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2017 Forester XT
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16 Posts
Discussion Starter #1
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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2015 Forester XT CVT
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24 Posts
I will be interested in your results with the standard exhaust. I have a '15 and installed a '15 STI exhaust a couple of years ago. I did not notice a mileage reduction but did have the drone. It was really bad at low speed in I mode.

You can remove the drone by blocking or partially blocking one of two muffler outlets. There is a resonance and disupting the sound from one on each muffler will remove the drone. I reduced the area of the outer 2 pipes and the drone has gone. I think that, unless one is racing the Forester, the open 2 pipes will flow well enough. It is an exhaust system for a 2.5 l engine, the pipes are slightly larger and also have smoother bends
so I cannot see that my reduction of outlet area would make any difference. And I have seen no change in mileage or driveability.

There may be some differences in your '17 so my experience may not apply.
 

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2017 Forester XT
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16 Posts
Discussion Starter #3
STi EXHAUST ON FA20 Forester

I will keep you all posted. Is your F a 2.5 o did it come with a 2.0?



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07 Forester XT
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6,791 Posts
I wonder why you're seeing such a difference in fuel economy, just an exhaust usually doesn't make a huge difference in that department.
 

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2017 Forester XT
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Discussion Starter #6
I will be interested in your results with the standard exhaust. I have a '15 and installed a '15 STI exhaust a couple of years ago. I did not notice a mileage reduction but did have the drone. It was really bad at low speed in I mode.

You can remove the drone by blocking or partially blocking one of two muffler outlets. There is a resonance and disupting the sound from one on each muffler will remove the drone. I reduced the area of the outer 2 pipes and the drone has gone. I think that, unless one is racing the Forester, the open 2 pipes will flow well enough. It is an exhaust system for a 2.5 l engine, the pipes are slightly larger and also have smoother bends
so I cannot see that my reduction of outlet area would make any difference. And I have seen no change in mileage or driveability.

There may be some differences in your '17 so my experience may not apply.
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.



This is my city reading 10km/L I was at 5km/L...Big difference.



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2015 Forester XT CVT
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It is strange that you saw so much difference in mileage. On my 2015 XT I have the 2015 STI OEM exhaust cat back with 4 outlet pipes and average around 8.2 l/100 km (12 km/l) overall city and highway.
That is using S# almost all of the time running regular (87 AKI) gas. The mileage does drop in the Winter with cold starts and lower temperatures.

So very little if any change in gas mileage for me with the STI exhaust. Were there any other changes made?
 

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07 Forester XT
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6,791 Posts
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.
 

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2015 Forester XT Touring
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624 Posts
Backpressure wouldn't cause this big a change in mileage. Not sure what did it, but suspect your car is just setup or tuned a bit differently then normal. Perhaps if you also ran a Cobb Stg 1 map you would see more normal numbers (not that it's needed when just doing catback exhaust).
 

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2017 Forester XT
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Discussion Starter #10
No idea, i have done many bolt on upgrades to several of my cars but never have i had such a noticeable increase in consumption. Very odd. But im sure it has to do with the back pressure as well. Never did I think the exhaust would also screw with the CVT algorithms but apparently it did.


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Discussion Starter #11
It is strange that you saw so much difference in mileage. On my 2015 XT I have the 2015 STI OEM exhaust cat back with 4 outlet pipes and average around 8.2 l/100 km (12 km/l) overall city and highway.
That is using S# almost all of the time running regular (87 AKI) gas. The mileage does drop in the Winter with cold starts and lower temperatures.

So very little if any change in gas mileage for me with the STI exhaust. Were there any other changes made?


No changes made at all. I was getting in the city 5km/L. This car gives you an average of 13km/L combined. When I drive out to the country i get up to 17km/L I was at 11km/L being very gentle.




