Pre-cat. . . . . REMOVED!

[rdfcpete]

The pre-cat is soley to reduce cold start emissions, which is a requirement in some countries (NOT UK).

It's not designed to catch carbon like a DPF (as petrol engines don't make soot like diesel), it's so close to the turbo so it heats up quickly to do its job within 30secs of engine start (ecu dumps fuel into combustion chamber to heat both cats up quickly from cold).

I noticed much better turbo spool and a marginal mpg increase over the 18months I kept the car for. It's worth remembering that anyone with a Milltek, BCS (or any aftermarket downpipe) will NOT have a pre-cat either.

For a "free" mod, it's definetly a win win 

 

So most or nearly all turbo petrols on the market would have this part, including the M135i perhaps, for example?
@GrayMK5GTI

[Scottymon]

Yeap ^ I'd wager so mate; European Cold Start Emission requirement IIRC... removing it lets the turbo breathe a little better, knocks down EGT's, esp. if we're talking anything with the Pre-Cat slammed next to the turb/s like the K03 GTI!

[GrayMK5GTI]

 

The pre-cat is soley to reduce cold start emissions, which is a requirement in some countries (NOT UK).

It's not designed to catch carbon like a DPF (as petrol engines don't make soot like diesel), it's so close to the turbo so it heats up quickly to do its job within 30secs of engine start (ecu dumps fuel into combustion chamber to heat both cats up quickly from cold).

I noticed much better turbo spool and a marginal mpg increase over the 18months I kept the car for. It's worth remembering that anyone with a Milltek, BCS (or any aftermarket downpipe) will NOT have a pre-cat either.

For a "free" mod, it's definetly a win win 

 

So most or nearly all turbo petrols on the market would have this part, including the M135i perhaps, for example?
@GrayMK5GTI

I'm pretty sure all VAG turbo petrols do (mk7 has main cat near to turbo so doesn't have one)

Astra VXR does. . . Likely lots of others. 

[Lewo]

Another thanks for this guide. 
Took mate and me about an hour to do mine today, the turbo nuts came off easier than I expected which was my only worry.
He managed to get them off without any spray whilst engine was still warm, took me 10 mins to knock out the pre-cat and clean up with drill and wire brush.
Only done a short drive home, so hard to tell any difference at the mo.
Just relieved it went without any problem. 

[shoaybmakda]

Really want to do this on mine - just not sure about taking the bolts out from near the turbo..anyone near Leicester able to give me a hand? Lol

[l2azvan]

I would do the same thing, anyone in Bristol with jacks ?

[rdfcpete]

Got the thread spade out. Tooooo relevant though 

Has anyone done this to any of the MQB platform cars yet i.e. 8V S3, 7R or MK7 GTI/clubsport etc?
 

[GrayMK5GTI]

Got the thread spade out. Tooooo relevant though 

Has anyone done this to any of the MQB platform cars yet i.e. 8V S3, 7R or MK7 GTI/clubsport etc?
 

Ahh my old thread 

The latest platform cars have the main cat right up by the turbo, rather than having a pre cat.

[rdfcpete]

Got the thread spade out. Tooooo relevant though 

Has anyone done this to any of the MQB platform cars yet i.e. 8V S3, 7R or MK7 GTI/clubsport etc?
 

Ahh my old thread 

The latest platform cars have the main cat right up by the turbo, rather than having a pre cat.

Oi oi Gray 
So with these, Sports cat/cat mods etc would be the alternative to the original precat mods talked about on this thread?

Wonder what the BMW turbos are like... 

[MKDK]

So I'm having the thread spade out as well... 

I'm getting my GTI mapped... Only things done so far: Carbonio intake (just the box - got that dirt cheap!), GFB Diverter Valve, noise pipe delete with a new throttle body and the pre-cat removal.

I'm wondering what effect a 3" downpipe with 200 cell cat. would have versus a stock downpipe with the pre-cat removal done?

Any experience on this matter?

[pudding]

So I'm having the thread spade out as well... 

I'm getting my GTI mapped... Only things done so far: Carbonio intake (just the box - got that dirt cheap!), GFB Diverter Valve, noise pipe delete with a new throttle body and the pre-cat removal.

I'm wondering what effect a 3" downpipe with 200 cell cat. would have versus a stock downpipe with the pre-cat removal done?

Any experience on this matter?

Noise pipe?  I take it you're not from the UK as we didn't get that on our GTIs 

I found much more of a gain from a 3" downpipe.   The main restriction in the factory downpipe isn't actually the pre-cat, but rather where the gases converge at a rather nasty and acute angle, which is a weird triangle shape and quite restrictive.......plus the narrow bore once it leaves that restriction.

On top of that, the pre-cat carcass is very thin steel, so it sounded a bit blowy on mine after bashing the cat out, which was irritating.   It wasn't a leak, just the exhaust noise being audible through the empty cat shell.

[JMP]

I'm wondering what effect a 3" downpipe with 200 cell cat. would have versus a stock downpipe with the pre-cat removal done?

Any experience on this matter?

I first had a precat delete and after a while switched to 3" 100 cell sports cat ebay downpipe. I got more topend power with the aftermarket downpipe, however the turbo spools earlier with the precat delete. It felt better and felt like it had more torque in daily driving with the precat delete.

I didnt do dyno, but measured 80-120kmh pulls and I got about 2/3s of the performance gain from precat delete in comparision to the downpipe.

This was with k03 GTI revo stage 2.

[RetroRaz]

Not sure if this helps, but on my last GTI, I had precat delete, Ramair intake and GFB DV+, BWA engine, stock it made 211BHP and after stage 1 map it made 258BHP

[golfmck1980]

I had mine done a couple of months ago didnt feel any diff on the bum dyno but as the exhaust is now a full straight through its bloody loud I tell ya

[MKDK]

So I'm having the thread spade out as well... 

I'm getting my GTI mapped... Only things done so far: Carbonio intake (just the box - got that dirt cheap!), GFB Diverter Valve, noise pipe delete with a new throttle body and the pre-cat removal.

I'm wondering what effect a 3" downpipe with 200 cell cat. would have versus a stock downpipe with the pre-cat removal done?

Any experience on this matter?

Noise pipe?  I take it you're not from the UK as we didn't get that on our GTIs 

I found much more of a gain from a 3" downpipe.   The main restriction in the factory downpipe isn't actually the pre-cat, but rather where the gases converge at a rather nasty and acute angle, which is a weird triangle shape and quite restrictive.......plus the narrow bore once it leaves that restriction.

On top of that, the pre-cat carcass is very thin steel, so it sounded a bit blowy on mine after bashing the cat out, which was irritating.   It wasn't a leak, just the exhaust noise being audible through the empty cat shell.

You are correct, sir. I'm across the water to the east, in Denmark ;-)

This horrible thing (http://i7.photobucket.com/albums/y295/Raven6t9/246.jpg - not my pic) had to go. Replaced the throttle body pipe, so all the air goes to the engine. Definitely gave a better throttle response!

I have noticed that blowy sound on mine too after the pre-cat delete... was actually pondering changing the gasket. Didn't do that after the pre-cat delete, as the existing one looked fine.