WRX vs STI

[D2W]

I know this subject has been touched on in other threads but what are the advantages of a STI vs a WRX. I know the 6 speed may actually be a detriment. The brakes are bigger. If I was going to build an 818 with about 300 hp is it better to upgrade a WRX or just start with an STI. Any other differences that may make me choose one over the other?

[Oppenheimer]

Just to clarify, you're asking what are the advantages of an STi vs a WRX for use in an 818, correct?

From what I can gather, unless you are looking for really high HP numbers, I think WRX is the way to go. If you want better brakes, it sounds like they will have a Willwood upgrade avail (part of the planned 'track' stuff). The suspension, I think most of that is going to be FFR supplied. You arleady mentioned the trans.

Perhaps the only real advantage will be selling off all the STi parts you don't use. If you can find a wrecked STi, you might do so well there that it pays for itself.

[thebeerbaron]

One big disadvantage I see is that the STi is drive by wire. Who knows how that will play out with the 818. While you may be able to sell more bits off it, it will also carry a premium to buy.

[D2W]

Yes as a donor for the 818. Are there other differences in the suspension besides the brakes? I had forgot about the drive by wire, are there other complications in the wiring/ecu? I have driven a STI but not a WRX. It was kickass, how does the WRX compare?

[thebeerbaron]

I'm told the WRX has less grunt down low. Other notables are that anyone with an STi who is going for power is replacing their cast pistons with forged.

The low-end grunt is down to AVCS, the variable cam timing voodoo that Subaru uses. I believe it's tunable with the right aftermarket ECU programming or what have you, but I am not certain.

If you read my woeful tale, there are some people who actually prefer the WRX motor.

Part of my struggle in deciding between using an STi or WRX short block was in understanding what the 818 would enjoy the most. Does it really need low end grunt? How much power is too much?

I think chasing big numbers at this point is a mistake. I think the smart move is to see how the initial builds sort themselves out on the autocross course/race track and then decide what the right power source should be.

As far as the suspension and brake bits - the front lower control arms on the Open House chassis were very different from mine. They looked to be fancy aluminum bits. You'd have to ask Dave/Jim where they came from - they might be STi bits, or they might be aftermarket, I don't know. There were a couple of other arms that I wasn't sure whether they were aftermarket or stock. Again, I think the smart money is on waiting to see how things build out.

[PhyrraM]

In the US market:

STI '04-'07: 2.5 liter, Variable cam timing, 6 speed transmission, Drive by wire throttle, 4 piston Brembo calipers, Aluminum front control arms. ('05+ w/modified geometry).

WRX '02-'05: 2.0 liter, No variable cam timing, 5 speed transmission, cable throttle, 2 piston sliding front calipers. Stamped steel control arms.

WRX '06-'07: 2.5 liter, Variable cam timing, 5 speed transmission, drive by wire throttle, 4 piston non-Bembo calipers. stamped steel control arms ('06 only, aluminum control arms).

The 818 may have a hard time putting heat into the large Brembos on the street.

The '05+ STI has upgraded knuckles that may not fit the FFR supplied upper control arm adapters.

The STI and '06/'07 WRX motors are basically the same, differing mainly in turbo size, cam profile and tuning.

I, personally, feel the the '06-'07 WRX will make the best donor. I feel that the drive by wire will be an asset to a (slightly) faster and cheaper build. I feel that the STI transmission, knuckles, and brakes are total overkill for an 1800 pound car.

As long as FFR knows about, and accomodates, the different front control arm widths and geometries (and the fly-by-wire/throttle cable difference) donor possibilities go way up, get cheaper, and (IMHO) get better and more suitable.

[Gollum]

Other notables are that anyone with an STi who is going for power is replacing their cast pistons with forged.

It took around 400 wheel HP and E85 (huge torque) in order to finish off my buddies STI longblock that was already having ring issues on one cylinder that had been showing low compression since he bought it. That engine suffered a good full year and probably 15k miles at around 300 wheel hp and was fine. It's amazing what a motor can withstand if it's not pinging. We believe his motor wouldn't have blown if the tune had been ironed out better, but it was a new E85 tune and he was testing new ground with his part combination. He knew the risks and went for it anyways. Now he's got himself an all new longblock about ready to go back in that should hold 800 crank hp easy.

