My wife and I have owned several Subarus over the recent years. They include:
- 2006 Subaru STi - my current track toy, great bang for the buck
- 2006 Outback 2.5 XT wagon, 5 speed - a very good utilitarian car with the 250hp turbo motor, room for a couple of large dogs, luggage, couple of adults, fairly comfortable. We don't care for the ride height - unfortunately Subaru was not selling the Legacy wagon with the 5 speed in 2006, but unstoppable in the snow
- 2004 Subaru WRX - great little car, good size, could easily put a bike in the back
- 2004 Subaru STi - previous track car - learned a lot with that car...
History of the US-spec STi from Wikipedia
Rev. D (2004)
In 2004, Subaru of America announced it will sell the WRX STi. Subaru Tecnica International's president said in an interview with Road & Track magazine that he wishes to beat the Mitsubishi Lancer Evolution in the US. Thus, each iteration of the US-spec WRX STi was essentially the same as the respective J-spec STi Spec C. All the part numbers match up, including the part-numbers for the glass windows and dampeners. However, instead of the EJ207, the USA receives the first EJ257, a 2.5 liter version of the EJ207. Unlike the EJ207, it features hypereutectic cast pistons as opposed to the forged pistons in the EJ207. The steering rack is the standard STi's 15.2:1 instead of the Spec C's 13:1, which many find too slow.
Rev. E (2005)
As with the Japanese-spec C models, US-spec STis received additional rear fender flaring in order to allow an increase in wheel size. The wheel size went from 17" x 7.5" to 17" x 8". In accordance with the increased wheel width, steering lock-to-lock turns have been reduced. Wheel hub strength was improved. The P.C.D. was changed from 5 x 100 to 5 x 114.3. The Suretrac L.S.D. in the 04 model was replaced with the Helical limited slip differential. In the interior, the Stereo became standard. The badging has been revised and different look was given to the steering wheel, shift knob, HVAC controls, and center console.
Rev. F (2006)
The US-spec STIs receive the same facelift as the Japanese-spec STIs. Mechanically speaking, the DCCD and the engine mounts have been changed. Like the Japanese-spec STIs engine mounts were changed from metal to liquid-filled plastic mounts to reduce vibrations into the car's cabin. On the largest Impreza forum, North American Subaru Impreza Owners Club NASIOC, 2006MY owners have had issues with these plastic engine mounts. The manufacturer will replace them, under warranty, if broken, with the 2005MY rubber and metal mounts. Later 2006MY vehicles were equipped from the factory with 2005MY mounts. The center differential is updated with the addition of a mechanical limited slip mechanism to supplement the electromagnetic DCCD. The torque split is changed to 41/59. The 2006MY STI weighs approximately 3,350 lb (1,520 kg).
Rev. G (2007)
2007 US-spec Subaru Impreza WRX STi Limited. Only 800 were produced.
In 2007, quite a number of changes were made to the US-spec model. Due to Subaru's decision to reduce costs by cutting the amount of aluminum used, the US-spec STI no longer receives the J-spec Spec C control arms. The control arms are now the aluminum ones used on the Japan-spec revision A and B non-Spec C STis. The high caster angle has been reduced, which in turn reduces the wheelbase from 100" to 99.4". The rear sway bar has decreased in size from 20 mm (0.8 in) to 19 mm (0.7 in). The gear ratios of second, third and fourth gears have been made longer (higher ratio) in order to improve fuel economy and driveability, which inadvertently reduces 1/4 mile drag racing times due to the ability to trap 114 mph (183 km/h) in 4th gear, without the shift to 5th. The EJ257's cylinder heads have been redesigned to improve cooling, and the sodium-filled exhaust valves have been deleted. Pistons are the same as previous years also came with the new valves and cylinder heads. The alternator is changed from a 90A rating to 110 amps. The rear Limited Slip Differential is now a Torsen unit, considered an upgrade over the previous model's helical unit. The turbo has also been changed to the VF43, which has a different wastegate actuator than the VF39. The side cowl braces are stiffer than the 2006MY. The engine mounts are once again the hard rubber mounts used prior to 2006. On the interior, there is an audio jack that replaces the ashtray, a rear center armrest with trunk pass-through and a 120 W audio system.
The ECU was completely re-engineered in order to meet US LEV2 emissions requirements, which has caused throttle and timing issues. A secondary air pump was also added to help meet LEV2. Top Feed injectors replaced the Side Feed from the previous models.
The WRX STI Limited is introduced. It is similar to the Japan-spec STI A-line, except the mechanicals of the car are based on the 2007MY US-spec WRX STI.
The differences between the 2004-2006 STi and the 2007 STi are significant and many; making these two vehicles very difficult to compare to each other. The 07 STI with a proper tune will make massive power, more then previous years of STI's do to the unique cylinder heads for that year only.
