oem piston alloy

[97eclipseNT]

Does anyone know what alloy the mitsu 6bolt oem pistons are cast from? Im doing a project in my materials class at penn-state erie on a piston failure from my 91 tsi and need to know the alloy its made from. thanks

-Mike

 

[TunaTalon]

Hypereutectic.

I was unable to find a reliable source to confirm my memory of the alloy with Google but on the following thread Defiant is the proverbial "usually reliable source".


http://www.dsmtuners.com/forums/showthread.php?t=107649&highlight=hypereutectic

 

[fourreGsixty3]

Hyperutectic pistons are the same as normal cast piston's BUT they have increases stregth due to a higher amount of silicon in them. The amount of silcone is increased by 16-19% from normal cast to make them hyerutectic [hyperutectic means "Over-eutectic"].

PS: The silicon that is used with our pistons has the consistancy, and feel of powdered sand...not the same as Pamela Andersons ;D

 

[97eclipseNT]

haha thats fantastic. Does anyone know the actuall number of the alloy? We need to have a matweb printout for this. I think its 3 numbers suck as 388 or 398.

 

[TunaTalon]

haha thats fantastic. Does anyone know the actuall number of the alloy? We need to have a matweb printout for this. I think its 3 numbers suck as 388 or 398.

“suck as…”? Did you transpose a ‘k’ for a ‘h’ or just omit the trailing ‘s’?

The factory pistons are Hypereutectic which does not define a specific alloy. Google failed me on the exact alloy used by Mitsubishi. For what it’s worth, Keith Black Hypereutectic pistons are made from alloy 390.

Aftermarket pistons to compare with use either 2618 or 4032 alloys. The 2618 alloy is used in JE pistons and 4032 alloy is used by Wiseco. The properties of those two alloys are given on page 4 of the JE document ( http://www.jepistons.com/pdf/2006-sportcomp1.pdf)

 

[bpestilence]

Cool project. I did the same project in my materials class in college, but I was more concerned with pros and cons of the various allows. Fracture toughness, thermal expansion coefficient, etc. The hard part was running a Charpy V-notch test and keeping the pistons at the proper operating temperature.

Too bad that project is on another computer. I even did grain structure comparisons of the various allows. Alloy 390 looks really cool under the microscope.

 

[Purevil]

“suck as…”? Did you transpose a ‘k’ for a ‘h’ or just omit the trailing ‘s’?

The factory pistons are Hypereutectic which does not define a specific alloy. Google failed me on the exact alloy used by Mitsubishi. For what it’s worth, Keith Black Hypereutectic pistons are made from alloy 390.

Aftermarket pistons to compare with use either 2618 or 4032 alloys. The 2618 alloy is used in JE pistons and 4032 alloy is used by Wiseco. The properties of those two alloys are given on page 4 of the JE document ( http://www.jepistons.com/pdf/2006-sportcomp1.pdf)

Actually Wiseco's are also 2618 and so are the majority of aftermarket forged pistons for our cars. The only pistons that I know of that you can get in 4032 are Mahles. CP and Arias can make pistons using either alloy if you specify.

2618 has better high-temperature characteristics, it contains virtually no silicon. This material expands and contracts more, so greater bore clearances are needed to prevent scuffing.

4032 has higher silicone which makes a lighter piston that has less heat expansion, but the tradeoff is that it is much more brittle and cannot withstand abuse like a 2618 piston can.

Heres a link with more info for those that are interested.
http://www.stealth316.com/2-pistonguide.htm
Piston And Ring Technology- Car Craft Magazine

 

[97eclipseNT]

Sorry about the typo in my last post guys but thanks for the responses. We will be doing atleast a rockwell hardness test on the piston and probably a few other tests. We also have to have a matweb printout of all the properties of the specific alloy and a solid model made in pro-engineer. the last thing in the project is a report on it explaining why it failed and ways to make it better i.e. different material/manufacturing process. I just thought i'd give everyone an overview of the project for those who are interested.
thanks again for the help guys.

-Mike

 

[2gGSX]

All this talk makes me wish I had a cooler major

 

[TunaTalon]

Sorry about the typo in my last post guys but thanks for the responses.

-Mike

You just had a one letter typo. I posted bad data. Bad, bad, bad. During research on my stroker project in 2005 I selected Wiseco pistons for the lower piston/wall clearance because of my worry about piston slap and side loading friction. Sometime over the past two years I have conflated low clearance with low thermal coefficient of expansion. Wrong.

When Purevil corrected me I went back to the old post by Brian Nutter to prove my case. Guess what? In post 8 of http://www.dsmtuners.com/forums/cylinder-head-short-block/111079-arias-pistons-weisco-pistons.html Brian explains the low clearance and names 2618 as the alloy.

For more information about what can go wrong in the combustion process to cause those holes in your pistons please see http://www.jcmmachine.com/PDF files/JCM Tech Report ch3.pdf