[DMCForum] Re: Turbos
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[DMCForum] Re: Turbos

VW's with TDI systems have a common problem with their intake
manifolds clogging up. The turbos will blow their seals, seep oil out,
and the diesel soot released from the EGR circuit will then stick to
the oil, rather than just blow by. As more oil is leaked out, the soot
deposits will wick the oil up, and allow another layer of soot to
cling. And it'll do this until the intake becomes so clogged, that the
vehicle no longer has any power to properly drive.

Oil spraying out from the turbo is the number one cause of this. Also,
yes, the type of fuel used would make a HUGE difference in the
emissions of a vehicle. Gasoline doesn't produce as much soot as
diesel. But diesel has a greater ability to burn cleaner. Now factor
this in to an EGR circuit that has to feed this all back into the
engine intake, and one gooped with oil at that...

And yes, diesel engines do produce vacuum. ALL engines will produce
vacuum to suck air into the combustion chambers. Even if you have a
tubo-charger installed, there WILL be vacuum in the intake before the
compression kicks in. No, with no throttle plates you will not get as
high a surge of vacuum, or any at all when driving (depending upon the
turbo set up). But on start-up, before the compressor properly spools
up, you WILL get vacuum in the intake.


--- In DMCForum@xxxxxxxxxxxxxxx, Martin Gutkowski <martin@xxxx> wrote:
> >
> > There are the Island Twin Turbos, but while they're are powerful, it's
> > a crappy desgin IMO. On that car, the turbo charges sit between the
> > throttle plates, and the intake manifold. So let's say you're stomping
> > on the engine hard, and the turbos are running boost. The air passages
> > after the compressor are under pressure, which is normal. BUT, let's
> > say you took your foot off the gas pedal. Now the turbo units are
> > under Vacuum, which is not a good thing. The vacuum will break the
> > seals on the turbo, and allow oil to slowly seep out. Which is why
> > some turbo charged DeLoreans with the Island kit have black exhaust
> > pipes. It's not any internal damage to the engine, just a problem with
> > the seals breaking.
> The BAE turbo does the same thing and I've got one in at the moment
> thats burning oil.
> >
> >
> > With the Legend design, the throttle plates would close, and cut the
> > vacuum off from the turbo units. So you didn't really have this
> > problem. Many late modem VW TDI cars have this same problem. Except on
> > their cars, they also have to contend with diesel exhaust, so their
> > entire intake manifolds clog up.
> Eh, WHAT?! Number 1, diesel engines don't produce vacuum because Number
> 2, they don't have throttle plates. Number 3 what difference does the
> type of fuel make to the intake manifold "clogging up"?! Diesels by
> their nature are all injection and TDI's are direct injection! The fuel
> goes into the cylinders and nowhere else! They're suited to turbos
> because of the much higher compression and associatedexhaust gas
> expansion after the combustion chamber. ALL petrol turbo engines blow
> through the throttle plates, and most have a dump valve (or blow-off
> valve as you guys call them).
> Renault made 4 version sof the PRV turbo but apart from the basic
> everything was changed.
> Martin

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