high flow cat - good mod?

[rifftrax]

Just kinda wondering about the next steps I may take with the car... I know a guy who can weld pretty well and was thinking about just picking up say a $70 magnaflow cat to replace the likely crappy stock one on my jetta (95'). I figure it would likely reduce a lot of back-pressure and be a relatively cheap performance booster without having to start getting creative with the engine specifically. Think that may be the best next step?

I've currently got a Jetta III 2.0L with a cat back system and K&N air filter. I've heard aftermarket cats are pretty easy way to get a little extra boost...

 

[obi_waynne]

The stock cats in those are pretty rubbish. A sports cat will free up around 5bhp or so, not massive but it starts to get interesting if you do other mods as well, like cams and porting/polishing the head.

 

[rifftrax]

The stock cats in those are pretty rubbish. A sports cat will free up around 5bhp or so, not massive but it starts to get interesting if you do other mods as well, like cams and porting/polishing the head.

That's good to know...I've checked with a couple places here about porting polishing and one person I know said it's really not too hard to do with the correct (I assume like ceramic or some other very hard material) bits and a drill. Is there a typical price range I'd be looking at for porting/polishing if I went to a shop for a 4 cylinder engine?

 

[obi_waynne]

As far as DIY porting goes you can improve a stock non perfomance engine a fair bit, but a pro will do a much better job. I used a dremil with a few various shaped grinding stones and providing you do wide sweeping motions you should be able to tidy things up a fair bit, the trick is to match each cylinder.

A 20v Audi head will cost around £700 for a pro porting and polishing job on a flow bench, the exhaust will be a +1 and valves will have a 3 angle cut in them. A head like this is good for 400bhp but the rest of the engine will obviously need to be uprated to fully realise this potential.

Have a chat with CNC if you are serious about a pro job and see what they say.