Pre-cats

[Sena]

With all the talk about the Marks chip has anyone had their pre-cat's removed to enhance performance? Any advice / pro's / con's ?

Cheers,
Sena

[petros]

I've got ACT manifolds with the pre cats removed. Don't know about the performance but the noise is muuuuch better

[Sena]

More noise is definitely an incentive ;-)

Sena

[cerby4.5]

Better check the issues regarding MoT??? Clearly many things can be done, but unless it will get an MoT pass you are slightly buggered! I would like to get the car performing and sounding better, but much of the problem comes around the topic of "emmissions"!

[parrot of doom]

Just take your car in with the engine nice and hot, and the absence of precats won't be noticed.

[trinitycall]

Sena said:

With all the talk about the Marks chip has anyone had their pre-cat's removed to enhance performance? Any advice / pro's / con's ? Cheers, Sena

I had B1RBL's pre-cats whipped out on the advice of Mark Adams as they were buggered.

Such removal shouldn't cause emissions MOT failure.

Not sure as to any noise or popping changes as B1RBL sounds like a warzone in-any-case.

If you're having a Mark Adam's tornado conversion then he is probably the best person to advise you on the merits of pre-cat removal having regard to your particular circumstances.

N

[Sena]

Agree. Would have thought with the main catalisers in there the emission control should be OK still for MOT....

However, will look into getting a bit of professional advice on the subject!

[petros]

Pre Cat removal doesn't effect the MOT

[cerby4.5]

Thanks Petros,

Well at least now I know that for sure!!

Scott

[spend]

Pre cats, just aid when the cats not up to temp, part of the manufacturers regulations IIRC. They do affect MOT, you need to give the car a good thrashing to get it nice & warm before the emissions test, thats all. Just get them out.

Dave

[_dan_]

Had them out on mine, makes the ground shake on tickover when you stand behind the car!!

Awesome

[robertp]

What is involved in removing them? Has anyone got this done AND the silencer bypass?? Is it too much???

[steve1c]

I had mine out, nicer deeper grumble, but also put in non-reversal cones to counteract some loss of back pressure.

[slikk]

robertp said:

What is involved in removing them? Has anyone got this done AND the silencer bypass?? Is it too much???

I have nothing 'twixt manifold and tailpipe. Is the sound of an angry V8 ever too much ?

kim

[Sena]

Hmm. something tells me this is the way to go then! More noise & a bit more power. Heh heh.

I suppose having the pre-cats removed helps economy somewhat too. Tho' if that's top of anyone's list with a dragon like this under you, you're driving the wrong car...

S.

[steve1c]

robertp said:

What is involved in removing them? Has anyone got this done AND the silencer bypass?? Is it too much???

Is it too much? Ohhhhno, just about perfect.

[_dan_]

robertp said:

What is involved in removing them? Has anyone got this done AND the silencer bypass?? Is it too much???

Top-Cats did mine along with fixing a hole inbetween the four pipes. It was a bit of an experiment on mine, basically they took off both manifolds, chopped them in half where the join in the middle is, ripped out the pre-cats (bit of a nightmare apparently!) and welded the the hole from the inside as well.

I get a good few more pops and bangs, a raspier but still deep grumble, I'm going to try and get a video of the motor together soon in an aid to sell it so when I do I'll post a link on this thread.

Price-wise, I'm not too sure as they did a load of other work to the car at the same time. I'll dig out the receipt when I get back to Wales. I know it was cheaper than buying 2 new manifolds though.

[robertp]

Hmmmm - sounds very interesting but no ones actually answered two of my questions - whats involved in removing the precats and has anyone done this and the silencer removal? Think I can live with the noise consequences if it can get through an MOT.....

[victormeldrew]

I have no cats at all and it gets through MoT with no problems. I thought this might be a problem after the dealer who did the mod closed down, but I've had in MoT'd elsewhere several times since with no problems whatsoever.

[GreenV8S]

It may gain you 3-4 bhp which is enough to measure but not enough to be noticeable. On mine there was no measurable change to the noise level and it didn't sound any different to me.

The precats will either fall out when you tip the manifold up, or have to be chisseled out, or somewhere in between. You shouldn't need to open the manifold up to do this, but if the pre-cats are stuck, and you have access to welding and cutting gear, this might be the easiest approach.

Ideally, having removed the precats you would then fit a non-reversing cone in the hole. You would need to cut the manifold open to do this.