WRX vs STI

[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.

[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.

[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]

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)