2.2t rebuild questions

[gmanelan]

Originally Posted by doswald

Gemanelan, the heads were rebuilt, but not modified; the pistons are custom JE pistons for a 9.5:1, id #322283. The measured CR is 9.8:1, 9.4:1 when the crevice is included. To clarify, the cam is the Solex grind, not the mod.

Pete, yes, I’m very pleased!

dho

Thanks doswald. Were these the 4032 alloy?

[targa72e]

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

[doswald]

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

dho

[Turbo_pro]

Originally Posted by Henry Schmidt

The formula for milling 4032 pistons is:
Piston dome cc's to gram conversion: 1cc (volume) = 2.71 grams (weight)

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?

[RobFrost]

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.

Sent from my SM-S918B using Tapatalk

[RobFrost]

Originally Posted by Turbo_pro

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?

Density equals mass over volume.

Sent from my SM-S918B using Tapatalk

[Henry Schmidt]

Originally Posted by Turbo_pro

Henry, is there a formula for 2618?

2.8 g/cm³.

[gmanelan]

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?

[PeteKz]

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

[Henry Schmidt]

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.

[Henry Schmidt]

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.

[Henry Schmidt]

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.

[PeteKz]

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