Jaguar V12 - prospective new user

[JagGuy]

I have a 1992 Jaguar XJR-S and while it is running OK now, I am aware that the Zytec ECU it has is no longer available and the programming equipment long gone. So planning for the future, I'm going to start the Megasquirt journey. I've read a few threads here from Jag V12 converters but I don't see anyone starting from a Zytek system. It is different from the Lucas/Marelli systems in being an integrated fuel and ignition ECU, it doesn't have a crank position sensor - deriving ignition and crank timing from sensors in a modified Lucas distributor. Can I reuse any of this, or am I better off throwing it all away and following the path of a more normal Lucas type V12 conversion? Any pointers gratefully received.

[DaveEFI]

IMHO, you don't want the timing derived from a distributor - all the slop in the chains and gears driving it. On most vehicles it's not that difficult to fit a toothed wheel to the crank pulley. Someone like Trigger Wheels may even do a kit, or be able to advise. You can retain the dizzy for a cam position sensor if needed.

Generally, MS gives a big and easy improvement over the old analogue Lucas system used on the earlier V12. Not sure if the same applies to the later Zytech.

[JagGuy]

Unlike the Lucas and Marelli set ups the Zytek system was an integrated unit, controlling both fuel and ignition. It was good enough to power Tom Walkinshaw's Le Mans winning Jaguar V12 cars in the late 1980s and early 1990s, also the XJ220. When I bought my XJR-S it was 13 years old, the ECU had failed, and was replaced by the dealer when I got it. That was 15 years ago, so I don't know if I am living on borrowed time - it may last for a good few more years, but better to plan ahead. Even if it does go the distance I have no way of changing anything, the most basic of timing parameters are all controlled by the ECU. There is no adjustment ability at all without the fabled Toshiba laptop, the Zytek software, and a magic interface unit - all now unobtainium.

[Marek]

You are in a better position than most Jag v12 owners. Your starting point for conversion is a sequential v12 harness whereas others only have a batch fired fueling harness and nothing but a distributor for ignition.

Only the blue interface box is "unobtainable". The software happily runs in a DOS box on any primitive Windows PC. The software is available elsewhere. There are threads on jag-lovers.com regarding that. Depending on where you are, someone may lend you
(or let you use) the blue interface box if you are local.

kind regards
Marek