[Diy_efi] RE: Throttling intake air

[Adam Wade]

--- Perry Harrington <pedward at apsoft.com> wrote:

> Please state your reasoning.  If you plug up the
> intake of a vacuum cleaner or a water pump both will
> simply cavitate and draw less power.  I would expect
> a compressor to cavitate and draw less power from
> the turbine.

You caught me.  Neither fluid flow not turbos are my
field of expertise.

To what degree does cavitation have an impact? 
Realistically, I would imagine there being SOME
decrease in turbine speed when throttling the intake. 
Or does cavitation take over completely and allow
freewheeling?  I do see the point in the vacuum
reference; the motor obviously speeds up when you plug
the intake off entirely.

I imagine you can educate me on these points, since
you pointed them out, Perry.  ;)

>> Seems like that would be a worse solution than a
>> wastegate, in the sense that it would decrease
>> efficiency.  It could slow the turbine more than a
>> wastegate, but I doubt it would function very well
>> as an engine brake.

> What do you think an exhaust brake on a diesel is? 
> Since diesels have no throttle they use an exhaust
> brake to generate closed throttle torque.

Yes, but there would still be considerable boost in
the intake manifold, yes?  Would that not offset most
of the loss of combustible gases from the described
throttle?  Granted, you would then have the piston
using more work in removing the exhaust gases, but how
much more?

Seems to me like a throttle BEFORE the turbine would
be much better at achieveing the desired brake effect,
yes, Perry?

=====
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |

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