bump this, as im contemplating fitting the latest JE pistons in my road/street engine, per the pic below

Compared with 98mm Mahle P&Cs, what should i expect with 10.5 98mm JEs pistons in Mahle cylinders?

This recent blog suggest piston slap should be reduced with the latest coated skirts.

A Look at JE Perfect Skirt Coating and How It Compares to Other Coating Types

Should i expect any other ‘issues’ with JEs? Eg increased oil consumption, smoke at startup, smoke once hot - etc etc?

My engine builder is planning road spec ring packs, coated skirts and under-milled piston crowns

Thanks in advance

[lvporschepilot]

I have no noise nor issues with mine. Running .0025 clearance on 92mm cylinders.

[Trackrash]

NO piston slap with my un-coated 9.5 -1 JEs in my Mahle 95mm cylinders. 0.0015" skirt clearance and a measured 9.8 -1 CR.

BTW, I don't think the pistons in your picture are 10.5. The pistons I bought came with rings, Goetze.

[mikedsilva]

Interesting thread:
I have a 3.0 Carrera motor (6 bolt crank) and am contemplating changing out the stock 8.5:1 piston... Was contemplating just finding a set of used Mahle 9.3 or 9.8 pistons but am leaning toward either JE or CP pistons. So far, I have been told to only use the CP.
I know my Mahle P&C can come in 3 different tolerance groups and you should use the matching Ps with the Cs.. but I don't understand how you can just buy a set of either JE or CP and use them in any of the different cylinder groups.. ie, 1 size fits all?
(amateur builder here)

[sp_cs]

Originally Posted by lvporschepilot

I have no noise nor issues with mine. Running .0025 clearance on 92mm cylinders.

Originally Posted by Trackrash

NO piston slap with my un-coated 9.5 -1 JEs in my Mahle 95mm cylinders. 0.0015" skirt clearance and a measured 9.8 -1 CR.

BTW, I don't think the pistons in your picture are 10.5. The pistons I bought came with rings, Goetze.

Thanks both - were these recent builds? I ask as i believe the JE piston in my photo is the most recent design, and has the coated skirts to help reduce piston slap (as per my earlier link)

The piston may not be a 10.5 - it was a photo forwarded to me from another rebuild, where the CR hasn't been confirmed.

[lvporschepilot]

Originally Posted by sp_cs

Thanks both - were these recent builds? I ask as i believe the JE piston in my photo is the most recent design, and has the coated skirts to help reduce piston slap (as per my earlier link)

The piston may not be a 10.5 - it was a photo forwarded to me from another rebuild, where the CR hasn't been confirmed.

I have not run the coated skirt but just make extra certain the wall clearances are indeed correct with the coating.

[Trackrash]

Here are mine bought from our host about two years ago.

The difference in the cylinder's bore from smallest, {0}, to the largest, {3}, for the 95mm SC, is 0.028mm. Or about 0.001". Could possibly make a difference in piston fit, I guess.

[sp_cs]

Thanks both

In other news, I found this JE blog below - it suggests 4032 over 2618 for road/street cars

2618 vs. 4032 Piston Material Differences

[Rusty911]

I am curious if Mahle uses 4032 for its racing pistons? I have read that they use quite a bit of silicon in their forgings and they have a relatively low expansion rate. I think their recipe is a trade secret but would be interested if anyone knows for their Motorsport line of pistons/cylinders.

[Mark Henry]

I have Nickies and JE's in my 1967 bug with a type four conversion.

I have German RSR (style) Mahles and stock plated jugs in my 914/6

The Mahle have a much tighter clearance than the JE's, but both have worked flawlessly so far. The mahle had no skirt treatment so I DFL coated the skirts and ceramic coated the tops.
My 3.0 mahles didn't have a history, they were German NIB. From what we gather they were likely ordered by a race team for a stock based backup engine, as these pistons look like RSR but are made for a stock 3.0 head chamber size. pic below.

I've also built several 996 engines using the JE's/Nickies, IMO the JE piston is superior to the stock 996 piston.

[lvporschepilot]

Originally Posted by Rusty911

I am curious if Mahle uses 4032 for its racing pistons? I have read that they use quite a bit of silicon in their forgings and they have a relatively low expansion rate. I think their recipe is a trade secret but would be interested if anyone knows for their Motorsport line of pistons/cylinders.

I don’t think Mahle is going to let loose their exact recipe but you can bet it is 4032 or something very close to it for most of their high powered street designs while I bet they use 2618 for racing with high boost as it is indeed stronger. For Ferrari stuff I use JE almost exclusively as the price point between Mahle and JE is downright disheartening or just NLA. I really don’t think it matters between these two as long as the engine is built correctly. Frankly i think that’s how a lot of these rumors get started.

