De-catting - Further Help Required

[CockneyPlayboy]

As the title says... Have any of you COMPLETELY de-catted your V8s (not talking about better flowing Cats)

I realise of course the legislation and MOT issues but is there any mileage in removing the cats for a smoother flowing straighter system? Of course bearing in mind you would still have the cats to put back on if needed for MOT or sale??

Edited July 27, 2007 by CockneyPlayboy

[mike_sekinger]

Yes and yes.

It is a very personal thing..... environment vs. totally selfish pleasures.

Removing the CATs allows you to maximise turbo response and is something that I do not regret having done.

As the title says... Have any of you COMPLETELY de-catted your V8s (not talking about better flowing Cats)

I realise of course the legislation and MOT issues but is there any mileage in removing the cats for a smoother flowing straighter system? Of course bearing in mind you would still have the cats to put back on if needed for MOT or sale??

[hasuSan]

As the title says... Have any of you COMPLETELY de-catted your V8s (not talking about better flowing Cats)

I realise of course the legislation and MOT issues but is there any mileage in removing the cats for a smoother flowing straighter system? Of course bearing in mind you would still have the cats to put back on if needed for MOT or sale??

If you are an Al Gore deciple and a tree hugger, don't do it. If you want to leave the problem (if there is really a problem) to the next generations, then start hollowing the catz.....enjoy the autobahn.

[Paula&Marcus]

Hi All,

Yes, I'm a true tree-hugger and use high flow metal cats and regularly enjoy the real Autobahn without any speed limits ... mainly the Autobahn Nr.8 strip between Augsburg and Munich on Sunday morning 6 o'clock.

It's great to have the choice to pick the best of both worlds

Cheers

Marcus

If you are an Al Gore deciple and a tree hugger, don't do it. If you want to leave the problem (if there is really a problem) to the next generations, then start hollowing the catz.....enjoy the autobahn.

Edited July 18, 2007 by Paula&Marcus

[Kato]

We spoke to Lotus about this and with the low back pressure in the V8 system and the low psi the turbo's run, it's not really worth removing them for performance gains, as you'll hardly see any. If you do do this, you'll need to sort out the Oxygen Sensors before and after, as if you don't you'll be in limp mode!

[CockneyPlayboy]

We spoke to Lotus about this and with the low back pressure in the V8 system and the low psi the turbo's run, it's not really worth removing them for performance gains, as you'll hardly see any. If you do do this, you'll need to sort out the Oxygen Sensors before and after, as if you don't you'll be in limp mode!

Please...explain more about 'sorting out the Oxygen Sensors'. What has to be done and what is 'Limp Mode' lol

[Paula&Marcus]

Hi,

The V8 has 4 O2-sensors.

Two pre cat sensors, which are important ones for fuelling.

And two post cat sensors, which are only there for checking if the cats are working properly.

If you remove the cats, the two post cat sensors will give data like "cat is not working" and the ECU will throw a fault code and a check engine light.

Cheers

Marcus

Please...explain more about 'sorting out the Oxygen Sensors'. What has to be done and what is 'Limp Mode' lol

[Tentenths]

And limp mode also means restricted boost...

[david hopwood]

U.K. Cars seem to ignore post sensors many owners have removed cats without throwing cel light.Was told once post sensors are only looked at during ignition on however this dosn't make sense as no output activity would be available till engine is running

[Advantage]

I ran mine for two years without cats (from new - once run in) and a straight through stainless exhaust. (Torque Techincs, Wilton) No check engine light/ecu issues in around 25k spirited miles. Mine was a standard UK spec 1998 model, I know some of the USA/ROW might have problems but I'm fairly certain the post cat sensor isn't used on the UK cars of that era, despite it physically being there.

The turbos did seem to spool up faster and it was a completely different car. The sound is a high tech yowl when flat out but wan't intrusive in the cabin when just making progress. The turbos do a good job of damping down the sound.

One small problem occured after a particularly agressive weekend in France as we were in the queue for the ferry back home. The n/s turbo started to get a bit puffy (oil smoke) and required attention once back in the UK. I'd call that an anomaly, though. The car had been driven on the rev limiter practically all weekend chasing and keeping up/overtaking a pack of 18 bikes (R1/Blades/Dukes etc). (I was acting as a mobile leather+helmet storage facility every time we stopped! ) So it's not surprising a small mechanical failure happened.

I put the cats back on when I sold the car and it drove like I'd left the handbrake on.

[CockneyPlayboy]

Hi,

The V8 has 4 O2-sensors.

Two pre cat sensors, which are important ones for fuelling.

And two post cat sensors, which are only there for checking if the cats are working properly.

If you remove the cats, the two post cat sensors will give data like "cat is not working" and the ECU will throw a fault code and a check engine light.

