Re: non-roc (audi A4)

["Ian Overholt" <ioverholt@hotmail.com>]

A distributor is basically a switch that closes when you want charge to go 
to the plug.  What these distributorless systems do is forgo the mechanical 
rotating contact and replace it with transistors.  A distributorless system 
would have a FET for each cylinder which would only be turned on (and allow 
current to flow) when you want spark.  These systems could use individual 
coils.  Electronic distributors have a lot less loss in them.  There is no 
air gap to bridge and no contacts to wear out.  Sparks plugs are still 
required to ignite the mixture.

Mechanical distributors needed points or hall sensors to control when 
voltage was applied to the terminals anyhow, so this added to their 
unreliability.  Controling spark with electronics gives the manufacturer a 
lot of control of how the engine runs.

Ian Overholt
'88 16v
'78 Sidewinder


----Original Message Follows----
From: POTATO! <theforce@invasion.com>
To: scirocco-l@scirocco.org
Subject: non-roc (audi A4)
Date: Wed, 18 Aug 1999 01:59:58 -0400 (EDT)




the 1.8t uses a distributorless ignition, does anyone know how it
works?...does it use plugs at all?...individual coils?

jsut curious....looking under the hood of my friends' A4 today and he
didnt know how the ignition system worked

dave


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