Lindowkid

Trying to get a bit more info on difficulty in changing WRX exhaust system on newage for a PPP system. I've fitted a straight through instead of the resonator section and a PPP backbox, now just trying to plan the next bit which is apparently a bit harder.

Anyone got any advice on removing the up-pipe on a WRX (which has a cat fitted) and replacing it with a standard up-pipe from classic or newage STI without cat fitted. Does this affect sensors, is it difficult ?

Also anyone replaced the catted downpipe with a PPP sports cat downpipe, difficult ? any advice. Does the PPP centre section come without a cat and is that why everyone seems to suggest this is swapped too as the WRX has a cat in the centre section.

Oh and I need the parts....

aXeL

Should be a straight swap for the up-pipe. On my STI the AFR bung is actually in the header and yours should be too, according to the WRX service manual, so you won't have any problems there.

My PPP centre section has a cat or at least a big 'cat' shaped box - never opened it. Can't speak for the downpipe - never messed with it. All I would say is that it's almost certainly a straight swap as it has to mate with the turbo and centre section.

I'd also suggest port matching the front pipework while it's off the car - headers too. Given the gains to be had, I personally think it's a no-brainer...

Lindowkid

Thanks for that, but your going to have to explain what port matching is. I think from the other posts I've read that the next phase is to find a PPP fast flow catted downpipe and centre section. Fit that and then ask JollyGreenMonster if its worth the extra to replace the uppipe with a decat option. I gather from the posts that once I mess with the uppipe I really do need a remap. Trying to mod everything I can DIY before doing that and also trying to get as close to the magical 300bhp as poss.

Already changed the pannel filter to K&N and fitted straight through resenato section and PPP backbox which sounds v nice.

redwards

iTrader: (6)

If you had a choice, then I would go for a PPP cat over the std STi item. The PPP has a bellmouth design and only one cat





The biggest problem I had was removing the 2nd lamda sensor, so I left it in the cat and bought a new one.

aXeL

You'll make 300 - no probs.

Definitely replace the catted up-pipe to increase the acceleration of air into the turbo - will reduce the spool time and increase your boost response across the rpm range.

Port-matching: all standard exhaust headers and pipework, including PPP, are just cast metal that's been badly cut at the ends. When bolted together the joins actually don't match up! There are lots of gaps and lips at the joins which makes lots of nice big air dams inside, obstructing air flow. I did the work on my headers with a dremel and a drill, with the right bits, and ground the edges to a nice aerodynamic shape - a few hours and a hand full of metal slivers later the car's engine response was much more sharp.

Haven't done my up-pipe yet but that's next and then I'll do the manifold. Should see another 5-10% hp for the manifold all by itself from the dyno comparisons I've seen.

The other alteration which makes a big difference to the induction, without screwing up the MAF, is to take off the plastic air intake restrictor, cut off and grind down the edges and put it back on. Also cut a hole in the top lip of the grill so that air can actually reach the funnel! If you're feeling REALLY brave or just like me, wrap a lump hammer with a towel and then "carefully", if that's the right word, knock out that stupid ridge in the bonnet lid which closes almost completely over the funnel. I've not affected the surface appearance or alignment of my bonnet at all doing this. Or you can by an aftermarket kit but by modifying the stock restrictor there's no risk to the MAF which is waay further back.

Why go to all this trouble with the induction? My car used to peak at ~5500-6000rpm and then tail off. After only doing the induction work it pulls very hard all the way to 7600rpm which is the limiter so I don't actually know where the peak is now.

You will need the re-map though. My PPP map layouts are rather different to the stock WRX map. If your ECU is anything like mine, the MAF reading is used to help calculate the injector fueling so it will partly correct for the increased air flow in the induction - mine does at least, however you will run the risk of leaning so definitely get it mapped.

dnc

[QUOTE=aXeL;8930920]You'll make 300 - no probs.

Think that's very optimistic on standard turbo? More like 270-280 if it's on a TD04.
dnc

Lindowkid

[QUOTE=dnc;8932329]Thanks for the help. I heard 270-280 was a kind of cap, but was hoping the full exhaust mods (up & down pipes) would get higher, I think 285 is the figure I have spotted with all the mods excluding the uppipe. I've asked the question before what the gain would be vs the hassle of doing the up pipe.

Does anyone know if there is a difference between the standard WRX mid pipe (connects to the downpipe one end and resonator section on the other) and the PPP one, they look the same in the picture.

I just need to find the PPP downpipe and if its different the centre pipe.

redwards

iTrader: (6)

PPP is a straight through pipe. They just use the same heat shield on both.

danog

heres a guide to replacing the up pipe.
http://www.scoobymods.com/perrin_upp...669c3c4c8&
You will need one with the hole/thread in as the wrx has the EGT sensor in it.

dnc

[QUOTE=Lindowkid;8933264]Don't think it makes much difference what else you do with your set up, if you want a genuine 300+ bhp you will need a different turbo IMHO. FWIW I think de-catting the up-pipe give the least gains vs the other cats.

Try speaking to a mapper e.g. JGM, he is usually very happy to give advice and can give a far more realistic response than me.

HTH dnc