[Neil Harvey]

I have read with interest and with some intrigue this discussion about piston material. As a business that is involved everyday with piston design, it’s interesting to read what others are saying.

Every piston we use is designed from the ground up for its own purpose. We do not buy “off the shelf” pistons for any of our engine projects. This gives us a real insight into what materials are available, their use and requirements.

Reading some of the thoughts posted, I find it hard to understand how some can know what the composition the material used by some piston manufacture’s. My guess is, they are too.

I concur with Steve (Rennsport), Mahle and Pankl who we use exclusively, will not disclose this information. However, we do ask for certain heat treating and other processes that can only be done on certain materials with success. We rely upon our partners to supply us with the best possible product, and often are suggested to include additional features and or make changes, which continues our quest for the best piston available.

The choice between the two most common materials, 2618 and 4032 is not as simple as some have made out. Strength of material is only one factor that needs to be considered. The forging the piston is constructed out of must be considered as well. Most of the Pistons produced for the ‘off the shelf” Porsche world, commonly sold by the aftermarket are an open wide spread pin boss type, with simple skirt designs, large pin diameters, tall ring groove geometries, wide ring widths and long compression heights. These are made to fit multiple applications with the differences being in dome and static compressions. Large compromises must be accepted in these designs, performance and weight being two huge ones.

Many of the more modern forgings are made only from one material, so in our design process, we must also consider what forging we wish to use. Many of the modern “boxed type” forgings are limited to certain bore sizes as well. So, to say that a 2618 piston is stronger than a 4032 piston without considering the forging used is not totally correct.

Today, we are using more billet pistons as the limitations of available forgings becomes ever increasing. We have just started testing our first “printed’ piston which is an all new direction for us. We are on the trailing end of this technology and having to learn all about this and the requirements when using these pistons. I believe this will be the direction piston makers will go as the manufacturing process is easier. The cost to produce will become less once the technology becomes more mature.

Many of the “off the shelf” pistons sold to the Porsche aftermarket are typically copies of existing historic pistons. They are almost an exact copy of pistons supplied years ago. Many of those selling them are not engine people but parts houses where design is not important or understood. Even the piston manufacturer’s need a drawing to make something different. This continues the life expectancy of these older designs. They are well proven designs, will work just fine as a basic piston, but if you are looking for more performance, these early designs have limitations.

Material expansion, skirt “cam design” wall clearance, skirt length, ring widths, ring tension, cylinder coatings, etc., all play a huge role in the performance you will gain from a good design. In most cases, in the aftermarket, many of these factors are not so important, but in the performance world they play a huge role. But, even in street engines, a more modern design will help. It will never hurt. Friction will affect a street engine as it will a race engine.

Another reason why we use certain suppliers exclusively, is to control and eliminate the chance of our piston designs copied and sold. This can still happen, but we at least do not hand over designs without some chance of keeping these to ourselves.

[Speedy Squirrel]

Mahle uses M142. It is on all of their drawings.
Si 11-13%
Cu 2.5-4.0%
Ni 1.75-3.00%
Mg 0.8-1.2%
Fe <= 0.7%
Zn <= 0.3%
Mn <= 0.3%
Other <= 0.2%
Bal Al
M142 offers the dimensional stability of 4032 and the fatigue characteristics of 2618.
Mahle spends 60 Million a year on materials R&D.

[Rusty911]

That’s interesting. Thanks Speedy Squirrel!

[MST0118]

Good info. I am curious if the Mahle cylinders are also made of 142 alloys which might indicate that Mahle pistons are better matched with Mahle cylinders as compared to LN nickies cylinders to get closer tolerances or is that a flawed assumption?

I’ve seen posts where LN cylinders match JE pistons and CP pistons well but not sure if the same is true for Mahle pistons w/ nickies?

[Trackrash]

Originally Posted by Speedy Squirrel

Mahle uses M142. It is on all of their drawings.
Si 11-13%
Cu 2.5-4.0%
Ni 1.75-3.00%
Mg 0.8-1.2%
Fe <= 0.7%
Zn <= 0.3%
Mn <= 0.3%
Other <= 0.2%
Bal Al
M142 offers the dimensional stability of 4032 and the fatigue characteristics of 2618.
Mahle spends 60 Million a year on materials R&D.

I doubt that Mahle uses the same alloy in both it's forged and cast pistons. But what do I know.

[Speedy Squirrel]

I thought we were only talking forged pistons. M142 is a forged alloy.