My thoughts on 1.8T motors

[Mike Smith <Mike.s@ise.co.uk>]

Hi All,

My thoughts on the 1.8 20V (and 1.8T):

The engines in the A3 / Golf / TT are mechanically identical. The Golf / A3
have some slight 
differences in the layout of the inlet manifold on the non-T version. 
The Audi TT 'T' engine is slightly more powerful then the A3 / Golf 'T'
through tweaks to the 
management / turbo / cams, and also has variable valve timing as per the
non-T. The A3 / Golf
'T' engine does not have variable valve timing, but almost all the late
non-T engines do.

There are two versions of this engine though:

The version fitted to the A3 / Golf is a completely new block, which has an
integral water pump.
The exterior of the engine is very different to the Scirocco style lump
which we are so familiar with.
There are BIG problems with fitting the A3 lump into the Scirocco because
the engine mount
is **totally** different on the new block. You need to do some major cut and
paste on the chassis 
leg to get it to fit. 
(note - the very early engines are not like this, but anything you could buy
from the factory would 
be. See below)

The 20V engine in the A4 / Passat is almost exactly the same block as the
Scirocco, and will fit 
straight in. It has the same cylinder head as the A3 one, but the only
problem then is the exhaust 
manifold and turbo location, which is obviously completely wrong, being
arranged longitudinally.
The very first A3/Golf engines used this block, but they changed it for the
new one after a short while.

The ideal solution is the A4 engine, with the A3 exhaust manifold and turbo.
This would be almost bolt-in. 
The cylinder heads are the same between the two blocks, btw.

As far as throttle control, etc, these engines are cable throttle, but they
have a very sophisticated
'closed-loop' idle control which has a servomotor on the throttle body which
can move the throttle 
plate to control the idle. The engine management is extremely advanced as
well. Consider this:
Digifant II management for the 8V 1.8 Golf II engine uses about 16K of
memory for its 'map'. 
The G60 Digifant (Corrado) uses 256k. The Motronic used on the 20V engines
(T & non-T) uses 
2MB!!! This has control maps for virtually every aspect of the engine,
including the obvious ignition 
timing, sequential injection (on some versions), turbo boost control,
variable valve timing, idle-servo, etc.

Both versions of the engine are highly restricted in standard trim. The
turbo engine is trying to 
breathe through a manifold outlet of about 1 inch diameter! It also has
softer cams than the non-t, 
and a restrictive inlet manifold design. It doesn't have the variable valve
timing that the non-T has, 
and the management is programmed to produce exactly 150bhp and no more. All
the tuning of this 
engine that I have seen in Europe consisted of fitting a proper turbo, and
reprogramming the ecu. That 
will net you at least 280bhp, without even taking the cylinger head cover
off!
The non-T 20V engine will easily make 160-170bhp with decent inlet and
exhaust design.

Mike Truluck of Jabbasport (mkI Scirocco G60 20V 4wd) has used an A4 turbo
engine, a highly 
modified G60 supercharger, G60 management, and variable valve control from a
non-T. Other than 
ceramic coating the pistons, this engine has no internal modifications, and
makes about 350bhp!!!
(that said, I don't think even the original designer would now recognise it
from the outside!)

Sorry for the long post, but I have researched this quite a lot by virtue of
having just fitted an A4 20V 
engine to my Polo (without the turbo - I'll be using a Rotrex supercharger
when funds allow)

BTW, all this applies to European engines - whether the US versions are
substantially different 
remains to be seen...

Cheers!

	Mike

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