DIY_EFI Digest V2 #344

[talltom at espace.dcl.com]

The ECU on '81-'91 HE V12s is a bosch Digital-P. From the small piece
of info I have gleaned on the subject, it is a digital version of the
D-Jet. From all accounts it is pretty basic, and I have heard
unconfirmed rumours that it doesn't even have a micro on board, just
a ROM chip and a bunch of A/Ds and D/As and assorted analog crap.
 
The V12 injector wiring loom divides the 12 injectors into 4 groups
of 3 (wired in parallel). However inside the ECU, these are connected
together into 2 groups (like D-Jets). I believe this ends up batch
firing each cylinder bank.
 
There is also separate wiring for the peak current and the hold
currents (which go through a resistor). Bizzare to say the least.
 
When jag introduced the 6L version of the engine in '92 ?, it
reportedly got 5MPG better enconomy (13-26MPG vs 13-21MPG - imperial
 
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Well just to point out the lack of effort on jag's part, my 72
mbz uses a d-jet with four injector circuits, and yes it's crude
by today's standards, but it works well if you don't mind buying
fuel. Point is some D-jets had four injector circuits 9 years 
before jag did. As far as efficiency goes, to me it's amazing that
it took them until 92 to do better. My 8.5-1 compression 4.5 litre
eng outruns a customers xjs v12 with a 5.3 litre 11.5-1 compression
coupe.(mine's a 4dr sedan. with a stretched rear seat to boot)