hades

Chris - as you asked! Headers are also known as exhaust manifold. You need to remove the manifold to change the up-pipe. In true Subaru fashion, the holes in the manifold are much smaller than the holes in the cylinder heads they meet up to, and this diameter reduction is a square lip. There are a few other minor edges that slightly disrupt the gas flow too IIRC. Scoobysport - and many other places - can grind a taper into the headers, such that there is no lip to disrupt the flow of gas out of the exhaust, and polish out any other nasties they find.

Scoobysport charged £200 + VAT + gaskets + fitting. They have to take them off to gat at the up-pipe, so the gaskets and fitting are effectively reduced if you get them done at the same time. It is also possible to DIY it if you're confident, but don't leave shrapnel in there to go through the turbo!

[Edited by hades - 12/1/2002 6:37:11 PM]

chris singleton

Missing the wonderful sound and woosh I had on my old decatted MY96.

At present I have a MY01 PPP and want to upgrade to Scoobysport exhaust but not sure which components I need.

Is it worth getting the centre section and rear box when I already have the Prodrive equivalents? Is the back box where most of the sound comes from?

Would I be better of just fitting up and down pipes with CEL fix and keeping PPP parts or should I go the whole hog.

Most of the power increase comes from the downpipe, is it actually worth fitting the up pipe as well?

So many questions!!

Any comments/advice much appreciated.

Cheers

Chris

hades

A few comments from my (limited) experience, all IMHO.

The PPP backbox is quieter than the scoobysport. If you want the noise you had before, change the backbox. It is allegedly more restrictive too, but it will a very small difference to power - I'd say only worth changing it if you want the noise/looks. There will be very little difference with the scoobysport vs prodrive parts of the centre section, I wouldn't bother with that bit. Downpipe will give you some more noise, better spool up and more power - definitely go for that!

I have a scoobysport up-pipe on my MY02. It is certainly worth it. I got headers ported at the same time, net effect was much better spool up, more power, and it is now safe to run extra boost without worrying about the up-pipe cat breaking up. I believe porting the headers reduces noise particularly at low throttle openings, as well as giving more power, whether you think that is a bad thing is debatable.

WRXBOB

I have an 02WRX and have gone the full de-cat route, up / down / both centres and BB and its brilliant.

IMHO I would recommend you DO change the up-pipe as well as I found it DOES make a noticeable difference.

A mate of mine was in a similar situation to you, having an 01 WRX with a PPP. He did the down pipe and up pipes first and then a few weeks later replaced the resonator centre section for a TSL item and apart from a difference in sound(improved it obviousley) he said he feel a slight improvement in pick up. He still has the prodrive back box and short centre de-cat section fitted.

If your after the sort of sound you had before with you '96 then IMHO change the lot, up pipe/down pipe/ resonator centre and back box.
IIRC I think scoobysport advise you to re-gap your plugs slightly smaller when you de-cat a PPP'd 01/02 WRX.

Bob

chris singleton

Hades - Headers ported, whats that then and how much? Please exuse my limited technical knowledge

Bob - re-gap the plugs, do scoobysport do this when fitting exhaust and at what cost?

Cheers

Chris

WRXBOB

Chris,
All I know is that the mate with the ppp who had the de-cat fitted took his car into Scoobysport for a slight misfire.
Apparently, the PPP'd cars need a reduced plug gap when you de-cat them... With the plugs re gapped his car is running great!

Your better of speaking to Scoobysport...

Bob

chris singleton

Cheers Bob, will do

WRX-Driver

I don`t really understand what you mean with a reduced plug gap. What does it mean. Should i use other spark plugs?
I'm from Austria. So my English isn't perfect.

Daniel

WRX-Driver

Or can anyone explain me what re-gap means.
Daniel

BugEyed

WRX-Driver



Decreasing the gap on spark plugs is often required when running higher powers for a given ignition system - to large a gap means that the ignition is not strong enough to drive a spark at the higher gas pressures involved with the greater power, resulting in reduced efficiency or even a misfire.

Hope that helps.

Duncan

PS Getting rid of the uppipe cat is the best advice as if you run your car lean it is not unknown for this to fail passing chunks through the turbo. Removing it improves spool up as well as ultimate power.

chris singleton

O.K. decided to go the whole bang and fit up pipe, downpipe, centre section, CEL fix and back box.

I've just worked out that it's going to cost me approx £940.00 (and thats buying downpipe, centre & back box second hand for £470.00 - Deal is done, so no turning back) Feel a bit sick now.

Looking for some re-assurance that the end result is going to be worth such a huge layout! Has anyone fitted the full system to MY01 WRX with PPP and if so with what results.

Any comments much appreciated.

Cheers

Chris

BugEyed

RB5Scott has got a full de-cat on his UK300 PPP. However, I believe that he also changed the fuel pump and put a rising rate regulator on to avoid leaning out at the top end. Drop him a line and find out the details.

Duncan

PS I'm running a full de-cat, raised boost and a trick to avoid the ECU overfueling, and all is hunkydory. The only suggestion that I'd make is to consider lagging the uppipe and downpipe to reduce the NVH and (in theory at least), increase the power and efficiency.

RB5SCOTT

I have a full de-cat and ported headers plus an APS induction kit. If you have all these things you might find that it will be slightly lean at the top of the rev-range. I fitted a HKS fuel controller to put a bit more back in

A full de-cat alone won't make it run lean

Caronte

I run a PPP full decatted. The only difference is that I removed the cat in the uppipe maintaining the oe upipe itself and I replaced the cat in the downpipe with a resonator to keep noise down (that is in any case pretty loud anyway+some pop 'n bangs occasionally). It might not be the best solution for the ultimate BHP figures but at the last RR i got an indicative 270 bhp @6000 rpm and 270 lbft from 3000 to 4000 rpm.
The boost pressure is 1,75 bars held and 1.3 peak (just for a fraction of time).
The car pulls strong 'till 7000.
No misfires so far.
I also added a new wastegate and a pop-off.
The car is running pretty rich as my techtom suggests and as I can see from the tail pipe which has become black from residuals.

Very satisfied up to now.

Andrea

Caronte

PS: CEL fix is not necessary in the majority of cases.

chris singleton

Andrea, I thought that if you completely de-catted the car the check engine light would come on, hence the CEL fix to stop this.

Is this not the case as I'd quite like to save £50 odd and not bother with it.

Cheers

Chris

Caronte

Since I decatted (3500 miles ago) the only problem I encountered has been a EGT sensor failure. I then replaced it without incurring in a CEL anymore.
As I monitored on this BBS in the past, it seems that most of the MY01 decatted works fine.
Just on rare cases it had to be fitted.
I would in any case wait to see if it turns on and eventually in a second istance fit it.

Andrea

WRX-Driver

How can i decrease the gap on the spark plugs from factory. Or should i use other spark plug? What is the standard gap and which gap should i use, when getting misfire with a PPP decat?

Daniel

Caronte

Maybe a lower temperature Sparks would cure the misfires.

BugEyed

I'm running a colder plug gapped down to .026" - .028" (sorry I'm still into proper measurements, but I'd translate that to 1.1 - 1.2mm). The standard plugs ran fine at that gap, but when it was time to replace them I thought I'd try a colder set. So far no problems with starting or cold running, but we haven't had too hard a winter since I fitted them.

Duncan