valve needed

[john_carroll]

---------------Original Message---------------

Thank you for the suggestion.  The obvious answers often go right past me.

The literature I have available over the phone with my son shows an air control valve on a '86 Subaru SPFI system.  Is this the device? 


>
>
How about setting the mixture a tad rich, then add a calibrated air bleed,
using the duty valve from an electronic feedback Subaru EA81 2bbl setup? It
is designed to run on a PWM signal controlled by a black box in conjunction
with an O2 sensor, so should fit the bill perfectly. Was used on "87 Subaru
Chaser in Canada, not sure what else. A better idea might be to use a Bosch
KE Jetronic unit from, say, a VW FOX. The control pressure is controlled by
a balance valve - vary the voltage, and the mixture varies with it.\ Just a
thought, but I am seriously considering this system for my SOOB conversion -
hopefully in a CH601 or Sprint in a couple of years.>


>I need suggestions for an appropriate, available and affordable valve to
bypass some fuel from the distributor block in a port injected CIS system.
The object is to manage the mixture control of an aircraft engine.  The CIS
system is from Airflow Performace and much like the old Bendix systems.
This injection system is used because it is not dependent on electrical
power.  The main pump is mechanical.  The pressure is set at 25 psi, so the
distributor block pressure will always see <25.
>
>With the system I am building, the manual mixture control will always be
able to override the electronic control, again relieving the system of
ultimate reliance on electrical power.  We electronically spark one plug per
cylinder and let a magneto continue to operate the other for the same reason.
>
>The challenge is to find a valve that operates much like an injector so
that a PWM signal can slightly modify the injector pressure.  Other than
power requirements, the flow rating of the valve is not critical,the flow
can be controlled with an orifice. The valve needs to pass a maximum of 2
gallons of fuel per hour, so if the duty cycle is maintained at 30% for
cruise, a valve rated at 7 gph and capable of following a signal from 4 to 8
ms wide repeated as often as every 25 ms would be perfect.  Is this in the
range of injector performance?  Perhaps I could simply inject back into the
fuel system, using an off the shelf injector but the fittings and hardware
would likely require a lot of machine work.
>
>Perhaps a better alternative is to set the manual mixture control slightly
lean and then inject a small amount of additional fuel into the induction
system just past the throttle body with a conventional injector.  Will the
available devices operate at such low pressure? Is the hookup hardware
available for a single isolated injector used in this fashion?
>
>I agree this is a simplistic approach, but it avoids modifying the existing
hardware.  Your thoughts?
>
>-------------------------------------
>John Carroll
>jac at wavecom.net
> 08/30/97 00:33:59
>
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----------End of Original Message----------

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jac at wavecom.net
 08/30/97 23:22:21