RE return to fuel tank

[David Piper]

Hey Greg

What about wastegate control.  This one is all over the map, like 18 psi +/-
1 psi, which also effects the fuel press.  I think the bigger the diaphragm
, the better.  Those elec boost controllers are way too expensive.  Are the
effective?

TurboDave

At 09:23 PM 10/22/98 -0600, you wrote:
>>Greg Hermann wrote:
>>
>>> The most stable fuel pressure control will be possible if you use a
>>> variable drive fuel pump,  a pressure regulator,  feedback on what the
>>> regulator is doing from a fuel pressure transducer, and a controlled
>>> reference pressure on the back side of the fuel pressure regulator
>>> diaphram, as well as a fuel temperature transducer to allow proper
>>> correction for fuel density.
>>
>>It's a little easier to do, measure the pressure and temp in the fuel
rails and
>>just bleed a very small amount of fuel back to the tank (vent the tank
into the
>>air cleaner) and control the pressure with the pump (ECU).
>>
>>Regards  Tom
>
>You are right, the return bleed flow does not have to be all that big, but
>I DO think that the regulator has got to be the lead control in the loop
>for best stability. Let the pump follow the regulator so as to try to
>maintain aa near as possible to a constant return flow, so that the
>armature in the regulator is not needing to jump around all the time. Gets
>you to the same place, but with more stability in the loop. The controlled
>pressure on the back side of the regulator diaphram is what would give the
>computer an active input into what the regulator is doing. The voltage
>control to the pump gives it a second active input. The two active inputs,
>properly coordinated, is what will give the truly stable control.
>
>Without getting into another whole thread on control theory at this point,
>let's just say that a control valve needs to present a minimum of about 25%
>of the flow restriction in a given flow circuit when wide open in order to
>be able to do a decent job of controling flow in the circuit over a wide
>range---and if you can use subordinate controls to minimize the amount that
>the primary control has to stroke through its range, you will get a MUCH
>more  stable controlled variable.
>
>REALLY WAY OFF SUBJECT:
>
>In my mind, one of the neatest things that the development of digital
>technology has accomplished to date is to bring the cost of sensors,
>transducers, operators and the means to read them and tell them (logically)
>what to do down to a level where it is now economically realistic to try to
>apply control techniques and theories that used to only be economically
>justifiable for huge industrial plants to hobby level projects. The use of
>such stuff will literally explode as soon as just a few more people learn
>how to use the new capabilities.
>
>For example: I was pondering the other day on whether anyone has thought to
>apply a HEGO sensor to a domestic hot water boiler or furnace so as to hold
>it at (or pretty near) stoich mixture, rather than pretty far lean, as is
>now done to be on the safe side with varying operating conditions and the
>like. Even the highest efficiency units could gain another point or three
>of efficiency by doing this---
>
>Regards, Greg
>
>
>