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Old 08-10-2005, 09:22 PM   #1
13secwrx
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Default mahle pistons and oliver rods...

Has anyone experienced anything on these two manuf.

I am having a 2.5 sti block built and these are the materials they are using ....

a. are they any good ?
b. i cant tell if the pistons are forged from the website.
c. any input would greatly help...


thanks
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Old 08-11-2005, 12:15 AM   #2
ebeck
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I am not sure there are any better pieces out there. Anxious to hear if you have oil burning or piston slapping issues.

Look here as well. They actually move the rings to deal with a couple of issues as opposed to making them with features Subaru deliberatly avoided.

That is where I am likley going for pistons. At least today. http://www.techworkseng.com/
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Old 08-11-2005, 12:16 PM   #3
BigJ04STi
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I have held 2 sets of the Mahle 99.5mm pistons in my hands...

I must say, they are quite sexy, ridiculously light, and for the cost they come with everything (including their rings).

They are fully coated, skirts and tops, and have a dark grey coloration throughout. And again I must say, light as anything...

All in all I think I may have to use the Mahle pistons in my motor build. I am awaiting anothe rmotor to be built with them, and I'll see how that sounds and runs.

Again, I must say....very sexy pistons.

The rods I can't speak on at all, since I've never even seen those...

Good luck
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Old 08-11-2005, 01:02 PM   #4
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oliver rods are sweet. so are those pistons.

Sounds like some nice items being used for this build.

Please let us know how it runs when its all done......

-Matt
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Old 08-11-2005, 10:00 PM   #5
jaxscuby
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mahle, makes pistons for porsche and other euro cars.
yes they are good pistons.

oliver rods, good also but it has been awhile since I have
read anything on them.

my 2 cents
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Old 08-11-2005, 11:04 PM   #6
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Yes Mahle makes pistons for many exotic cars including anything from porsche to VW.. yes the air cooled SUBARU. From what I have seen alot of their pistons come with a side coating, so remember if you are using a piston with a side coating you would set that piston up about .001" tighter than a non coated piston.
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Old 08-12-2005, 01:43 AM   #7
13secwrx
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I will keep you posted...I just hadnt read much about these two manuf. and I wanted to make sure that my engine would be stout w/good parts...all you hear is crawford this and axis that..cp this and pauter that...so I was being a little different and I wanted to make sure it was good stuff.....500 whp here I come...hopefully
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Old 08-12-2005, 02:16 AM   #8
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I have used Mahle pistons in lots of VW's but never in EJ motors. They are respected and Mahle has ALOT of experience building pistons for Boxer motors. I would not be suprized if they work fantastic. I plan on using them in my next motor but not until this stock motor gives up the ghost.

Clark
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Old 08-12-2005, 02:02 PM   #9
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The PowerPak pistons are forged from 4032 high silicon aluminum alloy. So, you'll be able to run a tighter piston-wall clearance and reduce piston slap.

The ProSeries are a low silicon alloy, but they're only made in the 2L size.

I sent Mahle the sample piston to make these around a year ago. So, yes, I think they're good.
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Old 08-12-2005, 02:21 PM   #10
bboy
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I'm buying the Power Pak Mahle pistons made of 4032 alloy. I'm having a great deal of trouble finding out how small the bore clearance can be. CP says to use 0.0025 with they're 2618 pistons and the one person from Mahle I've talked to says the same for their 4032. Lot's of sites say that you can run the 4032 alloy with a tighter clearance but I've never found any proof that this is true.

In addition the thermal coating on the piston crown should also help reduce clearance.

The hypereutectic piston are suppose to reflect more heat up into the chamber than either eutectic (like 4032) or hypoeutectic (like 2618). This has something to do with the grains of silicone in the hyper U pistons. Both U and hypo U lack the silicone grains (deposits). The addition of silicone hardens the aluminum, so that it is more wear resistant than the low silicone variety (2618).

You might think that heat transmission would vary with silicon content linearly, but it seems that only the hyper-U alloy has the reflective property, making the eutectic and hypo U alloys similar with respect to heat transmission and thus the bore clearance as well.

As far as I can tell, the advantage of the 4032 alloy is primarily in the ring groove where the harder eutectic material wears better than the soft hypo U 2618 material.

More than you wanted to know, I'm sure.
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Old 08-12-2005, 02:29 PM   #11
13secwrx
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Why are they so inexpensive if they are soo good...I found em for as low as $450...other pistons are usually around 600-700 ....but I trust in my builder and your opinions/statements have eased my troubled mind...


thanks
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Old 08-12-2005, 02:47 PM   #12
Visceral
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bboy,

I am not a metallurgist. However, the coefficient of thermal expansion for 2618 alloy is approximately 15% greater than that of 4032 alloy.

In my "in progress" 2L engine, I have a 0.005" piston to wall clearance with the 2618 alloy ProSeries pistons (Mahle's reccomendation for my intended use). I know someone else who is running them with 0.004" clearance in Australia.

13secwrx,

Think of them as a good deal, though most 2.5L pistons I have seen are ~$500.
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Old 08-12-2005, 07:28 PM   #13
bboy
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Most of the forged pistons I've priced are around $500. The diff with the Mahle pistons is they are coated and come with rings (they come with rings now as per Mahle rep in NC). That's worth $100 or more.

I've read the 15% coefficient number in a variety of places but it does not tell the whole story. So it expands 15% more, that's a pretty small number. A 15% larger clearance on 0.002 is 0.0003, that's less than the tolerance of the piston. I think the real expansion is in the heat that is taken up by the forged pistons. They transfer more heat to the skirts, the skirt expands more, you scuff. Hyper U pistons don't "absorb" the heat but reflect it more, cooler skirts, less expansion, tighter clearance.

Then there is the thinness. Forged pistons are often thinner, less mass means less metal to heat, more heat to disapate, and so on.

Piston design is very complicated with multiple variables affecting bore clearance. We are left just reading the specs off of the instruction sheet, but we don't know much of why this 2618 piston has one clearance, and another, a different one.

CP directly told me 0.0025 for their 2618 alloy STI pistons
Mahle told me on the phone 0.0020-0.0025 for their 4032 alloy Power Pak pistons.

We'll see what the package insert says.

There is at least one Evo owner running the Power Pak pistons at 0.001, but we don't know what his cylinder walls look like.

At 0.0025 the CP pistons make no audible noise on start up, I'm guessing the Mahle ones will be the same with the same or slight less bore clearance, and the fact that the are coated. I'm hoping the Mahle pistons provide a bit more longevity give that they are harder material--but I must say the CP pistons are the tried and true route.
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