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2020 Subaru WRX STI
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Discussion Starter · #1 · (Edited)
Hello everybody. Just want to post here for others to have some comparison and to humble expectations. My goal was to see how far the stock motor and turbo can go. The limiting factor in this current build is the turbo. The tune has maxed out the turbo at about 22 psi. There is no more power to be gained until a bigger turbo is installed. Stock motor can handle about ~450whp so that still has some leeway for more power. I am mainly posting this to show what somebody can expect from such performance installations and tunes. So here it is...


Tuned by Paul from YimiSport

baseline run:
horsepower: 302hp @ 5,120 rpm
torque: 331lb-ft @ 4,483 rpm

dyno max run:
horsepower: 343hp @ 5,102 rpm (+41 hp) (+13.58%)
torque: 408lb-ft @ 4097 rpm (+77 torque) (+23.26%)

notable performance modifications:
  • Cobb flex fuel conversion kit + fuel system package
  • Cobb gesi catted 3" downpipe
  • Cobb fmic kit
  • IAG tgv deletes
  • Cobb SF air intake + box

note: stock motor and turbo

You can get a detailed list of my modification progress here: tinyurl.com/cornysubauwu

Rectangle Schematic Slope Font Parallel
 

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2020 Subaru WRX STI
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Discussion Starter · #2 ·
additional notes:

  • All power is measured at the wheels.
  • Stock UEL headers
  • Using Michelin all season tires at the time of the tune
  • Base run is not stock (close but not quite). Base is running on Cobb SF intake, Cobb OTS tune, and r400 catback.
 

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Are you happy with the turnout now that you've been driving it for a little while? I also am planning something similar on my 2013 Sti but I'm doing Tomie elh with up-pipe, full Cobb turbo back exhaust, 1050x injectors, all IAG PTFE fuel lines, AEM 340 fuel pump, Cobb cai and a protune. Debating on going the flex fuel route only due to the fact that it isn't very accessible by me. I could always add it on later but I would have to get it tuned again which isn't very cheap.
 

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I had a similar setup with my last STi - I highly recommend ELH. They offer better throttle response, slightly faster boost, and sound incredible. External wastegates are fun too. JR Barrios tuned my 2017 STi at P&L Motorsports and I got 335 WHP with the stock turbo, stock intercooler, FBO everything else. I spun a bearing and ended up selling the car to the shop but I have a 2021 now and am planning on doing a similar E85 build but going with a bigger turbo. I'm in SoCal now but we'll see what kind of stupid restrictions are put in place for the automotive aftermarket in the next few years.
 

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I also spun a rod bearing. I bought my car used from a subaru dealer and they never disclosed or knew about all the "glitter" in my oil. After a lot of phone calls and emails to corporate subaru I was able to get a new motor installed. Stressful!
I'm in NJ but I read and hear about all the Cali restrictions. Some days I wish I went with a catless dp but im definitely happy with Cobbs GESI. I'd rather know that I won't have any issues passing inspection. I just hope that I'll see my ELH sometime this year. Lol
 

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Very nice! My 2020 STi is just stage 1 pro tuned right now but my previous 2011 was FBO flexfuel with ELH and EWG and made about the same #s. Was thinking of adding a 20g or FP green this time around
 

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Discussion Starter · #8 ·
Debating on going the flex fuel route only due to the fact that it isn't very accessible by me
The best thing about Cobb's flex fuel is that you don't have to always put e85! It expands your range of fuel. If you have the EJ25 motor, you can run anywhere from 0% to 85% ethanol. If you have the FA, then I believe you need to keep at least e50 in the tank. I am completely satisfied with how the car performs. The turbo spool is surprisingly quick, but with a fmic, the turbo lag is a bit scary. I can hit max boost in a second but when that boost power comes in, it launches! So I have to be a bit careful in 2nd gear going around a corner fast because the boost will knock me off course if I am not careful. I definitely recommend e85 flex fuel upgrade! :D

I had a similar setup with my last STi - I highly recommend ELH. They offer better throttle response, slightly faster boost, and sound incredible. External wastegates are fun too. JR Barrios tuned my 2017 STi at P&L Motorsports and I got 335 WHP with the stock turbo, stock intercooler, FBO everything else. I spun a bearing and ended up selling the car to the shop but I have a 2021 now and am planning on doing a similar E85 build but going with a bigger turbo. I'm in SoCal now but we'll see what kind of stupid restrictions are put in place for the automotive aftermarket in the next few years.
I would like to keep my UEL, I will most likely upgrade to iAG UEL later on. Im not building this for maximum power/speed. I would like to keep it, as subaru says, "its what makes a subaru, a subaru". I like everything iconic about subaru STI and I think UEL is one of those things. I will eventually drop a bigger turbo and build the motor. I am also in SoCal. I havent modded any exterior parts besides wheels. Got to look stock and stay under the radar, amirite?? haha. STI already pulls a lot of attraction, I dont like to stand out.
 

