Just want everyone to know that Neil has sent a nice set of photos and
measurements of the ICU.  As I suspected, each cluster of blades matches a
standard relay socket.  Nice.  Neil also stated that there may be a
different pinout for Canadian models.  So no need for everyone to go out to
the garage and take photos & measurements.  Unless you want to; a good
excuse to crack open a beer  or something.

Brett

On Tue, Nov 26, 2013 at 7:23 PM, James <jk_eaton@hotmail.com> wrote:

> I think having this data is great - I could pretty much write the
> progamming now, if I make a guess/assumption about the ISV's behavior at
> speeds above idle.   ( Which one could do, as the amount of air being
> admitted is only a small fraction of the total air intake when the
> waterboxer is working.)  Thanks to those who took the time to make the
> measurements.
>
> I wonder if the jump to 55% duty cycle is really to compensate for lower
> available voltage while starting, or to aid starting itself?  I guess I can
> better rephrase my question as, does the ISV open more at higher voltages
> (i.e., is there any connection between the amount of air it lets in and the
> voltage applied to it?).  If the ISV were a motor, of course there would
> be, but I wonder if it is more like a pneumatic valve - and the pneumatic
> valves I'm familiar with don't open more with higher voltages, as long as
> the minimum voltage is met.  (I teach pneumatics as well, using German
> Festo equipment, and consult on pneumatic factory equipment.)  Pneumatic
> valves are rather 'digital' in operation - either they're on, or off, with
> no intermediate positions.  The vibraion the ISV produces reminds me of a
> Festo pneumatic valve in 'flutter' operation.
>
> The PIC microcontrollers I teach all have 10 bit (or 1024 step) PWM, so
> having a fine control over the ISV wouldn't be a problem, if we wanted
> something with a finer control than the 256 step.  For a cleaner design and
> possibly more reliability I'd avoid a separate PWM controller, if I could.
>
> James
> Ottawa ON
> '91 Westfalia Weekender
>
> > Date: Tue, 26 Nov 2013 08:10:00 -0800
> > From: brettn777@GMAIL.COM
> > Subject: Re: Arduino and Vanagons
> > To: vanagon@GERRY.VANAGON.COM
> >
> > We have some data to work with!  One of our members has generously put in
> > the time and effort to gather most of the readings we need.  Here is what
> > we have so far:
> >
> >     *Duty Cycle Under Various Engine Conditions*
> >
> >   *Condition* *Duty Cycle* *Peak Voltage*
> >   Engine Cold, Key On, Engine Off 34.0% 9
> >  Engine Warm, Key On, Engine Off 29.4% 9 @ 157 mA  Engine Cold & Starter
> > cranking (45 F) 55.0% 6
> >  Engine Cold & Idling 25.0% 10.5
> >  Engine Warm & Idling 20.5% 10.5
> >  Engine Warm & Running 2000 RPM
> >
> >  Engine Warm, WOT Signal
> >
> >  *Duty Cycle Under Various Load Conditions*
> >
> >  *Load* *Engine Cold* *Engine Warm*
> >  None 23.0% 20.5%
> >  AT in Gear 25.5% 23.0%
> >  PS 27.0% 25.0%
> >  AT in Gear & PS 30.0% 27.0%
> >
> >
> >  *Miscellaneous:*
> >
> >  PWM Frequency constant at 148.2 Hz
> >
> >
> >  Yellow Wire (11/ST1) PWM Power to Idle Stabilizer Valve
> > >
> >  White Wire (4/ST2) Ground Connection? (Needs to be confirmed)
> >
> > From this we can conclude:
> > **The idle air valve is very sensitive.  A 7% increase in duty cycle is
> > able to overcome the combined loads of AT in gear and PS at full
> pressure.
> > The built-in PWM output on the Arduino only has 256 settings, which would
> > give use increments of 0.4% in the duty cycle output.  This would work,
> but
> > I think that there would be a noticeable unevenness in idle speed.  Not a
> > big deal, it just means that we will need to use a timer interrupt to
> gain
> > fine control over the duty cycle(the percentage of "on" time of the
> pulse)
> > of the PWM.  It's just not as fun and easy as using the built-in PWM
> > functions.  I'll explain interrupts in more detail when we get to the
> > programming stage, but it basically is just a way to grab the computer's
> > attention and make it suspend its current operations while it attends to
> a
> > time-critical event, like a new hall sensor pulse coming in.
> >
> > **Most of the time, the duty cycle is pretty low, around 25%, but that
> > changes during starting.  While the engine is cranking, the duty cycle
> > jumps to around 55%.  When I first saw this figure I thought, "Wow, it's
> > really increasing the airflow a lot while the engine is cranking."  But I
> > don't think that is true because the current draw from the starter motor
> > drops the available battery voltage considerably.  The stock ICU output
> > voltage drops from 9v with engine not running to 6v with starter
> cranking.
> > I think the dramatic increase in duty cycle is not for increasing
> airflow,
> > but rather to compensate for the expected voltage drop during cranking.
> >
> > **The ICU apparently makes no attempt to send a fixed voltage to the idle
> > air valve.  With engine off, it sends 9v.  With engine running, it sends
> > 10.5v, which matches the increase in voltage from the alternator.  With
> > engine cranking, the output drops to 6v, reflecting the battery voltage
> > drop under the heavy load of the starter.  For running conditions, we
> don't
> > need to worry about the output voltage level because it will be
> > automatically compensated for by the engine speed feedback.  But for
> > starting, we could have the Arduino measure the voltage coming from the
> > battery and calculate the appropriate duty cycle change to have better
> > control over the airflow.
> >
> > **The idle air valve draws 157 mA when supplied with a 9v 29% duty cycle.
> > This translates to a 535 mA draw @ 100% & 9v or 4.8 W of power.  The
> final
> > drive transistor in our circuit should be chosen to handle 1A of current
> to
> > assure durability.  Lots of options here.
> >
> >
> >
> > What we're still looking for:
> >
> > What happens above idle speed?  Does the idle air flow shut down, or stay
> > at some predetermined level?
> > What happens at Wide Open Throttle?
> > What does the Hall sensor output signal look like?  I haven't found
> > anything definitive on the internet.  There are hints that it is a square
> > wave and that the peak pulses are up near battery voltage.  I would like
> to
> > know peak and base voltages and confirm that it's a clean square wave.
> > Also, has anyone taken apart an idle air valve?  Is it just a motor
> > operating against a spring?
> >
> >
> > Brett
> >
>
>
>

--
Brett in Portland, OR
"Albert" '82 VanaFox I4 Riviera