I have reproduced a PDF document attributed to Gene Thompson about the Rover 4CU Electronic Control Unit here (410kb)

A few of words of caution regarding its origin which seems to lean towards cars intended for the US market.

I have not checked it for authenticity or accuracy but it has clearly been prepared by a knowledgable engineer.

Although it refers to Rover SD1 it also includes information regarding Lambda control and other features which would not apply to Rover SD1's sold into the British market.

In other respects It seems to be a relevant and well prepared document and could be used as a source of valuable information for anyone familiar with the electronic features involved.

The Adjustable 4CU Electronic Control Unit for Rover SD1 Efi Systems

As might be deduced from studying the previously referenced document, during post production years of the Rover Efi SD1, various freelance engineers worked out how the otherwise mysterious Efi 4CU ECU worked and how it might be variously adjusted to alter the basic characteristics of the system. The adjustments, mainly to internal resistors, were essentially two-fold,

1, To increase launch or acceleration power and

2. To improve cruising economy.

The next step was to design extension unit(s) to make both these characteristics adjustable so owners might set up their ECU to a personal preference.

Because there was substantial income to be made from these after-market modifications, even to the point of charging more money for an exchange unit than the cost of a straight replacement, the modification process became a black art intended to protect that income stream. In itself not a problem at the time, but nowadays 20 years later, if an owner comes across an installed adjustable 4CU ECU then getting hold of the operating instructions became near impossible, not least because the worthy originators still keep their secrets of the black art, methinks!

Not any more though, the secret is out, and here is the original instruction set for one particular version of the Adjustable SD1 4CU Electronic Control Unit in PDF format. ENJOY - here: (163kb)

Errors and omissions gratefully received, and photograghs of the adjustable versions, likewise.

More SD1 4CU ECU circuits in PDF format here: (95kb)

Rover SD1 Efi Archive - The Lucas4CU - ECU

Click Here to Read or Download the PDF Article or Click for full list

Lucas 4CU ECU

The Diagnostic Challenge Continues

This above article is one of fifteen or so presentations on the key components making up the Electronic Fuel Injection System fitted to Rover SD1 Vitesse and Vdp Efi.

Pulling all these components together is the Efi Operations, Test and Instruction Manual enabling Home Enthusiasts to better understand its Purpose, Function and Maintenance.


Click here: for more information

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