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

Tue Mar 18 10:06:09 EST 2003

I run an AAZ turbo (1.9) on my 1.6.  The 1.9 doesn't have an over-pressure
valve, so I blocked mine off with a plug.  For the brief few times I drove
with it open (to air, as there's no port for it on the 1.9 air inlet pipe)
it would occasionally blow off before the wastegate, depending on how
quickly the boost was coming on.  My factory reman KKK turbo's wastegate
appears to be at or around the 11psi mark (at the top of the spec
according to the A3 Bentley) The blowoff valve, IIRC is around 10psi.
When it lets go, it _does_ result in a very dramatic decrease in power.
Not quite as bad as when I hit the 6200rpm rev limiter in my winter beater
(8V gas) though - that's when you're glad you have your belt on, lest your
head go through the windshield.

Drew

On Tue, 18 Mar 2003, Nate Wall wrote:

> 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
> > _______________________________________________
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>
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