Date:         Thu, 4 Oct 2001 02:56:45 EDT
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Turbo Audi 3A Project Update: Scavenger Pumps
Content-Type: text/plain; charset="US-ASCII"

The list seems remarkably quiet, so I assume I have been ejected for too many
unabridged posts. Oh well, for the archives then I shall search through the
keys trying to formulate words ...

When I last raised the topic of mounting the turbo on the Audi 3A engine at
the 50 degree mount angle, I indicated that it was critically important to
mount the turbo oil return flange above the mean oil sump level or else. In
the intervening weeks (months), I have had the privilege of fingering many
turbo's mounted without adherence to this advice. Let me say to monitors of
the TDi swap list that heady cash flow problems await if you follow much of
the "its no problem" advice given freely on that forum. I have fingered
several units returned to Garrett, Turbonetics and Turbo City returned for
feeble warranty claims related to this mounting problem. Admittedly, many of
these returns are for V6 and V8 engines, but the coked bearing and seal
problem is immediately recognizable from a low oil pressure problem.

In anycase, the solution is the mounting of a scavenger pump and a small
buffer sump for keeping the scavenger pump wet and for deaerating the
returned oil. The first problem was finding a pump and the second was
locating and fabricating a sump.

The pump: I posted here (and in much of the English speaking world) trying to
find out:

1. Flow rate requirements for the Garrett T3 turbocharger.

2. Conversion factor for needed pumping speed of a pump handling 10W-50
synthetic motor oil at 230 F.

3. Pumping speed (Gallons per minute) of VW power steering pumps (could they
be used as a scavenger pump). I had the mounting hardware and the pumps!

4. Alternative pump sources (electric or manual).

I found good information from several posters on the internet newsgroups, but
overwhelmingly, the vast majority of the information offered (with the
authority induced by certitude) was at least ill-informed, wrong or downright
dangerous (remember the 100 mpg carburetor that Detroit suppressed because
... enter your favorite conspiracy theory here).

So for a summary of the results. (Note, this information may only reside in
our list archives, because I don't have the time to post it to hell and
beyond!).

1. Garrett T3 flow rate requirements. Easy, just ask the Garrett engineering
staff. Very helpful. I told them I was checking out the turbo for a constant
pressure feed for a CO2 diesel running hydrogen for a long term power source
on Mars. They invited me in. Dangerous. Oh yeah, the answer. Turns out that
at nominal operation on a 2.0 liter engine running 6.0 psi boost at an engine
rpm of 3500, the Garrett takes a minimum oil inlet pressure of 23 psi and has
an output flow of 1.4 gallons per minute of deaerated oil at 250F. Note that
Corky Bell's book says 25 psi (min) at engine speed of 3500, and a flow rate
of 0.5 GPM. Big difference. Turns out the sleeve bearing Garrett turbo's have
the highest flow rate of return oil by a margin of no less than 2:1. The new
Garrett Ball Bearing units run less than 0.4 GPM. Summary: 1.4 GPM.

2. Conversion factor: This is another way of asking what the density of
whipped cream is. The details of the bearing design determine the air
injection rate into the oil and the oil film strength determines the rate of
gas coalescence (making larger bubbles and eventually ejecting air from the
fluid). Turns out these numbers are very dependent on the turbo, the oil, the
temperature, crankcase pressure, and the extent of turbulent flow. The best
data I could get ranged from a unbelieved (anecdotal) value of 2:1, and
observed (not quantitatively studied) value of 4:1, to a measured T3 at 45
psi on a twin turbo Corvette of 5.2:1 maximum. Taking into account these
numbers, I realized that I needed to search for a pump with a flow capacity
of about 6 gallons per minute at a drive speed of 3500 rpm from the crank.
Summary: 4 to 1.

