Hi people, im not sure in anyone here has done it but i went ahead, after a techy recommended it, and installed an STi exhaust on my Forester 2.0XT 2017. Here is my verdict:
1. Fuel efficiency sucks now
2. Sound is awesome but droning is pretty annoying
3. The CVT has a weird jitter.
I talk to Crawford Performance (they have nothing to do with this. I simply have good contact with them from other activities) and they said this should happen. Im now swapping to the stock exhaust and see what happens.
All back to normal...Mileage great again and torque is back. The awesome sound is gone. Bottom line, the STi Performance exhaust does not work for any vehicle equipped with an FA20 engines.
M FXT has the new 2.0 turbo and is not as torquie as the EJ25...That why maybe you did not notice any issues.
Final Verdict For now: NOT RECOMMENDED.
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I speak from experience. I had this exact same issue when I removed the stock mid-pipe and mufflers; and went to a Stock WRX and Namless single tip 5 inch mufflers. car felt down on power and loss of torque. boost would not go above 15 psig. CVT acting very weird too. one morning the battery died over night (unrelated to the exhaust and still dont know why, NO DOME LIGHTS ON). so I had to charge it an put in through the Throttle relearn procedure. what a difference but not back to normal yet. I also hated the drone, because there is no resonator in the stock WRX mid-pipe. so i switched out to the STI stock midpipe. big difference!!!! sounded much better still keeping the same Nameless 5 inch mufflers. I had the car stall and i brought it in to subaru to have everything checked out, i also discussed the drive-ability issues i have had been having. The tech decided to update the ECU and TCU with an update that was part of a TSB (the costumer has to complain of a drive-ability issue for this to happen or else they do not do it). they look through the multiple updates and pick one that matches correcting the issues and symptoms that you discuss with the service writer and/or tech. after the update and driving the car like hell for a week, boom all corrected. now the car actually feels like it has more acceleration at high speeds, then when stock.
I think your problem stems from not:
1) doing a throttle body relearn procedure afterward
2) having the dealer reflash the ECU and TCU with updated programming
I am still running the STI stock exhaust with the Nameless 5 inch mufflers, no modifications needed. I suggest getting the genuine subaru exhaust crush gaskets for the mid-pipe to the muffler. NO RTV, just a lite brushing of never seize.
there seems to be something else going on here... (I am not calling
@DannyPTY a liar, just hypothesizing on root cause)
fuel economy isn't impacted as much unless there is a LOT of restriction... the new exhaust has less restriction than the stock... performance (the ability for your car to 'exhale') is impacted by restriction...
this sounds like bad gas (like 87 being put in when it needed 91+)
and
There's probably a difference in back pressure between the 2.5 STI motor and 2.0 Forester, perhaps this is what has caused the difference. While a car can benefit from a free flowing exhaust, it does need a certain amount of back pressure.
the turbo is the largest exhaust restriction and in my eyes sets stage for any necessary back pressure, but a larger exhaust flows better, pressure is different from flow.
please read this below
@DannyPTY
to be quite honest i think it has more to do with the mid-pipe resonator being removed. the stock Forester XT 14-18 has one in the mid-pipe. the WRX stock does not. the WRX performance STI/SPT exhaust does not have a resonator either. BUT
The WRX STI performance STI/SPT exhaust does have a resonator.
I know the FA20DIT engine from 2017 and up is part for part shared with the WRX and Forester XT. minus the exhaust valve springs. yes i went through every part and compared part numbers on the long block of both cars. the only difference is the exhaust valve springs.
So one would think exhaust from WRX should be fine with Forester XT. FA20DIT butt buddies.
But i think Subaru put the stock resonator in the Forester XT mid-pipe for a reason, and when it is removed while trying to keep a stock tune the ECU does not like it. I suggest
@DannyPTY tell the dealer that install this part that they should have recommended the SPT performance exhaust for the STI. and since the dealer know that the exhaust
All back to normal...Milage great again and torque is back. The awesome sound is gone. Bottom line, the STi Performance exhaust does not work for any vehicle equipped with an FA20 engines. M FXT has the new 2.0 turbo and is not as torquie as the EJ25...That why maybe you did not notice any issues.
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I cry for you. it is not your fault, especially since the dealer installed this stuff and advised you on it.
I would put the ball in the dealers court. what did they say when you complained?
-find a used STI SPT performance exhaust
-put it on your self
-bring it to the dealer and discuss the same drive-ability concerns you have told us here.
-dont leave until they update the ECU and/or TCU. the update i got that helped me was "customers with complaints of bad rear wheel traction around turns". tell them that and i hope all works out.
you can have the fun dad car!!!!!