3.3L jugs on a 3.0L engine

[shanghai_todd]

Anyone know exactly what is involved to rebuild a 3.0SC motor into a lower compression turbo motor? I have herd about the use of 3.3 P&C's and also 935 pistons. Also not looking to drain out my wallet completly so I am open for ideas

I would also like to avoid splitting the case if possible and to be able to reuse my heads and cams.

[wmunchovie]

Figure out what you want in the way of a driver; if you are saying “low compression” then that means you want lower bottom end performance due to less bottom end torque in lieu of killer upper performance because there is more space for the turbo to pump into.

The compression ratio of the stock 3.0 turbo is 6:5:1 which is very low compression but allows for major boost volume in a given cylinder. The higher the compression, the higher the chances of detonation which virtually destroys the engine; the cylinder charge in the turbo is six sticks of dynamite instead of one on a normally aspirated engine (analogy only).

Since you are converting yours to a turbo, you obviously should realize that you will be instantly adding a great deal of H.P. on your engine that did not exist before, therefore you should ensure that your rebuild is going to take the extra power and therefore, abuse. On the 3.3L issue, the most important factor is sizing; on the 3.0 turbo the base of the cylinder, exterior, cylinder sleeve outer diameter is 103mm, so any new cylinders will need to be that diameter at the bottom in order to fit in the case. The Mahle 3.3L cylinder is partially finned - I still cannot figure why Porsche would opt for this design as one would think that losing part of the heat sink would increase overall engine temperature.

When you start talking about new pistons and cylinders then you are talking more money, quick; if you are thinking used then make sure you have mike’d them and ensure that they are in tolerance otherwise you will be bolting on garbage…

Munchovie.

[shanghai_todd]

Thanks Munchovie, BTW, I sent you an email on the wheels..

[psalt]

It can be done, but there are a few issues. The piston pin is a different diameter, so the rods need to come out and be rebushed. The con rod length is different, but offset bushings can compensate. The SC heads are made of a different material and use a different gasket.