I own a pretty standard 2004 wrx. 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 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 decatted version or sport catted one (for example hawkeye PPP)?
- Can I replace whole mid section with straight pipe?
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?

 

Always going get best results from a proper map,

Best you could do for spool would be get a harvey uppipe, go decat and get a proper remap,

Would make a huge difference,

This will prob start a big debate but you could possibly do the above mods with no map and it would run, however do the above mods then remap and it will run much better,

 

As above, a de-cat up-pipe will give the best spool benefits but only give a small amount more power. Removing the 3rd cat in the center section will give more power benefits but not effect spool.
As long as you've still got the main cat in the down pipe you shouldn't have any issues at MOT time. A sports cat here might be worth a look at
Wrapping the up-pipe and the exhaust manifold will also help spool (and under bonnet temps)
I think you will need a re-map, or a tweak at least, for the up-pipe otherwise you may get issues with over boost.

 

Am i correct in thinking if it spools early without a map it would be lean ?

or would ecu compensate ?

 

Logically it would make sense that it would be lean, but to be honest I don't know and I also don't know if the ecu would compensate.
I have remembered something I do know. If you do change the up pipe for a de-cat then you'll either need a map tweak to turn off the engine warning light or you'll need to trick the lambda sensor into thinking everything is ok (Google "egt resistor mod" for more info).

 

PPP had prodrive sports cat aswell didn't it?

The ecu will be programmed for sports cat and your using stock, this will be bad also.
Could explain the flat spot and poor spool up

 

There was a variety of combinations of cats and sports cats for the newages. Depending on year and WRX/STI model cars with the PPP may have had between one and three cats.
Either way, I think we're all suggesting that if you were to do this mod a session with a good mapper would be money well spent.

 

Even a map on its own would benefit with no mods by the sounds of things,

 

Something is amiss as the WRX has the small TD04 turbo and should start spooling by 2500rpm. Harvey Trick up-pipe and ported headers will help reduce spool. You aren't going to get much more low down power without something like a hybrid-td04 or an engine capacity increase. Everything should have a map tweak afterwards. I'd suggest getting it on a rolling road first, to see what's what.

 

For sure I have a leak before turbo (uppipe gasket) which is a part of the problem. Because I have to remove the uppipe I will try to replace it with decat version and heatwrap it together with manifold and see how it works.
Problem with the remap is, where I live, most of the mappers don't have experience with subaru turbo engines (VAG domination). The few specialized in subaru are on the other hand very expensive.
At the moment I want to get maximum of my current PPP setup - I am not interested in maximum HP, I just would like wider powerband. I think that this PPP map should be better prepared for some lightweight modifications than the stock one?

 

PPP is just a generic map, so fix the car first. Blowing exhaust will be an obvious issue. Decat up-pipe will have less of an effect than a downpipe, so could probably get away without a remap. But I don't advise it.

 

Any major changes would require a remap,

You want a wider powerband you will need a remap simply no other way,

If its blowing at the gasket I personally would rather buy a new gasket and a "Professional" remap, Instead of buying new up-pipe and no remap,

 

Problem is the cost of professional remap, cost of remap != cost of used uppipe.
What do you think about XPT stage2?