Date:         Mon, 23 Feb 1998 19:24:07 -0500
Reply-To:     Martin Jagersand <jag@CS.ROCHESTER.EDU>
Sender:       Vanagon Mailing List <Vanagon@gerry.vanagon.com>
From:         Martin Jagersand <jag@CS.ROCHESTER.EDU>
Subject:      Parts Sources for the TDI Conversion
Comments: To: vanagon@likeminds.com

To complete the swap Martin assembled parts from three
different sources: A TDI donor car, a diesel T3 bus
(Vanagon), and from the aftermarket.

From a T3 Diesel

If you already have a diesel you're in luck. Otherwise the
following parts are needed:

     The diesel motor mounts.
     Oil pan.
     Oil pump, or at least the pickup tube. (Which in the
     diesel is integral with the bottom of the oil pump
     housing)
     Diesel bellhousing.
     Suitable T3 transmission. (Helmut has a list of all
     the ratios available)
     The mounting bolts for the bellhousing and
     transmission.
     Coolant hoses and fittings. (jag: Are the expansion
     and overflow tank the same in gas and diesels?)
     A Turbo Diesel exhaust if availible (which it isn't in
     north america) Using the 1.5" naturally aspirated
     Diesel exhaust would be ridiculous. In the USA we
     would have to fabricate our own. This is what Bob
     Bellanca did.
     Flywheel
     "anfasser" I don't know what this is.

One has to decide whether to keep the accesories on the
TDI engine. The advantage is that the alternator is likely a
120A unit. The 1.6 diesels had 65A alternators. The
disadvantage is that the new alternator can/could interfere
with the oil filler and dip stick tube. (jag: I think there
were three variations on dip stick arrangement).

From the TDI donor

It's good to familiarize oneself with the installation in the
donor before taking out the engine.

     Engine.
     Engine wiring harnesses.
     Engine computer.
     Accelerator potentiometer.
     Intercooler
     Air mass meter and possibly air filter box.
     Catalytic converter.
     Alternator, if desired.

From aftermarket sources

     A special left motor mount to avoid interference
     with the turbo. The original TD in the T3 had the
     turbo low, but sufficiently offset forward to avoid
     interference with the mount. The turbo in the
     transverse mount TDI engines is located centrally.
     If desired, an aftermarket oil cooler.
     If desired, aftermarket air-water intercooler.
     (Oettinger makes one) Using the standard TDI
     air-air intercooler one has to somehow arrange for
     cooling airflow. A BIG blower and a snorkel from
     the unused passenger side air intake might be the
     best solution.

Results

Now lets look at some theoretical figures from the IDI
diesel, and try to extrapolate to the TDI: The full load
injection in the 1.6l TD is 0.0365 cc.

So fuel consumption at full load and 4500rpm is:

0.0365 (cc) * 4500 (rpm) * 2 (inj/revolution) * 60 (min/h) /
1000 (cc/l) = 19.71 l/h

In gallons:

= 5.34 gal/h

The same figures for the nat aspirated engine under full
load: 14.5l/h or 3.9 gal/h


With the standard gearing of the diesel (5.5 final drive
ratio) For a VW Westy diesel in perfect tune total drag
matches availible engine power at about 70-75mph. Given
the above figures the calculated milage at full speed is
about 20mpg. At a cruising speed of 60 mph the engine
power needed to overcome the total drag is 30hp or 21kW.
Roughly half of this is wind drag. Most of the rest is tire
friction. This figure assumes one is using the relatively
light rolling standard Continental tires. Engine speed at 60
mph cruise is 3600rpm. Repeiting the above calculation
assuming the same efficiency as for full load we get:

At 60 mph: 26 mpg

In reality the engine is somewhat more efficient at 3600
rpm than 4500 we could get an even slighly higher mpg.
But also in reality few people drive at an absolutely
constant 60mph in an absolutely flat place and with
absolutely no wind.

What is the best milage we could possibly get with the
VW IDI diesel? The best efficiency of the engine is
achieved when running at 1800rpm with a fuel
consumption of 264g/kwh. 1800rpm corresponds to about
30mph in fourth gear with the standard transmission. At
that speed 7.14kW is required to overcome drag.
Calculating best milage at that rpm gives a remarkable 60
mpg!

Now these three milages, 20mpg @70-75mph, 26mpg
@60mph and 60mpg @30mph, illustrate a typical pattern
with diesel engines: The economy improves dramatically
when one drives slow. In Otto (gas) engined vehicles this
difference in economy is not nearly as dramatic. The
resason is that while identical vehicles will have roughly
the same increas in drag when speed increases, the
efficiency of the diesel engine typically goes down
somewhat or is constant when rpm and load increases,
while the gas Otto engine starts out grossly inefficient, but
the efficiency improves with increased load.

So what about the TDI? Lower heat loss in the cylinder
head and improvements in the injection system and control
gives the base 66kW 1.9l TDI a specific fuel consumption
of 207 g/kWh at 1800rpm. This is about a 20%
improvement over the IDI. Comparisons in vehicles where
both TDI and IDI engine alternatives are offered also point
to about 20% improvement in miles per gallon. With a
leap in confidence we can predict that given suitable
gearing target milage for a 1.9l TDI powered T3 Vanagon
would be about 32.5mpg. Of course changing driving
habits from having more power availible with the TDI is
bound to affect this figure.

What was Martin's result? The milage he got from the
first tankful was 7,6 Liter/100km, or 31mpg.

/Martin
--
Martin Jagersand                 email: jag@cs.rochester.edu
Computer Science Department             jag@cs.chalmers.se
University of Rochester

        Slow down and visit the VW diesel Westy page:
          WWW: http://www.cs.rochester.edu/u/jag/vw
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