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cat removal / bypass how to on lew site things you do not need to do - Induction/Turbo/Chargecooler/Manifold/Exhaust - The Lotus Forums Jump to content

cat removal / bypass how to on lew site things you do not need to do

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hello everyone.

well after reading the how to on the lew site i would say that there are a few things that you do not need to do when removing the cat and fitting the by pass pipe or just replacing the cat and even the rear silencer (well that i have found today anyway)

1) you do not need to jack up the car or use axle stands.

2) you do not need to remove the rear wheel.

3) you do not need to remove the guard behind the rear wheel.

4) dont bother undoing the bolts between the cat and the silencer just cut through them.

so here is how i would do it after today

1) undo the nuts on the turbo (i used a flat rachet spanner) 17mm

2) grind off the three bolts holding on the cat to the silencer box (i used a dremil with a cutting / grinding disc) plenty of room just lay on a blanket and cut them off as they will be very rusty you may be able to get a grinder in there but i used a dremil

1 / 3 ) undo the 02 sensor (try this before undoing the turbo nuts or if you cant move it undo at the electrical connector depends if it wants to come out, mine would not budge with either warming up the car or using many tools blow torch large spanner / hammer / vice / stilsons etc) so i will replace the on that was there looking at it its been replaced at some time as the wires have been spliced could not see any part numbers so not sure which one.

4) the pipe with the cat on can easily be removed slide it off the turbo studs then slide it out from below.

(i have taken mine off today but the collars on the cat end is totally corroaded, cat looks good so i will replace the collar for the mot and clean up the pipe and cat)

5) epv valve as the lew site

6) the cat by-pass pipe (or replacement cat) can easily be put in place thread the turbo end up and through the space then bolt up, bolt up the cat end - job done.

although the studs on my s4 have splayed slightly so i need to get the three holes on the collar drilled (will do tomorrow) for a bit more clearance

(i know that there is enough room for the pipes to be put in from the bottom as i have had mine up there a couple of time today )

hope this helps anyone who may be trying this in the future.

It's Oogies turn to boogie

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I did mine without removing anything, and without jacking. The pipes can be fed through from below as Peter says.

The only problem I encountered was removing the old silencer. Having the car raised would have made cutting the corroded bolts a lot easier and quicker. The cat came off easy, but the silencer bolts were corroded solid. At the time I did not have any new mounting blocks so had to preserve what was there, but these were later made available very cheaply at the first parts sale. If you have new mounts to hand cutting straight through the old rubber to cut the bolt would be a lot easier, as there isnt much room for cutting the bolts without damaging the mounts. Replacing the mounts should not be too difficult with the silencer out the way.

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hello Gary. after taking the car for a good drive up the m1 and m18 today i would say that the car is much better both in sound and in pulling (i also fitted a new universal 02 sensor as well it seems fine and at

It's Oogies turn to boogie

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I have been told by two mechanics from Melbourne to do the following:

1) Remove cat from car, take to it with a mallet and block of wood and simply knock the innards out.

2) Remove EBPV from car, grind off the pins holding the butterfly to the shaft and remove the butterfly.

3) Replace both items back in the exhaust where they came from.

Result: A car that if anyone looks, it will appear to be completely original so should not give you a problem with inspections etc. If the EBPV fails, it doesn't matter as there is no butterfly to close and no innards in the cat to come loose and block the exhaust flow.

So somewhere down the track soon, that will be a job for the weekend for me.


All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

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yes you can hollow out the cat, but some cars need on for the emissions so replace otherwise you need another cat

indeed, as in Belgiu ... MOT do not know sh*t about that sort of cars, but they do know emission limits ... bets proof : our SMOG-alarm.

It's not a joke, we're allowed to do only 90 km/hr now, until SMOG has disappeared (smog that comes from German Ruhr-gebiet :) )

Anyway, I'm still speeding, in this kind of weather it's with a VW ... :P

- Nulla tenaci invia est via -

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