RomRaider

I own a pretty standard 2004 wrx (eu version). Previous owner added a PPP to it (which coonsists of modified ecu, silicone y-pipe and a backbox). Cars pulls signifantly better than stock, but the low range rpm is very weak. Turbo starts waking up above 3000rpm, full boost is achieved about 3900rpm - which in connection with 5spd long ratio gears, requires a lot of downshifting to drive dynamically.
That's why I am thinking what I could do to make the turbo treshold lower in rpms without the custom remap.
With which modifications will PPP ecu work without any danger to engine:
- Can I replace stock catted uppipe to decatted version?
- Can I replace stock catted downpipe to sport catted one (for example hawkeye PPP)?
- Can I replace whole mid section with straight pipe?
Which of these mods are safe without any modifications in ecu? Which of these mods will give me better spool on my ecu? Did anyone tried playing around with blobeye wrx PPP map, what it can handle? Do you have any experience with PPP / Prodrive map from a blobeye wrx?

in my experience the PPP map isn't as happy as a stock map once you start tinkering. Your spool up sounds to slow for a healthy car though, TD04 should be well on it's way by 3000rpm - maybe your turbo is just getting old now and needs a replacement?

Have you taken any logs off the car, checked the IAM to make sure all is well?

I couldn't say what would happen without a remap, but I made the same sort of changes to my PPP car and then had an Ecutek remap on top. I was aiming for better low end response as I'd come from a V6 and found the turbo a little 'frantic' in general driving (PPP still leaps and bounds over standard at the low end, but I wanted better)

I replaced the standard primary (downpipe) cat with a sports cat from a PPP Sti. I also replaced the up-pipe with a ported / decatted item. I actually used a lower diameter up pipe than an STi to try and help increase velocity for low RPM response.

Result: 2500rpm with the PPP kit made 60lbsft. Increased to 90lbsft.

bludgod, I have taken some logs, I can attach them so you could look at it. One possible cause of late spool could be a leak. On midrange with pedal gas pressed I can hear a 'whistle', while in the higher rpms and WOT, I can hear huge blow of air from outside (from under the bonnet). One mechanic, that I reported the problem to, told me that a cause could be blown gasket between uppipe and a turbo (he noticed some carbon there).

konan555, don't you have any dyno graphs or logs which compares your car with PPP and with decat and custom remap? A the moment I am thinking about very similar mods. How the car feels now, compared to the PPP?


And what do you think about replacing only the oem catted uppipe with the decateted version? Could this work without a remap on my '04 wrx?

yes you can remove the uppipe cat OK but if your not going to map out the codes for it then you need to fit a resistor to fool the ECU into thinking the sensor is still there.

If you think you have an exhaust leak just go get it checked out, a decent garage should be able to tell you if the exhaust is leaking or not - if it is leaking then new gaskets in and see how it runs.

I am going to investigate it on my own firstly. I am going to have it fixed by a mechanic eventually, the problem is, it's not that trivial task and I don't want to pay for it twice, I would like to swap the faulty gasket and the uppipe at once. But I need to be sure, that I can run my car with decatted uppipe without any trouble.
I remind you that my car is '04 EU - blobeye. I've read that earlier ecus (on Bugeye) were more tolerant and that they could even work fine with full decat (uppipe, downpipe, center) without a problem. But decatting uppipe only, is much smaller difference, and I keep wondering if it will be ok without a remap (I would like to see how PPP works without the leak, and on the other hand I don't want to pay for the uppipe job twice, in case of deciding to go the TBE decat/remap route).

you can change the downpipe without touching the uppipe so if the upipe needs doing go ahead and fit the decat one - you'll be grand without a map but you'll need to get the resistor in place to stop the engine light coming on (uppipe has a EGT sensor in it that you remove).

Then add downpipe/remap when the time is right.