I hesitate to start yet another chicken-and-egg thread about extractors which may lead nowhere, but I have found a guy locally who is happy to look at my XJR with a view to making a set of 6-2-1 extractors, and I would use Andy’s pipe dimensions. I can get flanges cut by Autobend in Christchurch, NZ.
The guy I spoke to has built a very impressive set of equal-length extractors for a V8 stockcar,and has worked for 3 V8 supercar race teams in Oz.

The cost won’t be cheap, my guess is at least NZD$2000 for a single set, but he is open to the idea of making a jig which would lower the cost of further sets.

I will try to visit him in the next 2-3 weeks, and see what he thinks. If it’s a go, I will proceed, perhaps get a few sets made, then sell them on. I don’t want to profit from this, and I have no idea of packing/shipping costs from NZ to other countries. But it is feasible.

I’ll post back once I know more..

 

Good luck with your initiative. Remember that the downpipe of an XJR6 is different to the naturally aspirated cars. In fact the XJR6 had different downpipe between manual and auto. There were also two different types of joints between downpipe and under-floor system using either an "olive joint" or "slip fit" joint. If you look on the Jaguar classic parts website you will see that there is a bewildering list of different part number for 6 cylinder X300 exhausts system parts. If you want to maximise the demand for your product offering you will need to consider the issue of part complexity. If you just tried to replace the front and rear manifolds, these could be made "universal", if you added the bosses for air injection and EGR, then blanked them off. Alternatively, just make what YOU want, and if anyone else wants them, then its a bonus. I've always designed my parts for myself, and if anyone else has wanted them, then its a bonus.

 

Thanks Andy
Why are the downpipes different? To my untutored eye, the exhaust side looks the same on NA and SC engines - is it a diameter issue?
I would just get pipes made to just beyond the Ox sensor bosses then let anyone who wants a set sort out the rest with his/her local exhaust fitter. As you say, “here it is..”
I will try to emulate the “TT’ long secondary pipes that AJ6 Engineering sell, which I believe are good for midrange torque
.. and perhaps a royalty for each set to the man who determined the pipe dimensions!

 

AL NZ, like you I am puzzled by the downpipe issue so I have started a separate thread entitled Downpipe for supercharger engines.

As for the log-type manifolds previously sold by AJ6 Engineering, a member in Norway recently fabricated two sets on his own and here is the thread entitled XJR6.-95 exhaust manifolds. I think he has one set extra for sale, and maybe you may gain some inspiration contacting him for details.

 

https://www.jaguarforums.com/forum/a...7092011089.jpg

Qvhk, here is a pic of extractors on an XJR, sort of thing I’m after - Doc, who used to own this car in Oz, posted these a few years ago. I think he moved on to an aluminum 2000s XJR

 

I think Doc had these exhaust manifold made to my design, though he chose to join the front and rear flanges. I wouldn't recommend doing this, as it increases the stress between the two flanges as they heat up and expand at a different rate to the cylinder head.


I think that the downpipes for the XJR were a larger diameter at the joint to the under-floor to reduce the back pressure at the higher mass flow rates compared with the NA engines. Also the auto gear box on the XJR (GM Hydramatic 4L80E) is a different shape to the auto on the naturally aspirated cars (ZF 4HP24E or 4HP22)

 

Andy, I’ll use two separate flanges.
Do you know any source for the Oxygen sensor mounts? I know you give dimensions in your pipe plans, it I wondered if they can be bought off the shelf? Thanks.

 

I get the oxygen sensor bosses made at my local machine shop. I don't know of a source "off the shelf". Be careful if you think you find a source, because these NTK Titania sensors are a smaller thread size than the Zirconia sensor made by Bosch, etc.


I can get some made for you in the UK and posted to you. Contact me directly , if this is of interest to you.

 

A round O.D. boss or a hex nut to weld on as a boss can be found at the auto parts store or the hardware store 12 mm , can't remember the pitch but you can sample the hardware store stock . Stainless steel would be the better option .

A $ 5.00 Motorcraft 12mm spark plug is a source of a crush washer . Got a part # in one of my post .

A BOSCH 13789 is a cheaper connector ready equivalent to Jaguar # LHE1682BA

There is something about the depth of the installed sensor into the gas stream that I don't have full information on . But I read that you can reduce the depth by putting additional spacers on them to bias the signal with the 420 and 430 CEL codes . The gas velocity and temp will be reduced as you get closer to the pipe wall but the O2 concentration should be the same . Might have something to do with the temp and the sensors response to it biasing it . I could be wrong .

 

AL NZ, thanks for the clarification. I tried that route and ended up with lots of issues installing the equal length extractors and hooking up with the downpipe which required extensive modifications, but of course my problem arose primarily because the manifolds were made in the UK, only then shipped to Hong Kong for final assembly. I have documented the problems I experienced in this thread Exhaust Manifolds and Downpipes Modifications. The learning was (a) have the manifolds (extractors) custom-made AND installed by the same exhaust workshop with your car present; (b) a log type similar to the set-up of the factory original manifolds would have better universal compatibility to all X300 models, and hence lower costs, greater demand and more certain return to investment. The performance type like Doc's or the one you are contemplating is a nice-to-have option, but would be far more expensive and a challenge to install as each car has some differences in terms of fitment details. I for one am now scratching my head to find a new XJR downpipe (rare to find and expensive to ship), with a view to professional modification at the workshop for seamless installation, as the earlier attempt is proven to be not very well done giving rise to frequent leaks and need for periodic fixes.