Alternative to Idle Speed Motor...

["content22207" <brobertson@xxxx>]

My PRV idles with bypass & balancing screws (like a Volvo). Works
excellent, but lacks ability to fast idle -- especially useful on 28
degree mornings. Have engineered an "auxiliary air valve" from BMW 530
to accomplish this (am not partial to that particular model; was
simply soonest ending eBay auction when I got bright idea). Uploaded
JPG's to #5939's photo album. Text below:

Aux air valves were apparently used by most other manufacturers of the
time. Are solenoid or coil operated valves similar to heater core shut
off valves. Cold, valve is open, allowing additional engine vacuum to
operate sensor plate (fast idle). Warm, valve closes, limiting sensor
plate movement to bypass screw.
My valve has 3/4" ports. Stepped down to 3/8" with brass fittings.
Vacuum source port also turned 90 degrees with an elbow (would have
preferred model that passes straight through, but hey, this one
works). Converted two 1/8 NPT nipples to 10x1 to fit manifold and
upper air assembly (anyone else noted how close those thread patterns
are? Die down right nicely). Used mega hose to avoid collapsing under
vacuum. Line to air sensor plate makes pretty severe bend under
driver's intake rail, so I reinforced with an internal spring. Also
had to move spark advance to a smaller adjacent port (see old pic
titled "R30 - Front". That's extent of my engine vacuum system BTW).

Was hoping for a coil operated valve but got a solenoid. Oh well, what
do you expect for $5. Next time intake manifold is off will attach
ground wire to thermal switch in coolant pipe. Until then is triggered
by a switch under the dash left over from earlier experiments. 12v
supply is taken from old idle speed motor harness.

Couldn't be happier with performance of this low tech idle speed
system. Removes all the gremlins that plagued my automatic motor.
Total investment: $20.

Anyone want to buy a surplus idle speed motor and ECU?

Bill Robertson
#5939