Hi, I wanted to outline my experience of the Subtech Legacy Downpipe.
You can see the pipe and deno chart on this auction. Max boost is 11.5psi
http://www.trademe.co.nz/motors/car-parts-accessories/subaru/engines/auction-440662123.htm
My car is 2003 BP5 Legacy Wagon GT (2L turbo)
I had the factory downpipe replaced with a Subtech Downpipe a couple of months ago now. I also had the airbox modification done (they remove the silencer and put in a feed down to the bottom of the car.)
The downpipe is cat-less but the two O2 sensors plug-in in the same position as the factory downpipe.
Before i put on the downpipe i always felt when driving generally or cruising that there was some resistance, like the handbrake was slightly on. The power didn't really kick in until 2800rpm and i would often drive around in sport mode so that it felt more powerful. Going up hills i would often flick it down a gear on the triptronic to get up a hill easier.
The overall result of installing the downpipe is a big increase in power. Noticeably the boost comes on much quicker down low. The car feels much better to drive in standard mode and it glides up hills compared to before. So for general driving it is a much more pleasent car to drive. If you put your foot down there is heaps more power too. It really is quite a bit quicker. Start using the triptronic on the highway and its quite fun.
I didn't like the sound of the air box modification and got it changed back to factory (has a high flow filter though). Haven't noticed any drop in power from putting it back to factory and now it sounds better too. I wouldn't recommend that mod. Waste of time and money.
Noise
Because the downpipe is catless it is quite a bit noisier. Down low and up high the sound is fine, but accerating from slow speeds it can be quite loud, a raspy sound, which can be unpleasent.
Rest of exhaust
Subtech say they are developing a rest of system exhaust which will address some of the sound issues. Although this will be another $800-$900 dollars.
Mixture
Because the sensors are in the same place as the factory Subtech tell me the mixture will be fine and that it won't run lean or rich.
Tuning
Subtech also say tuning isn't require for this modification.
Questions
I really like the extra power and torque. But am concerned about a couple of things:
To reduce the exhaust sound i was thinking about removing the factory resonator (after the downpipe) and replacing it with two coby resonators running in-line. Is this a good idea?
I want to keep it quite quiet, so quite keen the keeping the factory mufflers and trying to sort the sound with resonators.