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2020 WRX STI, Magnetite grey,
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Base run is not stock (close but not quite). Base is running on Cobb SF intake, Cobb OTS tune, and r400 catback.
Great numbers on E85! Nice to see multiple dyno sheets showing these 19 up motors clearing 300 whp on only stage 1 plus. Car has to feel beefy and fun @ 343/408 wheel. 💪🏻🏁
 

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Discussion Starter · #10 ·
Great numbers on E85! Nice to see multiple dyno sheets showing these 19 up motors clearing 300 whp on only stage 1 plus. Car has to feel beefy and fun @ 343/408 wheel. 💪🏻🏁
I'm not 100% sure that the baseline is 'stage 1+'. They could have installed multiple parts without running e85 for the baseline. Then ran e85 for maximum run.

That torque increase is amazing though. I feel like the sluggishness feeling has gone away. The car doesn't hesitate to keep going at high speeds and its smooth throughout the whole range. I attribute that to the expertise of Paul's tuning though. The parts help open up the car, but the dyno just glues its all together chef's kiss
 

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I also spun a rod bearing. I bought my car used from a subaru dealer and they never disclosed or knew about all the "glitter" in my oil. After a lot of phone calls and emails to corporate subaru I was able to get a new motor installed. Stressful!
I'm in NJ but I read and hear about all the Cali restrictions. Some days I wish I went with a catless dp but im definitely happy with Cobbs GESI. I'd rather know that I won't have any issues passing inspection. I just hope that I'll see my ELH sometime this year. Lol
There was actually a class action lawsuit against Subaru for weak rod bearings that were more prone to fail. I forgot the span of years but I think it was 2014-2017. My VIN was included. My car had 82,000 miles on it when it died - I bought it new. It was Stage 1+ for most of its life, then FBO E85 for only about 3,000 miles LOL. Maybe it would've lasted longer if the bearings were not compromised but who knows. I do miss it dearly though - was just too expensive to fix, and I had it paid off. I'm liking the 2021 I have now but def can't wait until I mod it. I won't be in Cali for too long, so maybe I'll be back in the Midwest once I start to increase the power.
 

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Having had very similar set up and running E85 since the old days of 2012 lol. We tested ethanol content at the gas station will with test tubes, I can say the best thing about stock turbo E85 set up is how Early that torque comes on! It’s not a highway pull set up but for a daily on backroads it’s pretty insane.
 

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Discussion Starter · #13 ·
Having had very similar set up and running E85 since the old days of 2012 lol. We tested ethanol content at the gas station will with test tubes, I can say the best thing about stock turbo E85 set up is how Early that torque comes on! It’s not a highway pull set up but for a daily on backroads it’s pretty insane.
I am actually scared to go into boost on quick corners after corners. Maybe I am not a decent enough driver but when I have a straight into a corner, I can control the boost going into the corner. But when its back to back corners, I have to really control the throttle to not boost into the second corner?? I dont know if I am driving that correctly. Because when the boost comes on, it feels like the car lurches forward and keeps going when I really just want to maintain or slow through the corner so I dont understeer with boost.

I get consistent 80% ethanol in my gauge readings. So lucky me?
 

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Very nice! My 2020 STi is just stage 1 pro tuned right now but my previous 2011 was FBO flexfuel with ELH and EWG and made about the same #s. Was thinking of adding a 20g or FP green this time around
What are the advantages of having an ewg?
 

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What Ethanol content for the max power dyno numbers? I just got done with an E75 log on my STI. Thanks!
 

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Discussion Starter · #16 ·
What Ethanol content for the max power dyno numbers? I just got done with an E75 log on my STI. Thanks!
Best would be 85% ethanol, hence e85 tunes. In my opinion, anything above 65 ethanol is hitting optimal performance. The higher ethanol content the better (up to 85%), but there is a drop off rate when going above 65% ethanol. Running 75-85% ethanol is probably ±5whp, dont quote me on that.
 
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