Pre cat removed

[Ecomatt]

I eventually got around to removing the pre cat and boy what a difference it has made. It has made the turbo spool up a lot quicker and you can really hear the turbo working now. The exhaust has got a deep burble and the engine sounds more meaty. It only took me 1.5 hours to take off the downpipe, knock the cat out and put back together. Very easy job and since doing it I get 5mpg extra going to work doing the same speed etc. Well worth doing as it is not really needed on the car and I do not know why VW / Skoda wasted their time and fitted it. It sure feels like it has released about 10bhp the way it pulls and goes. My car is stage 1 Shark and it was quick, but now its even quicker and it cost me £0 to do

[Bogwoppit]

I also removed my precat on my vRS. It made no difference on the MOT emissions either!

[vRS_Pagey]

I eventually got around to removing the pre cat and boy what a difference it has made. It has made the turbo spool up a lot quicker and you can really hear the turbo working now. The exhaust has got a deep burble and the engine sounds more meaty. It only took me 1.5 hours to take off the downpipe, knock the cat out and put back together. Very easy job and since doing it I get 5mpg extra going to work doing the same speed etc. Well worth doing as it is not really needed on the car and I do not know why VW / Skoda wasted their time and fitted it. It sure feels like it has released about 10bhp the way it pulls and goes. My car is stage 1 Shark and it was quick, but now its even quicker and it cost me £0 to do

This will be occurring on mine when some new engine mounts are fitted, but hopefully just a stop gap prior to the acquisition of a replacement DP/Sport cat.

With regards the reason for having a pre-cat in the first place. Apparently it significantly reduces emissions from a cold start before the main cat gets up to working temperature.

[Bogwoppit]

If you want the part numbers for the gasket and 4 nuts that you are supposed to change they are:

Nut, (4 off) Replace, Coat stud bolts on exhaust manifold with hot bolt paste. (40 Nm)

Part no - N 102 861 08

Gasket, Replace. Part no - 1K0 253 115 AB

Edit: These are for a TFSi (BWA engine code)

Parts cost less than a tenner.

[vRS_Pagey]

If you want the part numbers for the gasket and 4 nuts that you are supposed to change they are:

Nut, (4 off) Replace, Coat stud bolts on exhaust manifold with hot bolt paste. (40 Nm)

Part no - N 102 861 08

Gasket, Replace. Part no - 1K0 253 115 AB

Parts cost less than a tenner.

I already hav 3 replacement gaskets just in case, although from what I understand the original may not need replacing anyway.

Good shout on the bolts though.

[donovan]

Is your car a tfsi or diesel mate?

[vRS_Pagey]

Is your car a tfsi or diesel mate?

If your asking me, mine is a Tfsi.

[Bogwoppit]

Sorry, I should have said those part numbers are for a TFSi (BWA engine code).

[martziniuk]

Smack it all out and get the full effect

[donovan]

I was asking 56OctyVRS mate? So if his is a TFSI does this mean you can pass mot with cat material knocked out of the precat?

[vRS_Pagey]

I was asking 56OctyVRS mate? So if his is a TFSI does this mean you can pass mot with cat material knocked out of the precat?

Lot of discussions regarding this subject on the mk5 Gti forum, the basic answer is yes.

The pre-cat filter is there for reducing emissions from cold start, which afaik is not part of any current MOT. You need to bare in mind, even with this filter removed, you still have an OE cat, if you were to fit a large bore down pipe and 200 cell sport cat this will still pass an MOT.

[donovan]

so would the route be knock out pre cat as funds are tight then when i have some cash get a downpipe with sports cat? May knock out pre cat next weekend if weather allows if you say it makes a nice difference.

[vRS_Pagey]

so would the route be knock out pre cat as funds are tight then when i have some cash get a downpipe with sports cat? May knock out pre cat next weekend if weather allows if you say it makes a nice difference.

That's the plan, my mechanic is going to do it in conjuction with some other work.

