berni29

Hi Geolab

I have had a look at my Mahle piston crowns and cannot see any number stamped on there. Maybe it is too fine to see under the thin layer of carbon. Can you tell me more precisely where I would find the stamp. Or the piston weight because I have suitable scales.

I did try to look up further information about this on the net but could find nothing on revised pistons for the 993.......

All the best

Berni

berni29

Hi

My new pistons have the part number 100P47 and the old ones 100P45. I have posted a question on the Pelican engine rebuilding forum about this, but no answer yet.

Berni

IXLR8

Paint stripper does an excellent job of removing carbon. You know, the stuff that smells like ammonia...use in a well ventilated area. Do not scrape with metal.

IXLR8

Berni,

This Mahle site shows info for a few models including the 01/94 to 12/95 and 1996 to 1997 Carreras.

When you open each up, Show Engines icon and then select of of the Show Products icon and then Show Details icon for the piston, some show the P45 and others the P47 designation.

Have a look at your hood label and check to see what engine designation you have.

Maybe they're just production numbers.

I'm sure some of the engine builders on here will shed light on the subject.

berni29

Hi IXLR8

Thank you very much for posting that information. The "47" pistons are for variorams, and the "45" non varioram. Mahle list the compression ratios as being different as well. I just had another look at the pistons, and although both types look identical, they are not. The profile is the same but the centre depression is narrower on the later pistons.

I will post a new thread asking about this.

Tks again... Berni

trophy

The information there is very interesting, my understanding was that all 993's (road cars) were 11.3:1 compression whether it is Varioram or not.

I would be really surprised if the Mahle piston is infact 12.3:1, every bit of literature I have (Porsche factory and other) list all 993's at 11.3:1, and most measure somewhere in the 10.8:1 area.

If this is true and the Mahle piston is 12.3:1 then I will be buying a set if I ever rebuild, I have an aftermarket ecu and can take advantage of the extra compression. Will be interested in finding more info on this.

berni29

Hi Trophy

If you have a look at that Mahle link you can see the following....

504 28 00
100 P 45
M 64, .08,
B 6 petrol, 3600 cm³, 200 kW (272 PS), 11,3:1
air-cooled,

504 37 00
100 P 47
M 64, .22,
B 6 petrol, 3600 cm³, 210 kW (285 PS), 12,3:1
air-cooled,

And the pistons are different. The narrower centre area says to me that it could be a higher compression piston.

Tks

Berni

IXLR8

Hi Berni,

That is what I thought at first as well, but if you look at some of them in the -95 range, they are listed as P47 as well.

For example, look at each M64 05 designation (one has 270 and the other 272 HP). I do note that each has a different piston crown profile. But both of those are in the first series...up to and including 95.

trophy

There is nothing that i can find (other than Mahle) that indicates the change in compression for the varioram cars.

The difference in profile comes about because of the different valve size in the Vario Ram vs Non. To Alex's note they are switching between the 45 and the 47 within the 270/272 hp non v cars. I would say that even though the top profile of the piston is different it is all about the volume of piston above the first piston ring, and from the pics it is impossible to determine what if any difference in volume there is.

geolab

Hello Berni, the answer to your questions is in post 15 of this thread. Yes you can mount the 47's on your engine , and you can even mix them with the 45's (balanced). Please read workshop manual, piston section.
Stamped 01 or 02 on top
100p45 or 100p47 inside the back of the piston
Since your are changing all pistons, stick with the lighter 47's
Weight them and you will see the difference

berni29

Hi Geolab

Thank you very much for that. I was starting to confuse myself. i will read the manual.

All the best

Berni

IXLR8

If some are lighter, how are they balanced if you mix them.

geolab

here is the text from the manual

Compensating for weight differences
The new and the old pistons can be installed
in the same engine.
However, the weight difference must be compensated.
Compensation is effected by installing a 14 gr.
heavier replacement piston pin (dimensions
23 x 11 x 54).
To install the piston pin, special tool pressure
piece 9500/4, order no. 000 721 950 O4,
must be used.

IXLR8

As usual Geolab, thanks for the explanation. That would make sense as Mahle/Porsche would match the pin to the piston (not available separately on PET) and of course the cylinder since they are Nikasil. Same as the BMW motorcycle cylinders; the pistons are matched to them.

Damn, and I even have that 8-binder set of Porsche manuals, but haven't looked at them much since all I had to do so far is general maintenance.

You've come up with other hard to source info for RLers. Do you have an "in" at Porsche or operate a shop?

geolab

Alex, I work in finance, I trade fixed income (interest rate) options
Met a gentleman (now friend) in year 2000, he convinced me to buy his car two years later, he is at Porsche
I do rent a small garage loft outside the city, where I installed a two post lift, and all my tools, just for the 993 DIY's. I go there saturdays or sundays (or both). You are welcome whenever you have the chance.