Re: PRV engine control system from LOTUS Cars U.K.

["content22207" <brobertson@xxxx>]

I may be qualified to answer this one too...

As many are aware, my D is re-engined with a Volvo PRV. Is certainly
recognizable as PRV, but differs in several respects from DMC's
application. Am missing frequency valve (port on fuel distributor was
never tapped & fitted). Do have a warm up regulator, but it doesn't
look anything like anyone else's. Have experimented running the car
without the idle speed motor. Am no expert, but do have a working
knowledge of the systems that could be used by any DeLorean owner
looking to simplify their vehicle.

Cold start valve: only receives a signal when the starting circuit is
engaged. Needs a ground to actually inject fuel (for some reason
Europeans love to switch the ground, not the hot). Thermal switch does
not close when engine is warm. Switch has it's own heating element to
open during extended cranking even on a cold engine. This bad boy
doesn't fool around -- throws raw gas into the intake. Can flood the
engine very quickly. People who use warm up regulator circuit to
overcome hot start problems often need to crank engine twice: once to
shoot too much gas, swap plugs back, then again to clear everything
out and start the car. If you wire to your VW's starting circuit, make
sure you've included thermal switch to avoid flooding. You could also
trigger manually from a switch on the dash.

Warm up regulator: serves same function as old fashioned choke plate.
Limits air into engine when cold by increasing counter pressure on
piston attached to air sensor. Is a fantasically complicated piece of
hardware (bimetal plates, diaphragms, and heating coils, oh my). Am
surprised mine has survived this long, if it has in fact survived.
Won't really know until weather turns cold. Engine runs fine now
whether regulator is plugged in or not. If your environment is 
moderate, this guy may be optional. But you may need to retain fuel
lines with 22+ psi counter pressure (is that what closes air sensor
plate?). Ask a K Jetronic expert on this one.

Frequency valve: EMISSIONS. Adjusts fuel mixture on the fly by
regulating pressure below diaphrams that feed each cylinder in fuel
distributor. Responds to signal from onboard computer, itself
responding to O2 sensor. I believe a microswitch on the throttle cable
spool shuts it down completely at full pedal. Can guarantee your
engine will run just fine without it because this isn't even an option
on mine.

Idle speed motor: serves same function as cracking throttle plates.
Has advantage of being variable. As engine loads increase (A/C
compressor, headlights, etc), will increase amount of air let into
engine. Mine works excellent. Experimented running car without it
(that's what brass screws are for by the throttle plates), but
without variable capacity had to set idle way too high (A/C compressor
kills about 500 rpm). Stock DMC PRV has a microswitch triggered by
closed throttle plate bracket to start motor. Mine is hard wired on
all the time. Wonder what the onbard computer thinks about that! (uses
RPM counter to adjust). Unless you've transplanted the computer in
your VW, you'll have to set idle manually. Could always have two idle
settings for summer and winter.

"CO2 adjusting screw": another fuel mixture adjustment located between
the air sensor and the fuel distributor. Apparently stock DMC PRV has
tamper proof plug in access hole. Mine has a threaded screw. This guy
controls how much piston movement you get inside fuel distributor from
corresponding air sensor movement. Turn in micro movements -- a very
little bit goes a long way.

Of course don't forget the basics: fresh ignition components (don't
overlook resistors, coil and all contacts), ignition timing, A CLEAN
AIR FILTER (for every gallon of gas burned your car sucks down tens of
thousands of gallons of air), no vacuum leaks, etc.

Bottom line: a PRV will probably run fine without cold start valve,
warm up regulator (again, ask expert about minimum counter pressure),
frequency valve, or idle speed motor. But you may sacrifice some
driveability until engine warms up. And without a frequency valve the
thing could fail emissions test unless timing is retarded and/or
mixture is leaned. As you adjust your engine remember you're walking a
fine line between burning too lean (bad idea in an aluminum block) and
burning to rich (dirty engine). 

FWIW: PRV seems to be a hearty little engine. Don't want to burst any
bubbles, but it IS low compression (87 octane isn't high compression
folks). Moving my idle speed motor to the driver's firewall was the
best thing I've ever done for access. Compared to the rocket science
on today's car lots, is mercifully simple. Don't really see why anyone
with moderate mechanic skills couldn't have his engine purring like a
contented kitten.

Good luck with your VeeWee...

Bill Robertson
#5939


>--- In dmcnews@xxxx, Senatorpack@xxxx wrote:
> Hello Everyone,
> 
> I received this email from an Engineer at Lotus in England. I'm sure
that all of our technical knowledge about the DeLorean engine can
assist this gentleman about the K-Jetronic management system.
> 
> Best Wishes,
> Michael R. Pack
> RE/MAX COLUMBIA
> 800-899-7629
> 
> Subject: PRV control system. 
> Date: Wed, 25 Sep 2002 6:09 EST 
> From: "Grewcock. Charlie" <CGrewcock@xxxx> 
> To: "'Senatorpack@xxxx'" 
> 
> Dear all,
> I have recently transplanted a PRV 2.7 from a R25 auto into my 1967
> VW camper van,it is coupled it to a Renault GTA gearbox just incase
you were
> worry about 5 fast reverse gears.
> I'm a little concerned that the engine is not running correctly as I
have
> removed a lot of the what I believe to be controlling systems for
the engine
> to car loom (Idle control for the auto). The engine does run fine at
present
> but it seems to be running rich. Does any one know what controls the
cold
> start injector/system as I think I may have removed it from the
engine loom.
> Also , what can be done to check if the cold start injector is operating
> correctly,where does it take its signal from.
> 
> I have Digi pictures of the conversion and will send them soon, Its
quiet a
> site.
> Charlie Grewcock
> Product Support Engineer
> Lotus Engineering
> Hethel
> Norwich
> Tel. (01953)-608-908
> Fax. (01953)-857-006
> Mob (07768)-404-672