PTE

I was working with a local Rotax Engine rebuilder & This is the shop I use to, work at on my days off. MJ & I were disscussing new piston designs he was doing for a 104 mm bore 3cyl. 4 stroke Rotax. So I went to the truck and pulled out a January Issue of Racecar Engineering. From the UK. There were these really cool new pistons . They had a thermo image picture , Slipper style skirts, Enforcement ribs,. Like brand new & only F-1 teams have them!! Well MJ goes off to the office with a smirk on his face . Spins the dial on the safe Pulls out a new unmarked box of these pistons. I Quick run to the truck & get out some new AMG Mahle pistons for a E-55 & start comparing the measurements!!! The New Piston uses the same ring package as MB These are a Forged piston and will have a slight rattle on cold stat up
I don't have much info and probably will not answer many of the questions But I will read all your OPINIONS Thanks for your Kind particapation ___PTEngineering___

rflow306

Very nice looking piece, but it does not surprise me they are CP's.

Yacht Master

Looks like they are cooling the piston via the rod.
If MJ keeps them in the safe, I am not even going to a$k.

Zod

am lost, bring it down a lvl for us non engineers please

PTE

The thermo imaging pic , shows the head transfer is done through the rings , then to the Cylinder bore. This is why piston type & fit is Critical. You want the piston to run parallel to the bore so that the heat on the dome travels down to the ring land . then to the ring. If the ring is parallel to the bore ,It then has max contact , for the heat to be transfered , to the bore ,then off to the cooling jackets & coolant. Now, not all the heat will be transferred. Some will make it to the skirts & Gudgen pin bore. Rotational thrust will move the piston to one side of the bore . Some of the heat will transfer at the skirt some will travel to the Gudgen / wrist pin bore . To much heat in either part / area is not good. Gudgen pin bores open up & pound out. Skirts drag on the cylinder bore. This piston tech can get very involved , Try to encapsulate all of what is expected from a performance 4 door auto. Performance / HP , low oil comsumption. Low emissions, N V H. And of course Long Life. Hope this helps a little ___PTEngineering

BrianS

Me neither! CP makes and excellent product. Here's another example of their work for an unrelated project I had them custom make a couple sets for me.

blackbenzz

How many oil passages are drilled into the piston? Also why is the underside of the piston so thin compared to "conventional" aftermarket forged pistons? Do you plan on coating them in order use them with the alusil (or nicosil, dont remember which one our block has) block?

PTE

If I were to have some pistons made . ??? I would specify them to be built to use the MB OEM ring package . That way ,all would work with Alusil Liners. I was also thinking of having them build .003 over , so when we hone the cylinders , we would have the right RMS finish & piston Fit with a straight bore. and thats one thing good about using a seasoned Block . Cheers ___PTEngineering

vrus

Oh man.. those pistons look SWEEEEEEET!!!!!

The set that Brian posted kinda resemble the shape of mine from the inside view.

BlownV8

You need iron coated pistons to work in an Alusil bore. You can't run aluminum pistons in an aluminum bore unless either the piston or bore is coated. The metals have to be disimilar or you will be building an expensive grenade.

PTE

Not any more !! OEM AMG 5.5 kompressor Cast piston is not IRON Coated. The Skirts have a Small Patch of break in slide coat of sprayed on break incoating. And it is gone at 8000 miles. Your info is very old 70 & 80 tech. Go find a January 08 issue of Racecar Engineering , from the UK. you will find it at Barns & Noble, The article is Nascar Pistons . Newer alloys & Smaller skirt designs with minumial patch contact area are discussed . In fact they have already said that the use of coatings may nolonger be needed. My guess is not many of our forum readers have had a M-113 v-8 Kompressor apart. There is a oil spray rail , that sprays oil on the under side of the piston dome. Used to cool the piston dome. And if you look closely at the new type of oil control ring package , it is very small. . In fact if you may notice the the oil return holes at the lower ring land actually create a small 1/2 pipe passage for some of the oil to weep / wick down to luburcate the shirt. Why do I know this.?? I've have had to many M-113 engine apart lately . Funny thing here , because even the new OEM replacement MB pistons I got from the dealer were new in the box & I open them right at his counter for inspection. The poor guys Eyes got real big, When I found the 2nd ring installed up side down. marking dot goes up. and missing upper scraping oil ring on the oil control ring package. on 3 of the 8 pistons .The parts manager & SLR tech was called in right then . They were very surprised. Heir Johann at AMG was human on that day & made several mistakes that week. Cheers ___PTEngineering

BlownV8

There are other types of coatings available but you must run a coated piston in an Alusil bore and Mercedes adheres to that rule. It's still applicable now.

PTE

Blown V-8. You are correct ! but the coating is not Iron. It is a Break in Slide ,low friction coating they have applied . It does the job well , and is not cheap. It is 3 additional manufacturing steps done to the piston before it makes it way to the cylinder. They would like to get rid of those 3 steps. New technology in piston design & manufacturing has already proven they can work in modern engine cylinder bore materials & electrical hard coatings
Thanks for your insite ___PTEngineering