I really need help with the centre section of my 2004 WRX saloon. I bought a 2.5” Cobra back box and deresonated centre section second hand from someone who had it fitted to their Blob Sti saloon.

I have now tried to fit it and something isn’t right. The design of the centre section has a bend just before the flared end which means it comes in at an angle and does mate properly with the second cat.

I have taken photos without the dome gasket to show the problem. The lack of alignment means the bolts are way too short and the flange by the flare is be forced unevenly. The second cat end is sitting straight and fine.

I just don’t understand what is going on and how it could possibly have fitted another Blob. Please can anyone help. The back box is Cobra but the centre pipe has no brand markings, but it does have the same type of exhaust hanger spur.

 

Ok it seems that the problem is the 2nd cat delete pipe. I got it secondhand already joined to the prodrive sports cat. It has the original stock heat shield but is a straight pipe inside, so assume it is also prodrive.

Was the prodrive centre section a different design to normal centre sections to accommodate this? The stock 2nd cat that I removed has s separate welded bit at the end with the flange to angle it downwards and at a slight angle.

Can anyone identify the 2nd cat delete pipe on the car in the photo. I need to know if it is prodrive or not as I don’t want to buy the same thing again.

 

Prodrive downpipe and 2nd cat bypass fits a standard centre section

I'd mine mated to a scorpion centre section and prodrive backbox on mine

 

Why not join the Centre to the Prodrive decat pipe first, then try to hang the Centre pipe up after?

 

What downpipe did the seller have the centre and B Box connected to and what car?

 

The Cobra back box and centre section were both fitted to a Blob sedan just like mine.

The 2nd cat delete is the problem, even if I tried to join it to the centre section off the car it would make no difference.

I just don’t understand how the 2nd cat delete isn’t correct. Are there lots of different designs? I mean you can see in the photo that the standard 2nd cat I took off has an angled end welded where it meets the centre section.

 

hat looks like a normal Prodrive 2nd cat delete so no reason why it shouldn't work??

were either off bumped cars as have seen exhausts out of shape after being rear ended??

 

The cobra centre and back box definately was not in an accident as I saw the car it came off when I bought the bits.

The downpipe and second cat delete came joined together. I really don’t think that car was in an accident. The user is still active on here so I have messaged him to ask if he can shed any light on what is going on.

I still don’t understand how it is that the Sti and WRX second pipes are different shapes. Today I am going to take the second Sti pipe off and put the WRX one one to see how that aligns with the centre pipe.

 

age for age they are not different - should b identical fitment as std

 

I wondered if the seller had replaced the full turbo back system as it would all fit from a classic and OP still has his newage DP on.

 

I have been going round in circles stuck in a loop on this and can’t believe I can’t find the answer anywhere on Google.

The prodrive sports cat and second delete pipe with heat shield came bolted together off a Blob Sti.

The back box and centre pipe came off a Blob Sti and were apparently joined to an original downpipe and fitted fine.

The questions go like this.

1. Are the second cat pipes the same in shape and design for both Blob WRX and Sti other than the Sti having no cat in that pipe?

if yes then

2. Why is the shape of the end (centre pipe join end) on the second cat less pipe I have fitted, different from the WRX second cat I have removed. You can see in the photo of the comparison the difference.

if they are different

3. How is it possible that all the aftermarket centre sections are advertised as fitting both WRX and Sti if they required to join different second cat pipes.

if we accept that the second Sti cat pipe is correct

4. Why did the Cobra centre section fit on the previous owners Blob Sti with stock down pipe?

 

1. Yes
2. No idea
3. because they are identical a std
3. No idea

is it possible the flange between the sports cat and 2nd de-cat has been altered / re-welded as from the little shown the 2nd de-cat appears to be the correct Prodrive one?

 

I really don’t think the prodrive sports cat or second delete have been modified/repaired. There is no evidence of it. Also they were bolted together as if they had never been undone before.

Because I am working on axle stands in the garage under the car and the bolts were so rusty, I had to cut my stock WRX centre pipe to get it off so it is wrecked and I have no way of using it for comparison.

I was going to take the Sti second pipe off and refit the WRX second cat to the prodrive down pipe and see how the centre one lines up with that instead. The flanges are badly rusted and I don’t want to leave it on. I haven’t done it yet because I keep having to order new gaskets and so am thinking about it all first and asking on here etc.

I have to work it all out though because if I order another exhaust section (centre or second delete) and it turns up and doesn’t fit either, it is going to be a nightmare and expensive exercise.

Two things I find strange also are that the centre section has a flare and lose flange on the relevant end whereas all images of cobra systems and others show fixed flanges on both ends like the stock Subaru one. The other thing is that the back box says cobra sport but I can’t find any others like it on the website or the internet.

 

This is the thread with the sports cat I bought. I have messaged the guy to see if he can give me any more info but have not heard anything from him yet.

https://www.scoobynet.com/subaru-par...ports-cat.html

 

That is the later bellmouth style prodrive sportscat with the divider in the middle....that divider can foul when fitted to a td04 from what I remember

have you had the sport cat fitted up properly to the turbo and also downpipe bracket bolted to gearbox?

