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Old 02-19-2018, 01:07 PM   #1
rumatt
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Default Anyone else wish you could get a WRX the STI AWD system?

I test drove an '18 WRX and liked it a lot. In most regards its a better fit for me than the STI
  • I've never chased horsepower
  • I like low end torque and flatter torque curves
  • I don't need a stiffer suspension than the WRX
  • I don't want 19" wheels
  • I' d prefer to run 17" wheels in winter
  • I don't like the idea of getting the gas mileage of a half ton pickup

But I do want a great AWD system. It's just something I appreciate and notice while driving - whether accelerating around a corner in gravel, or in snow, etc. A RWD biased center diff and LSD's front and rear sounds absolutely fantastic.

The non-STI WRX AWD system is not getting me excited, and quite honestly is quite primitive. The 2017 Imprezza (auto transmission) nearly failed the diagonal test in the video below. Loads of wheel spin before torque is applied to the wheels with grip. Several other vehicles' modern awd systems do a better job than this.

I'm sure the WRX system is reasonable in real-world driving, and it's possible I'd be perfectly happy with it. But I guess I should go test drive an STI and see how it makes me feel. And if it fixes the absurd 1-2 rev hang (seriously WTF is Subaru thinking?) without needing to void my warranty that's a plus. Or I'll just wait and see what 2020 brings. :-/

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Last edited by rumatt; 02-19-2018 at 01:26 PM.
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Old 02-19-2018, 01:48 PM   #2
Pwersha
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The full STI system would probably be an expensive option, making it too close to the price of the STI. It would be nice if the WRX at least had a rear LSD, without the adjustable center diff.
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Old 02-19-2018, 01:59 PM   #3
jamal
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Well, that's always been the difference between the two cars, and until 2015 when they had the same engine that was pretty much it.

As far as that test goes, with wheels in the air you pretty much need clutched or locked diffs to go anywhere. Even the sti's helical diffs would be unable to do anything and traction control applying the brakes would be the only thing getting you moving.

With all the wheels on the ground of course the sti works a lot better and dccd is pretty cool.

As far as a few of your points go, the 15+ WRX and sti spring rates are actually pretty much the same, and you can put 17" wheels on a 2017 or earlier.

And of course, if you want a wrx with sti diffs, you can always swap them in.
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Old 02-19-2018, 02:48 PM   #4
rumatt
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Quote:
Originally Posted by jamal View Post
As far as that test goes, with wheels in the air you pretty much need clutched or locked diffs to go anywhere. Even the sti's helical diffs would be unable to do anything and traction control applying the brakes would be the only thing getting you moving.
Well, that's not quite true. Most vehicles are using the brakes to slow the spinning wheel, which sends more torque to the other side. And other vehicles are doing a better job at it, like the BMW X1 below

And with the helical/torsen diffs, the amount of brake the system needs to apply is significantly reduced.

Quote:
As far as a few of your points go, the 15+ WRX and sti spring rates are actually pretty much the same
Cool. Is the data on the spring and shock rates available anywhere? I wasn't able to find it anywhere.

Quote:
And of course, if you want a wrx with sti diffs, you can always swap them in.
I'll read up on it. Seems like a fairly elaborate swap.



Last edited by rumatt; 02-19-2018 at 02:55 PM.
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Old 02-19-2018, 02:58 PM   #5
jamal
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Quote:
Originally Posted by rumatt View Post
Cool. Is the data on the spring and shock rates available anywhere? I wasn't able to find it anywhere.


Ohh, interesting. They're the same size and directly swapable?
RCE did a comparision between the springs and dampers here

https://forums.nasioc.com/forums/sho....php?t=2640177

Spring rates for previous cars should be around here somewhere.

And well, no, what I mean by swapping diffs is swapping the transmission and whole rear diff housing and adding an aftermarket dccd controller. But that is a $4-5k process usually.
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Old 02-19-2018, 03:07 PM   #6
rumatt
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Quote:
Originally Posted by jamal View Post
RCE did a comparision between the springs and dampers here

https://forums.nasioc.com/forums/sho....php?t=2640177
Awesome, thanks. The only significant difference is the rear shocks rates, which would probably be great for helping the car rotate when turning in. Hmmmm

I'd be curious to see the '18's remeasured.

Quote:
And well, no, what I mean by swapping diffs is swapping the transmission and whole rear diff housing and adding an aftermarket dccd controller. But that is a $4-5k process usually.
Yikes. That would pay for a lot of gas for an STI.
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Old 02-19-2018, 09:58 PM   #7
RussianTiny
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As my daily driver... and from a couple test drives I could not tell the difference with the STI modes. I personally think the WRX is perfectly balanced. Yes it would be cool for a little more rear bias to let it slide out but I really like the way my WRX handles with stock suspension. It might be placebo but I think the 2018 WRX corners better than a 2017 WRX. As a track car I have no doubt the STI would be better.
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Old 02-19-2018, 11:18 PM   #8
subezero
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There's no replacement to true mechanical limited slip differentials. Even today, the whole "torque vectoring" brake-applying electronic diff still doesn't feel the same. There's still that computing lag that makes it very noticeable. The average daily driver wouldn't really notice but start pushing the car hard in mid corner through the exit, you really start to notice the inside wheels spinning.
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Old 02-20-2018, 08:37 AM   #9
aggarcia
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A big piece of the price difference between the WRX and the STI is the different AWD system and stronger 6 speed transmission. That $4-5K is installing used parts and a DCCD controller.

Under casual driving you will not notice the difference is AWD systems. Push the car and itís apparent very quickly. Also the STI AWD system hurts fuel economy as your having to turn those locker diffs all the time.

There is a distinctive difference between the WRX and STI. They look the same in most aspects, but there are lots of differences between the two. When Subaru introduced the STI Sedan in 2011, they released a video showing all the differences between the WRX and the STI. One cannot swap out everything to make a WRX a STI for as cost effective as the factory does.
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Old 02-20-2018, 12:43 PM   #10
PhatPhillyPhrank
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Quote:
Originally Posted by aggarcia View Post
A big piece of the price difference between the WRX and the STI is the different AWD system and stronger 6 speed transmission. That $4-5K is installing used parts and a DCCD controller.

Under casual driving you will not notice the difference is AWD systems. Push the car and itís apparent very quickly. Also the STI AWD system hurts fuel economy as your having to turn those locker diffs all the time.

There is a distinctive difference between the WRX and STI. They look the same in most aspects, but there are lots of differences between the two. When Subaru introduced the STI Sedan in 2011, they released a video showing all the differences between the WRX and the STI. One cannot swap out everything to make a WRX a STI for as cost effective as the factory does.
Do you know where I could find this video?
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