I personally feel that most changes made to the engine for a 818 setup should be to make sure the turbo setup is as efficient as possible and stays cool. I'm a huge believer in E85 and I know with a good tune it should be fairly tolerant to heat soak at the track, and it will offer much better spool times for the turbo. The hard part is that since it's so darn detonation resistant it's really tempting to turn up the boost and find your weak links easily... What short bock you start with matters very little in the end in my opinion, it just changes some of your course of actions as to what to change first.

[Wayne Presley]

I would use the WRX since the kit is being designed for this donor. I've built 18 FFR roadsters and done track events in them. I can tell you when you use brakes that work well on a 3400lb car on a car that weighs 2300 lbs (33% lighter), braking power is not an issue. So going from 3140 (06 WRX) to 1800 lbs (43 % lighter), put Hawk HP + pads on it and let'r rip.

[jimgood]

I would buy the cheaper donor (WRX) and use the extra money you'd save to upgrade the motor, turbo and engine management as you want/need to. I think the 6-speed tranny is a waste on an 1800 lb car. I also agree that the STi brakes are a waste. By losing 1300 lbs, the drive train and brakes will move and stop this car very easily. It also might mitigate some of the supposed issues people have overpowering the stock tranny. I would imagine that one would be able to stay in 3rd gear in places where the WRX feels like a slug.

[BrandonDrums]

In the US market:

STI '04-'07: 2.5 liter, Variable cam timing, 6 speed transmission, Drive by wire throttle, 4 piston Brembo calipers, Aluminum front control arms. ('05+ w/modified geometry).

WRX '02-'05: 2.0 liter, No variable cam timing, 5 speed transmission, cable throttle, 2 piston sliding front calipers. Stamped steel control arms.

WRX '06-'07: 2.5 liter, Variable cam timing, 5 speed transmission, drive by wire throttle, 4 piston non-Bembo calipers. stamped steel control arms ('06 only, aluminum control arms).

The 818 may have a hard time putting heat into the large Brembos on the street.

The '05+ STI has upgraded knuckles that may not fit the FFR supplied upper control arm adapters.

The STI and '06/'07 WRX motors are basically the same, differing mainly in turbo size, cam profile and tuning.

I, personally, feel the the '06-'07 WRX will make the best donor. I feel that the drive by wire will be an asset to a (slightly) faster and cheaper build. I feel that the STI transmission, knuckles, and brakes are total overkill for an 1800 pound car.

As long as FFR knows about, and accomodates, the different front control arm widths and geometries (and the fly-by-wire/throttle cable difference) donor possibilities go way up, get cheaper, and (IMHO) get better and more suitable.

This is spot-on. I agree.

To elaborate on the drive by wire thing, since we're going to have to relocate the engine to behind the driver, the physical cable-driven throttle line will be longer and will have more friction working against it. Drive by wire will work the exact same way wherever you put it making pedalbox installation much easier so you only have to worry about the clutch and brake connections.

For a full racing 818, brembo's won't be a terrible thing to have but weight is weight and with the elise/exige as a model, fade is less of an issue with a lighter car, you'll be better off overall probably with the 06-07 4/2pots.

As for the transmission of the STI vs WRX, the 6 speed is far more complex than the 5 speed and will be difficult if not essentially impossible to convert into 2wd in a cheap way since it's center diff is a fancy electronically controlled one. If you bought an STI, it would be to have the larger turbo, larger intercooler, larger brakes but you'd probably end up having to sell/trade the transmission for a WRX 5speed.

In a couple other threads we talked about turbo spool as a function of load, with the lightweight of the 818, you'll probably want taller ratios anyway to make more power and have faster acceleration. A 5 speed with a PPG gearset will be ideal for many reasons although the 5 speed will also probably need the addition of a limited slip front diff for a high hp engine. Fortunately, the STI 6speed is worth a good amount since so many subaru guys want them in their impreza's, forresters and legacies. If you bought a STI as a donor, you could sell off the 6 speed and get enough cash for it for a broken 5 speed, a PPG gearset and nice limited slip front diff to drop in. A good 6 speed with the read diff and axles is worth a good 4500 bucks.

