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 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 120 of them.

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 went on to complete a 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.

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

 

Hi Andy, this sounds very interesting.
Can you offer any further info, any examples of prior sales and to any members that can help to backup your claims?

Sorry, I don't mean to offend but as you've been involved with Jaguar you'll understand about the scepticism around power upgrades / claims etc.

Please tell us more.....

 

Sounds like a very common sense approach. The logic is very appealing in its simplicity.

 

I have one of Andy's brackets. Works exactly as advertised ! Well worth the money...which isn't all that much. :-)


Cheers
DD

 

If it's good enough for Doug ...

So, how about one for the AJ27?

 

Please tell us what you have seen on your car!

 

Iv been trying to figure out how to get one.
would love the info.

 

You can contact me directly at the email address at the start of this thread.

In reply to an earlier question, it is not as convenient to apply this approach to the Jaguar V8 engines, such as AJ27, becasue the crank sensor is mounted in the back face of the sump. It would be necessary to machine a new hole into which the sensor mounts. It is possible but only really with the sump removed from the engine, so would be best undertaken as part of a major engine rebuild project. At this point it ceases to be a DIY proposition for most people.

 

Improved performance and better fuel economy is what everybody is looking for but "gizmos" come and go. Now, I ain't saying that this "bracket" is a gizmo but is there any chance of some facts and figures from the folk that have one fitted.
For example, what MPG did you get before and what MPG do you get now?
Also, when you push it, what are the comparative 0 - 60 MPH and 60 - 100 MPH times?
Plus, how many miles per week/month do you need to be doing before the frame becomes viable?

 

Figured as much after looking at the engine assembly manual.

Still, the general approach is entirely valid.

I would be tempted to do a little filing to elongate the hole to the proper offset.

It could also be done electronically.

 

You are probably aware that Doug is one of the people around here whose opinion is worthy of careful attention.

The bracket is much like restoring the lost ability to tweak ignition advance on a conventional distributor to a more optimal value. The results are well known ... or at least, were well known in the past.

Payback is not always measured in dollars ... sometimes it is SPM(smiles per mile).

 

I also have the Andybracket fitted to my XJR. Easily one of the simplest mods I've ever made to a car and one where I can really feel the difference in power.

 

I guess I am one of the latest buyer of one of these brackets. Got it mounted 1-2 weeks ago and I think I can feel the difference, even though it's very hard to put down power on the roads this time of year. Gave it a spin yesterday, trying to test the bracket. 255 winter tires, 5 celcius, dry roads and 1 passenger. The car steps sideways sereval times during one single acc, even with antispin engaged. Up to 80 kmh does the rear wheels spin when acc hard. Not sure that was the case before.

I believe this approach is close to what go-faster chips do on normally aspirated cars? It doesn't give you the 100 hp a K&N filter does on NA cars, but they tend to gain about as much as the difference between a full vs almost empty gas tank, or one fully grown male passenger. That was enough to make it worth while for me on the BMWs I've owned, before getting a jag.

 

I have read almost all of Andy's posts on the XJRI6 site and respect his knowledge and opinions. Many members on that site have installed his timing bracket and none said it did nothing or made their car perform worse. One member, using a GPS type speed/time unit, actually found a faster 0-60 time averaged over several runs compared to his stock bracket. All felt a seat-of-the-pants improvement, most notably when flooring it - a more instant response. On the other side, 'Plums' is correct if you are willing and able to file the bracket, you may be able to duplicate what Andy has already achieved. The next question would probably be, have I installed Andy's bracket - no; I have two XJRI6's, one I do not touch the other I am modifying for hillclimbs, and want to see what performance gains are there using the stock ignition system.

 

That was really addressed at using the technique on the V8 where there is no eqivalent bracket available or even possible. Otherwise a prefabbed unit is more accurate and proven.

 

What happened to xjr6.co.uk?

Can't seem to find it anymore. Renamed?

 

And you dont want to file on the bracket. Its cast and breaks easily. But thenyoude have to buy the advanced bracket then now wouldnt you

 

People are welcome to attempt to modify a standard bracket rather than use one of mine, butIi suggest that you consider than the air gap between the sensor tip and the trigger wheel must be maintained at 1.0mm with a tolerance of 0.5mm. To maximise signal quality the sensor should be radial to the trgger wheel and in the middle of the width of the teeth in the axis of the cranksahft. All in all, you will find it much easier to use something that has been design specially for the job.

 

I sent you an email last night about cost,shipping, etc

 

www.xjr6.com has had a few occasions over the last couple of years when it went off. This appears to be the longest spell. I do hope it comes back as the information contained within it's pages was priceless. I keep checking regularly.