[Diy_efi] RE: Banjo Dis. Pic

[Mike]

At 07:45 AM 14/1/2003 -0700, you wrote:
>>when we have a wastegate bypassing flow around the turbine, in
>>general control systems parlance it makes les sense to do it that
>>way - but is justifiable (so far) because we don't have fly by
>>wire in general user
>>
>>rgds
>>
>>mike
>>
>You hardly would need drive by wire to control either a blow through OR a
>draw through throttle in the manner you describe.

Uh, yes I should have explained the context a bit more, what I meant was
that in a conventional (read 'cheap') mechanical throttle linkage where
its direct from pedal it would be harder and more complex to 'intervene'
and reduce the actual throttle movement if the dumb bunny of a driver
still wants more and more power despite the ECU saying 'no way jose',
and trying the throttle the engine back. Sure, it can be done but
needs a floating heavily spring loaded servo like arrangement so
the ECU signal to throttle back is not overcome by more pedal pressure.
With fly by wire its *much* easier since the ECU that knows the
boost level and what the driver is asking for can always over-ride
the driver <sigh> - I say <sigh> because this is what happened
to an Air-Bus which crashed into a forest in France some years ago,
it was a fly-by-wire, with computers on each turbine plus a conputer
in the cockpit getting a throttle up 'request' from the pilot.

Suffice it to say the pilot wanted and need to throttle up dramatically
to avoid crashing but the cockpit computer or the turbine computers
said 'no thank you'. From what I recall it had to do with a software
lockout because the turbines on each wing were not fully synchronised
and the software wouldnt let either turbine be throttled up until
a subroutine had finished resynchronising the relevant thrusts,
ended up only killing the pilot and 2 crew (flight was demo at
air show I recall), so three people dead for the sake of Beta testing.

Pity isnt it, we cant fly sideways anymore with fly-by-wire and just
hope there is enough digital experience in the 15 million lines of
computer code in the cockpit computer to account for wierd air
movements that a pilot can feel and experiment with by selective
throttling but, thats a bit drastic. I think since that 'accident'
or rather 'bug' the pilot has more buttons he can press, hopefully
in the right order - if he finds the page in the cleverly written
manual,  to over-ride that particular stupidroutine er subroutine
<cough> and make a landing safely (at the time the computer agrees).

>The accelerator pedal controls maximum throttle position in the usual
>manner on these carbs, but there is an extra spring loaded piece built into
>the linkage so that a centrifugal vacuum switch (located in the dizzy) can
>closoe the throttles partially to completely--without affecting the feel or
>position of the accelerator pedal-- when maximum engine speed is reached.
>NO reason this sort of a control could NOT be actuated by boost level,
>leaving no need for drive by wire.

Ah yes - gald you said that, this is what I was alluding to somewhere
above - if I can get something like this for my car (as I dont have
flybywire and dont want to), does anyone have a pci of this sort of
thing ?

>Regulating either a draw through OR a blow through throttle in this manner
>would, however, create a situation where the compressor was being run at a
>higher pressure ratio than otherwise necessary at times, thus raising the
>IAT, and obviously , therefore, lowering efficiency. And, in the case of a
>blow through, pushing the compressor closer to, if not into, surge.

In this case it likely changes the sizing requriements, knowing you
wont need to bypass any gas and have full control over inlet, changes
things a bit, the dynamic where you're throttling back shouldnt place
more static load on the compressor but of course there will be
a transient as occurs when changing gears on a manual under full load.
Besides, I guess, the old 'whoosh' blow-off valve could also be used
- as seems very common around here in Perth, with o/seas uni students
and their 280sx's and gtrs...

Of course I'd never put a blowoff valve on my turbo automatic
for obvious reasons :)

rgds

mike





>Greg
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