[Diy_efi] RE: Throttling intake air -- references

[Mike]

Yes I hear what you say and accept it will be more complex, but
its sensible to consider input throttling (ah lah foot) is likely
to be more fuel efficient as you arent wasting the energy of
the exhaust gas through a wastegate and by having an exhaust turbine
housing without the paraphenalia of the mechanics of the wastegate
should all the flow dynamics to be improved. This would be more
difficult for standard throttle linkage but easy to do with
flybywire. Yes the loop appears long but its comparable to the
loop from post compressor diaphragm to wastegate linkage - it might
be a little longer but not by much. I'm looking at this from both
the perspective of improving flow post turbine to improve economy
and power and to reduce fuel consumption in the situation where
a wastegate would normally be venting - as it should never get to
that stage.

I suppose what I should do first, for my current setup, is plumb a
couple of pressure gauges, pre turbine and post turbine or better
still log these with manifold boost pressure vs a digital input
so I know when wastegate actuated. Might be of interest.

So far I can see there are commercial issues re existing wastegate
configurations but given the implicit experience in already controlling
power output via foot pressure then in concert with control systems
pre-requisites regarding where to control the most active variable
etc it seems feasible to extend the TB existing control issue to
handle a boost max limit, and it shouldnt be hard to do and could
well be a challenging experiment if I approach it differently from
the rumours that seem to be out there  ;)

rgds

mike



At 05:55 AM 16/1/2003 -0500, you wrote:
>It still sounds to me like you are regulating the input to the turbo charger,
>the device we are controlling, by using the compressor output. Granted I have
>seen what you are saying but suspect the reason it works that way is
because the
>amount of exhaust gas flow goes down so there is less energy to drive the
>turbine. The only drawback i see is it makes the loop long. You change the
>throttle position the engine produces less power then the exhaust gas flow
and
>energy goes down then the turbine slows down... Three things need to
happen all
>with there own delays and particular response times to come back up. Or you
>regulate the exhaust flow to the turbine directly, short loop right next
to the
>turbine, delay time is very short response time should be very quick as
long as
>the bypass is sized properly. If you lengthen the loop and add more variables
>doesn't it make the control scheme more complicated and prone to problems?
Maybe
>if the name of the controller was changed from 'waste gate' to 'turbine over
>speed valve' or 'exhaust system back pressure reducing valve' or 'turbine
input
>modulator' it would seem less 'lossy'...  back to lurk mode..
>Dave
>
>Mike wrote:
>> 
>> What I was refering to was before engine *and* turbo,
>> few mls of air and fuel vs lots of mls of exhaust gas.
>> 
>> Thing about this:-
>> 
>> You are driving along watching your boost gauge sit at say 8psi
>> and you can reduce pedal/throttle pressure with no ill effects
>> to reach say 4psi, no problems...
>> 
>> So clearly, the input to the engine/turbo combination is
>> the uncombusted (unamplified) input,
>> 
>> rgds
>> 
>> mike
>
>
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