In part three, Jim Randle speaks candidly about what was possibly the XJ40’s most controversial aspect – its advanced electronics system.
It’s been suggested in the past that Jaguar were over-ambitious in attempting to introduce electronic controls into XJ40 when this technology was still in its infancy, but Jim Randle points out a key precedent. Preparing XJ-S prototypes in the early 1970’s, he produced a carburettor and an electronically controlled version for comparison purposes, making the following discovery.
“The electronically controlled car was so much more reliable than the carburettor car that we never looked back. Of course we’d got that setting our thinking when we did XJ40, so we had a good reason at that stage to believe that if we went that way we were going to get something much more reliable.”
Reliability was traditionally Jaguar’s bête noire and with the necessity of adding systems and convenience features an entirely fresh approach was required. The electrical system proved to be one of the most ambitious and fiendishly complex aspects of the car’s development but was intended to catapult Jaguar out of the dark ages.
“We did try quite hard with [XJ40]. It was the most tested car we had ever produced and we did some very dangerous stuff with it. We tried to do a fully computer controlled electrical system, the sort of thing people do nowadays and it got quite difficult. We talked to the MoD, because they were doing the same sort of thing with their tanks and they were having difficulty as well. Because we’d got so many parameters we were trying to both operate and to use as a diagnostic system, the best way to do it was to introduce earth line switching. The advantage of that was you were using very small wires and therefore assembling the thing into the front bulkhead (which is always the most difficult part on a car) was much easier. I mean everybody has the same sort of difficulties, had we waited another ten years we’d have done it differently.”
Nonetheless, not even the Jim Randle’s of this world can quite foresee what happens when customer’s cars start rolling down production lines. “What we didn’t recognise was if you do a bit of macho building and some guy bends it over his knee to get it into the bulkhead area you break the wires. And that was a problem we had. You have to be a lot more careful when you do that sort of thing.”
I put it to Randle that for all Jaguar’s efforts, early XJ40’s gained a reputation for fragility in some quarters and with the frustrated sigh of a someone who’s no doubt heard it all before, he quietly fires up. “I’d like to see the data on that. I’ve heard this story, [but] the thing is it wasn’t being thrown back at me. Every week we would have meetings, usually on the line or certainly in manufacturing areas where we would be going through whatever problems there were. But it was very rare it was an engineering problem – you’d often find an engineering solution to a problem maybe.”
When I ask if an analogue electrical system might have been a more pragmatic solution in retrospect, Randle won’t be drawn. “If we’d done both I’d give you an answer – it’s difficult to say isn’t it? Unless we’d developed a car alongside it that was less complex but using standard technology – would it have been better or worse? I don’t know, it seemed like a good idea at the time and maybe we could have done better with a conventional system, but we couldn’t have done some of the things we did. We put the self diagnostics in and so forth and everybody has sort of followed along now. The switches and connectors went from typical lives of about 1,500 cycles on a switch before it failed, we got that up to one and a half million. Those were the sorts of improvements we made and in fact, in the end, properly fitted we didn’t know how long an XJ40 system would live. It might live forever for all we know! It was a big step we were taking.”
No car, especially in the early stages of series production is fault free, and XJ40 wasn’t just new from the ground up. It was breaking new ground. In his recent book, Saving Jaguar, Sir John Egan ascribed most of XJ40’s early issues to manufacturing deficiencies and the quality of bought-in components. But even the best engineering minds can make the occasional lapse.
“We had one very silly one: The way in which the spring and damper unit is connected to the lower wishbone on Jaguars has been with a pan underneath the wishbone, bolted through – since forever – and we did the same thing on XJ40. First winter came along and we got spring pans being fired onto the road surface. Then we found out what happened was that a guy in purchasing, very sensibly had come along to engineering and said look, if we make these bolts, – (which were high tensile strength bolts) – if we have them in boron steel, we can save a few pennies. The guy in engineering looked at the specs and sure enough, it looked okay.”
“Now what he didn’t see in the specs is that if you have a boron steel bolt under relatively high tensile load in the presence of road salt that they fail at stresses way down from the conventional. Now in truth, that was probably my fault. Because I didn’t give an edict to my guys that nothing that had been tested should be changed. I mean that was an embarrassing one but it was the early part of the programme; we’d launched it at the motor show and this was the first winter, so there were only a few cars out there we had to put right. But that was definitely down to us.”
A documented early XJ40 issue was premature corrosion. Was this an oversight in conception? “No, I’ll tell you what happened there. We wanted to have double-sided zinc coated steel panels to give full protection. Couldn’t do that because the zinc was being sheared off in the press and contaminating the dies. We could do it if it were single-sided and we kept the zinc on the punch side, so all the doors and mostly all of the panels were single sided zinc and on the whole that’s pretty good. There was one panel on the boot which couldn’t be done… well, not for a while anyway and ultimately that was done. But those did rust – there was a good reason for it – we weren’t able to produce the specification we had put on the part.”
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