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07 Forester XT
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I agree, there's something particular about this car. I've seen a million people put an STI exhaust on the 2.0 WRX 02-05 and never heard of this happening before. Some cars are just "unique"
 

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2017 Forester XT
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Discussion Starter #13
The best way I can describe it is I only got 250 to 350kms from a full tank combined and and my Infiniti Fx35 gives me 500km combined being a V6 with 305bhp. Its my first experience with Subaru and I cant say its been the best. The dealer hates me because I have honestly been a nag about this but hey, they recommended the STi exhaust from the get go and said it would not hurt the warranty...Of course I said yes....because I wanted a invidia or a nameless catback "designed for the FA20" and they said it would screw my warranty up... So, I went ahead with the STi.
I have heard in other forums about the CVT acting up though...You feel the jitters much more with a free exhaust i suppose and it gets annoying. Its my first and last CVT thats for sure.
Im 46 yrs old and I have had several Jeeps from Sahara to Rubicon's, Infiniti, Corvette, Honda Si, Mazda, VW GTi, Suzuki Swift GTi and I so wanted a Subaru but its been a bitter sweet experience so far.


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2015 Forester XT Touring
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Wait a second here. I'm not sure what's happening to your car, but there's absolutely nothing wrong with running the STI performance exhaust on the FA20. Check the WRX option sheet, it's listed right there as an option. Highly doubt Subaru would offer it as an option on an FA20 car if it did the things you are describing. I've had that exhaust on my XT for over 15,000 miles without any issues, OR any loss in fuel consumption. I ran this both on the stock tune and now on the Cobb Stage 1 OTS. I'm going to guess that you either had an extremely horrible leak going on, or some other issue.

 

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2017 Forester XT
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Discussion Starter #15
Wait a second here. I'm not sure what's happening to your car, but there's absolutely nothing wrong with running the STI performance exhaust on the FA20. Check the WRX option sheet, it's listed right there as an option. Highly doubt Subaru would offer it as an option on an FA20 car if it did the things you are describing. I've had that exhaust on my XT for over 15,000 miles without any issues, OR any loss in fuel consumption. I ran this both on the stock tune and now on the Cobb Stage 1 OTS. I'm going to guess that you either had an extremely horrible leak going on, or some other issue.
Are you running a CVT or manual?


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2015 Forester XT Touring
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It's an XT, so it's a CVT. I've never seen an SJ XT with a manual.
 

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Discussion Starter #17
Wait a second here. I'm not sure what's happening to your car, but there's absolutely nothing wrong with running the STI performance exhaust on the FA20. Check the WRX option sheet, it's listed right there as an option. Highly doubt Subaru would offer it as an option on an FA20 car if it did the things you are describing. I've had that exhaust on my XT for over 15,000 miles without any issues, OR any loss in fuel consumption. I ran this both on the stock tune and now on the Cobb Stage 1 OTS. I'm going to guess that you either had an extremely horrible leak going on, or some other issue.
I honestly do not know. Had no leaks but fuel consumption now is much much better. Im honestly bummed out because it looked great and the sound was awesome...If it had been a little difference in fuel, fine. But it was really dramatic. Im getting and invidia or nameless and a custom tune.


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I don't see how that could have happened. You have to have had something else going on. Perhaps a bad batch of gas, etc. There's no situation where any catback exhaust should impact your fuel economy that much. A catback is a catback, no matter who makes it. If it was the catback that was causing your issue, you're going to have the exact same issue with an Invidia or Nameless exhaust as well. They are all just pipes, nothing fancy about them.
 

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2017 Forester XT
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Discussion Starter #19
It's an XT, so it's a CVT. I've never seen an SJ XT with a manual.


True. Well, I honestly do not know what went wrong but bottom line is that consumption is back to normal. I did ask the dealer and they said that they sales guy did offer the STi P Exhaust when he should have offered the WRX P exhaust but they did not have have the WRX P exhaust in stock. They do offer both P exhausts but one for WRX and one for STi. Im putting up the options sheet.




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2015 Forester XT Touring
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Only difference between the two is the resonator. Since the stock STI doesn't have resonators in the downpipe, they add one in the midpipe. Meaning that that one would be a bit quieter on your car than the WRX one, but that wouldn't impact your fuel consumption like that. For what it's worth, I do have the one without the resonator on my car. But I'm sure you saw that enormous resonator on your stock midpipe. I'd highly doubt a higher-flow resonator like the one on the STI version would affect performance in any way.
 
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