However, the half-shafts and hubs aren't all universally compatible between 5 and 6speed trannys. Therefore you'll either have to convert half-shafts or convert the output spindle on the 5 speed.

In short, I'd say just get an 06 or 07 WRX and leave the part swapping to people who are keeping their WRX's in tact.

[BrandonDrums]

I'm told the WRX has less grunt down low. Other notables are that anyone with an STi who is going for power is replacing their cast pistons with forged.

The low-end grunt is down to AVCS, the variable cam timing voodoo that Subaru uses. I believe it's tunable with the right aftermarket ECU programming or what have you, but I am not certain.

The 2.0 WRX has less grunt because it's a smaller engine. AVCS is nice but it's there to offset flow losses from the emissions equipment it seems. If you install a TGV (Tumble Generator Valve) deletes, a non AVCS 2.5 is the same as a AVCS engine in low-end grunt. At least on paper.

TGV's are just restrictor butterflies in the intake to make better emissions in cold-start and idle situations. It seriously restricts intake flow. AVCS is just a intake-side only variable valve timing offset. It doesn't change the duration of the intake opening time but just offsets the period along the stroke that the valves are open. It's neat but it literally is only viable up to 3500 rpm then it's disabled. 06+ WRX's have it as well but it's not as much as a power advantage as you might think. It's more smoothing out the power-band for daily driven cars. At least in my opinion. I haven't seen enough of a difference with or without to be that impressed personally.

[StatGSR]

why does everybody keep saying is impossible/difficult to convert a 6spd to fwd. its not, pick up phone, order parts, receive parts, install parts = FWD 6spd.......

on the plus side. at least a couple people are providing correct information in here...

[thebeerbaron]

why does everybody keep saying is impossible/difficult to convert a 6spd to fwd. its not, pick up phone, order parts, receive parts, install parts = FWD 6spd.....

If you know, please share so we can know to. Where is this place or person?

[PhyrraM]

Folks get stuck on the complexity of the 6 speed center differential, making it seem harder to bypass. It's not.

The simple reality is that making ANY Subaru transmission FWD simply involves locking the front and rear outputs together. This can be accomplished either by welding the proper components, or installing any variety of locking sleeves. Then you simply remove the rear output components.

In RWD terms, it's like replacing a rear diff with a spool. It doesn't matter how complex the original differential was (Open or Torsen or clutchpack), it gets pulled - and the very simple spool takes it's place. Once the spool is installed, you can completely remove the axle from one side and the car will still move. The Subaru center diff is no different, other than the way it looks and fits in the housing.

[thebeerbaron]

I got stuck on the idea because the few sites I saw selling those "spools" that convert the box to FWD emphatically stated that they did not work for the 6-speed, and IIRC made it sound like they were never going to have a product for the 6-speed. Mea culpa, but I'd still like to see a link to someone actually selling this part.

[PhyrraM]

Ah, true. I would assume they state "for 5 speed only" because they physically don't fit the 6 speed, not because it can't be done.

Here is a link to a pricelist that has a 6-speed RWD conversion spool. I do not know if it will also work for a FWD conversion. Functionally, it's simply a matter of machining something that locks specific splined shafts together on the inside of the transmission while also maintaining any bearing or retaining functions that the original parts my have done.

On that note, I am curious if FFR plans on working with an existing 2WD conversion kit or having parts machined to thier spec from a company they might already have a relationship with.

[StatGSR]

If you know, please share so we can know to. Where is this place or person?

Had to dig it up from a TR-42 thread.. but anyway

take a look at the "Center Diff Lock Tube" on this page
http://www.possumbourne.co.nz/trans_diff_parts.html

[PhyrraM]

Forgot the link in my previous post, however StatGSR's is a better one anyways.

[StatGSR]

The 818 may have a hard time putting heat into the large Brembos on the street.

Just had to comment on this since there are plenty of pad options that don't need heat to work well, in fact most street pads/autox have great initial bite (cold), on the downside, they have a lower heat tolerance, but that probably wouldn't be and issues as they would tend to stay cool on their own and would never see temps above 1000deg F unless you drag the brakes all the time. Axis Ultimates come to mind as a good pad in that application.

I would also guess that brake modulation would still be improved with the brembo over the standard 2 pots, maybe not noticeably different from the FHI 4pots in the 818 application though, hard to say, starting to make to many assumptions at this point.