[donovan]

cool i already have a stage 1 and it seems i have some timing pull higher in the rev range which seems to be down to EGTS so maybe doing the above will sort this issue out. My plan looks like it will be precat knocked out, Induction kit either evoms or forge, then exhaust

[Bogwoppit]

I was asking 56OctyVRS mate? So if his is a TFSI does this mean you can pass mot with cat material knocked out of the precat?

Mine is a TFSI also. Last MOT I still had the precat fitted, this MOT I didn't have a precat fitted. My emissions results were exactly the same for both MOT's and the car easily passed.

Precat removal piccies:

[vRS_Pagey]

Mine is a TFSI also. Last MOT I still had the precat fitted, this MOT I didn't have a precat fitted. My emissions results were exactly the same for both MOT's and the car easily passed.

Exactly, that's because the engine is left to run because the cat is most efficient when its hot.

[bettsy]

would this have the same effect on the tsi

[vRSy]

yes it would.

[rob_e]

yes it would.

:evil:

[Ecomatt]

Is your car a tfsi or diesel mate?

Yes mate, mine is a TFSi.

Just to update you all. Since removing the pre cat the engine is working more efficiently. I was cruising home last night on the road home (A617) at 60 mph. Normally with the twisty bends and hills I would average about 29mpg on the trip computer. Doing the same run last night I was averaging 35mpg on the trip computer. I havent altered anything else on the car and using the same fuel, Momentum 99. When not under any load the engine is whisper quiet until you push the loud pedal! I am going to re visit R-Tech and see what difference it makes on the rollers when funds allow. Last time I was there it made 236bhp with a small boost leak, which is now fixed. So I would expect it to make just over 240 bhp. But once done I will post back on here

Cheers Matt

[vRS_Pagey]

Yes mate, mine is a TFSi.

Just to update you all. Since removing the pre cat the engine is working more efficiently. I was cruising home last night on the road home (A617) at 60 mph. Normally with the twisty bends and hills I would average about 29mpg on the trip computer. Doing the same run last night I was averaging 35mpg on the trip computer. I havent altered anything else on the car and using the same fuel, Momentum 99. When not under any load the engine is whisper quiet until you push the loud pedal! I am going to re visit R-Tech and see what difference it makes on the rollers when funds allow. Last time I was there it made 236bhp with a small boost leak, which is now fixed. So I would expect it to make just over 240 bhp. But once done I will post back on here

Cheers Matt

Excellent and unexpected side affect there.

Think I might book mine in sooner rather than later as I now have a set of VF Engine mounts to go on.

I pressume you are just running stage 1 software with no additional mods' other than the filter removed?

[martziniuk]

I never noticed any mpg difference, but the warmer weather we're having does make a big difference in mpg.

Was your boost leak at the pipe connector which goes into the intercooler? I changed them two seals and fitted a Rev DV yesterday.

[rob_e]

Think I might book mine in sooner rather than later as I now have a set of VF Engine mounts to go on.

Which mounts are you changing? Any links to a before/after comparison or similar?

[Ecomatt]

I am running a Stage 1 Shark with a K&N panel air filter. I also have the 'D' rev DV valve and the PCV valve refitted as I will be fitting a BSH catch can soon.

I am not sure which pipe or where the boost leak was coming from to be fair. All I know is that I changed all the boost hoses to Samco and the fault code and leak went away thankfully.

We had similar air temps last week and I was only getting 29mpg on the run home. I made sure that I did not alter (raise or lower) any tyre pressure etc, which I now set at factory spec of 29psi front and 31psi rear, so I could give it a fair comparison before / after and I am always hitting higher mpg figures.

I dont think I will be going stage 2 now as I bet there won't be that much 'on road' performance difference, certainly not £600 worth anyway!

[vRS_Pagey]

Which mounts are you changing? Any links to a before/after comparison or similar?

I have a full set of VR Engineering mounts:

As soon as they are fitted I will post my findings, however vRS Carl originally had them fitted on the bullet and my observations were almost no engine movement under acceleration so more throttle response, and for some reason the engine sounded like a V6??