Re: Work output - back to ceramic EM - somewhat long

[The Murphy-Fahlgren Family <efhome@master.adams.com>]

QSHIPQ@aol.com wrote:
> 
> Not exactly.  A turbocharger generates 2 things, work output and heat.  Work
> output is measured in terms of efficiency on a turbo map.  Imperical test?
> Run your turbo really hard at night, open the hood.  What is glowing red?

Scott,

I assumed in your first post that you were speaking strictly of
the exhaust turbine when you said "a turbine is," when in fact
you restate above that "a turbocharger is a heat generator."

But, ...

Back to the ceramic EM.  I think that when you measured the 0-60
times with and without ceramic, you were probably measuring the
wrong thing.  Consider the scenario where you put 100 octane
fuel in a car with fixed ignition, and lo, no change in behavior.
Why?  Because you did nothing else to take advantage of this change;
in this example, advancing the timing _along with_ higher octane
fuel might result in improved performance.

So, maybe you should have measured the wastegate frequency valve
duty cycle under full boost, both with and without ceramic.  My
guess is that you would have seen an obvious and measureable
increase in wastegate activity with the ceramic.  What can this
do for us?  Well, it would indicate to me that you can increase
the A/R ratio of your turbocharger without impact on lag.  Increasing
A/R lowers back pressure in the manifold, which increases the VE of
the engine, which ..., which increases HP.

Here is a snippet I sent off to Bob Myers this morning, he didn't
call me crazy, so I'm assuming that I'm not. :-)

(Note for those of you without chemistry or physicks background,
an adiabatic reaction or process is one where the temperature
remains pretty much constant.  In terms of the ideal gas law,
this means pv = K, where K is some constant taking into account
the starting temp and the quantity of gas involved.)

> I wrote:
> >Does
> >the ideal gas law (or an approximation) work ok [in these conditions]?  
> 
> Bob responded:
> More or less.  The conditions will be quite a way from those at which
> "ideal" seems to apply.  Much closer here, though, that in that tank of N2O
> of infamy.
>
> >If so, then
> >I can see where pv is constant (pressure goes down proportional
> >to volume going up), and hence T remains more-or-less constant
> >as the gas passes the exhaust turbine.
> 
> Subject to conduction losses from the EM, yes.
> 
> >It follows then, that maintaining the temperature in the EM would
> >be accompanied by a proportional increase in pressure.  Does the
> >following seem reasonable?
> 
> Seems that way to me.  You reduce the heat loss (make it more nearly
> adiabatic) with the ceramic coating then the pressure should increase some.
> 
> > Io = original (no ceramic) EM gas temp, deg F
> > Ic = new (ceramic) EM gas temp
> > dP = improvement in ressure differential across exhaust turbine
> >
> >      Ic + 460
> > dP = --------
> >      Io + 460
> >
> >Increasing dP in itself will not increase HP (in fact may hurt, since
> >the exhaust turbine may now be "too small," increasing back pressure
> >and reducing efficiency).  But, by resizing the exhaust turbine,
> >we could improve the spin up of the turbo (a direct result of dP > 1),
> >while concurrently improving its high flow efficiency (a result of
> >putting in an exhaust turbine with a higher A/R ratio).
> >
> >If we can believe the marketing literature published by the coating
> >vendors, the temperature in the EM is increased by 200-250 deg F.
> >Let's assume that means that Io = 1000 and Ic = 1200.  We have
> >thus realized an improved pressure gradient of almost 14%, which
> >seems not too shabby (I always consider engineering improvements
> >in terms of salary increases, it puts things in perspective for
> >management types :).
> 
> Bottom line econonics, huh?  :-)
> 
> >My off-the-cuff calculations seem to indicate that $20 spent on
> >ceramic coatings in the EM is money well spent, _if_ they are part
> >of a bigger picture rework.  Am I missing something here that flaws
> >my logic?
> 
> If so, I'm missing it too. ...

If we really want to extract that last little bit of energy out
of the exhaust stream, we would put a deLaval nozzle on the turbo
outlet and point it towards the back of the car.  Hmmm, if we put
on an afterburner...

Hoping this spurs further conversation,
Eric Fahlgren
-- 
The Murphy-Fahlgren Family            Try to take over the world.
efhome@adams.com                                  Canton, MI, USA