Hi Chaps,

I'm thinking of going full decat on my current exhaust system (currently TSL GrpN backbox and decat centre) but someone recently advised me against fitting a downpipe to complete the decat, without a remap, due to serious lag problems resulting.

I drive an MY02 WRX and was previously given to understand there would be no problem with this - have any of you done it, and were there any problems?

cheers
DaveR

 

I have seen no problems since fitting mine.

Steve

 

Full Scoobysport decat on mine and NO problems whatsoever.The car pulls HARD now to the redline and is a great upgrade.You'll need a CEL fix though when changin the downpipe to stop the 0420 error code (Or whatever it's called!)

Nick

 

Nope wrong, less lag

 

Not heard of this either - I would have thought the reverse was true. The ECU on the newer cars will adjust to take account of the different flow of air etc.

Never had a problem with mine (Scoobysport dp, mid and back box on MY01 WRX)

Chris

 

No problem here.

MY01, SS DP, SS Centre, TSL BB. Sounds soooooooo much better!

 

Dave,
Go ahead and do it best single mod that you can do, Im running a my02 with hayward & scott uppipe/downpipe decatted centre and wrc backbox revs much cleaner best thing iv done so far.

 

Right i been looking into different systems in quite a big way.. I spoke to the expert at prodrive (really nice guy btw). He said that if you change your exhurst you need to get your engine remapped. The only thing you can safely is to change the back box.
This is due to the reduction in back pressure, which the ecu does not know what do to with.. Yes it will give you more power and a really super sound.. but will also cause your turbo to over boost which can easily result in you damaging that lovely engine :s
Some times this wont happen.. some lucky people will just have a happy car and carry on cruising.. but im not gonna risk it... bah i never thought i was going to say that.. im gonna stick with a back box for a while and get it all decatted and chipped later (when im pretty happy that the car isnt going to let me down)

Dunno if that helps but it made my mind up.. the prodive guys didnt recommend or condem it he just told me how it was!

 

I'm extemely paranoid abou the performance and reliability of my car. My eye's are always glued to my boost and oil pressure gauges and I've yet to see any overboost since the full decat was fitted.

Steve

 

Vash

I'm not sure who you spoke to but would suspect he was the chief tea maker, pretending to know something about these cars. Whoever he was he knew nothing about road going Imprezas.

You do not need to remap a WRX or STi7-8 if you want to fit a full system.

If the car is an STi7 or 8, you will need to change the boost control restrictor to prevent spiking, but this is £5 worth of brass tube. An exhaust change on an STi will give you full boost 800rpm sooner and it only spikes because the standard exhaust is so bad. The car performs despite the design of the standard exhaust, not because of it. You will not get any spiking on a WRX, but will get better spool up and up to 260bhp from a full system including up pipe. On an STi, this figure is over 300bhp.

The boost level on all Imprezas is controlled by the ecu and you will not run more boost by fitting a full system. You will just achieve full boost more easily and have better volumetric efficiency from the air and fuel that is going into the engine, so more power and torque.

 

From everything I've seen, the boost spiking is a big problem with the STi, but not generally the case with the WRX.

Without in any way criticising Prodrive (or claiming to have as much knowledge as them) they have to say that. The Prodrive pack only changes the backbox and is the only system they provide with warranty backup. They can't advise you to do anything else as they haven't proved it through their thorough in-depth testing.

I had full exhaust (APS sports cat) for a month, with de-cat up-pipe and ported headers for a week before I remapped (purely for power reasons), and detected no problems. Many people have had similar experiences.

Edit to add - as Pete says, restrictor change eliminates the problem on the STi

[Edited by hades - 5/27/2003 6:51:50 PM]

 

woot that is the answer i have been waiting for.. i want a HKS system on my STI8 when it arrives.. im sorry but a rally car should sound like a rally car

Refined my ***

 

Without intention to hijack your thread mate could someone tell me what power/torque figures could I achieve “decatting” a 03WRX, as far as I know it hasn't up pipe cat and some more boost (1 bar max) compared with the MY01-02 but haven't seen anyone that changed his exhaust yet due to warranty reasons, only PPP modified cars!
Thanks
JIM

 

Jim

We've supplied plenty of 03 WRX owners with exhaust systems but I haven't heard of any going on the rollers yet. Results will be virtually identical to 01-02.

 

Just to re-iterate what Pete has said,my fully decatted 01 WRX (With ITG panel filter) on a recent rolling road made 262bhp!!

Cheers

Nick

 

Do HKS and Blitz for full decatted systems to fit a STI8 uk??
Spoke to my local tuner and they cant find a listing for the uk ones only the jap! What have you guys got fitted?

 

Nick,

Which RR did you see those figures on? My car is the same spec as yours and saw 250bhp at Well Lane. Not quite as high as yours but very pleasing all the same!

Steve

 

I have been told Pete that WRX03 Imprezas don't have the same CEL issues with bugeyes due to different EGT and rear O2 sensors thus they don't need the CEL fix device neither.
Is this true and what about boost levels after decat, usually the downpipe gives slightly more boost at 3000+ rpms? Questions, questions, but I guess that I am not the only 03 owner that have these queries!
JIM

 

Guys --> haven't been back to this thread for a while even though I raised it! (lost the email forwarding)

but THANKS to everyone who has responded, I will now definitely be making the leap from MY02 decat centre and back to the full system very shortly indeed.

(Pete I guess I may be coming your way.... )

cheers
DaveR

 

Jim

I think some of the EGT failures were down to a dodgy batch rather than decatting. I did suffer an EGT failure, but there have been many cases of the exact same failure occuring on cars with standard exhaust systems.

Personally speaking, my car is now close to 40K miles. I have run one of Pete's full systems (H&S version) for close to 32K miles. Very pleased and never suffered any problems. The only thing that has happened was a broken bracket on the downpipe, which H&S repaired FOC.

Chris

 

Steve,
Funnily enough,mine was also done at Well Lane!!

Cheers

Nick

P.S: It was running std unleaded at the time of the rollin road but is now on Optimax

 

i stoped boost spiking on my 2002 wrx (jap) by fitting a Dawers device spool up is better too with full decat ....chris

 

Also Nick and Steve iirc it was in January and was Fooking freezing whch would have made a bit of difference, what with ambient temparatures and all that.

Zippy

 

UHF whom I 'bumped into' this morning on 'was it you' mentioned that after getting a full decat I ought to consider getting a 'link' instead of Tek3 --> any of you guys know what the difference between the two is?

or which is better for an 2002 car?

thanks

 

http://www.ecutek.co.uk/tuning/aftermarket/

 

Thanks Pete --> that helps

 

Vash

I have been doing a lot of research on the best exhaust for the my STi 8.
I wanted Jap quality with the perfect balance between "noise" and boxer sound.
I think you would agree this sounds the bomb

http://www.hks-power.co.jp/sound/sound.html

My HKS Silent HiPower arrived yesterday from Japan, looks awesome and fits perfectly with my pre-MY01 scoobysport downpipe. The JDM catback systems are too long for the Downpipe and cat-placement centre pipe for the MY01->.

Waiting for my Tek 1 from Scoobsport to arrive Monday next week ;-)) thanks Pete, and will let you know if it sounds as good as on the web.

rupert