[Vwdiesel] [VW-TDI] Re: 01 Golf TDi TURBO issues

[Tad]

Further.. one way to test this theory would be to pull the vacuum line to
the EGR and plug it.  This would result in an EGR code (but you already have
that, right?) but should restore your vacuum charge and boost control.

...assuming of course that it's not leaking somewhere else, which is quite
possible.

On Wed, Jul 7, 2010 at 12:33 PM, Tad <tadc at europa.com> wrote:

> Hold the phone... if the turbo was not functioning due to being
> mechanically broken somehow, you'd likely have more serious issues than loss
> of power.  Typically a broken turbo will fail catastrophically and cause
> collateral damage.
>
> Early-on you said "we DO have a known bad EGR valve - shop tested, does
> NOT hold vacuum".
>
> If I'm reading that right, your EGR valve is leaking your vacuum charge.
>  If you don't have sufficient vacuum, you won't have boost.  Simple as
> that... it's a failsafe design of the system.  The turbo defaults to "no
> boost" mode when it isn't commanded to produce boost by application of
> vacuum to the actuator.
>
> Make sense?
>
> On Wed, Jul 7, 2010 at 11:40 AM, Rolf Pechukas <rbp at 4u2bu.org> wrote:
>
>> >> but are you saying that the turbo puts out more air than the engine
>> sucks in?
>> >
>> > Normally, yes.
>>
>> but not if the turbo's not functioning, correct?
>>
>> mine is not now, and has not been since the alternator 'repair'
>> no way to know when in the course of events it was disabled, but it's
>> possible that boost was weak or non-existent at the time the pipe was left
>> disconnected
>> in that case, intake suction could have been more of a issue, correct?
>>
>> >> i.e. how much 'suction' does the intake create, vs how much pressure
>> >> does the turbo produce?
>> >
>> > Enough to make boost pressure, hence more air goes there than is pulled
>> in
>> > by suction of piston displacement. If the intake produced more suction
>> than
>> > the supply, there wouldn't be any boost pressure now, would there.
>>
>> well, there would be a lessening of intake resistance...
>>
>> > Boost pressure refers to the oversupply of air, creating pressure in the
>> intake
>> > system, so the pistons don't have to suck air in, the air just follows
>> them.
>> > You're kind of saying something along the lines of a balloon sucking the
>> air
>> > out of your lungs as you blow it up.
>> >
>> >> by definition, since the turbo comes from the exhaust, and the exhaust
>> >> comes from the intake, and the intake comes from pistons drawing down
>> >> and sucking air in, due at least to friction losses, wouldn't turbo
>> >> pressure inherently be lower than intake vacuum?
>> >
>> > Don't forget the part about the burning fuel.
>>
>> you're right, I HAD forgotten that
>> I was thinking simply that the displacement of the piston downward
>> (intake) had to be equal to the piston upward (exhaust), so, barring valve
>> opening differences, volume of intake and exhaust had to be more or less
>> equal
>> but of course you're right - intake stroke is drawing in cold outside air,
>> while exhaust is expelling hot, probably still expanding, combustion fumes
>> so even though the throw is the same, volume and pressure could be much
>> higher
>> I get that
>>
>> (for the record, though, theoretically the majority of the energy of the
>> expanding combustion gasses goes into pushing the piston down, right?
>> and the better/more efficient the engine, the more completely that energy
>> is spent
>> so the upstroke to exhaust, while expelling hot gasses, shouldn't be
>> fighting any real pressure from sill-expanding fumes, should it?)
>>
>> > It's a heat engine, the exhaust volume is many times the intake volume
>> > because of heating from burning fuel ( boyle's law), and volumetric
>> change
>> > from fuel and air changing through speedy oxidation to stuff that takes
>> up
>> > more room such as CO2.   The turbo takes a tiny portion of the available
>> > waste heat, and uses it to run an air compressor that blows the manifold
>> > full.
>>
>> like I said, I know nothing about turbos
>> thanks for the instructional
>>
>> >> and if that's the case, AND the pipe was disconnected, so at least SOME
>> >> turbo pressure was spilling, wouldn't there be a fair amount of sucking
>> >> happening at that disconnected pipe of whatever was floating around
>> >> under the hood - dust, dirt, insects, loose screws, old oily rags? I'm
>> >> lucky I didn't get sucked right out of the driver's seat
>> >
>> > That's why you should wear your seat belt, you never know when a brake
>> > booster line, or especially one of those lines used to actuate the
>> climate
>> > control flaps can come off. They are vacuum too, and that's like space,
>> > where it would suck you right in. Pull you right out of your seat if you
>> > aren't careful. Keep both hands on the wheel too.
>> >
>> > Bugs, leaves, rocks, stray bricks, neighbor's cat all would get blown
>> out of
>> > the car. Post turbo line's under pressure, real pressure, far more than
>> the
>> > sucky part.
>> > ;-)
>> > -james
>>
>>
>> yea, unless it's not working :(
>>
>>
>> anyway, all that said, I am thinking the best place to start is simply
>> replacing lines
>> several people have said it's hard to see/find leaks, and the turbo simply
>> not working since the repair seems fishy
>> who's to say they only left one thing disconnected?
>>
>> any advice on what tubing to buy and where?
>>
>> thanks again, all
>> Rolf in MA
>>
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>