[D2W]

Great info, thank you.

[Gollum]

Just had to comment on this since there are plenty of pad options that don't need heat to work well, in fact most street pads/autox have great initial bite (cold), on the downside, they have a lower heat tolerance, but that probably wouldn't be and issues as they would tend to stay cool on their own and would never see temps above 1000deg F unless you drag the brakes all the time. Axis Ultimates come to mind as a good pad in that application.

I would also guess that brake modulation would still be improved with the brembo over the standard 2 pots, maybe not noticeably different from the FHI 4pots in the 818 application though, hard to say, starting to make to many assumptions at this point.

I'm betting that good cold bite will be VERY important to a lot of people building an 818, simply because so few people will be getting the brakes all that hot on a regular basis. Remember that with the lower weight it'll be that much harder to get heat into the brakes to get aggressive pads to work. I myself would have aggressive pads on hand for track use, but I also understand the importance of great cold performance on the street. I've known a few people to get into accidents on the street because they were a bit too dim witted about their "performance" pads when it came time to stop on a dime on the freeway...

[Steve91T]

I'm betting that good cold bite will be VERY important to a lot of people building an 818, simply because so few people will be getting the brakes all that hot on a regular basis. Remember that with the lower weight it'll be that much harder to get heat into the brakes to get aggressive pads to work. I myself would have aggressive pads on hand for track use, but I also understand the importance of great cold performance on the street. I've known a few people to get into accidents on the street because they were a bit too dim witted about their "performance" pads when it came time to stop on a dime on the freeway...

That's why I have two sets of brakes. Street pads and rotors, and track pads and rotors. It's actually cheaper to have two sets of brakes in the long run.

Steve

[Cooluser23]

For the 818 specifically, which is what I assume you're asking:
I think the regular WRX will be crazy fast already. What worries me that STi motors/parts usually demand a premium. (I'm hoping someone with junkyard experience with Subies could chime in exactly how much that is)
The other problem is competition for parts/cars as the STi is much more desirable.

I prefer a 6-speed over a 5-speed, but that is more due to personal preference rather than performance reasons. To me, the Porsche, BMW, MINI, Fiero layout where reverse is to the left and forward of 1st is much more intuitive.

examples:

[Cooluser23]

Edit: NVM, I guess the point is moot. A quick search revealed that the 6-speed pattern on Subaru's is not the above pattern I like.
(on the Miata I always feel as if I accidently put the car in reverse, rather than 6th.-probably irrational fear, but still something I think about)

[Steve91T]

You won't get it into reverse at speed...you'd have to try really hard to even get the gears to grind.

[Cooluser23]

You won't get it into reverse at speed...you'd have to try really hard to even get the gears to grind.

On the Miata I drove (2002 I believe) I feel as if I can move the lever 1/2 way into the reverse gate (to the right, but not down) It's quite disconcerting to not know if I'm in 6th, or attempting reverse. I'm assuming there is some sort of idiot proof device that actually prohibits fully engaging reverse.

[Wayne Presley]

I'm assuming there is some sort of idiot proof device that actually prohibits fully engaging reverse.

They're called brains...

[Steve91T]

You can't actually engage reverse. You'd have to force it, but even if you do, all that will happen is it'll grind. It's honestly not an issue.

[Horhay]

The STi has a reverse lockout lever. Without lifting the metallic ring below the shift knob you can't engage reverse, even if you're stopped. Accidental reverse selection is simply not an issue.

I made a quick vid in my STi:
http://i19.photobucket.com/albums/b1...y/c200dd2e.mp4

[mmahan]

Noob to the forum...
I am REALLY excited about this whole idea!! As the fates would have it, I have an 04 STi turned Track Toy. I am reeeeeeeeeeeally hoping that I can use her as the donor car. At this point, with the amount of mods & time I have spent on the car (she's been a non-op trailer queen for a few years now... belches fire; BEAUTIFUL!!!) I'm hoping that I can keep as much of her guts as possible. I'm sure I will be mocked accordingly, but I just keep thinking about my current toy turned Mid/RWD under 2K #'s and, well, I'm not going to lie... all I do is smile! I won't even have the skill to keep her in a straight line; I'm so spoiled from AWD.
Anyway... my vote is that we can somewhat easily use STi parts on this concept. That would rock.
Regardless, I am super stoked about this concept!!! I already have a spot reserved in my shop for this build...

