Porsche 964 intake manifold

[Turboman]

One simple question, to the knowledge participants.
Early 964s have a aluminum intake manifold. (1989/1990)
Late 964s have a plastic intake manifold (1991/1994)

Is there a performance advantage or a cost savings move?

Appreciate your comments

Francisco 1970 914-6 1991 964 Cabrio.

[Marine Blue]

Some older Porsche documentations suggests a slight improvement in performance and weight savings. It doesn’t mention cost savings but it’s pretty hard to argue that wasn’t part of their goal.

[LM964]

One 964 I had came with Al intake manifold and the other plastic. Plastic easier to keep clean.

I imagine it was less about performance improvement over a cost saving for sure. Any performance improvement would be negligible.

[Rank911]

The plastic manifolds are generally more durable in terms of heat resistance and less prone to cracking, which can be an advantage in the long run.

[Cobalt]

The aluminum intake came on the earlier ringless engines. The cost for the AL casting I have little doubt was far greater than a plastic intake. Not a chance that the AL casting would crack and heat is not an issue. They also eliminated the magnesium center casting for a plastic one so I suspect it was mostly cost as the Mag casting was probably more than both AL intakes back in 1990's. At the same time the internal surface finish of the AL casting was not great with additional surface roughness that created turbulence so it is possible it had something to do with fuel economy and performance. Although my bet is on cost.

They also switched from Mag valve covers to aluminum ones about that time. I also suspect that was a cost driven change.