Thanks doswald. Were these the 4032 alloy?

I built several 2.4 and 2.5 motors and dynoed them all in the same car, same exhaust system and on the same dyno. You can read the results i the link below.

https://forums.pelicanparts.com/porsche-911-technical-forum/1151593-dyno-summary-testing-early-2-4l-2-5l.html

john

Gmanulan, I don’t know the alloy. Perhaps you could search the id # and identify it.

dho

Wow, who knew? This simple formula allows you to order off the self pistons with entirely too much compression for your particular build then use this formula to custom machine them for a more exacting result.
Henry, is there a formula for 2618?

I bought the AA piston package and I'm happy with my choice. Instead of oil squirters I have notched my con rods on the big end, to squirt oil onto the piston crowns.

An experienced UK engine builder says the T crank is happy up to 7,200 revs.

I did the oil bypass mod manually. It was easy. And I got a 964 oil pump to supply the extra oil. To get it in I had to file down one of the case webs.

One of the most experienced engine builders around told me the 5 studs that it's most important to pull and put case savers on. I left all the original cylinder studs in.

I was also able to boat tail the case by hand with the long 13mm reamer previously used to clean up the valve guide bores.

Don't underestimate the amount of work involved, though. I did.

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Density equals mass over volume.

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2.8 g/cm³.

Hi - would appreciate some help choosing between these two sets:

https://aapistons.com/products/porsche-911s-2-2-2-4l-86mm-cp-p-c-kit-c-r-9-5-1-10-7-1

https://aapistons.com/products/porsche-911-86mm-je-piston-cylinder-kit-2-2-2-5

Am planning on DC30 cams but was going to leave my T heads stock. I would prefer CP pistons based on feedback, but despite the fact the CP pistons claim 9:5.1 (I think fine for my single plug application) they seem to have a very high dome height. Would I be better off with the lower comp JE pistons?

All aluminum alloys used in pistons have almost exactly the same density. In fact, almost all aluminum alloys have the same density.

The conversation about piston material is an attempt to source the correct piston design/material for a specific application.
4032 is generally better for cast irons liners because the high silicon content lowers the expansion coefficient. Full circle skirts will often create a quieter cold engine.
The quest about density differences is simply an excellent way to reshape pistons with having to CC each process. 4032 and 2618 are different enough to require a different formula to calculate CC based on weight.
After machining it makes sense to CC the final product.

http://forums.pelicanparts.com/uploa...1758148253.jpg
http://forums.pelicanparts.com/uploa...1758148253.png

First two sets of a new run of 95mm cylinders for 2.0-2.7 case. Obviously, a 7R case offers the best cylinder/head stack stability
They are in essence a 2.7 cylinder bored to fit a custom Ductile iron sleeve.
The completed cylinder is then Nikasil coated.
The special order CP pistons will run 4032 full, circle pistons with a 10:1 compression.
On a 66mm crank it's a 9.5:1, 2.8 and on a 70.4 crank it's a 10:1, 3.0.
The challenge was to source a set of rings that fit a ring stack I wanted in this low expansion piston and still be compatible with Nikasil coating.

http://forums.pelicanparts.com/uploa...1758151362.JPG
http://forums.pelicanparts.com/uploa...1758151362.JPG

When considering the density of aluminum variants I decided to compare the weight difference between the alloy used in making Mahle Nikasil cylinders vs the KS Alusil.

Of course both cylinders were decked to an equal height and both cylinders were fresh Nikasil coating. The results were interesting. The KS cylidner was 17.11 grams heavier suggesting a denser material. Almost 2% heavier.

Different manufacturers, probably different castings. How did you determine that each cylinder had the same volume of material?

Wow this thread went in an interesting direction. I started out as a newbie just wanting to learn about the basics, but ended up learning about different alloys!

Those 95mm pistons for a 2.2 look interesting! In the end I went for the CP s 9:5 pistons in AA Birals to go with my DC 30 cam choice. Based on some previous posts I found I'm a little worried about the consistency of the bore but we will see.

If somebody could help me work out my dynamic CR I would appreciate it. Also any advice on ring clearance when using the 2618 alloy in birals.

Wish me luck and thanks for the help.

Static compression ratio of 9.5:1.
Effective stroke is 2.29 inches.
Your dynamic compression ratio is 8.49:1 .
Your dynamic cranking pressure is 172.95 PSI.

A piston gave up on my stock 2.2T and I'm pondering what's the best path to rebuild the engine. I would like to get 150-170 wheel HP, nothing too extreme, and definitely a long lasting engine.
- Cost wise a set of Mahle motorsport 2.2S P&C costs 4500 Euros, and it comes with the great advantage of being all aluminum.

- Next option is AA biral cilinders at 700 Euros + 1300 Euros for a set of nice pistons, 2000Euros total. Add maybe another 4-500 if I get them nikasil coated as Henry suggests.

- Boring out my Cast iron cylinders is probably going to cost me as much as a set of AA biral cilinders, so I'm not sure it's worth it.

I was inclined to follow the Mahle route, but it would cost me 2000-2500 euros more, and it looks like most people here use biral instead. Is only cost the reason why people use biral over Mahle, or is there a technical advantage?
2500 Euros will buy me a lot of other parts, but I cannot make my mind of whether is worth it or not.

If I go the Biral route I could also go to 86mm bore and make a nice 2.3 engine.