High flow cat

[Blue9N3]

I did mine in 3 stages (saying each time, this is the last). Dump pipe, rear muffler (straight through oval) and then high flow cat. Each seemed to make a noticeable difference. Dump and cat - better response and top end. Rear muffler, better top end.


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[ZR36]

Any error lights after each change? Brand of cats you installed, and cost?

[sambb]

With our cars if you are on a standard tune or a stage 1 generally and you swap in a high flow you could get an error. A 200 cell maybe not but a 100 cell almost definitely. Initially I'd fitted a 200 cell and dump pipe whilst still on a stage 1 tune (that didn't ignore the cat sensor signal) and had to use a right angle fitting between the cat and the second sensor to avoid the code. It basically stands off the sensor and orients it so that it only gets a sniff of the real exhaust flow and tricks the ECU into thinking that all is good. It could be that your car doesn't have these fitted in which case you're laughing. The fittings don't cost much- maybe 30 bucks each, but there has to be room for them and the angle they put the sensor at. For performance, high flow cats will help yeah. I'd say go 200 cell to be on the safe side. If you get errors then get the stand-offs fitted - just make sure that the cats that are fitted have the bungs oriented so that you can fit them once they are welded in.

[ZR36]

Im not keen to spend 'turning money' on something im not going to be keeping long term. i would rather get myself into a new toy. And i need to get my roof lining replaced before i sell it.

[Blue9N3]

I got the spacer with the mini cat inside just to be sure. The spacers alone are about $7 on eBay, the o2 ones around $50?


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[Catfish]

Seriously cut it off and get an exhaust shop to weld on a single straight pipe and just run sans muffler. Its civil in traffic (it'll crackle a bit on over run) and fires up when you are up it even if you have the centre resonator (early models) and you'll notice a jump in power. I can only vouch for a 2/1/3 tail pipe out the back though. If you tried 2/1/2 straight through it'd rattle your ear drums then I think.

I want to try this - but just to check with you first. I infer that you now have NO resonator or muffler, so the only silencing comes from the turbo and the cat. I have a stage 1 tune and the no resonator system, so can I get away with it?
Cheers.

[sambb]

I have the resonator still. I'm about to put in a non resonator length instead because I have one spare just sitting there ready to go. I have no qualms about doing that from a noise point of view. From what I've picked up over the last few years lots of people have de-resonated their cars and found that it has absolutely no effect. The resonator is a straight through design and is a small diameter chamber so I doubt has much effect at all. I'm guessing its placement was designed to pick off droning frequencies at cruise speeds (it obviously wasn't effective for the outlay because it was dumped by VW after one year) but at full noise I doubt it has much dB cancelling effect at all - that's not what resonators are for. If you are worried about permanently welding on a straight section you can do what I did and buy a set of exhaust flanges for 2/1/4in pipe. Put a cut in right against the muffler, flange the exhaust pipe and then flange the straight pipe section that will go out the back. Whoever does the job will have to weld on two hangers onto the straight pipe that will support the pipe. If its too noisy for you then buy one more flange and get it welded onto the short length of the pipe left on the muffler and just bolt that back in. I'd intended running the muffler on the street and removing it for the track but now the straight pipe just lives in there. My straight pipe is a funny size because I did it in aluminium (because its light, I could make the hangers at work out of aluminium too and also make the aluminium flange) so is 2/1/3in which is bigger than the OE steel pipe. That might make mine noisier than a continued section of 2/1/4 with a single tip but its hard to say for sure.. If you're ever in Sydney, I still have two OE mufflers. You can hack off the twin tail pipes and get them welded on so it all looks stock rather than my single.

[Blue9N3]

I think the resonator removal idea came from people with mk5 golf gti' and newer where it is a much larger oval thing.

I've got a straight through muffler and factory resonator and it's just past my tolerance level for noise...

And way past my wife's who now hates the car even more


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[Catfish]

I have the resonator still..........................................

Thanks for that. I'm going to remove the muffler, flange the pipe and replace it with a long hotdog. If the noise is too great, I'll try again with a full size straight through muffler.

[Catfish]

By the way, don't you guys complain about being over 40. I'm 73 and love flogging my gti.

[sambb]

ha ha good stuff.