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Old 07-20-2019, 02:16 PM   #1
Nahoward
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Default Turn a WRX into an STI?

I've got this crazy idea to turn the FA20/CVT into something closer to the STI, and I'm curious what's the differences are. So, aside from the obvious FA/EJ engine, transmissions, and steering, what's different between the 2015+ WRX and STIs?
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Old 07-20-2019, 02:24 PM   #2
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I think your CVT is going to mess up your plans for an STI drivetrain swap. The 6MT seems easy enough to sti swap, but I think the cvt ecu/tcu will be a problem.

Seats, headlights, fog bezels, side badges, trunk, center console, gauge cluster, steering wheel, door cards, midpipe.

Edit: probably mounts/bushings too
If you are serious about this you should just trade in your current car. I get wanting to swap in some better oem parts but doing a full 'conversion' is too expensive and too much work. In the end you're just getting a higher trim stock car with a lower resale value.

Last edited by DarkGreyMetallic; 07-20-2019 at 03:31 PM.
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Old 07-20-2019, 02:31 PM   #3
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Old 07-20-2019, 02:47 PM   #4
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every few months someone comes up with the same idea. its cheaper to sell the car and buy a sti.
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Old 07-20-2019, 03:50 PM   #5
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So let me chime in!! Sell WRX and buy the Sti!! Done.

I fully swapped trans, subframes, steering rack, drivetrain (except engine) and upgraded tons of parts, brakes, etc.. etc.. The headaches and cost, time etc..

All in all yes I did upgrade even what would have been many STI parts, yet cost wise I spent over 30k ( yes I have a fully built rallyX car which would have cost me half if I'd started with an sti). I fully voided any warranties and my insurance wont cover all my parts (that 30k was cause I did all the work myself, having a shop do that labor you can double it). Should have just bolted an LS in the mini :-).

If you have $$ to burn like I seemed to have had?? Stop before you go down the road I did! wish I had those nice sti seats, and interior etc.. that would be another $$

I got mine the day they came out, I thought this platform was a bit better, and I was a bit hyped being my first subaru, yet live and learn.

Good luck
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Old 07-20-2019, 03:52 PM   #6
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Differences

Engine
Transmission
Exhaust
Brakes
Steering
lights
Interiors
Console
Etc... etc..
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Old 07-20-2019, 06:41 PM   #7
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Quote:
Originally Posted by killadawg View Post
I fully swapped trans, subframes, steering rack, drivetrain (except engine) and upgraded tons of parts, brakes, etc.. etc.. The headaches and cost, time etc..
So as far as suspension and body goes, what's unique to the STI?

I'll take a look into the exhaust system, and I'll have to decide if I want to with the STI system and combine it with the a Cobb J pipe, or just go with a full cobb turboback exhaust.
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Old 07-20-2019, 06:55 PM   #8
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Originally Posted by DarkGreyMetallic View Post
I think your CVT is going to mess up your plans for an STI drivetrain swap. The 6MT seems easy enough to sti swap, but I think the cvt ecu/tcu will be a problem.

Seats, headlights, fog bezels, side badges, trunk, center console, gauge cluster, steering wheel, door cards, midpipe.

Edit: probably mounts/bushings too
If you are serious about this you should just trade in your current car. I get wanting to swap in some better oem parts but doing a full 'conversion' is too expensive and too much work. In the end you're just getting a higher trim stock car with a lower resale value.
So ignoring all the dress/cosmetic/interior cabin stuff, can you go into more detail on the differences, specifically relating to the suspension, brakes, and drivetrain from the front and rear diffs to the wheel?

Also, where in the exhaust does the STI exhaust connect in with the WRX's exhaust sytem?

I'm not thinking a "full" conversion, but I am interested in stiffening up my suspension and handling (sans screwing with the steering), and I'd like to explore what makes the STI different while still retaining what I like about the CVT. This is very much a serious first look into this, as I'm gathering information before deciding what direction I want to go in.
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Old 07-20-2019, 07:12 PM   #9
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Unless you are planning on tracking your car on everyday, don't waste your time and money. STi couldn't shake off a FA20 WRX sport pack at the VIR...

https://www.caranddriver.com/feature...storical-data/
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Old 07-20-2019, 07:50 PM   #10
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Quote:
Originally Posted by Nahoward View Post
So ignoring all the dress/cosmetic/interior cabin stuff, can you go into more detail on the differences, specifically relating to the suspension, brakes, and drivetrain from the front and rear diffs to the wheel?

