Hi all
I want to replace the second cat with a decat section. I have looked at the usual places and they seem to be around the £120.00 mark with postage.
I got a quote from a company called Lifelong Exhaust for £99.00 fitted! this seems really good has any one used a fabricator? do you know if they will be able to refit the heat shield? Cheers Gonzo.

 

I wouldn't bother TBH

 

What makes you say that!
I'm trying to mod the same as a prodrive pack but in stages and I thought it would be a good start.
I have read that it needs no remap after fitting and should give me a few horses and a little more rumble!

 

Fit the pipe but don't worry about whether the heat shield will fit.

 

Oh i see what you mean
Do you think its worth wrapping with that heat wrap stuff?
just looked at your spec D same as mine but with loads more mods.
just what I am looking to do .

 

I have my sports cat wrapped but didn't bother with the second decat. If you have the time why not wrap it, not essential but wouldn't hurt.

 

I'm assuming you mean replacing the downpipe, and the heatshield you're referring to is the one over the turbo? It should go back on real easy with a bit of trimming. Leaving it off will increase underbonnet temps, and as its right next to the master cylinder that ain't good.

You *may* get a CEL when you remove the downpipe cat- some do, some don't, and you'll probably get boost spikes. It will also likely run like a bag of crap unless you have it mapped.

 

Reading that again, maybe I've misuderstood; I took the '2nd cat' reference as you'd already removed the first.

Is thats not the case, and you're planning on removing the 'rear' cat for want of a better word, then don't worry about heat shields or remaps as neither will be necessary. I really would recommend that you go for a 'named' backbox though or you could just end up with 'noise' if that makes sense?

 

Yeah sorry for the bad wording it is the rear cat!
do you think I will be able to notice any power gains
Already have a Prodrive back box so hoping to get a little more rumble as well!

 

My bad reading is as much to blame

You'll maybe feel a little power increase, and it may rev a bit easier, but not a lot

 

It is a waste of time replacing just the second cat. you will gain about 2bhp if you are lucky... Most people, including I think the PPP replace the cat in the downpipe (either decat or sports cat) and the second cat with one pipe. This obviouslt removes the second cat in the process. There is a resonator, not a cat, in the centre pipe. This can be replaced to make the exhaust louder.

Basically, replace the centre pipe (£100) and get either a decat or sports cat downpipe (£150-£400 depending on what you go for) and that is all you need. Then a remap, which you only need when you replace the downpipe.

 

In the 2.5 PPP they just replace the second cat pipe. That coupled with a remap will surprise you

 

You're quite right they do just replace that cat on the PPP for the 2.5. Surely it is better value for money doing the downpipe properly (i.e. sports cat/decat) if doing it yourself?

 

Just to make things clear I will be changing the 1st cat (down-pipe) to a sports cat at a later stage.As at the moment I do not have the money for a remap.
I thought it would be a good start to get rid of the rear cat,And spread the cost of things
Does the 2.5 struggle come MOT time with just a sports cat??
If prodrive leave the standard downpipe in do you think its worth changing?? maybe you can still achieve good power figures with the standard after all a sports cat is not cheap!

 

It should be fine with a sports cat at MOT time, but then again so is a decat in selected outlets

A decat is best.
A sports cat is almost as good.

The standard cat is restrictive and the turbo will spool up slower. You could still achieve around 320-330bhp with the standard cat and a remap I think, which is very respectable. Every tuner worth his salt will tell you to sort the cat is the first and best mod you can do, but it does require a remap especially with a 2.5 engine (or so I have been told).

If funds are limited, I would just save up and do it right personally or you'll end up paying more in the long run. If you are thinking of just changing the second cat and not remapping then you will not really notice a difference. With a remap you will, but then you might as well sort the cat before doing that.

You could just change the backbox and centre pipe for a better sound, which is cheap but completely ineffective performance wise.

 

Aye centre pipe will improve the revs, smoother and less juddery on pull off IMO. Get it all done at once I would. Second cat is dirt cheap and wouldn't add much to the greater cost of remapping anyway. Problem you will have without remapping is the potential for overboost without remaping. People reckon the second cat removal is ECU friendly but this is not necessarily the case with the 2.5's

 

2.5 sti spec d fitted with secondhand hawkeye ppp exhaust (same as RB320 mot friendly) get a remap from Andy Forrest circa 335bhp and 372ft/lbs
Keeps standard cat down pipe, 2nd cat replaced by prodrive ss silencer with standard heat shields re-fitted no problem , standard resonated mid section, prodrive ss back box, standard fuel pump has enough spare capacity

My priority at present is for car with standard parts & dealer friendly, sounds good and has plenty of push down the road

 

53WRX, doesn't the PPP for the 2.5 consist of a straight through pipe in place of the second cat?
Or do you mean that even when replacing the 2nd cat with a straight through pipe a remap is recommended?

I have the same goal
Isn't the PPP exhaust basically a straight through decat pipe (I didn't know they replace the 2nd cat with a silencer) and backbox? At least for the WRX?

 

I'm now all confused, As far as i can make out you have only taken out the rear cat and had a remap to achieve 335bhp that sounds to good to be true!!!
Or does this ppp exhaust from the RB320 have a sports cat as standard?
Does Andy F dyno map or road map? as I have heard some dyno maps are all for figures?

 

Sounds good but it all depends on the formula you used to generate your fly wheel figure. I have 288WHP and 323Ft Lbs at the wheels and I use 16% as a guide for my flywheel figure 335/375. I am running a sports cat and find it hard to believe you would have the same figure at the wheels using the standard DP

Not essential but the 2.5's ECU and its ability to control boost is different to the old 2ltrs ECU. Even changing the second cat for a decat pipe may cause you overboost in some circumstances

 

Thanks again!
Prodrive must make a few Quid for 2 bits of exhuast and a plug in ECU ????
£1700 I must be in the wrong game! Think I will start Doing similar for £1000

 

Hi greatgonzo
Fitted a secondhand ppp exhaust from a 56 reg 2.5 hawkeye wrx, bought from a scoobynet member, for £170 delivered.
My investigation/experience was that the same ppp exhaust components are sold to fit both hawkeye 2.5 wrx and sti and are also fitted as standard on RB320, ie all the same parts fit all and the changes are, 2nd decat replacement with a ss silencer (small, fits inside refitted heat shields) and back box.
Andy Forrest road map flywheel figures quoted, Andy has also mapped an unmodified standard spec RB320 (which has ppp comprising of exhaust as described, prodrive re-mapped ecu and uprated fuel pump) and achieved similar figures
Agreed that you will get more power and earlier spool up with a de cat downpipe or sports cat, but figures are not bad for the minor changes with approved parts at less than half the dealer £1700 price

 

Road maps only give you ATWheels, the flywheel will be a conversion % and therefore open to speculation I am sure its great though Broadly speaking the PPP parts and a remap are 110% worth it