WRX PPP Decat Downpipe
Discussion
I've just got a WRX wagon with PPP (2005) and want to fit a de-cat downpipe. My other car is a RB5 WR Sport (ie classic with PPP) and I've had that with a no cats running fine for 4 years.
My question is will it run ok, I know I should have a remap but my classic runs fine and feels a thousand times better with no cat in the down pipe (plus sounds better).
Will it run ok and will I have engine light issues. Does the new age have a lamba in the downpipe?
I don't plan any other mods so dont want to get into remaps.
Thanks for any advice.
My question is will it run ok, I know I should have a remap but my classic runs fine and feels a thousand times better with no cat in the down pipe (plus sounds better).
Will it run ok and will I have engine light issues. Does the new age have a lamba in the downpipe?
I don't plan any other mods so dont want to get into remaps.
Thanks for any advice.
Fitting a decat Downpipe allows the engine to breathe better and the turbo to spool up that little bit sooner and quicker but consequently you might overboost a bit, specially in 4th and 5th gears.
Replacing the std uppipe as well with a decat version will further help engine breathing and turbo spoolup but again you might experience a little more overboost without remapping.
Whenever you make major changes like exhaust parts you should always remap for those changes, not just to get the full benefit of those changes in terms of increased power/torque but also to ensure the car runs as well as when it left the factory.
My first change would have been the uppipe, then downpipe, and finally centrepipe and backbox, either one by one or all in one go (much better). Paying for a full remap after your first mod/s would ensure that subsequent mods only require ECU tweaks and therefore cost a lot less than a first remap.
Your new downpipe will have the rear O2 sensor fitted at the end of it. My other recommendation is that if you have an O2 sensor bung and plug in the bell of you new downpipe where it bolts to the turbo you should relocate the front O2 sensor there for more accurate AFR's and screw a plug/bolt into the old location at the end of the outlet manifold.
Replacing the std uppipe as well with a decat version will further help engine breathing and turbo spoolup but again you might experience a little more overboost without remapping.
Whenever you make major changes like exhaust parts you should always remap for those changes, not just to get the full benefit of those changes in terms of increased power/torque but also to ensure the car runs as well as when it left the factory.
My first change would have been the uppipe, then downpipe, and finally centrepipe and backbox, either one by one or all in one go (much better). Paying for a full remap after your first mod/s would ensure that subsequent mods only require ECU tweaks and therefore cost a lot less than a first remap.
Your new downpipe will have the rear O2 sensor fitted at the end of it. My other recommendation is that if you have an O2 sensor bung and plug in the bell of you new downpipe where it bolts to the turbo you should relocate the front O2 sensor there for more accurate AFR's and screw a plug/bolt into the old location at the end of the outlet manifold.
Edited by ScoobieWRX on Tuesday 16th February 14:01
Thanks for the advice.
I'm assuming the newage has 3 cats as standard but PPP removes 1 in the centre section so if I remove the downpipe cat I'll still have one left, plus a resonator and the back box?
I'm just going to change the downpipe, so no plans for any other exhaust parts to be changed.
I know I should re-map to get the best but I think I'll run it and see how it goes.
The downpipe I'm looking at is from TSL so has an 02 sensor at the top near the open neck so goes along with your advice to put the sensor nearer the turbo.
I'm assuming the newage has 3 cats as standard but PPP removes 1 in the centre section so if I remove the downpipe cat I'll still have one left, plus a resonator and the back box?
I'm just going to change the downpipe, so no plans for any other exhaust parts to be changed.
I know I should re-map to get the best but I think I'll run it and see how it goes.
The downpipe I'm looking at is from TSL so has an 02 sensor at the top near the open neck so goes along with your advice to put the sensor nearer the turbo.
If you're going to leave the uppipe as standard with a cat in it leave the O2 sensor exactly where it is in the exhaust manifold otherwise your ECU is going is going to get lean AFR readings from the O2 sensor.
Front O2 sensor always goes before a cat and the rear O2 sensor after a cat.
Front O2 sensor always goes before a cat and the rear O2 sensor after a cat.
You have 3 cats on a WRX, none are removed for a PPP but the std downpipe cat is replaced with a Prodrive sports cat.
If you fit a decat uppipe and a decat downpipe you still have one 600cell cat left and that's the one in the center pipe. That's enough to easily get through emissions testing for the MOT. With decatting start at the front and work your way back.
If you fit a decat uppipe and a decat downpipe you still have one 600cell cat left and that's the one in the center pipe. That's enough to easily get through emissions testing for the MOT. With decatting start at the front and work your way back.
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