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We were the first to dyno the 08 STI, we were the first to bring you intimate pics of the car, and we were the first to tune the AccessPORT on the STI! In stage 1 form (bone stock car), with some initial testing we did, we got great gains! We saw roughly 40ft-lbs and 35WHP with nothing other than an ECU reflash! Its not very often that you can get those types of gains from a bolt on/flash on.

Stock ECU tune vs. PERRIN Stage 1 Tune

This graph shows our initial dyno plots vs. our initial Stage 1 tuning. The above graph was release a long time ago, when we were doing a lot of testing on the car. With quite a bit more road/dyno time under our belt it was time to go to the next level! Stage 2, the stage that 90% of the STI community will be stepping up to after they buy their car.

Stage 2 for most companies consists of a Turboback 3€ exhaust. This is true for the PERRIN stage 2, but with a little twist. Our Stage 2 down pipe consists of (2) cats, where most companies have (1) or no cats. For legal reasons we build our downpipes with cats to keep the EPA has happy as possible. Many people think that cats are restrictive, but this really isn€™t the case when dealing with less than 400WHP. We will show you the huge HP you can gain with (2) cats.

Before we can got tuning a stage 2 car we need an exhaust. Ok, simple! We have (2) types of exhaust we are working on, one that fits to the OEM exhaust pieces (so you can buy just a muffler or just midpipe) and another that is a complete catback, that is all inclusive and a little simpler. We have shown the prototype OEM fitment system before a few times. But here it is to refresh your memory.

PERRIN Muffler bolted to OEM midpipe.

Dual Single Tip€™s for this system. This tied to our 3€ midpipe is a great sounding exhaust.

But for this test we will be dynoing our car with our 3€ system that doesn€™t interchange to the OEM pieces. Of course it still bolts to the stock downpipe. It consists of the same basic 3€ piping, resonator, and muffler. The muffler has a central chamber where the exhaust splits into a 3€ core. Both the above and below systems have a similar design, one is just a different entry.

This shows the central entry of the 3€ tube into the muffler

Up close shot of the 4€ dual Single wall tip

A shot from the back showing the tips and the straighter shot of the 3€ piping to the back of the car.

This the first shot of the exhaust we have posted up, so feel free to critique us with suggestions of tips or other things. Like our other current systems this will be available in a black thermal coating.

The rest of the €œturboback€ exhaust consists of our off the shelf downpipes with cats. The cats are high flow, metallic core cat, like we have been using for quite some time. Before we go and dyno the parts and start to tune our stage 2 setup we tested our latest version of our stage 1 map we have building/tweaking.

Preliminary PERRIN Stage 1 results, vs the most current Stage 1 results.

The above graph shows our first iteration of the 2008 STI stage 1 mapping. This was a huge gain over stock and with some tweeking we did with more agressive boost control and some Exhaust cam changes we netted an additional 15-20ft-lbs of torque at lower RPMS. This mapping represents the 92/93 octane maps that we will be sending out to our customers that buy our custom map program and AccessPORTs.

So we as quick as we could, we yanked the OEM exhaust off the car and installed the newest version of our 3€ catback exhaust. Like our other exhaust this fits to the OEM down pipes. With the coolant still above 160 degrees we did a few quick runs back to back. With other catback exhaust testing we did, we would see about 8-12 WHP, with doing no other mods

PERRIN 3€ catback exhaust test on 2008 STI using stage 1 mapping.

What is different about this test is we left the stage 1 tune on the ECU. So its running a little leaner, little more boost, and more timing that it would be instock form. Just for fun we flashed the ECU with the stock programming before and after the catback. The results reminded us why the reflash was so important. The inconsistencies and rough graphs didn€™t give us any proof of the exhaust doing anything. With our Stage 1 reflash(which fixes many of the OEM ECU tunings shortcomings) and the catback exhaust installed, the runs were very consistent and consistently showed a 10WHP gain.

Next up is the downpipes! As we have explained before, our downpipes replace the stock (2) cats with 2 high flow cats. While this is not the normal type of downpipe you will find, we will show you how you can make lots of power and still be legal.

This is the graph of the HP and TQ gained from PERRN Dual cat downpipe being added to the catback.

This is the graph of the HP and TQ gained from PERRN Dual cat Turbo back exhaust System

These graphs are showing the gains had by installing the downpipes and the catback. Again we are using the mapping from the Stage 1 setup we did. You can see that the Catback and both downpipes are about a 10WHP each, making 20WHP. This is with NO retuning done and the same boost levels. The torque went way up because the turbo spooled up quicker by a couple hundered RPM. Now lets do some more tuning and see what we get!

This graph shows the HP we got with just bolting on the Turbo back and the HP we got with further ECU tuning.

The results with further tuning with the complete Turboback exhaust are amazing! Before the ECU didn€™t like any additional timing up top, now with the freer flowing exhaust the engine was much less prone to knock and liked to run a little leaner. The leaner mixture, and additional timing up top is very noticeable, and no longer does the car feel like it totally falls flat on its face above 5500rpm.

This is our Stage 1 results vs. our stage 2 results.

While our Stage 1 results we very impressive over stock at 35ft-lbs and 30WHP, Stage 2 takes the cake! For under $1500 you can take your Stage 1 2008 STI and turn it into a Stage 2 monster with another 50ft-lbs and 35WHP. Not to mention a sweet new sound!

This is the stock 08 STI results vs Stage 2 results. Don€™t forget this is with 2 cats!

This the stock 2008 STI Horsepowrer and TQ results we got the day we started tuning our Stage 1 setup. For under $2000 in parts, you will find very similar results on your 2008 STI.


There are 3 important things to note on the results. One is this is all done on Oregon 92 octane fuel, Two is we used our dual cat down pipes, same as the ones we sell, and three all runs were done in the manor as before. This means same gear, same start RPM, same load time, and same run time. We just want to be clear about how the results were obtained.

Other important things are the HP gained from our Exhaust system installations. The catback exhaust was worth about 10WHP and 10ft-lbs of torque, the turbo back was worth about 20WHP and 30ft-lbs or torque. This is with out any ECU tuning.

Add in the AccessPORT to those numbers and add another 20WHP and 20ft-lbs of torque. This makes for an incredible 35WHP and 50ft-lbs of TQ gained over Stage 1, and a crazy 60WHP and 80ft-lbs of torque over a stock car! Look for our Stage 2 setup to be under $2000, which includes the exact same parts as are tested here, plus the AccessPORT.

Like we did with our other Stage 1 STI mapping, we will do some minor tweaks over the next few days after we beat on the car a bit more. Stage 2 for us is important, as this is the most popular setup for the Subaru enthusiast.

We feel this is where most people go with their cars, exhaust system, and ECU flash and they call it good. Because this is such a popular setup, expect a lot of refinement. So what is next up on our plate? Stage 3 of course. We will be doing both TMIC and FMIC mapping and proving, along with water injection maps.

Finally this car feels fun to drive!

Thank you!

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