1.8 Vs. 2.0 Revisited AKA why 1.8 instead of a 2.0 head

[Rabbit16v@attbi.com (Rabbit16v)]

> I don't really understand why the AVAILABILITY of the 2.0 head was even
> brought up.  That particular head had been around for 3 years in 93'.
What
> does the AVAILABILITY of the head have to do with the performance you get
> out of it, especially when you do the exact same thing to it as you do to
> the 1.8 head.  I mean sure, maybe they weren't exactly a dime a dozen, but
> still.  We're still talking about a DOHC 16v VW Engine here.  I could
> understand if it were a VR6 and we were seeing test done in 1995 or
> something.

Brandon, your answering your own question here.  To get a 2.0L head in 93
would be like getting a 2000 head today.  You don't see a bunch of 2000 cars
in the wrecking yard to pull a head off of and do a port job on.  When this
article was written in 93 TT was probably using the 1.8L head for their
"streetport" head because in 93 the 2.0L heads were not ass accessible as
maybe an 86 Scirocco head or an 87 GLI/GTI head which were 1.8s.  As it was,
only the GTI and the GLI got the 2.0L 16v so that made them even less
available due to the fewer number of them around.  Besides, the majority of
Golfs and Jettas that were sold were 8vs.

> And yes, I do agree that smaller ports mean a faster air velocity, but
look
> at the big picture and take into consideration Volume of air moved.  When
> the exhaust valves are closed, the slight increase in "how quick" the air
> reaches the combustion chamber isn't as important as "how much" air gets
in
> there.

How much is important but apparently how quick is very important too.  Most
of us (including myself) cannot even comprehend the speed all of these
cycles are happening in a motor at 2 or 3K RPM, let alone 6 or 7.  And since
the only thing on an N/A engine that is moving the air into the head is the
suction/vacuum created by the piston moving downward then it makes sense
that on both heads the intakes are larger to help the movement of air into
the head.  When the exhaust leaves the head, like I said, it is up against a
much higher force so the ports don't need to be as large but if they are
then more of the exhaust gases leave the head and in a quicker fashion which
is also a very good thing.  My argument was that since the 2.0L head has
better flowing exhaust ports that this would be an advantage over the 1.8L
head when the advantage the 1.8L head has over the 2.0L head is a tiny bit
more flow into the head (which could easily be taken care of with a very
minor port job).  Again, overall, since the 2.0L head is newer and has less
wear, it would seem that it would be the better choice between the two.  I
also believe that if you used the 2.0L head in it's stock form that doing
something as small as adding a euro intake cam would make it head and
shoulders above the 1.8L head.

> But I do agree with you when you say the shape is important.  However,
when
> you mention cooling, it seems that the more material in head the more it
> would insulate right?  Well yes, but maybe too well, just remember, it may
> take longer to heat up (resist heat longer), but that just means it's
gonna
> take a whole lot longer to cool down.

I thought of this too but mainly my idea was that since the exhaust ports
are larger that the hot exhaust gases would exit the motor more quickly and
a larger amount would exit also.  At mid to high RPMs not all of the exhaust
gases exit the head before a new mixture of air and fuel is introduced and
the more that leaves the head the better.  Even with the valves open there
is still quite a bit of compression on the exhaust stroke and not everything
has enough time to leave the head before the valve is closed again.  With
larger exhaust ports the pressure is reduced so more exhaust gases leave the
head.

> *******NEW TOPIC******
>
> Is the Throttle body on a 2.0 16v the same exact size as it is on the 1.8
> 16v?  I need to know, I am starting to design an intake manifold for the
> 16v.  I've started some cad drawings, and eventually it will resemble a
> Shrick VR6 manifold.

Firstly, Brando, if you start a new topic I would defineately start a new
thread since it doesn't seem that everyone is as interested in this topic as
us so you won't get as many responses plus it throws off the topic we are
already on.  But, to answer your question, no, the 2.0L TBs are not the
same.  Some have the same parts but there are a few different type of 2.0L
TBs are I don't remember any of them being the same as the 1.8L TBs.  You
can make them the same but they don't come that way.  Some resemble the
earlier 8v TBs that have a little donut in them to add torque but the donut
is permanant, some don't have that.  I think the automatics may be different
also.  HTH!

Dave