engine/turbo theory question
SIMON HOLTBY
sholtby at yahoo.co.uk
Tue Oct 17 21:33:50 EDT 2000
--- Todd Phenneger <tquattroguy at yahoo.com> wrote: > No,
> The turbo does hamper flow and cause a power loss. It just
> makes WAY more power than it loses. If you could have no
> restriction at all, you'd get even more power. Hence the
> development by Garret of that Hydraulicly driven turbo they want
> to make. No restriction at all makes for FAST spool up, and
> instant full boost at low RPM.
Todd,
I remember talking to a guy who was a diesel engine designer for Cummins
and he told me that the exhaust system is carefully designed so that the
turbo uses a very small amount of power. You know how exhausts are tuned
to scavenge from cylinders as the exhaust valve opens well the same can be
done with a turbo, some how pulling the gasses through.
He told me how some people who had failed turbos were removing them and
running N/A but this was destroying the engine as the exhaust was totally
out of tune.
He also said that it is not the exhaust gas pressure but the heat of the
exhaust gas that turns the turbine. I cannot remember his explenation as I
was confused by it.
Something else he said was that the turbo shaft has a spiral groove in it.
This prevents oil from getting past the oil seals, as the oil is 'wound'
back in.
His latest project was designing a JET engine that can run on coal dust
for countries without oil. Its use being for electricity generation (not
aircraft!)
Biggest problem with turbo engines is their lower compression which means
that they are inefficient when the turbo is off boost. I read an article
about a new Saab engine with variable compression allowing very high boost
pressures without detonation and efficient running at low boost. It does
this by raising and lowering the cylinder head, wow!
Regards
Simon Holtby
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