[Vwdiesel] 1990 Turbo diesel Fox 2 dr Wagon

Wed Apr 18 12:45:23 PDT 2012

Great job Brian,  Great experiment engine and I respect your trials.
nothing wrong with 45mpg and lots of power and emph.
that is what it is all about in my book.

Bryan Belman, Pt. Pleasant, NJ
04 Jetta Wagon TDI PD, 100hp, 5sp -- running :<)
92 Jetta 1.6 Eco-Turbo Diesel, 5sp -- running :<)
82 Diesel Westy 1.9NA -- running :<)
70 Type 1 stock Elm Green Beetle -- Under Restoration :-)

From: Brian and Ruth Decker <decker at toledotel.com>
To: 'Andrew .Libby' <libbybapa at gmail.com> 
Cc: vwdiesel at vwfans.com 
Sent: Wednesday, April 18, 2012 11:29 AM
Subject: Re: [Vwdiesel] 1990 Turbo diesel Fox 2 dr Wagon

Hi Andrew;

                You are probably right on all counts although I doubt there
was much thermal coating left on the piston tops ( if there was ever any
there). This was a used Turbo 1.6 that I bought at an auction complete with
alternator , starter, injection pump, ETC. It had obviously pulled from a
wreck. I paid 45 dollars for it complete so I didn't have a lot to lose. I
considered milling valve pockets in the pistons to make it non-interference
but decided not to for two reasons. One I believe it would make the piston
tops too thin and my machinist would have wanted much more than the 30 bucks
he charged me to take a few thousands off the tops. I'm sure I disturbed the
"squish and quench". That I believe is why the stock settings in the Bentley
didn't produce more than about 32 mpg and just decent power. I couldn't
tweak it better using any of the tricks I had learned from my previous 1.6
turbo engine. When I came to the realization that I must have surely screwed
with the squelch I just did what the engine seemed to be trying to tell  me
and that was to give it a ton more injection pump advance. When I did that
my tweaking with the idle and the fuel screw brought out the tiger.

                Right, wrong or in between I will find out in the long ( or
perhaps short) haul. If it is still performing well I will be taking it to
Avoca Iowa in 3 weeks.

Brian Decker

From: Andrew .Libby [mailto:libbybapa at gmail.com] 
Sent: Wednesday, April 18, 2012 6:46 AM
To: Brian and Ruth Decker
Cc: vwdiesel at vwfans.com
Subject: Re: [Vwdiesel] 1990 Turbo diesel Fox 2 dr Wagon

IMO removing material from the piston tops is a bad idea for a couple
reasons.  First, it removes the thermal coating on the pistons.  The other
reason (and also the reason using a larger than spec head gasket is bad) is
because it disturbs the "squish and quench" or the proper turbulence in the
combustion chamber (probably not a deal breaker on an IDI) and the transfer
for heat from the piston crown to the cylinder head during its time close to
TDC.  If you want to lower the compression ratio, a better way to do it,
IMO, would be to increase the depth of the cloverleaf pattern in the piston
crown or to increase the size of the pre-chamber in the head.  

Andrew

On Wed, Apr 18, 2012 at 12:00 AM, Brian and Ruth Decker
<decker at toledotel.com> wrote:

Hi Folks;

              I got busy so the Turbo Fox project was somewhat delayed. I
rebuilt a 1.6 turbo diesel engine that I had bought at an auction. It must
have been from an Audi or Quantum and had an automatic. Through the years I
have wondered why our 1.6 diesels had 23 to one compression and wondered if
they might run better with slightly less compression. Where I live in
Western Washington it doesn't get incredibly cold so I felt perhaps starting
with less compression might not be impossible. The block has 1mm over
pistons.  I took them to my machinist and he took enough off the tops of the
pistons to take out about one half of the swirl chambers. I reassembled it
with all new bearing, seals and a 3 notch head gasket (the thickest
available). We were guessing we might have about 20 to 1 compression. We put
new exhaust guides in the head plus new valve seals and lapped the valves.
It has a rebuilt injection pump and rebuilt injectors. It also has a two and
a half inch exhaust system and a turbo Quantum 9Q 5 speed tranny.

              Now the fun begins. We set it up using the recommended pump
setting from our Bentley. The engine started somewhat hard and truly wanted
the cold start pulled. After warming up it ran pretty strong but was getting
about 32 mpg. I then started fooling with the idle settings and the fuel
screw. I have a pyrometer so was careful not to get the exhaust gas
temperature too hot. I could get good power but mileage didn't improve.

              I finally decided that since I have lower compression than
stock perhaps stock settings weren't what the engine needed. We upped the
pump timing to 1.10 and  it ran better, started  better and the mileage
improved. We now are at 1.30  and the Fox wants to run hard, fast and the
EGT's are good. It loves going down the freeway at 70-75 and would happily
cruise faster if I wasn't afraid of the law. The mileage is around 45 mpg
running hard and fairly fast. We pulled the injectors today and did a
compression check and all cylinders are very close to 360 lbs. For some
reason it just loves lots of injection pump advance.

Brian Decker

Toledo WA

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