Also, where in the exhaust does the STI exhaust connect in with the WRX's exhaust sytem?

I'm not thinking a "full" conversion, but I am interested in stiffening up my suspension and handling (sans screwing with the steering), and I'd like to explore what makes the STI different while still retaining what I like about the CVT. This is very much a serious first look into this, as I'm gathering information before deciding what direction I want to go in.
there isnt much difference suspension wise between them. the wrx premium and limited have under dampened shocks/struts and give up a lot of performance. sti struts are a direct swap but bilstein b6's are a better choice. spring rates and suspension geometry are nearly identical between them.
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Old 07-20-2019, 09:44 PM   #11
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Originally Posted by Straight6 View Post
Unless you are planning on tracking your car on everyday, don't waste your time and money. STi couldn't shake off a FA20 WRX sport pack at the VIR...

https://www.caranddriver.com/feature...storical-data/
Errrrrm except that the current STi shares more with the RA than the 15 you’re comparing it to... that shorter third gear does wonders for the power band
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Old 07-20-2019, 10:14 PM   #12
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Errrrrm except that the current STi shares more with the RA than the 15 you’re comparing it to... that shorter third gear does wonders for the power band
its still slower 0-60 and 1/4 mile vs. the 2015.
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Old 07-20-2019, 10:23 PM   #13
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its still slower 0-60 and 1/4 mile vs. the 2015.
It’s also “ slower” than the 15 sti in the quarter, that’s not what the car is for.
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Old 07-20-2019, 10:57 PM   #14
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Originally Posted by simpleJ View Post
It’s also “ slower” than the 15 sti in the quarter, that’s not what the car is for.
I'd imagine the CVT is as well, as launching a CVT is a bad idea. That said, I'm thinking the CVT is a bit of a dark horse for stuff like autocross and other racing where starting from a dead stop isn't going to hurt you as much due to the CVT acceleration characteristic in S# mode.
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Old 07-20-2019, 11:41 PM   #15
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Errrrrm except that the current STi shares more with the RA than the 15 you're comparing it to... that shorter third gear does wonders for the power band
We have a 2019 STI in the family. I think my 2015 WRX with a very mild etune would take it, never mind E30.

Last edited by Straight6; 07-21-2019 at 06:49 AM.
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Old 07-21-2019, 07:41 AM   #16
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We have a 2019 STI in the family. I think my 2015 WRX with a very mild etune would take it, never mind E30.
My 19 sti in the stock tune pulls as hard as my wrx did on the OTS Stage 2 map did, IMO. Objectively gear for gear the wrx is faster once you really get into tuning and a it's a better highway car. My wrx was FAST on the highway thanks to the powerband and gearing but it's slower everywhere else.

Otherwise the STi is faster everywhere, and at autocross, especially a fast autocross that requires 3rd gear, you really feel the difference. The stock STi ran times the same as modded rs3's at autocross (and I'm a total n00b) at the last auto x I ran which was a fast autox reaching near 80 at multiple points.

OP should follow these steps if he wants an STi:
1. Get in car
2. Drive to dealer
3. Trade in wrx for sti
4. Drive off in STi
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Old 07-21-2019, 12:20 PM   #17
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Quote:
Originally Posted by n2oiroc View Post
every few months someone comes up with the same idea. its cheaper to sell the car and buy a sti.
+1 on this.. if you want a STI get and STI
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Old 07-21-2019, 12:27 PM   #18
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Quote:
Originally Posted by Straight6 View Post
Unless you are planning on tracking your car on everyday, don't waste your time and money. STi couldn't shake off a FA20 WRX sport pack at the VIR...

https://www.caranddriver.com/feature...storical-data/
163 is a 2015 wrx sti
171 2018 wrx performance package

????
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Old 07-21-2019, 12:47 PM   #19
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You can swap the transmission and rear LSD, add a dccd controller and get that better gear ratio add BBK of your choice, coilovers or a better strut spring combo. SuperPro bushings, cusco and beat rush bracing and white line or SP suspension components.. and most important of all your TIRES!! Your contact patch is the only thing that matters. Whatever allows maximum grip and transfer of power. My current setup will our run and out maneuver any stock STI, but again this is apple's to oranges as mine is not stock.

