RE: [T2] Re: DP to SP conversion

[George Lyle <glyle@xxxxxxxxxxxxx>]

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On Mon, 1 Oct 2001, Stockton, Andrew wrote:

> [...]
>
> I believe VW went to dual port to meet emission standards.
>
> Single port provides slightly higher low end torque because of the
> higher velocity of the air fuel mixture as it enters the cylinders.

I think that VW had to go to dual port to flow enough mixture after the
displacement increase to 1600.  Keep in mind that the same basic head
design had been used from 1200 through 1500, and there wasn't enough metal
left to make the holes bigger.  Since they had to make a casting change
anyway, they went all the way to the dual port design.

> > Single port heads are not subject to
all the cracking that you find > in dual port heads.

I'm not sure that the cracking worries apply to the long-reach plug dual
port heads.  Anybody have any data on the long-reach heads?

> Single port provides more engine access especially when changing
> number 1 and 3 spark plugs.

Very true.  They also make it easier to seat the spark plug boots.  On
dual port tin, you have to be careful to get the boots behind the manifold
nuts.

George Lyle