afternoon people.

I've got the chance to remove both my cats with some straight through pipe on my LPG'd 99 XJ-Sport by a cousin.

I'm wanting to know if, as I have read, my car will still pass its UK MOT emissions test? Has anybody had this done to theirs that can verify that it will?

Also, if the fitter wants to keep them [the cat converters], how much should I ask for them both (entire exhaust looks like it the original one - that's 123k miler/12 year old).

And finally, of the sound, what difference will it make? I dont want it changing to sound like some Jap'd EVO type, but a nice deeper, throatier noise would be nice.

Any relevant comments appreciated..

Steven

 

AJ26 engine has 2 O2 sensors located in the cats, if they're not present the engine warning will register a fault and you'll have a light on the dash. You might pass an MOT, but I doubt is as the engine takes the readings and adjusts the fuel flow to suit.
The only way to do it is to weld bosses into the straight pipe and bolt the O2 sensors in place, similar to the cats? I might work, it might not.
If you search for "nameless performance" they've made some I think for track use, and might have a fix.

 

Ok, thanks for the advice Sean - although, and I don't want to sound obtuse here, but what if I just remove the 02 sensors too? The fuel flow works from the sensors? So by removing them, what..? Also, when I de-Catted my previous car, an Impreza, a laptop was connected to the ecu to simply switch the sensor off - could this be perhaps done here too?

Having said all this, if. by removing the cats it messes about with the fuel flow then I might be giving myself problems unecessarily. Hmmm.

thanks again..

Steven

 

I checked with my MOT tester mate and he said that the car would definitely fail the MOT on emissions. Without the O2 sensors it would run rough, if at all, so you need to consider the previous advice re the O2 sensors. Not worth it in my opinion.

 

OK thanks for the advice. On the MOT failure front, I was needing confirmation that as it runs on LPG, the emissions would still pass the test even without the cats as I have heard/read.

I wasn't aware that these sensors change how the car goes. I just thought it was another light on the dash.. Oh well. Keep the Sport for now, and get the XJR next..

S

 

look for a O2 Simulator. or Cheater O2 sensor.

 

I assume LPG is Liquid Propane. Out of curiosity what company did the conversion?

To answer the O2 Question.... Yes the sensors will need to be installed in the new pipes.
The upstream checks the Air/Fuel and reports back to the ECU. It could care less if a cat is there or not.

The downstream sensor is looking for the difference between it's readings and the ones from the Upstream sensor. Without a convertor there won't be a difference so it will likely trip a CEL and give a code.

 

What I don't know is if a Downstream O2 Sensor fault will case the ECU to default to Open Loop which is a given set of parameters and not a true dynamic Air Fuel mix resulting in lower mileage and performance. (I know for sure an Upstream failure would.)

That said, you might be able to fool the ECU by telling it what it wants to hear with the neat toys Thundercat mentioned above.