Date: Mon, 18 Aug 2003 15:13:18 EDT
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Turbos, exhaust manifolds and engine mounts
Content-Type: text/plain; charset="US-ASCII"
In a message dated 8/18/03 7:51:34 AM, scbrian@pacbell.net writes:
<< Have 83, 5 spd, Westy and thought needed modified L/cradle to clear turbo
but current ebay add for this manifold(item 2428331463) says can use stock
mounts with this manifold as well as allowing for better exhaust flow than
jetta? Any comments.....?............thanks, Brian >>
Wrong eBay ID number, should be 2428482509.
Nonetheless I thought I'd use this question to add some comments regarding
turbo manifolds and turbo conversions on I4 engines for Vanagon use, whether gas
or diesel.
I have obtained and studied the Quantum TD manifold (cited here), the regular
stock Golf/Jetta TD manifold, the Audi 5000 TD manifold, the Golf/Jetta
single downdraft gas manifold, the Golf/Jetta dual downdraft (4 and 6 bolt flange)
gas manifold, the Audi 80 single and dual downdraft gas manifolds and the ATP
aftermarket 8V turbo exhaust manifold. I have examined all from the
perspective of turbocharging my Audi 3A 2.0L 8V engine. There are several issues.
Simple mount interference questions:
1. For diesel engines using the original VW/KKK or Garret turbochargers, the
quantum TD manifold will fit with an airflow quenching inlet tube (rubber) to
jog around the close Vanagon engine mount. Turbo oil return is below the
static oil level in the pan. Short life predicted despite factory Vanagon TD
configuration.
2. Again for diesels, the golf/jetta manifold will clear with minor
machining. I believe it works best inverted and places the turbo oil return in the
right configuration for simple gravity drainage to the oil sump. Details need to
be checked as I'm doing this from ancient memory and haven't looked at the
diesel configuration in several years. The clearance key here is the diesel intake
manifold.
(Comments 1 and 2 related to use of either the Quantum TD intake or the
Golf/Jetta TD intake configuration.)
3. The Quantum TD manifold needs an adapter to mount a Garrett T3 turbo for a
gasoline motor application and the Vanagon stock mount must be extensively
modified or a custom design used (see archives for several solutions). Oil drain
problem persists. Custom inlet and exhaust fab required. Machining of Quantum
TD manifold required for clearance with any gas intake manifold.
4. The Golf/Jetta TD manifold requires the turbo to be mounted below the
horizontal axis of the manifold because of the intake manifold bulk and causes
severe interference with the Vanagon engine mount.
5. The Audi 5000 TD manifold strongly interferes with the engine mount.
6. The aftermarket ATP 8V turbo manifold strongly interferes with the Vanagon
engine mount.
(For 4-6 a custom engine mount is the only solution and in some cases, the
engine cradle and motor mount point must be changed.)
7. The gasoline exhaust manifolds for the Golf/Jetta including the single and
dual downdraft units can be fitted with flange adapters, but the turbo mounts
low, the oil return problem remains and exhaust and intake plumbing is a
nightmare.
8. The Audi 80 gasoline manifolds are unusual in that the downpipe flange
face is actually about 45 degrees from the horizontal plane of the manifold (in
contrast to the parallel location in the Quantum TD and the other gasoline
manifolds). With an appropriate flange adapter, one can mount a T3 turbo level in
the true horizontal plane of the vehicle. The turbo is perpendicular to the
long axis of the block. Oil return remains low. The turbo inlet now faces the
block requiring a short radius coupling. In my configuration, the exhaust
downpipe from a SAAB 900T fits perfectly, directing the exhaust path to the front of
the vehicle with no interference with engine cradle, engine mount or motor
mount. I'm currently porting the single downdraft Audi 80 manifold and should
have installed pictures available soon.
But, the proper choice of manifold requires assessment of more than just
interference!
The questions of flow and of thermal stresses are critical. Of all the
manifolds discussed above, the flow through the Quantum TD is literally the worst -
even worse than the standard Golf/Jetta single downdraft ball mount. The
highest flow was obtained with the Audi 80 dual downdraft manifold. The Audi 80
single downdraft tied with the 6 bolt Golf/Jetta dual downdraft. These results
were qualitative (taken on my crude airflow bench).
The next (and arguably most important issue) is that of thermal stresses. For
both gas and diesel applications, the manifold can glow red. In the case of
the diesel, the Quantum TD manifold glows for an area of 3 to 5 inches back to
the head from the turbo mount flange. For gasoline engines, the whole manifold
is emitting. Manifold casting thickness of the Quantum manifold is
significantly less than the G/J TD and the gas turbo manifolds but similar to the G/J
single downdraft unit. Extensive cracking is found with the G/J unit and similar
problems have been reported with the Quantum manifold with gasoline
applications. The Audi 80 manifolds are far more massive than any of the VW
counterparts.
In conclusion, the Audi 4 to 2 manifold would be the optimal choice for
non-turbo gas engines or for turbogas engines using the split input turbines like
the T4. The optimal turbocharged system (my POV) is the single downdraft
(California emission spec) Audi 80 manifold. The single outlet tube matches the
input area for the T3 turbine and the adapter flange shows no reduction in flow. I
would also council the use of interior and external ceramic coatings to
minimize heat load on the engine and engine compartment.
Frank Grunthaner
