DIY_EFI Digest V5 #23

[ECMnut at aol.com]

>  G'day all,
>  I'm fairly new to this news group, I've been lurking for about a week, and
>  I've got a question about ECUs in general. I'm currently building an EFI
>  computer for my 83 Pusar Exa turbo, and have the fuel running great,
>  currently I'm working on spark.

Greetings Andy,
it's great to have you aboard..   
There are two ways that the GM turbo 
car ECMs handle timing.

1. Without using a MAP sensor, they rely on mass air flow & RPM 
numbers to determine engine load (LV8).  in the maf systems, they 
assume "high air flow" + "low rpm" must
mean that the engine is heavily loaded.  
The chip has a timing table that uses LV8 & RPM lookups.

2. With the MAP sensor system, they use a MAP vs RPM table
for the lookups.  
Each system has its strong / weak points. 
HTH
Mike V
.