Volvo turbo Control Pressure Regulator, help

[The Dupuis]

I got'cha!

Take a manifold pressure reference (Boost and vacuum), feed it to some kind
of a ported thermal vacuum valve that is open when cold (or use a Dodge
Turbo vacuum solenoid and a toggle switch), feed the other end of the
valve/solenoid to one end of a tee.  The second end of the tee goes directly
to the top port on the CPR, and the third end of the tee goes through a
check valve, providing a constant vacuum to the bottom port.

The idea is this:  When the engine is cold, the valve/solenoid is open,
allowing a vacuum signal to the CPR.  This signal puts equal vacuum pull on
the top and the bottom of the piston inside the CPR.  When you are idling or
at high vacuum, this piston stays in the top position, which adds pressure
through a spring to the CPR valve, raising the control pressure, leaning the
mixture.  When you open the throttle the vacuum falls away from the top of
the piston but is held in the bottom of the piston by the check valve, which
draws this piston downwards.  This releases the spring pressure, lowers the
control pressure, and enriches the mixture.

When the engine warms up, the valve/solenoid closes, which shuts off the
vacuum signal to the CPR, and any difference will eventually equalize
through the slightly leaky check valve or CPR piston, so the piston returns
to the top of it's stroke, pushing the spring into the fuel pressure valve,
raising control pressure, leaning it back out.

You might think "Wow, a boost-referenced enrichment!", but it's too much
fuel unless the engine is dead cold, and even then if you get into boost the
engine loads up and chokes out.  When the engine is warm, the valve/solenoid
should be closed to keep the control pressure up.  There is a pressure
switch set to 3 psi that enriches the mixture under boost, and if that's not
enough you can add another at 12 psi or so to trigger "terminal 11" on the
computer.  I don't like t11 in my car - it prefers to be lean.

Interesting use of a Volvo Turbo computer!  Maybe I'll throw that in my
wife's Digifant Cabriolet when I upgrade to the Megasquirt.

I can't do ASCII graphics, so if you want a sketch or a further description
I can provide it.  There are no really good pictures from manuals that I
have seen.

Matt

p.s., if you have that kind of a CPR, I believe it's from an '83 or earlier.
My '83 has it, but the early '84 (non-intercooled) that I pulled my wiring
harness from didn't.

> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Stephen Webb
> Sent: January 7, 2002 2:40 PM
> To: diy_efi at diy-efi.org
> Subject: Volvo turbo Control Pressure Regulator, help
>
>
>
> This isn't strictly an EFI question, and I've been hesitant to post the
> question.  After spending many hours trying to figure out the answer, I've
> decided to ask here.
>
> I'm using the fuel injection (K-jetronic with lambda) from a 1984 (I
> think) Volvo 240 turbo.  (The application is a VW cabriolet turbo)  The
> control pressure regulator from the turbo is designed to enrich the
> mixture under boost, but there are two vacuum ports on the side of the
> unit.  I'm trying to figure out which one needs to be hooked to boost, or
> what the proper connection is.  Vacuum schematics from Volvo repair manual
> would be perfect.
>
> Thanks in advance.
>
> -Steve
>
> ----- End of forwarded message from owner-diy_efi at diy-efi.org -----
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