Catalytic Convertors

[greeban]

I have a 95 4.0L celebration - can anyone help with the type of exhaust my car has! From what I can see, looks like one cat in the down pipe and a double cat where the exhaust becomes two pipes, or is this an elaborate silencer?

I have heard that the middle cat can be replaced with straight through pipes and still pass emissions. Sounds too good to be true although these cars are designed for the rigorous Californian emissions.

Does anyone else have experience of this?

[nigel1]

Repaced the two center boxes on my 93 4 Litre with straight pipes, no problems with passing emission test. They are not really catalytic convertors, but for some reason, thats how the parts book describes them, well, more accuratley as:
Intermediate Exhaust Silencer and Catalyst

[ptjs1]

Graeme,

Your 95 Celebration obviously has the AJ16 engine. You can replace the centre boxes with straight through pipes and it should pass emissions OK. These centre boxes are not catalytic convertors and therefore not really doing anything for emissions. You can buy suitable pipes in stainless from "AJ6 engineering" and they will release extra low and mid-range torque (as well as sounding nice, but not too loud!). The AJ16 back exhaust boxes are different from earlier ones, but these straight-through centre pipes should mate OK to the back boxes. Contact "AJ6 engineering" to be sure. You could also buy their stainless back boxes as well and then you'll know that the centre pipes will fit. Not sure what price the centre pipes are, but their back boxes are about £200 per pair which compares well with the standard Jaguar ones at £85 + vat each.

Hope that helps.

Paul

[greeban]

Thanks Paul - this is really useful. I like the sound of releasing some low end torque and perhaps giving more of a burble to the exhaust note. The car is a true gentleman at the moment but I am not quite ready for the pipe and slippers!

[ng4xjs]

On a slightly different tact. The catalytic converter on my Jap Spec AJ16 is leaking quite badly (noisy). I'm a bit desperate in truth, as I think the correct replacement carries a price tag of some £1500, where as an aftermarket UK/EU spec is about £200. As far as I am aware the only physical difference between the two is that mine (Jap) has a heat shield and two over temperature sensors on the down pipes. Is it possible to not use the heat sensors and thus use a UK Spec unit or does this completely upset the ECU?

I may just remove the heat shield and see if t he leak is repairable but sods law Etc. is probably not in my favour. Any thoughts/observations greatly appreciated.

Nick

[ptjs1]

Nick,

You may remember my writing on the common repair of the catalyst downpipe many years ago. The UK cars do have a heatshield like yours.

The common failure is the split of the weld where the two pipes merge into one. The means to crimp the two pipes and put a welded join pipe on them was a fairly crude piece of engineering by Jaguar IMO.

I found that if you carefully cut open the heatshield about 5 inches from the end, you can expose the weld split. If you remove the pipe, a good engineer would be able to reweld it and probably charge you £30.

I'll dig out the photos and post them here for you.

Cheers

Paul

[ptjs1]

Nick,

Found some of my pics on this thread:

viewtopic.php?f=50&t=11353

Paul

[ng4xjs]

Paul

Many thanks for this, Gives me heart. Next week is the earliest I can have a look. I'll let you know how I get on obviously. It has to be said that some XJS parts are becoming increasingly difficult to source. I'm also thinking that there are generic O2 sensors that can be substituted rather than the £500+ for the JLR item, as well as finding a couple of temp sensors if needed. Hopefully a resolve will be found, fingers crossed, but again, your help (as always) greatly appreciated.
Nick

[ptjs1]

Hi Nick,

When I first changed an O2 sensor many years ago, I discovered Gendan. I rang them and asked them to open the box of their direct-fit sensor for my car and they confirmed that it was an NTK sensor. This was identical to the original Jaguar item on my car. So I bought it. I've since bought other items from them including generic sensors that I fitted to my XJ8. Their prices have always been very good.

Give them a ring and ask them to confirm if this part that they are selling is an NTK item. This is the front sensor that is fitted on a UK car, but a quick check on the JCP site should confirm if it's ok for your car.

https://www.gendan.co.uk/product_LB1034.html

Cheers

Paul

[ng4xjs]

Hi Paul

Thanks for the information. I'll call them in the morning. Who knows they may also be able to recommend an over temp sensor.

Best wishes
Nick

[greeban]

I managed to break the welded joint when replacing cracked manifolds - put too much stress on the downpipe
Took a chance with a replacement I found on eBay that had been welded up and has been fine for the last 6 years or so! They had removed the heat shields so I put some exhaust wrap around the cats when refitting and have had no problems.

[ng4xjs]

Thanks for the confidence greenban - greatly appreciated.
Nick