beware VW turbo repair scham

"Harry K" > writes:
> Nate Nagel wrote:
> > JohnH wrote:
> > >>But the "same" car with a NA engine with the same power output as the
> > >>turbo... now you have much greater efficiency with the turbo, for
> > >>various reasons.
> > >
> > >
> > > which reasons would these be?
> > >
> >
> > first and foremost the lighter weight of the turbo engine giving a much
> > more favorable power/weight ratio...
> >
> > nate
> >
> >
> > --
> > replace "fly" with "com" to reply.
> > http://home.comcast.net/~njnagel
>
> Did you forget the "same engine" bit? How does adding a turbo to an
> engine make it lighter? A turbo squeezes more power out of an engine
> and the only way you can do that is use more fuel. There is no device
> that yeilds an over-unity result (more energy out than you put in).

When you are wrong is assuming that all your energy "out" is used. If
you reduce the amount of energy wasted, then you get more energy out
without more fuel in. Turbos (partially) do that as they use part of
the energy contained in the exhaust gases.

These are simple energy balance considerations.

--
Ignasi.
(using SPAM trap e-mail address)

> without more fuel in. Turbos (partially) do that as they use part of
> the energy contained in the exhaust gases.

Where do you people GET this?

A turbo doesn't "use" any *energy* of the exhaust gases. The turbine pump
uses the exhaust pressure (as supplied by the piston) to spin the turbine.
Since the turbo presents itself as a restriction to the exhaust, it creates
MORE work for the engine in the form of backpressure.

"JohnH" > writes:
> > without more fuel in. Turbos (partially) do that as they use part of
> > the energy contained in the exhaust gases.
>
> Where do you people GET this?
>
> A turbo doesn't "use" any *energy* of the exhaust gases. The turbine pump
> uses the exhaust pressure (as supplied by the piston) to spin the turbine.
> Since the turbo presents itself as a restriction to the exhaust, it creates
> MORE work for the engine in the form of backpressure.

The pressure (differential) of the exhaust gases IS energy. If you
want to discuss these issues with any sort of accuracy you need to
brush up on your thermodynamics and transport phenomena. Otherwise is
pointless.

--
Ignasi.
(using SPAM trap e-mail address)

Ignasi Palou-Rivera wrote:
> "JohnH" > writes:
> > > without more fuel in. Turbos (partially) do that as they use part of
> > > the energy contained in the exhaust gases.
> >
> > Where do you people GET this?
> >
> > A turbo doesn't "use" any *energy* of the exhaust gases. The turbine pump
> > uses the exhaust pressure (as supplied by the piston) to spin the turbine.
> > Since the turbo presents itself as a restriction to the exhaust, it creates
> > MORE work for the engine in the form of backpressure.
>
> The pressure (differential) of the exhaust gases IS energy. If you
> want to discuss these issues with any sort of accuracy you need to
> brush up on your thermodynamics and transport phenomena. Otherwise is
> pointless.
>
> --
> Ignasi.
> (using SPAM trap e-mail address)

Yes the turbo is using what would be waste energy. In the precess it
is causing more back pressure for a negative effect. Then the LOT
kicks in saying that you can't get more energy out of the turbo than
went in the front end. Thus a net loss in energy (across the turbo).
The gain in HP comes from being able to add -more gas-. That makes up
for the increase in backpressure plus the loss across the turbo then a
bit more gas and you get the increased hp. You can not beat the laws
of thermo.

I think someone else pointed out that if you have an accurate instant
fuel use gauge you can see mpg go in the toilet as soon as the turbo
kicks in.

Harry K