[Oppenheimer]

Probably the only STi parts that you might not be able to easily use in the 818 would be the tranny (it might be too big). You could always sell your trans, buy a 5 sp, beef up the internals to handle your monster motor.

The other stuff good stuff, your motor, the Brembo's, etc should all be OK.

[Gollum]

I'm betting the 6 speed will work, it just won't be support. This will mean sourcing the FWD conversion parts on your own, mounting it yourself, making required axles if necessary, and making body alterations on your own.

It's the same as any engine swap. Will it fit? Depends on your time and budget. Never say never! :-)

[PhyrraM]

An idea would be to sell/trade your STI 'special bits' for WRX (or even lowly Impreza) equivalents. Money in your pocket on trade values, less overbuilding for the weight of the car, less 'custom' work, less unsprung weight, less expensive upkeep.......

In any case, it's been beat to death. Virtually all STI parts can be made to work with enough effort/time/money/skills. Most won't even need all of those together. Axles and '05+ front knuckles will be the biggest challenge.

[Flamshackle]

just on a side note you REALLY want an STI gear box for our 818's... from (i think) 1996 onward they come with a mechanical limited slip diff in the front (rear on our 818) So if you don't want to be wheel spinning all the way to 4th gear go with an STI gearbox...

Knowing what I do about subarus I cant think off the top of my head a single STI thing that wont work in place of a WRX part for the 818...

[2KWIK4U]

I thought that I read somewhere that only special cars had the limited slip available in the front of the Subaru. I know that they had them in the rear but since we are using the front trans axle in the rear on the 818 we will have to have on installed if you want one.

Anyone know more about this?

[PhyrraM]

All STIs in North America had a 6 speed with some type of front LSD.

Outside of North America, STIs before '01 had 5 speeds with, or without, LSDs. IIRC, most are without. '01+ had 6 speeds with, or without LSDs. However, the vast majority of 6 speeds did include an LSD of some type.


Also, in North America, NO 5 speed came from the factory with a front LSD.

The '07-'09 Legacy spec.B had a version of the STIs 6-speed, but I do not know if it came with the LSD.

As long as the suspension is designed properly, a LSD will not be needed until HP reaches 'ludacris speed' levels. The first Elises did not use one and were greatly praised for the handling and power delvery.

[StatGSR]

Knowing what I do about subarus I cant think off the top of my head a single STI thing that wont work in place of a WRX part for the 818...

You mean besides the obvious fact that the transmission is physically larger and has different mount locations then the 5spd which could have a substainal impact on how easy it is to use in the 818....

[Steve91T]

All STIs in North America had a 6 speed with some type of front LSD.

Outside of North America, STIs before '01 had 5 speeds with, or without, LSDs. IIRC, most are without. '01+ had 6 speeds with, or without LSDs. However, the vast majority of 6 speeds did include an LSD of some type.


Also, in North America, NO 5 speed came from the factory with a front LSD.

The '07-'09 Legacy spec.B had a version of the STIs 6-speed, but I do not know if it came with the LSD.

As long as the suspension is designed properly, a LSD will not be needed until HP reaches 'ludacris speed' levels. The first Elises did not use one and were greatly praised for the handling and power delvery.

I disagree. Even at 300 HP in an MR2 turbo, LSD was very important coming out of a turn.

[Evan78]

just on a side note you REALLY want an STI gear box for our 818's... from (i think) 1996 onward they come with a mechanical limited slip diff in the front (rear on our 818) So if you don't want to be wheel spinning all the way to 4th gear go with an STI gearbox...

Or you can install an aftermarket LSD in the WRX 5 speed trans.

[Gollum]

I disagree. Even at 300 HP in an MR2 turbo, LSD was very important coming out of a turn.

Completely different car through and through. Apples to Oranges. The LSD Elise is so similar to the Non-LSD Elise that you can find forums filled with owners who've owned both who have varying opinions.

The point was that "if the suspension is designed right" then we won't be desperate for a LSD, which I think has some truth in it.