Date:         Thu, 14 Nov 2013 23:01:42 -0500
Reply-To:     James Eaton <jk_eaton@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         James Eaton <jk_eaton@HOTMAIL.COM>
Subject:      Arduino and Vanagons
In-Reply-To:  <BAY0-MC2-F21ssgaIwb005ab636@BAY0-MC2-F21.Bay0.hotmail.com>
Content-Type: text/plain; charset="iso-8859-1"

My understanding is that the ISV controller gets signals from the AC and PS pump
because of the slow response time of the current controller and ISV design - if you disconnect those 
(as was the case with the PS pump in our van when we bought it) then the ISV doesn't respond fast 
enough when the engine is cold to keep the engine idling.  (Scenario - Vanagon with automatic.  
Cold start. Back out from garage, down driveway to road.  Pause, then take foot off gas and turn 
steering wheel hard for 90 degree turn.  Have engine die 50% of the time.  Reconnect PS sensor
 [or rather have Frank Condelli reconnect it while he was doing other servicing] and 
watch that engine keep turning at cold idle!)

My thinking is that by the time the ISV controller has responded to the slowing of the input signal from 
the Hall sensor, the engine is already on its way to turning too slowly to recover - possibly because the ISV is only 
directly changing the amount of air the engine is receiving, not the fuel injection timing and quantity, or 
the ignition timing, and each of those systems in turn takes time to respond.   The PS and AC
signals get to the controller before the increased load from those auxiliaries has a chance to reduce the 
engine speed too much.  A modern 20MHz microcontroller may respond fast enough that the PS and AC inputs 
are not needed - but that would need testing before I'd be comfortable with deliberately leaving them 
out.  They cost VW considerably to wire in - so I'd at least consider sampling those inputs.  The AC 
compressor is quite a load on an idling wasserboxer.

While I teach the Microchip PIC (because that's what the industries our grads work in expect them to know), I'm 
not fixed on it - the Arduino certainly has ease of programming and lots of support as well.  If needed, the 
solution developed on the Arduino could always be transferred over to MIL-spec PICs for an actual 
production run.  But I imagine that it's not the chip where failures will occur, but in the circuit design and 
assembly of the board and connectors.

The next month is, unfortunately, frantically busy in the community college world.  I will try to find some time to 
measure inputs and outputs, but can't guarantee much will get done before mid-December (at which point it's 
getting cold here in the Great White North, and I don't keep the Vanagon in a heated garage). If perhaps others in
more temperate climes (or with heated garages!) can help with measurements, I'll try to aid with circuit design.
I might even a student or two involved.

James
'91 Vanagon Westfalia Weekender (automatic to boot!)
Ottawa, ON




> ------------------------------
> 
> Date:    Thu, 14 Nov 2013 13:48:24 -0800
> From:    Brett Ne <brettn777@GMAIL.COM>
> Subject: Re: Arduino and Vanagons
> 
> Okay, now it's time for a dumb question: why do we need input signals from
> the power steering pump and air conditioner?
> 
> We already have input from the Hall sensor telling us what the engine speed
> is, and if it's too low we increase the idle air flow & if it's too high we
> decrease the idle air flow...who really cares whether the change in idle
> speed is from AC, or PS, or from a belt driven coffee grinder accessory
> that someone has installed.  If the throttle valve is closed, then adjust
> the idle air flow to keep the rpms within a narrow range.  When there is
> partial throttle, keep the idle air flow at a moderate level to avoid
> shutting down the engine if the throttle is released suddenly.  What's
> wrong with my thinking?
> 
> Brett
>