As some of you know, my latest tuning session was this past weekend. Before you get excited, I have no official new numbers yet. Mods this time around (new ones listed in this
obnoxious color) included the following:
ACL race main/rod bearings
ARP head studs
Cobb AP V2
Cobb catted dp
GrimmSpeed 3 mm phenolic spacer
GrimmSpeed 3 port ebcs
GrimmSpeed air oil separator
GrimmSpeed ported/polished stock headers w/ high flow crosspipe
GrimmSpeed turbo heat shield (replaced Cobb turbo heat shield)
HKS Hi-Power Carbon-Ti cat back
IAG Big MAF intake
IAG TGV deletes w/ air pump block off plates
Injector Dynamics 1000 cc injectors
Invidia up pipe
Kelford 264 cams
Killer B ultimate oil pickup
Manley 99.75 mm pistons
Manley H-beam rods
NGK one step colder Iridium plugs
Perrin crank pulley
Perrin turbo inlet
STi 11 mm oil pump
Walbro 255 fuel pump
The first problem that arose was that my car was producing an abnormally high volume of air out of the exhaust tip - enough to blow over the O2 sensor that was mounted on a jack stand and braced with a sand bag. Easy fix - the O2 sensor was clamped on to the exhaust tip, no big deal - just pretty cool
The next problem that arose was that my car was making the same power (low 300's) at 16 psi as it was up into the low 20's (turning up the boost didn't produce more power like it should). After some discusson and pondering, the issue was narrowed down to several potential sources. The first, being a leaky stock BPV. The solution: get a rather large socket and a BIG fing hammer and crush the BPV slightly to increase the pressure needed to open the valve inside. Ultimately, this didn't solve the problem.
The next thing we tried was swapping my Cobb catted downpipe to a catless model. The thinking here was that the catalytic converter might possibly be clogged. The catless dp caused the car to breathe so much easier that it was boost creeping like crazy! It would build boost when it wasn't supposed to and spike pretty high when it was supposed to. This was happening because the engine was forcing so much air through the turbo that the internal wastegate, even when fully open, was not allowing the air to travel through fast enough so it was backing up before it could get out.
At this point, it was decided that the Cobb catted downpipe would be put back on and I would have a temporary map that is rev-limited to 5,700 rpm and boost-limited to 16 psi. Fortunately for me, there is another tuning session scheduled for the weekend after next and I was able to schedule a timeslot for the following mods to be installed before then:
GT Spec unequal length header (to replace GS PnPnC w/ high flow crosspipe)
IAG up pipe w/ external wastegate (to replace Invidia catless up pipe)
Invidia catless bellmouth dp (to replace Cobb catted dp)
Prosport turbo blanket (to replace GrimmSpeed turbo heat shield)
TiAL 38 mm external wastegate
Since the headers have to be removed to get to the up/ewg and they're another potential restriction (although not likely), I might as well upgrade them to be safe. I decided upon the unequal length headers because (1) I want to keep the Subaru stumble because I still love the way it sounds and (2) even though the unequal length headers provide less horsepower than equal length, they provide more torque which is what you really feel when you drive. I don't have a monster turbo and I'm not looking to make huge numbers, so I'd rather feel a bit more on the street than be able to brag about having slightly higher horsepower numbers which don't mean a thing.
I'm going to dump the ewg directly to atmosphere under the car instead of plumbing it back into my exhaust because (1) plumbing it back into the exhaust piping causes a horsepower loss because it would disrupt the exhaust flow and (2) it would cost more. I know I said I wasn't worried about sacrificing horsepower in the previous paragraph, but I lied
I wanted to install a turbo blanket from the moment I upgraded to the 20G, but I found out that I was unable to use it with the internal wastegate because it would interfere with the wastegate actuator arm. Since that won't be an issue any more, I'll finally be able to use a blanket. It will be nice to efficiently block some heat directly at the source - especially because I still have a tmic. I thought about header/up/dp wrap, but there are too many issues associated with it and although I enjoy keeping up with maintenance, I wouldn't want to have to re-do it on a regular basis since it's a wear item. I'll save that for the serious racers and die-hard temperature freaks.
The 38 mm wastegate should be plenty for my application. The 44 mm model might sound a little deeper, but it also costs more and I don't want to spend too much more on this car if I can help it.
I'm contemplating getting a Cobb bpv and fully recirculating it, but that can be done after the tune. I'd just hate to get on the rollers again and find out that after this round of work, my stock bpv is indeed leaking. Thoughts on that? :: cough, cough Joshua ::
P.S. I'll probably be selling the Invidia catless up pipe and GrimmSpeed ported/polished/ceramic coated stock headers w/ GrimmSpeed high-flow crosspipe. If anybody is interested, the up pipe will fit an 02-07 WRX/STi and the headers will fit an 06-07 WRX/STi (sorry 02-05 folks, the design is a little bit different so it won't fit yours). The cat in the Cobb downpipe is partially blocked, so if you want to buy that, you could cut the cat out and weld in a straight piece of 3" pipe and a new flange and it'll be good to go