Date: Sat, 19 Oct 2002 12:57:47 -0700
Reply-To: Gary Lee <gary2a@TELUSPLANET.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Gary Lee <gary2a@TELUSPLANET.NET>
Subject: re. Calling all turbo charger / Diesel experts!!
Content-Type: text/plain; charset="iso-8859-1"
David wrote:
Now, what I want to do is increase my boost pressure by a few PSI after I
install an intercooler. How do I accomplish this? There is really not much
information on the Internet about this - looking at the Honduh pages that
are out there everyone seems to be using adjustable blow off valves. Why
aren't they using adjustable waste gates? My assumption would be that the
procedure to increasing my boost pressure would be; 1 - disable the waste
gate by removing / plugging the control line. 2 - replace the factory waste
gate with an adjustable one and set it to the desired level.
Now, what is too much boost on a Turbo Diesel? My feelings on this is to
install a intake boost air temperature gauge prior to doing any
modifications and go for a drive on my favourite 'load you engine up to the
max' series of hills that are just a few km from my house and monitor the
intake temps. Then install the intercooler and do the same drive again and
monitor the intake temps. In theory the intake temps will be lower due to
the presence of an intercooler. Then start increasing the boost pressure
until the air temps are the same as what they were prior to the intercooler
installation. Does this make sense? Shouldn't I be increasing the injector
timing when I increase the boost - is there a set ratio for this?
------------- reply -------------
David,
My experience is with 1986 - 1995 A2 - A3 series jettas with IDI engines,
which is basically the same engine as in your van.
Here is what I always did:
1. Install a pyrometer to measure EGT. I never bought the expensive Isspro
or Autometer ones, just cooked up my own with a K thermocouple and a gauge
or digital meter. If you are feeling lazy, just weld a boss to the cast
downpipe as it exits the turbo, it can be done while in a jetta. A better
place is before the turbo, but you have to remove it from the vehicle.
2. Turn up the fueling under boost, meaning adjust the boost enrichment
aneroid. Unbolt the top and turn the indexed collar, can't remember which
direction. Now you get more fuel as boost builds, and thus boost builds
faster, and thus more power. The downside is that you get more smoke. But
it is only under boost, so its not all the time. And it's free, no cost
involved.
3. Watch EGT, it's not a problem with the Jetta but the vanagon is heavy
and I remember EGT got on the high side.
4. Install intercooler if desired. I have a two channel fluke pyrometer
and I would slip a thermocouple bead under the hose at the inlet and outlet
of the intercooler. Then you know if the intercooler is actually doing
anything and when. You should also see a reduction in EGT which corresponds
directly to the temp drop through the intercooler. If you don't have a 2
channel pyrometer, get a cheap indoor/outdoor digital thermometer. They are
thermistor based so they are not responsive enough, but will give you an
idea of what is going on. By using instruments and gathering data, I was
able to see if ducting and shrouds were actually doing anything. I was
surprised to see that what I thought would be effective was in fact not.
With the VW 1.6 or 1.9 IDI engines, the blow off valve does not play any
role unless the the wastegate fails. Don't bother with it unless it is
adjusted too low for some reason.
You can easily make an adjustable wastegate. Just get an ordinary pressure
regulator as found on any home air compressor and place it in line with the
wastegate pressure line. I found that at stock fueling, the vehicle did not
make much more boost anyway, so I never spent much time trying to increase
max. boost pressure. I did find that increasing fueling improved power.
I've seen VW diesels with propane injection, fumigation. It works, but is a
little complicated and involves a tank. If I had the time and desire, that
is the way I would do it. On the other hand turning up boost enrichement
only takes 5 minutes and costs nothing. Of course these fueling
modifications disregard any concern for emissions.
First thing you should do is install a pyrometer. Any modifications you do
will be governed by what your EGT is. This was not as important on the
jetta, but I found that the vanagon could generate very high EGT. Water
temp and oil temp were normal, but EGT could go through the roof on long
hills. I would modulate the throttle based on what the EGT was, one eye on
the road and one on the pyro. This only applies to turbo diesel vanagons.
NA diesels don't have this problem of course.
Gary Lee
http://www.telusplanet.net/public/gary2a/rack/vanagonrack.htm