3. Pumping speed of VW Power Steering pumps: Now (expletive deleted) it, I
don't want any of you loose lipped listees to pass this info on to VW (at
least not on to VWOA). A call to VWOA netted the following response "Our
pumps only have a pressure, sir, they don't have a flow rate!" Comes from
hiring Liberal Arts Majors! Again I digress. Turns out that Saginaw, ZF and a
couple of other smaller manufacturers make the VW power steering pumps.
Saginaw US, says they have never shipped a power steering pump to VW. ZF says
they have supplied more than 12 different pumps to VW for the Golf, Jetta,
Transporter, Audi and Passat applications in the time window of 1982 to 1992.
The most abundant version has a flow rate of 0.7 liters per minute! This
seems to be the small unit VW uses on the G/J group. For the Audi 5000, a
large combination unit is used which includes a PS stage and a brake booster
stage. The Audi 4000 mounts a larger version, also often seen on the Passat
or Quantum. This pump has a flow of 7.8 liters per minute at idle, and 4
liters per minute at 3000. Add to this the fact that the VW power steering
pumps are vane pumps which fry readily if run dry, you can see why I gave up
on the VW PS pump approach. Summary: NA.

Sadness,

4. Alternative pump sources. Many possibilities. Several companies support
the Motorcycle market with electrics. Also several turbo kit manufacturers
provide electric pumps. Costs range from $100 to $300. But, all of them go
back to the same manufacturer (Shurflo) which basically has no elastomers
operating much above 225 to 250F. Further, failure of these units has been
accelerated by high engine bay temperatures and voltage variations. Many of
these units are unable to handle voltages higher than 12.4 volts. Current
draw (CW) is between 6 and 12 amps. I decided to go mechanical.

Following an Internet Newsgroup tip, I went to J. S. Barnes/Haldex
hydraulics. Turns out they make bidirectional hydraulic pumps (can also be
used as motors) that are essentially identical to the gear pumps used as oil
pumps in the engine. These gear pumps are self priming, can be run dry for
extended periods, are equipped for mechanical (pulley) drive and are rated
for 300F continuous operation. These pumps have a maximum speed rating of
5500 rpm at 3000 psi pressure and an intermittent operation max rpm of 7200
rpm at 100 psi. Well, I decided this was the answer. I went to Grainger
Supply (www.grainger.com) and purchased a model 4F655 pump and pulley (v-belt
sheave, set screw locked) for about $155. With a few minor mods, this pump
can be mounted with the Audi 4000 PS hardware. Driven with standard pulleys.
So, final arrangement: Turbo oil return to sump (see below) to oil screened
pickup, to scavenger pump to oil cooler to main oil sump. Robust. Clean look,
quiet! Does require rerouting oil filler pipe (another story). Pump speeds:
flows 2.0 GPM at 1200 rpm, 2.4 GPM at 1800 rpm and 5.0 GPM at 3600 rpm.
Summary: Mechanical hydraulic pump, Barnes 4F655.

Sump: This was also a big problem compounded by the need to put the turbo in
its correct physical location. I have been playing around with different
mounts using Quantum and G/J exhaust systems. I'm sure you (all two of you
still reading this) are bored to death, so I'll cut to the chase. I have
taken a VW (air cooled beetle) extra capacity oil sump extension (all parts
$20. Love that Pomona Swap Meet). Holds 1.5 quarts. Has top and bottom
covers, drain capability, etc. I cut and rewelded the unit to reduce its
width. Also welded the turbo inlet pipe to the top of the sump. Short for
closest approach to the turbo. Brought the inlet for the scavenger pump to
the center of the top flange with an extension to the strainer for the normal
VW oil pickup. This plate also has a fitting that goes to the crankcase
ventilation system to keep pressures at nominal levels. The cast aluminum
sump pan mounts to the left side engine mount and an unused engine mount bolt
casting. Final sump capacity is probably around 1.0 quart.

Other solved issues: SAAB Al air-to-air intercooler and integrated mount with
air inlet system. Looks stock. Turbo mount. Pressurized air ducting to
throttle body. Addition of two new oil coolers (one engine, one turbo)
integrated as per intercooler, addition of oil level sensor to diesel oil
pan, redesign of oil pickup tube.

Other unsolved issues: Exhaust routing, heat shields, modification of left
engine mount bracket, possible addition of oil pan baffles to reduce oil
starvation during turns/braking, oil filling tube mods, addition of turbo
timer circuit, addition of auxiliary water pump for afterrun cooling,
addition of dial-a-cam camshaft sprocket, completion of new dash instrument
pod.

Onward and upward.

Frank Grunthaner