My caveat is my car is loud, uncomfortable and attracts the wrong attention. And no need for a stereo as it rattles and clanks so much it is pointless (or add 500lbs of sound dampening crap and you are back to being slower..) I've added 1.5way cusco LSDs and at parking lot speeds my car also jerks and pops, not fun for DD. Again what are your goals? That should define what the correct actions should be.

Good luck
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Old 07-21-2019, 12:58 PM   #20
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Originally Posted by subaru_gc8 View Post
163 is a 2015 wrx sti
171 2018 wrx performance package

????
You would think that the STI would be more than 1 second quicker at a course that is over 4 miles long, specially that the WRX run was done on a wet/damp surface. You can even see some standing water in some spots. My main point being is that what OP is trying to do makes little to no sense. It would be much more cost effective just to trade up for a STI.
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Old 07-21-2019, 02:51 PM   #21
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Originally Posted by Nahoward View Post
So ignoring all the dress/cosmetic/interior cabin stuff, can you go into more detail on the differences, specifically relating to the suspension, brakes, and drivetrain from the front and rear diffs to the wheel?

Also, where in the exhaust does the STI exhaust connect in with the WRX's exhaust sytem?.
Suspension has different struts and spring rates front/rear, read the 2015+ suspension tech thread. RCE told me that 18+ WRXs are in a pretty good place with suspension and an STI swap won't help. 18+ STI suspension is softer because of the 19" wheels so you'll want 2015. Springs & LCAs will probably make a bigger difference than a swap. Coilovers even more so.

Brakes on STI are brembos and they're bigger. Any brake swap thread should give exact differences. Bigger brakes will help with heat/fade but stopping distance is grip limited not brake limited.

Drivetrain has a mechanical shifter linkage, DCCD, LSDs, and shorter gear ratios compared to 6MT. it's also much stronger.

STI exhaust has a resonator in the midpipe that we don't have. Connects at jpipe, swappable. If you look under the back of your car, it's the pipe that splits. Downpipe and headers are different too but you can't swap those.
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Old 07-21-2019, 02:55 PM   #22
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Originally Posted by killadawg View Post
You can swap the transmission and rear LSD, add a dccd controller and get that better gear ratio add BBK of your choice, coilovers or a better strut spring combo. SuperPro bushings, cusco and beat rush bracing and white line or SP suspension components.. and most important of all your TIRES!! Your contact patch is the only thing that matters. Whatever allows maximum grip and transfer of power. My current setup will our run and out maneuver any stock STI, but again this is apple's to oranges as mine is not stock.

My caveat is my car is loud, uncomfortable and attracts the wrong attention. And no need for a stereo as it rattles and clanks so much it is pointless (or add 500lbs of sound dampening crap and you are back to being slower..) I've added 1.5way cusco LSDs and at parking lot speeds my car also jerks and pops, not fun for DD. Again what are your goals? That should define what the correct actions should be.

Good luck
Something is wrong with your LSD. Is shouldn't be popping or jerking. What fluid are you running and how do you have it configured? I'm willing to bet that unless you configured it to perform as a 2 way LSD, you are simply using a fluid that the LSD does not like. Try using the Motul Competition fluid. I use their 75W140 and my LSD is quiet, doesn't pop, doesn't jerk.
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Old 07-21-2019, 03:14 PM   #23
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You would think that the STI would be more than 1 second quicker at a course that is over 4 miles long, specially that the WRX run was done on a wet/damp surface. You can even see some standing water in some spots. My main point being is that what OP is trying to do makes little to no sense. It would be much more cost effective just to trade up for a STI.
Apples to apples it’s over 5 seconds quicker...
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Old 07-21-2019, 03:27 PM   #24
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Apples to apples it’s over 5 seconds quicker...
Yes because the brake pads failed on that WRX during the hot lap. You can abuse the STi a lot more at the track, specially when it comes to brakes, heat soak and stock tuning. Again, really worth it if you autocross and track a lot. It really comes down to priorities.
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Old 07-21-2019, 03:51 PM   #25
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Quote:
Originally Posted by Straight6 View Post
You would think that the STI would be more than 1 second quicker at a course that is over 4 miles long, specially that the WRX run was done on a wet/damp surface. You can even see some standing water in some spots. My main point being is that what OP is trying to do makes little to no sense. It would be much more cost effective just to trade up for a STI.
i totally agree, unless your car is something really special its never cost effective to do this.... but im not really one to talk I have a built 2004 wagon with a 2.1 stroker and jdm heads 6 speed brembo brakes..... yeah
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