So many posts on this forum talk about throwing a bunch of money at high flow cats.

I am truly amazed that nobody suggested electronic bypass of the O2 sensor, which is less expensive and with welded pipes where the cats were removed, and straight 401 stainless pipes were installed.

The sensor is left in and the bypass prevent any CEL's

Any dialogue is appreciated, excluding those that want to preach about the legality of the sensor bypass

 

One good reason; sniffer tests will fail if the cats are removed.

 

So why do I want to breath the emissions you dump into the air again?

Notice that this has nothing to do with your preemptive strike against
"legalities", but rather social responsibility.

 

The downstream O2 sensors are also used by the ECU to manage fuel trim "skip" so putting a simulator or even the old-school extensions or "minicats" on them screws up the AFR's especially on transition from part throttle to full throttle.

Many threads here on the forum on the topic, perhaps a search using the term "minicat" might reveal a few.

Have a look here https://www.jaguarforums.com/forum/x...-light-152177/

And here was the original thread which includes the dyno sheet with the AFR measurements with and without the rear O2 sensors tricked https://www.jaguarforums.com/forum/x...0/#post1217278

The downstream sensors are for more than just checking cat efficiency.

The technically correct ways to prevent the CEL for cat efficiency are:

1. Change the emissions setting in the ECU to Euro 2
2. Switch off the P0420 & P0430 codes in the ECU

Now let me tell you, cars running unleaded fuel and no cats STINK I mean they smell awful, especially if you drive them hard. The smell alone is enough of a reason for me to say no to catless cars, without even starting on the legal, social, environmental, etc...

And i presume the CA in your location is California, isn't that the strictest place in the world for emissions testing?

 

This type of mod discussion seems to come up on various site I am involved with and the arguments seem to go both ways but usually over ruled by state and federal laws. For the every day joe this is most likely a non issue as the intent of removing the cat is to try to enhance performance. That being the case the argument for removing the cats is aimed at the track driver who is looking for a little more performance but I assume along with its removal there needs to be some remapping to get the desired results. I haven't looked under a modern racer like a trans-am car so I don't know what they have done nor if they have high flow cats or if they remove them. Then last for a street car both the practicality and cost for doing this along with the legal hurtle in some stated where you get a smog test. It also would be interesting to see the results of either removal or high flow and how does it affect the everyday driver. If my 0-60 goes from 4.6 sec to 3.8 it would be a fun drive but then again it would exceed my tire budget.

 

And there you have it.

 

Seems there's a whole lot of easier and more efficient ways to get more power out of an already powerful engine than stripping out critical parts, and then bandaiding the side effects. Seems tweaking the supercharger would be easier, cheaper, and have fewer negative effects than removing any critical part of the exhaust system.

 

Be prepared for heartache if you start screwing around the Jag V8 to that level. They did an excellent job getting what they could out of it while maintaining longevity. Seems like a waste of money to me, but I am modest working class guy.

 

The smell, unburnt fuel pouring out the exhaust, just not what a recent year Jaguar should be doing.

Get a vintage E-type if you want the smell of emissions.