I can understand people's potential scepticism just reading the title of this thread. Could there really be a cheap and simple modification that improves both performance and fuel economy? If it was that simple why didn't Jaguar do it?
Well the reasons are quite complex, but I will try to explain them.

When I worked at Jaguar between 1988 and 1995 it was std policy to map the ignition timing 3 degrees retarded from borderline knock on a mid-limit compression ratio engine, at all speeds and load where the engine was knock limited. The ignition timing to achieve borderline knock was determined by running the engine steady state on a dynamometer at each speed and load until the combustion chamber temperatures were fully stabilised. This is not a condition that tends to happen in normal driving in the UK where it is difficult to operate the engine at wide open throttle for more than a few seconds at a time, during which time the combustion chamber temperatures due not reach their high stabilised values.

Consequently the lower temperatures that occur during normal driving mean that the mapped ignition timing is significantly retarded from the level at which knock would occur.

A couple of years ago I designed a revised crank sensor bracket to take advantage of this situation. It was initially designed for the AJ16 engine and moved the position of the crank sensor with respect to the engine. As a result the signal to the engine ECU which should indicate when each piston is at TDC is generated 5degrees early.

Consequently each ignition event generated by the ECU occurs 5degrees earlier than the mapped value. It's a bit like advancing a distributor in the days when they contained contact breaker (unlike the one on an AJ6 engine). The extra ignition advance increases the performance at all speeds and load where the engine was deemed to be knock limited when tested on the dynamometer. I initially implemented my bracket on the AJ16 engine as the engine management system on this engine also has a knock sensing system, which I helped to develop.

This meant that in extreme circumstances should the extra 5 degrees cause any knock, then the system would simply retard the ignition timing out of knock. This bracket proved very successful and I have now sold over 150 of them. If you want to read all the feedback from those people who have fitted this bracket then go to the similarly titled thread on the X300/XJR forum of this website.

About a year ago I was asked to produce a couple of brackets for some AJ6 engines which were fitted to race cars running on super unleaded fuel. At the customer's request, the bracket was designed with an extra 7 degrees of ignition advance. The two engines fitted with these brackets have gone on to complete 3 season's racing and the cars they powered were quite successful in their class in terms of performance. This was quite a severe test of an AJ6 engine to run at this level of ignition advance.

I was recently asked by another Jaguar owner to design a bracket for AJ6 engines. Having produced a batch of these brackets which provides an extra 5 degrees of advance I thought I would offer these to other owners as well.

It takes under an hour to replace the std bracket with one of my brackets using nothing more than std tools. In fact, if like me you have had a lot of pratice, you can do it in 15mins on an AJ16SC engine which is the most complicated installation due to the neeed to remove the SC drive belt tensioner.

I currently only have a couple of AJ6 brackets left, but I can always make some more, if there are sufficient numbers of confirmed orders.

If you would like any more information about these revised crank sensor brackets for either AJ6 or AJ16 engines then feel free to email me directly andystodart@metronet.co.uk

 

I have only just read your thread. wow!! As a matter of interest & as a result of your engineering competence, ( my father was a supremo with the spitfire engines coming of the production line) are you able to confirm that the XJ8 from 96 to 2000 has the "Nikasil cylinder liners??

I am interrested in purchasing one but with all the "adverse" comments re the above & the high transmission failure, I am somewhat reluctant....

You view would be appreciated.

Michael Prichard

 

Your question is a bit off topic, but here is the answer.

The early XJ8 engines had Nikasil bores, but these were superseded by steel linered blocks at 10:43 am on 18th August 2000. The first of these engines had the number 0008181043, which corresponds to the time and date that it was built. All subsequent engines had steel liners and all ealeier engines had Nikasil coated bores.

 

how do we go about purchasing one?

 

Todays idotic question (maybe) is:

Woudl anyone know if the AJ6 be persuaded to run on kerosene?

And if it can, what would be the likely consequence? (If it will run reasonably well but would reduce the service life of the engine, I still wouldn't rule it out, as with a mean saving of around £1.10 per litre (if I elect to pay tax) and the cheapness of AJ6 replacements (they always seem to outlast the chassis) it might be a viable option for me.