Hi Folks,

I've done a bit of reading and searching on this topic but I am yet to find a definitive answer. There is as many people saying you definitely need a remap if you decat the up pipe on a 2005 wrx as there is people saying you do not need a remap.

There are two sensors in the up pipe I believe, EGT and Lambda.
The Lambda works with the ecu to richen or lean out the fuel mixture dependant on exhaust gases. The EGT can just be unplugged when changed due to the heat being produced is no longer issue as the cat is removed.

The available Decat up pipe has both the EGT and Lambda bungs present that can be used if you like.

Due to the CAT being removed I assume there will be more un-burnt hydrocarbons in the exhaust system as the gases have not passes through the pre-cat in the up pipe.

Does this mean even if both sensors are plugged back in the Engine Check Light will come one and throw the ECU into safe mode? I don't believe boost spikes would be an issue due to the remaining 2 cats are still present in the exhaust system after the turbo.

I basically want to swap the up pipe for a decat pipe to gain some spool and protect against the cat potentially breaking up into the turbo.
Also £500 for a remap plus between £200 and £1000 for an exhaust system is a lot of money.

Would an open source map to switch off the engine check light work? As paying £150 for an Ecutek license plus labour to switch off the CEL seems a bit daft lol.

Thanks!

 

yes it will need a remap,you wont feel any difference if you just swap it

a mapper can come to you and live map your car for around £350 and yes they can switch the cel light off as thats what i had done.

£1000 for an exhaust system? ? ?

second hand headers £200

new jap speed de-cat downpipe £130 ish

second hand system £150-£300

loads of scoobs being broken so look around for parts,i picked up a set of roger clark headers with a venturi up-pipe for £240 delivered so bargains can be had.alyn at as performance can port your standard headers as well if you cant find any second hand ones,just dont buy any cheap **** from ebay as its garbage

 

Hi Shreksta,

I wouldn't be looking for any power gains at the moment, just to do away with the cat. The fact the STI runs with up a cat in the up pipe makes me wonder why the WRX will need a remap. (I do appreciate they will have slightly different maps from the factory)

In fairness that is a good point about the exhaust system, will just need to shop around and see what deals I can get!

Thanks for taking the time to read my post!

Cheers.

 

The wrx uppipe doesn't really reduce the emissions once the car is warm but the theory is that it does help during the warm up period only. There is only one sensor in this pipe, EGT temp sensor. As you said the sti uppipe is catless. You can connect a resistor to stop the cel light on dash if you put an sti uppipe on. I have spare resistors if you require one, PM me. But as said before really need a remap for this mod to control the changes safely. I have converted my Wrx exhaust system into an sti ppp one and got great gains after a 350 quid remap from Racedynamix :-)

 

If I buy an after market up pipe with the a bung available for the EGT sensor, will the CEL still come on? I know the pipe would run hotter with a cat so therefore a decat pipe may not produce the temperatures required to activate the EGT sensor correctly. If so could a different EGT sensor be purchased and fitted with a different temp range? And I'm not really bothered about bhp gains, I get my fun in the corners!

I take it the resistor (is it a 2.2 kohm resistor?) would just be fitted into the lose EGT sensor and tied up out the way?

Cheers,

Marty

 

Yes Marty if you can get an uppipe with threaded hole to take the sensor, then no cel light Will come on. I believe the actual sensor is before the cat and should get just as hot so shouldn't make any difference, but don't quote me on it Only one type of sensor i believe. just don't go for one of them flexi uppipes from ebay as can split rather easily. I went for the sti version. And yes the resistors i have is the 2.2oh type and worked for my blob Wrx.
Cheer Phil

 

Magic, that sounds good enough for me to have a go and change it, worst case I have to refit the old up pipe
I will have a look at the up pipe and see where the sensor is but I think your right!
Yeah I've seen those flexi ones, they do look a tad rubbish...
Awesome, will let you know how I get on with it all!

Cheers
Marty

 

Just be aware Marty if you get an aftermarket uppipe, the bore needs to be around 42mm ish otherwise it may affect spool up. 42mm is standard size for wrx and sti uppipes. And only use oem gaskets.
Happy hunting
Phil

 

Ah ok! Thanks for the heads up!

Cheers,

Marty