Cats vs. DeCats

[Juddder]

Since I've owned my Cerbera it has always been de-catted, but I now have to move MOT station and I fear the new station will instantly fail it on emissions because of this

I noticed from reading the MOT spec that the emissions is based on meeting the manufacturer's published specifications, not some arbitrary emission levels which I had assumed in my head so I'm thinking of putting the cats I bought as a backup into the car to aid with passing it's MOT

So the question is...

What's the disadvantages of putting the cats back in?

I think I remember reading that the floor panel gets warmer as there is more heat generated by the cats burning up the waste gases (?) and potentially the car is a little quieter but I wonder anything else?

I'd like to keep the snap and crackle over-runs it makes as they're half the fun of owning a cerbera to me

Thoughts all welcome and hope everyone is having getting ready for Xmas!

Alex

[tejr]

My 4.2 popped and banged like mental with or without cats. Cat = quieter too. I've not had the cats in the 4.5 yet, so not sure, but one of them has a big through the honeycomb, which is to be expected from the popping/banging/overfuelling.

The heat generated from the cats is horrible though, cabin gets ridiculously hot and it caused hot stalling issues, in the 4.2, from fuel vapourisation/heatsoak of the fuel rail.

On that note - does anyone know where to get a spare cat for a 4.5?

[Jhonno]

Cats rob power, worse MPG, heat up your knob and remove a portion of the pops and bangs.

They do however make the exhaust note a bit deeper/quieter...? If that is a positive..

[Byker28i]

Pro's
In my testing, Cats take around 8-10db noise off the system. Might be needed for trackdays, I can get down to 98db with cats and trackday silencers. To offset the daily noise I fitted an ACT quiet system.

Emissions- Cats should be in place to pass a proper MOT. Some garages are more favourable, some need them putting back in. I always have mine put back in for the MOT and it passes emmisions.

Cons
The heat - the main reason I took mine out is that the cats sit in the tunnel next to the gearbox and clutch. They heat up everything including the cabin, and if in traffic even the gearknob becomes very hot to touch. I considered this wasn't good for my car.

Weight - there's a slight weight saving...

Either way
Pops, bangs, flames. I get more pops and bangs with the cats out, and it can flame coming down in revs from 4k-3k.


So for me the real issue is the heat they generate and where it manifests. Thats why I run decatted.

[ukkid35]

Jhonno said:

Cats rob power, worse MPG, heat up your knob and remove a portion of the pops and bangs.

On the continent in the summer, either I have to put a sock over the knob or wear gloves when cats are fitted, that or get burnt

[Phil.]

Was your Cerb re-mapped for the de-cats? If so, you might have to reverse the re-map to avoid cooking the cats once re-fitted.

[Juddder]

Thanks Phil and good point!

As the car came without cats and from chatting with a previous owner knowing that it went through various tuning levels (Julien who then bought a 4.5 and James Agger) that would make sense

Also from everyone's comments above it sounds like I don't want the cats in full-time anyway so what would be the effect of putting them in just for the MOT and leaving it tuned as is?

I also have a switchable ECU map in my car that I built the circuit board for and copies of a few stock EPROMs so I think I should be able to switch back to a non tuned map just for the MOT :-)

Happy New Year to all BTW!!

Alex

Edited by Juddder on Wednesday 1st January 12:52

Edited by Juddder on Wednesday 1st January 13:49

[Jhonno]

Juddder said:

Thanks Phil and good point!

As the car came without cats and from chatting with a previous owner knowing that it went through various tuning levels (Julien who then bought a 4.5 and James Agger) that would make sense

Also from everyone's comments above it sounds like I don't want the cats in full-time anyway so what would be the effect of putting them in just for the MOT and leaving it tuned as is?

I also have a switchable ECU map in my car that I built the circuit board for and copies of a few stock EPROMs so I think I should be able to switch back to a non tuned map just for the MOT :-)

Happy New Year to all BTW!!

Alex

Edited by Juddder on Wednesday 1st January 12:52

Edited by Juddder on Wednesday 1st January 13:49

You could just stick the cats back in for the MOT, it will just change the adaptives a bit. The ecu should compensate enough for them to run OK.

[Juddder]

Jhonno said:

You could just stick the cats back in for the MOT, it will just change the adaptives a bit. The ecu should compensate enough for them to run OK.