Cheers

Marcus

SO...how do I get round this?? Last time I DeCatted the ol' GTO we had to cap them off........?

[Advantage]

SO...how do I get round this?? Last time I DeCatted the ol' GTO we had to cap them off........?

Make sure the decat pipe(s) you buy has the threaded holes for the sensors and re-fit your current sensors to your new decat pipe. That's it.

[mangel]

worst case you'll have to unplug them and slap in a couple of appropriate resistors which is a fave fix on a lot of decatted car!!

[andyblackman777]

I think you can buy a unit(s) from Jegs which plugs in instead of the post O2 sensors. Its on LEW somewhere

cheers

ps my cel did not come on when i decatted the car but it sounded like a tractor so i put in PNm 100 cell cats

[chstephens]

I think you can buy a unit(s) from Jegs which plugs in instead of the post O2 sensors. Its on LEW somewhere

cheers

ps my cel did not come on when i decatted the car but it sounded like a tractor so i put in PNm 100 cell cats

I have Random Technology race cats with straight pipes and personally it is too loud in the cabin. I will be adding some form of race muffler (perhaps Flowmaster Delta 40) to mellow the sound.

The O2 sensor "trickery" devices are on ebay as well. I installed one on a cat-less 2006 Exige and it works perfect - no CEL.

Craig

[Rgardner01]

I have fully de-catted my cats, straight through center exhaust conversion ( no muffler ) and Johan ECU chip on my USA 98 Esprit with 9,000 miles. No problems. Car runs a little cooler and sounds great!!! . I also have wrapped my exhaust in heat wrap from the cat section back. My car clearly had one cat replaced by the previous owner as when I took them off to hollow them out, one was new. The orignal one only had half the core left in it!! It was a easy fix to rid the car of the rattle. I have no inpsection in my State so....no worries on passing any tests. No check engine codes.

[JNemeth]

Just put straight pipes in from JAE. They make the car sound much more like an exotic, and less like a muffled motorboat. The JAE pipes have the threaded bungs for the O2 sensors. I have a USA car, and I'm not getting a CEL, except under WOT in 3rd gear...which I've always had. So I don't think that's caused by the decatting. My codereader gives no error code, so either my USA car doesn't look to the rear o2 sensors, or it has the car in closed loop mode and not giving an error code. I feel like my car has always run less spectacular than an Esprit should. I think there is some other problem I've yet to track down.

One other question. What exactly is limp mode? If my car is running in limp, would I have been able to do 150mph this afternoon?

Jay

[2003 V8 TT]

Go with high flow cats...they are within 10% flow rate of test pipes (at least the Hyper-Flows were reviewed as such) -- has all the sound without the pollution. ;-)

[CockneyPlayboy]

There seems to be some contradictions.........

SO.... is there going to be a problems with my sensors and if so what is the solution should I wish to rid myself of cats?

[CockneyPlayboy]

There seems to be some contradictions.........

SO.... is there going to be a problems with my sensors and if so what is the solution should I wish to rid myself of cats?

Anyone??

[andyblackman777]

Paul,

As long as the rear sensors are connected you wont get a cel the rears are there for comparison with the fronts to see if your cats are knackered but this is only an active test on the USA cars . My car ran fine with no cel with straight through pipes and with 100 cell cats.

If your going with straight pipes just have an aditional boss welded in for the rear sensor. You could just plug the sensors in and tuck them out the way somewhere but this is not reccomended because they have a heater in them and may burn!!!

PNM do both straight pipes and sport cats and are good value

If you have the Lotus sports exhaust and you run straight through pipes then you have no baffles and its VERY LOUD. sounds crap i rekon thats why i went with the sport cats and less mot hassle

cheers Andy

[CockneyPlayboy]

Paul,

As long as the rear sensors are connected you wont get a cel the rears are there for comparison with the fronts to see if your cats are knackered but this is only an active test on the USA cars . My car ran fine with no cel with straight through pipes and with 100 cell cats.

If your going with straight pipes just have an aditional boss welded in for the rear sensor. You could just plug the sensors in and tuck them out the way somewhere but this is not reccomended because they have a heater in them and may burn!!!

PNM do both straight pipes and sport cats and are good value

If you have the Lotus sports exhaust and you run straight through pipes then you have no baffles and its VERY LOUD. sounds crap i rekon thats why i went with the sport cats and less mot hassle

cheers Andy

Cheers for your help guys! May wait and take the sport cat route then.....

[Paula&Marcus]

Great decision !!!

Please tell us what cats you ended up with and how the installation went and how everything works for you ...

Its always good to get some reports

Cheers

Marcus

Cheers for your help guys! May wait and take the sport cat route then.....