[Vwdiesel] Rabbit 1984 Diesel Turbo ( My understanding now )

[Nate Wall]

<<<There's also the "overboost safety valve" as I call
it.  It's set a couple pounds higher than the
wastegate.  The wastegate, though regulating
the boost works quite differently than a regulator.
It bypasses the exhaust around the turbine so that it
won't make it spin faster.>>>

I did a test one day. I hooked a pressure guage to the
intake and disconnected and plugged the boost feed
line to the wastegate (disabling it) and took the
Jetta for a brisk drive up a slight hill on the
interstate. Before, boost under a fairly hard
drive/acceleration would max out at about 8.5 or 9
PSI. After, it was hard to get it much above this
WITHOUT the wastegate. I could get about 10 PSI. The
blow-off valve is set to dump manifold pressure at
about 11 PSI. Then I pushed it as hard as I could, and
at about 80 - 85 MPH going up the slight grade at full
tilt, I hit 11 PSI on the guage and I heard a loud
"Woosh" as the blow-off valve opened, and power just
dropped off, like the key was turned off. The valve
stayed open till about 3 psi was reached (I had to let
off the pedal to get it to reset) and then the valve
closed again. I'd NEVER drive the car like that,
unless I was fleeing for my life! so bottom line, for
my Jetta anyway, I feel neither the wastegate, not
blow-off valve are needed. These must be in there to
negate engine warranty claims from the uneducated
(average) abusive owner.

One other thing: What IS the turbo supposed to sound
like? Well, mine's ALWAYS been noisy, it seems to have
a droning/vibration in a certain RPM range. Passengers
think the cops are behind us. Before a rebuilt
cartridge and after, all the same. I think its just
normal. It happens as boost builds, then when it gets
really going, it quits down, to an almost non-audible
hi-pitched sound. Play with the throttle during this,
it sounds like throttling a jet engine. Kind of cool,
but it will hit the raspy RPM. Its not rubbing its
housing(s), I don't think. I think its just the air
whistling thru it, or something like the wastegate
spring vibrating. Matt Bulley's '85 Jetta TD I bought
has a whisper quite turbo, I never hear it. Its a KKK,
My Jetta has a Garrett. I tempted to put by brand
spanking Garret on it that's in my office and see if
it changes. I'm also suspicious I'm not getting the
proper boost at lighter loads, and maybe at full load.

--Nate

--Nate
--- LBaird119 at aol.com wrote:
> > Ok it is a Garrett exhaust gas turbine driving a
> air pressure impeller.
> Boost
> >   about 10 psi overpressure.(a lot),
>
>   Until you see a setup that kicks out about 200psi
> over atmospheric!  :)
>
> >  Aneroid on top of injection pump responds to
> increase in boost.(more fuel
> as
> > pressure increases)..Wastegate regulates
> boost.(like a pressure regulator).
>
>   There's also the "overboost safety valve" as I
> call it.  It's set a couple
> pounds higher than the wastegate.  The wastegate,
> though regulating
> the boost works quite differently than a regulator.
> It bypasses the
> exhaust around the turbine so that it won't make it
> spin faster.
>
> > Never driven or seen a turbo Rabbit before, so how
> does one know what is
> > normal?  . Incredible power on first spin. And
> lots of smoke. 1984 Turbo ?
>
>   The smoke isn't normal.  It should almost feel
> like you're driving a gas
> engine only instead of as rapid of acceleration you
> get more of a really
> strong, steady push.  Tires don't generally break
> loose unless you're on
> sand or gravel.  You should have a huge grin and
> wonder why you ever
> drove one WITHOUT a turbo, for the first few drives.
>  :)
>
> > how long do these things last ?. 251 000 Km.on
> clock.
>
>   With proper oil and a little reasonable cool down
> time, right after hard
> working, and a clean air filter, they'll last a long
> time.  Failure is
> usually
> heavy oil smoke from oil consumption or contact
> between a wheel and
> the housing, from excessive wear.
>
> Does the turbine need
> > cleaning at times ??.---Fools and questions ????
> you bet. Ah yes as soon as
> > brakes and tranney is ok ---the turbo will be
> tried again.
>
>   Yeah, stopping and shifting are important too.  :)
>  Any cleaning would
> require disassembly and that would only be for
> coking inside the center
> section.  Cool down and good oil will prevent this
> and also clean out
> (slowly) any minor coking that's present.
>
> By the way --if
> > turbine is doing 100 000 RPM how fast does the air
> impeller turn ???? --is
> > there a gearbox in the turbo ???.
>
>   100,000 rpm.  It's a straigt shaft from the
> turbine to the compressor
> wheel.
> That's more of a maximum speed rather than typical
> speed.
>      Loren
> _______________________________________________
> vwdiesel mailing list
> vwdiesel at vwfans.com
> http://www.audifans.com/mailman/listinfo/vwdiesel


__________________________________________________
Do you Yahoo!?
Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop!
http://platinum.yahoo.com