I'm thinking you might have an alignment issue with the fitting

 

Did the seller have a facelift Blobeye or preface lift? As some 2005 models had the facelift dash like the Hawkeye and the same exhaust as the Hawkeye which is a different layout to the preface version.

Saying that they didn't do a Prodrive downpipe for the Hawkeye, or 2nd Prodrive decat.

If not maybe it needs the Cobra downpipe to work correctly? Worth messaging Cobra and asking.

 

Yes you are correct, the divider does make contact with the TD04. I have taken a few millimetres off the divider and also rounded the ends to fit the profile of the turbo with some room to spare.

The downpipe is bolted up to the turbo. The sports cat doesn’t have the mounting flange that goes on the gearbox like the stock downpipe. The second cat delete is bolted to the flange further back on the gearbox where it should be. It was tight and required pushing it hard to one side but it is bolted up.

The second cat delete end is pointing up in the air which looks weird. The stock WRX second cat end has a bend to compensate for this. That makes me think the second cat delete is wrong, but then it came off a Blob Sti PPP.

 

I’m not sure really. The guy made no claims and made clear it was on the car when he got it so couldn’t make any comment on it. The guys profile name on here is GONZO01. I only mention it in case you know him and can help find out.

The crazy thing is that I bought the centre and back box really just for the centre section as I already had a prodrive back box. Although the Cobra back box is obviously branded the centre doesn’t have any codes or labels so I don’t know how to identify it. Also on the cobra website it doesn’t seem like there is a special centre section specific to a downpipe. I can call them Monday though and check.

 

I'd be inclined to loosen off the mounting bracket and see can the get the centre section lined up then nip up the bracket or improvise.

I'd defo think you have an alignment issue more than incorrect fitting issue

In relation the jay comment about later downpipe on Hawkeye they have a slightly different downpipe and second but are still same length as all other uk downpipe but this does not affect you in any way as it refers to standard downpipe and hawkeye never got a prodrive sportcat option either

 

The problem is that although the second cat delete mounting bracket alignment was tight, it is where it should be.

The angle of the centre pipe compared to the second cat delete is completely wrong, the angles are almost complete opposites.

If it was close but just out I be would be inclined to think that fettling with the fit would sort it but it is so far out of alignment that I’ve got to assume that either the centre or second section is wrong.

 

I'd go with the centre section being wrong rather than the 2nd decat - I've never seen a prodrive sport cat that's ever been split as there is never a reason to so

I'd also try fitting the sportcat flange to the turbo without a gasket given that a gasket is only a few mm just to make sure you are defo not fouling with the divider

If still not lining up then get a different centre section, the scorpion one will work for sure, and sell the cobra one

Or get an exhaust place to alter the centre section.

 

So I’ve been doing some more thinking and searching. The point is something is wrong because the angle of the two flanges are almost opposite angles.

I have taken some photos of my centre section and from what I can tell from searching images of other centre sections like Haywood and Scott. The flared end of my centre pipe that joins the second cat delete is pointing in the opposite direction to what it should be.

Can you help in confirming this as it is so difficult to tell by looking at generic images on the internet.

I have also been concerned that this exhaust is so different and not on the Cobra website that it may even be for a non turbo Impreza. I know that would mean the pipe would be 2.25 instead of 2.5 so I got my digital callipers out and measured. The OD is 2.5” but the ID is 2.37”.

It is also weird that the bolt holes in the flange that slide up to the flared end were too small to accept the special Subaru spring bolts. The holes were 11mm ish but the bolt holes need to be at least 12mm. So I had to try and enlarge them slightly.

 

I have a full cobra system on my blobeye, from what I can see the prodrive downpipe has a slight angle at the bottom near where it joins that the cobra system doesn't (could just be the picture tbh), if it isn't the picture then I'd assume the centre pipe is angled too, maybe try rotating it and see if it lines up?

I have both a sports and decat downpipe, the sports cat being brand new and it fit no problem. Other option is maybe the headers/up pipe/turbo is slightly off angle, loosening all 3 and trying a refit then tightening from back to front may give you the slight adjustment you need.

Personally this is why I just bought the cobra sports cat to match my system, it wasn't worth the risk of the hassle your currently experiencing.

 

Yes I know the Hawkeye doesn't have a Prodrive option, although you can still fit one to the Hawkeye.

I thought the Centre pipe on the Hawkeye models was a different length than the Bugeye abs Blobeye models?

 

Exhaust diameter are measured as OD so its correct bore of 2.5inch

If you look in this thread there is a pic of a scorpion centre section that you can use to compare shape

https://www.scoobynet.com/subaru-par...e-section.html

 

no they are the same length. Only difference in length is for the JDM cars which again doesnt apply to OP

As mentioned i had the prodrive downpipe, scorpion centre section and prodrive backbox on my old hawk sti and all fitted perfectly. All uk newage bug/blob/hawk exhauts are interchangeable

 

Is your Cobra back box the same as the one I gave in the above picture or is it a different design?

Also is your centre pipe the same as mine with a flared end and loose flange? Also do you have any opinion on the left/right angle of the flared end and whether it is correct or not?