You to have the Cats with all the little Cells inside to do their thing to the Engines Exhaust gases as they pass hrough the Catalytic Converter....Remember, you have (1) Oxygen Sensor on the inlet that reads the Gases coming in from the Engine and another that reads the Gases after they have gone through the Cells of the Cat Converter, where there is another Oxygen Sensor that reads what the change was...….This is what directs the ECM to add or subtract fuel to the mixture that is being fed to the Engine so that it will run at it's optimum efficiency...…

If you took the Guts out of your Cat the computer would not know what to do and the Engine would not run.....or if it did run, it would not run correctly, as simple as that...It's basically the same thing as the Carburetor jet size and the air screws on the side that regulate the mixture...

Billy Clyde in Houston

 

 

Bluegrass,

What are you trying or wanting to do?
More Power?
More Noise?

Billy Clyde

 

 

You could look into high flow cats. They will yield a slight increase noise and power with no CEL. But really, unless you open up the exhaust behind the cats, you wont notice much.

I had the high flow cats for a bit, then ended up going completely catless (replaced cats with 2.5" downpipes). I'd say the response was better and top end felt a bit stronger. The noise is nice if that's what your looking for; I get compliments on it all the time. I have a friend also with a 4.2 XJR that kept, but gutted his cats and he will tell you the same thing. We both used J-spacers on the 2nd O2 sensor to simulate the difference in the exhaust measurement. Gutted cats or no cats at all would work even without the J-spacers though considering these cars use the upstream (before cat) sensors to measure AFR and adjust fuel trims. The reading on the downstream sensors would trigger either a catalytic inefficiency or O2 Sensor malfunction code with your CEL. They would not influence how the car runs though.

I can assure you this as I also have cutouts installed right after my catless downpipes, which when opened up, completely bypass the downstream O2 sensor (CEL lights up for downstream O2s not reading) and makes an insane amount of sound, and some extra power on the high end of the rev range. I did dyno to confirm this.

Search a couple vids on youtbe XJR, S-Type R or XKR exhaust and you will see and get to hear a couple different options on how the exhaust would sound. Its better to have an idea of what exactly you want first before chopping up your exhaust.

 

del

 

 

Last year I had both my CATS replaced. Unknowingly I went from 400 cells to 200 cells. The difference was quite marked. Definitely louder, much more burble, just starting to get used to it and there is also a feeling of more power. Touch wood etc no fault codes etc shown up so far.. So it may be something to consider.

 

 

Here you go. https://www.xk8-parts.com/2016/10/ja...-gallery-page/

If you do speak to Dave tell him the Malvern XKR Guy Frank recommended him.

He has always been quite helpful.

This is some of what happened to me last year..........My new Cats fitted

As I previously stated though it was not my intention go to a louder exhaust note etc. I explain the dilemma I had here :- Cat Change

I kept the Cats and must admit just starting to enjoy the extra 'growl. Even if the extra punch is in my imagination it certainly sounds more high performance now.

(If you have any problems with the links let me know. The first time around they did not take you where I intended. They took me to the first page rather than the page required.)
Just changed the link format, again, should be working now.

 

re. what jazzyjags said about deleting his cats and it still running o.k. it would seem that the ECM might have compensated for the lack of cats?
I did a custom exhaust on a U.S. car using a X pipe configuration and deleting the cats. I placed the O2 sensors in the exhaust headers and the second ones aft of the X pipes about where the cats would have been. The results were as desired, good performance increase, and sound. Has anyone tried this on an XK8 or XKR?