Results 1 to 6 of 6

Thread: pre-cat and de-cat...what does it do?

  
  1. #1
    Status
    Offline
    stevejoshlay5's Avatar
    AOC Fanatic
    Join Date
    Sep 2009
    Posts
    487
    Mentioned in
    0 Post(s)
    Quoted
    0 Post(s)

    pre-cat and de-cat...what does it do?

    without sounding totally stupid what does a pre-cat and de-cat do?, i hear of people buying new ones and i hear of people removing them...could someone explain to me exactly what these pipes do or dont do?

  2. #2
    Status
    Offline
    Mk4SXi's Avatar
    AOC Fanatic
    Join Date
    Apr 2007
    Posts
    396
    Mentioned in
    0 Post(s)
    Quoted
    0 Post(s)
    2.0 Turbo models and 2.2 models have both a Pre Cat and a Main Cat and all other models just have a Main Cat. A Cat being a Catalytic Converter - what cleans the emissions coming out of your engine. The Cat can be restrictive and hinder gas flow through the exhaust, a De-Cat is basically an empty piece of pipework that replaces the Cat so there is no restriction...

    Removing the Pre-Cat for a De-Cat isn't illegal as the main Cat cleane the emissions enough to pass the MOT, however if you remove the main Cat also, you will run into trouble.

    Hope that clears it up bud

  3. #3
    Status
    Offline
    frostvalve's Avatar
    AOC Newbie
    Join Date
    Oct 2009
    Posts
    46
    Mentioned in
    0 Post(s)
    Quoted
    0 Post(s)
    The pre cat is there supplement the main cat during warm up. As the MOT is done at normal temp, the pre cat can be removed and the car will still pass the emissions test. It's said removing it can give up to 10bhp. I'd like to see a before and after dyno test though to see what it actually gives.
    Dave

  4. #4
    Status
    Offline
    Ffoeg's Avatar
    2170:01:06
    Join Date
    Jun 2003
    Posts
    34,591
    Mentioned in
    2 Post(s)
    Quoted
    0 Post(s)
    The precat is only they to make the car Euro4 Complaint - it just warms up quickly and start controlling emissions almost straight away.

    Other Z series petrol engines don't have a precat, beacuse the main cat was moved to manifold, thus enabling quicker warm up.

    Z22SE and Z20LE(X) don't have the room to have mani cats, hence the precat being an easy work around

  5. #5
    Status
    Offline
    Mk4SXi's Avatar
    AOC Fanatic
    Join Date
    Apr 2007
    Posts
    396
    Mentioned in
    0 Post(s)
    Quoted
    0 Post(s)


    Quick pic just made up mate... Thats off a 2.0 Turbo...

  6. #6
    Status
    Offline
    stevejoshlay5's Avatar
    AOC Fanatic
    Join Date
    Sep 2009
    Posts
    487
    Mentioned in
    0 Post(s)
    Quoted
    0 Post(s)
    thanks to all you guys for clearing that up for me

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •