Hello all,

In reading more about the FI on my Series III, I've become confused as to exactly who's fuel injection system is on this car. I thought it was a fully Lucas system, but what I've read suggests that the system is at least partly based on Bosch's L-Jetronic. Further, I have read that the ECU is a Jetronic unit. That certainly surprised me, and baffled me. I thought Lucas developed their system on their own, and that Lucas injection had also been around for quite a long time before the XJ6 and XJ-S received it, albeit in a mechanical form rather than electronic. That then makes me wonder if the "Lucas" electronic injection in the Series III is even related to the older mechanical Lucas injection. As always, looking for some insight from those knowledgeable.

 

Not partly based on L-Jetronic. It is L-Jetronic.

Lucas labels appears on many of the parts. I'm not sure what the business arrangement was. And perhaps Lucas did some of the manufacturing under license? I dunno.

Cheers
DD

 

The system is certainly the Bosch-developed L-Jetronic as Doug says, but that doesn't mean all the components are Bosch-produced or sourced with just a Lucas label attached. Lucas certainly had a licence to produce it as it also had for the D-Jetronic system on the V12s. It's very difficult with these things now being well over 40 years old, to know what Lucas made and what it bought in. I doubt Lucas just bought Bosch stuff off-the shelf, as in those years they could develop and produce their own stuff, and actually supplied fuel sustems for aeroengines. Heavens, we actually still had engineers in the UK then, unlike now with just City spivs everywhere !

There's some good stuff on Jaguar EFI systems in here: -
https://www.jagweb.com/aj6eng/

 

It was in that Jag Web AJ6 Engineering article that I first read about Jetronic being part of the Lucas system. That article notes how the Jag engineering bulletin on the system described some of the principles of the system completely incorrectly. It may indicatr that this system was not introduced because it was the next natural evolution, rather shoehorned in by mamagement or needed to meet emissions regulations.

I'm confused on the timing of these things, as Lucas had it's own mechanical fuel injection before the electronic. Was that also a Jetronic system, and did Lucas keep developing it? Also, I think I heard somewhere that the V12 or the XJ-S, not sure which, was designed with injection in mind. If it was the V12, why would Jag produce it in carbed form for a decade before introducing injection? Further, was the XJ-S always run with D-Jetronic, or did they upgrade to L?

Since the system is Jetronic based, does that mean off the shelf Jetronic parts will fit, like injectors? Strange that the Jetronic name would be applied to fundamentally different types of injection, like K vs L.

 

Everything I have seen of the Series III system is that is Bosch parts with a Lucas label on top. The mechanical injection is a completely different thing, developed in the 50's. I'm not sure if it was entirely a Lucas development or not. I'm speculating, but my guess is it was probably something that came out of aircraft technology during the war. It's not related to the Bosch L-Jet in any way, it's much more closely related to the types of systems used on diesel engines.

The V12 was developed with EFI in mind, the EFI system was a joint development by AE-Brico. Close to when the V12 was to be launched, AE ran into technical difficulties and decided not to go any further, so Jaguar had to use carbs. They had developed carbs as a "Plan B" backup in case the EFI wasn't ready.

There are two very broad groups of EFI: MAP and MAF. MAP stands for Manifold Air Pressure. What that does is measures manifold vacuum as a load signal, in conjunction with other engine parameters, such as coolant temperature, RPM, throttle position, air temperature and a look up table of volumetric efficiency of the engine to calculate the mass of air entering the engine. From that, it can fuel accordingly to arrive at a target air-fuel ratio. All production V12's used this style of EFI right to 1997. Bosch D-Jet is a MAP type system, and L Jet (L for "luft - air in German) is a MAF

MAF stands for Mass Air Flow. That uses an air flowmeter to measure reasonably directly the mass of air entering the engine and bases the fueling on that. The XJ6 uses that system, as does the later XJ40 and X300 6 cylinder cars. All modern cars use MAF. The Series III uses a Bosch air flow meter called a "barn door" type meter, which relies on the flow of air to move a flapper against a spring, and the amount of deflection determines the amount of air going past it. The drawback of this system is that the flapper creates resistance to the air flow, and for the XJ6 it was known to cost 12% of top end horsepower.

Jetronic was a generic name for Boschs' EFI systems. Sort of like Hydramatic was the name applied to many models of General Motors transmissions.

Injectors are generally matched to a particular engine. If you found an injector with the same flowrate, impedance, and mechanical size and fuel connection, it would work.

 

I was head of an aerospace company purchased by Lucas Aerospace. They do not spend development money without a monopoly supplier arrangement, with a significant market share player in the business. Jaguar was too small of a auto assembly company to risk development money on.
My view is that it was a Bosch system developed for the German market and they were well on their way to releasing newer systems, when Jaguar/Lucas got involved.
Emission regulations were driving Jaguar in the North American market, they spent very little on development, preferring mature system from GM (or GM vendors i.e. BW) that had been service tested, with a wealth of spares and trained technicians already in the market place... Jaguar/Lucas just adapted these systems to Jaguar current production through license agreements, to purchase and in some cases manufacture the components. Fuel injection, Automatic transmissions, CEI ignition, Air-conditioning, Emission Rule compliance components. They bought the BW transmission rights and tooling, when GM switched to new modern transmissions. From memory, the first Rover V8 engine was a discontinued Buick engine. What was uniquely Jaguar were cylinder heads, intake manifolds, and suspension systems.
The one area where Jaguar spent money was 24 Hour Racing, it gave them feed back for reliability and tweaking for performance improvements, Great Marketing Too!!!

My first XKE automatic transmission overhaul, was done by a one-man-shop, a former Ford mechanic that overhauled BW Thunderbird transmission for the Ford Dealership. Same transmission and parts suppliers. He knew what had to be replaced before he opened it up.. What caused him grief was getting the transmission out of the XKE without removing the engine.
Rgds
David

 

In the 50s-60s a lot of the automatic transmissions were provided by Borg Warner or were BW designs. Ford and AMC used them, as did BMW and Volvo and Jaguar, and who-knows-how-many others. The Model 12 used by Jaguar, for example, was the "FMX" used by Ford in hundreds of thousands of cars. Maybe millions.

Actually, GM may be the only big car company that didn't use BW transmissions...owing to GM having its own Hydramatic division.

The Series III XJ6 must surely be the last, or nearly the last, to use use the old BW designed 3-speed automatics. However, they were not manufactured in-house by Jaguar. They were manufactured by BW in England.

That Rover V8 was Buick's aluminum 215. With some tweaking and continued development Rover/BL got decades of use out of that design

Cheers
DD