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Our customer Jay recently picked up a new 2011 STI. He got an extra set of wheels with Dunlop snow tires and we ran the car on our dyno to baseline it before the modding began.
Unlike past body style changes which had to grow on me, I liked this one right away. It looks great, and mean.
Onto the baseline results: 215-217 whp and 222-226 wtq. Not bad at all for stock.
Then we got Jay an Invidia catted downpipe and a Borla cat back to help open the car up while keeping it relatively quiet so Jay doesn't get hassled. The Borla cat back arrived with a donut style flange that won't work with an aftermarket downpipe so the cat back was modded to work with a flat flange, and to get rid of the bottleneck near the flange.
Jay also removed the silencer from the stock airbox. More on this later...
The car went back on the dyno, the Cobb stage 2 93 v.106 variable boost mapping was loaded, and I ran the car a few times on sport mode. Boost was higher than stock, but power was lower than stock. Something was definitely up.
It turns out that removing the silencer on this new airbox and MAF REALLY throws things off. As you can see from this dyno graph, I was able to make a huge improvement over the Cobb mapping at the same boost level on sport mode. After seeing this I very strongly advise against removing the silencer if you're not going to get a custom tune immediately. This is not an error in the Cobb map as their stage 2 maps are not designed to be used with the silencer deleted.
After completing the sport mode tuning, I switched to sport sharp and just as I expected I was able to crank the torque up considerably, but there wasn't much room to safely add horsepower up top.
This graph shows the Cobb map and pulls on my map in sport and sport sharp modes.
This graph shows the best baseline pull when the car was stock and pulls on my map in sport and sport sharp modes.
The weather here is awful at the moment. Jay and I went out on a test drive to check drivablity and made a few partial pulls. We'll complete the road testing when it's not snowing and roads are totally clear and dry. The car seems to run great, but it's hard to say when you're tip toeing in poor road conditions.
The fuel system is maxed out. I had to back things down up top to keep the injectors from going static. I also adjusted the new wastegate and boost target trims per intake air temperature to help keep the injectors from maxing by dropping boost as it gets colder.
Jay has been into modding turbo diesel trucks and this is his first foray into modding a turbocharged gas setup so we're exited to see what we can do with it together. After today's tuning session I'd say the engine is broken in and we'll see what the future brings for this great new car.
Yeah talk about shooting yourself in the foot with the air box silencer removal. But as you can see Mike was able to tune around my hiccup. My thoughts are already leaning toward injectors and an intake.
I have to say, Mike is awesome and I'm sure this car will be just as silly as most of my other vehicles once it's all said and done.
No worries Jay. I was just caught off guard by how much the silencer delete affected the MAF readings on this model. At first it seemed there must be something more serious going on to throw things off that much. On older models the airbox only had one inlet and removing the resonator didn't affect much. On this one it opens up a second inlet which is 90 degrees off the primary inlet and it requires some big MAF calibration changes to get the car running properly again.
Barry I did some research and figured out that the Borla cat back for 08-09 WRX sedan would fit, but as I mentioned the donut style flange had to be replaced with a flat flange to use it with a flat style flange that aftermarket downpipes come with.
When you took out the silencer delete part, did you simple recover the open hole?
I took out that piece and used a tennix ball cap and then used duck tape to make it nice and snug and the car ran like a top, no issues what so ever, reading were fine.
are you sure that the car was in cobbstage2? that dyno looks just like the stock one
I imagine the airbox is the same as all GRs, i think people would notice a drop of 50hp in stage 2 when removing the silencer.
I didn't notice any change in MAF readings via ODBII when i took mine out and again when i put it back in.
When cobb did testing on intakes and maf readings (on 07 models i believe) they did say anything pre MAF, including the silencer, had some effect on the MAF.
As I mentioned, "the Cobb stage 2 93 v.106 variable boost mapping was loaded."
If you look carefully, you'll see that the Cobb map and the stock map pulls are shaped rather differently, with the Cobb map ramping torque up all at once and sooner than the stock pull, then holding the torque it does make until around 5000 RPM vs. the stock pull which shows torque tapering after 4000 RPM. They also set the map so the IAM defaults to 1.0 and full advance was run immediately.
2011 Subaru STI baseline pulls, initial mods, custom dyno tuning 
