How does a DIS work ?

[WEG1192 at aol.com]

In a message dated 05/13/2001 2:18:51 PM Eastern Daylight Time, 
Webmaster at lotus-carlton.fsnet.co.uk writes:

<< If anyone knows how the DIS works, rather than just guessing like me, could
 you please put me out of my mysery. >>
 Malcolb,

you are close. this is a simplified description. the REF line goes from DIS 
to ECU and tells the ECU the RPM of the engine. the ESt line goes from ECU 
back to DIS and tells the DIS when to fire the plugs, so this is how the 
timing is altered from the default 10 degrees. the bypass line goes from ECU 
to DIS and tells the DIS when to ignore the ESt line and use its own default 
timing. When the bypass line is high, the DIS uses the ESt signal. WHen 
bypass is low, the DIS uses the default internally generated signal. the 
fourth line is just a common ground line between DIS and ECU. A word of 
caution. the DIS has its own built RPM based advance curve. When in bypass 
mode (bypass line low or timing connector dsiconnected), the DIS will advance 
the timing by a fixed 11 degrees at 2000 RPM. this can confuse you if you 
aren't expecting it. been there done that. All this applies to a distributor 
system but I'm sure it has a similar function with DIS as well. Please 
correct me if I'm wrong list. JW
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