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Sensor location, MSD installation, and the HKS ECV

Greetings brothers and sisters of commiseration!  New problem just occurred
on my '87 5kCSq... whether engine is cold or hot the low-speed mode of the
radiator cooling fan stays on as long as the ignition is on.  I think this
is part of the after-run-turbo-cooling function. Removing the relay from
position #6 stops the fan, swapping with the one from position #2 gets the
same result.  My bet involves a continuous signal from the sensor, or a
grounded sensor line.  

Now, which of the several thousand sensors controls this after-run cooling
function?  One at a time I have disconnected all that I can find, including
the one next to the knock sensor that causes cramps in your hand when
reconnecting it.  My hard-copy parts fiche (thank you, Avi) shows a
thermoswitch sensor near the side of the head/block below the spark plugs,
but its location remains occulted.  Guidance please!

Have completed installation if an MSD-6a ignition system.  But it doesn't
work... no spark during cranking.  Manually firing the unit by grounding
the trigger line produces a near-blinding buzz of sparks from the coil
wire, as it should.  Problem is that whatever triggers the coil to 'fire'
is not apparent.  It is _not_ the green wire on the coil, as one would
think.  I've called the MSD folks in El Paso and faxed them several pages
of schematics from Bentley and await their council.  A custom set of their
spiral-wound ignition wires is next.  

I'm still fiddling with... excuse me, that should read, fine tuning... the
HKS Electronic Valve Controller which is now the only control on my
wastegate.  It is two-stage programmable, Low and High, to control the
boost to whatever level you set... that your system is capable of
producing. It's internal sensor will handle up to 2.0bar gauge, 3.0bar as
Audi reads it.  It has a fuzzy-logic circuit that 'learns' the boost curve
of your engine/turbo combination to enable the controller to anticipate
when it needs to exert control.   I've used it with a shimmed stock spring
and now with Scott Mockry's heavy spring, which is much better.  I've set
low range to a 0.9 bar limit, and high for 1.2 bar, that's gauge.  

Mid-range part-throttle response is _vastly_ improved... feels like a good
NA engine under there now.   

Stock, my 30-70 third gear runs were 13.5 sec.  After Graydon's QLCC it was
10 sec.  After the HKS, set for 1.2 bar, and an average of four runs, is 8
sec.  Total investment, $500. 

I still have the ECU pressure line hooked up to give a bit of ignition
retard at high boost and rpm, and to still retain the knock sensor.  I have
the fuel pump shut off relay disabled, not a permanent situation... but
first things first.  Please, no shrieking 'but what if...' scenarios need
be relayed.  I have modified the system for increased boost, it is my
responsibility, and am therefore ever vigilant to anomalous happenings...
if the car begins to do a rocket sled imitation then something isn't
normal, back off and investigate.  I intend to restore the cut off relay to
regain the accident/impact fuel pump cutoff capability.  

Single-pass intercooler (mod to OEM), suspension and brakes are next.

Regards,  Gross
Bumper sticker seen in Carmel, "Horn Broken -- watch for finger!"