[Vwdiesel] Outlet on Turbodiesel Injection Pump

LBaird119 at aol.com LBaird119 at aol.com
Mon Apr 14 01:17:51 EDT 2003

> If the pump actually has a extra port for the boost enrichment vent,
>  what if one where to hook that to a sealed metal tank as a reference
>  pressure, so that it kept 14.7psi at all times? Wouldn't this make the
>  fuel metering more accurate at high elevations (for climbing mountain
>  passes, etc.?) It would have to be big enough to not alter the fuel
>  curve much as pressure increases when the aneroid moves. It seems like
>  otherwise it would think that you are running more boost than you are,
>  and run excessively rich, which could cause high EGTs, which is
>  especially bad when climbing a steep grade in thin air with a heavy
>  load.

  Actually no, or not really.  Full enrichment is full enrichment.  Lower air
pressure would just allow full enrichment a teeny bit quicker is all (at
slightly lower boost levels).  In theory it would make for a "richer" setting
but very marginally.  You're pushing against a pretty good spring to start
with.  The atmospheric difference would be minimal as it would only based
on pressure and not air density.  I'm not sure but the two aren't necessarily
directly proportional are they?  I've never heard of barometric readings
stated as being compensated for Denver altitude or such that I can recall,
is why I say that.  Otherwise I'd assume them to relate directly.
  Gas engines are running the same (or more) throttle opening with thinner
air going across at the same velocity, pulling the same fuel as at lower
altitudes.  This makes for a rich mix.  A diesel, although capable of the
same scenario, is only capable of it at full throttle since that would be the
only point where excess fuel to air can occur beyond sea level conditions.
Gas run at a "constant" A/F ratio.  Diesels don't.  It's all over the place.
  I've driven the Dasher over the pass into Cheyenne.  I had one of the
fastest cars on the road!  It beat the crap out of the 4000Q doing 50mph
over the same road!  I had no smoking nor any noticeable difference in
performance at the higher elevation.  Thinner air lets the turbo spin a
faster, pumping more air, giving a fairly constant density in the intake
manifold regardless of the ambient atmospheric pressure or density.  Within
reason of course.

Is this what the altitude compensator does (I think I read in a
>  manual somewhere that these were equipped on models sold at high
>  elevation)?

  I believe that is only available on the NA engines.  It would prevent
at full throttle in thin air, or allow more power at lower altitudes,
depending on
it's "zero" setting.

I am also thinking about removing the wastegate from my
>  turbo after I install a intercooler, because it never runs full boost
>  anyway except when ran very hard, slightly more boost is okay with a
>  intercooler, and the wastegate gradually opens as boost increases, which
>  likely causes it to spin up slower, and run a little less boost at
>  cruise.

  The wastegate is either opened or closed.  The gradual part is a pretty
short range.  It starts to open about 10 or so psi and is full open at about
10.5.  It doesn't (shouldn't) start at 8 and work up.

The test Nate did without a wastegate makes it seem like running
>  without it isn't a problem, any ideas?

  Until you hit a big hill with 4 people in the car on a hot day.  Then you
have no idea what it might go to.

Do you think maybe his car is
>  under-fueled?

  Depends on your definition of under fueled.  For him it's probably got
of fuel.  He drives it pretty easy.  For average driver conditions it
probably has
plenty as well.  If you want optimum performance then it's under fueled,
under boosted, under intercooled, etc.  ;) When you get closer to the limits
you need the gauges, understanding and attention to them, to make sure
you don't burn things up.  High performance under "most" conditions is
usually hot enough to do damage under maximum conditions.  They come
set for a margin of safety under maximum conditions.  :)

Also, does anyone have an idea as to how much boost can
>  safely be run on a VW Diesel? I know many other turbo diesel engines run
>  well over 30psi.

  I've heard of one vanagon running 30psi.  Not sure I'd really want to do
over 14 though.

I would think that the stock Garrett should be good for
>  20psi or more (obtainable with more fuel and no wastegate?) with a
>  intercooler, without too much heat, the Garrett is a pretty good sized
>  turbo, but I haven't looked at the maps to see how much heat it would
>  put out at these pressures.

  I didn't think the maps gave boost temperatures.  At least not the
regular turbo maps.  The turbo is probably capable of at least that
but not likely with only a 1.6 engine pushing it.  You can only generate
so much volume regardless of how much fuel you dump in there.  To
get more than the mid teens in pressure, you need a "smaller" turbo IMO.

Also, if the aneroid adjustment is the main
>  thing that determines maximum boost with no wastegate, than perhaps that
>  would be a good way to set the aneroid adjustment without a EGT gauge (a
>  boost gauge is much cheaper, and easier to mount).

  I have maximum boost long before I reach maximum EGT.  Of course a
wastegate has a lot to do with that.  However, ambient temperature and
intercooler efficiency have a direct effect on EGT.  When Jake did some
testing it was about 50F outside and I believe he was running over 300F
at 10psi.  It was nearing 200F @ 6psi as I recall.  The temps climb much
faster than the pressure I remember.

I am still not sure
>  how I am going to mount my EGT gauge in the stock exhaust manifold, but
>  I do have a manifold from a newer engine (that had a PCV valve port) and
>  possibly a small plate could be made to cover this port, and include a
>  welded on nut, to provide a place for a EGT sensor.
  You might be able to drill out and re-tap one of the heat shield bolt
There's a stud for a small, squarish heat shield, on the outer edge of the
exhaust manifold.  The hole is through rather than blind.  Otherwise you
can make a new exhaust downpipe for less restriction and weld a pipe
fitting in it.  In the Jetta, I have it down by the steering rack since I
want to try welding to the cast downpipe and wasn't ready to do a new
exhaust yet.  Jake drilled and tapped right into the turbine housing, pre
turbine!  :O

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