I’ve been following the discussion here about turbodiesel and Tdi exhaust 
manifolds , turbo mounting issues and motor mount interferences. There are 
several other options that I have put into the Vanagon list archives, but have not 
been discussed here. 

First, in my exhaust manifold collection, I have two quantum TD manifolds, 
three Jetta TD manifolds, several Audi 5 cylinder turbogas and turbodiesel 
manifolds, several VW NA diesel manifolds, several VW 1.8L NA manifolds including 
the single and dual port versions, three Audi 3A single and dual port manifolds 
and a 1Z TDi exhaust manifold and turbo. These were accumulated to study flow 
and thermal properties while I have been playing with the turbo Audi 3A 
project as well as my current TDi engine build. 

I have mapped out the flow characteristics of each and analyzed the 
cross-sectional area of all of them. The worst flow is that of the Quantum TD. This 
manifold in either diesel or gas application gets hotter than any of the others 
due to poor flow and tube resonances. The Jetta TD manifold flows much better, 
doesn’t get nearly as hot as the Quantum. The VW 1.6L NA diesel manifold has 
better flow than the Quantum TD, but worse than the 1.8L gas single port unit. 
The 1Z TDi manifold is a bit better than the Jetta TD, and the ALH unit with 
turbo outflows the 1Z with turbo. The VW 16V dual port gas manifold flows quite 
well ( better than all of the previously cited units), but the Audi 5 
cylinder and 4 cylinder manifolds out flow all the VW units. Looking at the design of 
the Audi 5 cylinder manifolds, one can only be impressed with the level of 
careful engineering and SOA scientific design that went into them. The Audi 4 
cylinder 3A dual port manifold has the best flow character of the 4-pot 
manifolds (much better than the 16V VW unit. The Audi 3a single port manifold (used on 
CA spec Audi 80 and 90 cars) is on a par with the 16V dual port VW unit.   So 
what is the point one might ask?

Well, I worked a series of adapter plated to mount the Garrett T3 to all of 
the above as I engineered the turbo addition to the Audi 3A gas engine. I 
designed and built a modified engine mount to go with the Quantum TD mount of a 
Garrett T3 that featured straight in air inlet to the turbo through the engine 
mount instead of the factory flow quenching jog.   But in the course of my 
experiments, I discovered a far better solution. Namely, the audi stock single port 
manifold with an adapter plate. 

Here I found that the Garrett T3 turbo could be rotated 90 degrees from the 
QTD position (that is the axis of the turbo is perpendicular to the 
longitudinal axis of the engine). In this position, the turbo is mounted nearly 1 inch 
(from memory) higher than the QTD configuration and has no interference with the 
engine mounts or carrier bars. I found that the SAAB turbo with right angle 
exhaust exit fit like a glove. Also the long axis of the turbo was parallel to 
the ground in the 50 degree mount position. Finally, this was the highest flow 
turbo configuration I could develop including aftermarket 1.8L turbo 
manifolds. Pictures of the manifold and turbo install are (I believe) on Alistair Bell’
s website. The AAZ and 1Z turbos are significantly smaller than the Garrett 
T3 and would work with this manifold perfectly with even more clearance! I can 
provide CAD drawings of my adapter plates for you to use as a model to start.

I have discussed the diesel motor mounts and my hydraulic mounts previously 
as well (again pictures and detail on Alistair’s web site). I use the SAAB 
9000T mounts for reasons I have already offered. For my TDi project, I completely 
redesigned the engine mount, built it for the hydraulic mounts and for 
clearance for the VNT ALH turbo manifold I have installed on my 1Z engine. The mount 
supports turbo and manifold and stabilizes my oil return setup (correctly 
entering the block above the static oil sump level in the 50 degree install. I 
will post the CAD drawings and pictures of the mount when I next get back to the 
USA at Alistair’s site if he has any room left.   I’m currently in Austria, 
wandering around trying to find junkyards next to some interesting castles! 

BTW this mount design has let me incorporate the engine front end snub damper 
used by Audi in longitudinal engine configurations. It is also consistent 
with the plumbing I use for intercooler mounting.

So, I would recommend a modified Audi 3A single port balanced branch manifold 
with adapter plate (I use 0.5 inch thick Stainless steel) to mount the small 
diesel turbo with no engine mount or carrier mods (Nada). I also have a few 
spare 1Z wastegate turbo’s. 

Caution, you’re experience may vary.

 Frank Grunthaner