If you have bought the STi and plan on tracking this car, there is a lot to think about. When I say 'track', I mean more than 10 track excursions a year and less than transforming the car into an all out race car. Either extreme requires a very different approach. I tend to do about 20 track days a year and drive the car on occasion during the summer. In the winter, the car is up on jack stands, and being freshened up and fixed. The first suggestion I would make is that if you are going to track it significantly - say 20 plus or minus days a year, you should be able to write off the car and have another form of transportation, because you will either hit something or break something both of which can be a problem.
- Engine Oil Temperature
- Wheel Bearings
Get yourself an oil temperature gauge, then an oil cooler. In the northeaset I was seeing oil temp 260+ DegF. This is not good, even if you are running a synthetic oil. There are a lot of choices for the oil cooler from a over-priced kit to something you can do yourself for well under $200.
Yep, you got those nice big shiny gold brakes. You also have a car that weighs in around 3500 lbs with driver, fluids, etc. Just because these brakes say Brembo does not mean they are remotely similar to the Brembos found on Porsches or other expensive cars. When you push the car hard, you will quickly exceed the capabilities of these brakes, Until then, these brakes NEED a good brake fluid - lots to choose from including Motul, AP Racing, they NEED a good brake pad - I like Performance Friction but once again, there a lot of choices here including Pagid, Hawk etc, They NEED ducting - not so many choices here, RCE and Quantum Motorsports.
The STi 6-speed transmission has a small problem with the gear ratios - they are lousy. The biggest problem is that the shift from 4th to 5th drops the engine RPM by almost 1500RPM. The real issue here is when you downshift from 5th to 4th, you are working the syncros hard and they WILL give out. This leads to the 5th gear grind that a lot of folks complain about. The BEST solution here is two-fold: First replace the USDM 5th and 6th gear with the JDM 5th and 6th gear. Turns out that the US got a very low 5th gear and an even lower 6th gear because of the mileage issues. The rest of the world got a far saner ratio set. The gear set will cost around $375.00, and the installation will cost around $500. A transmission rebuild will cost around $1400, and once you get a grind, it is only a matter of time. The second part of the solution is to add yet another cooler - this time for the traney fluid. This is easy to do on this transmission. I have a gear vs rpm vs speed spreadsheet here if you want to see the numbers
Did I mention that this car weighs in around 3500 lbs with fluids and driver... Corvette, Porsche both weigh in around 3100 lbs. The newer BMWs on the other hand are a bit heavy as well...
The wheel bearings on the 2004 STi were designed for and Impreza that weighed substantially less, had skinny tires, and was never intended to be put on the race track. The heat from the brakes as well as the forces from tracking the car, especially if R compound tires are used will very quickly destroy the bearings. I lost 4 sets in one summer - It is a wear component In 2005 one of the notable improvements was to update the wheel bearings in the front, and the updated bearings can be retro-fitted to the 2004. Unfortunately this can be an expensive proposition since it will affect the rims (2004 bolt pattern is different), the shocks (2004 bottom shock mounting flange is narrower than the 2005). My 2006 now has a problem with the rear bearings. They last me less than a summer and must be regarded as a wear item.
Areas to improve
There is a LOT of compliance in this suspension. The BEST Bang-for-the-Buck solution is to buy the Group-N suspension parts and install them. They are relatively inexpensive, are well tested, and work well. The part numbers for the suspension parts (as well as some other good parts) can be found here.
Sway Bars - Very few cars cannot benefit from some after market sway bars. Decided on what you will be doing with the car eg AutoX, Road Racing, Rallying, and then add in what kind of handling attributes you prefer - understeer, oversteer, neutral, decide on your spring shock arrangement then do some searching on some of the popular web sites such as IWSTI and NASIOC in the respective Motorsports or Suspension sections. There are lots of choices and opinions, many of which are worth exactly what you paid...
Springs and Shock - Once again there are lots of choices, some good, some bad, and some true garbage out there. Same basic rules apply here as with Sway Bars, try and view all the bits as a complete system and then make your choices
I just described the logical way of doing things, the reality is that few folks have the money or the car related information to go out and buy all of THE correct parts at once, so start simple. Once again the STi parts bin has hardened rubber strut hats, lower springs, even shocks. They are not the full race stuff you will end up buying, but it is a great and somewhat expensive way to start and learn the car.
Regardless of what you change, get an alignment. If you have an adjustable suspension then get the car corner balanced at a shop that understands what a tracked car will need - VERY different than a street car, otherwise get a regular alignment at one of these shops that service track cars. You can find them by asking on your favorite boards, friends...
In my reading it seems possible to get 300-350WHP out of this motor and keep some level of reliability. The key issues seem to be that the pistons are the weak point in the stock motor - so ANY detonation will quickly become a new motor... The other point is that HEAT is the single biggest problem for this car, this translates into a bigger radiator, oil coolers (both engine and transmission), airflow management, and if you are very serious loose the AC.
The front seats are VERY heavy and not that good for the track, especially if you have a 5 or 6 point harness. Adding a set of your favorite racing seats will probably loose up to 50lbs and provide added safety. I tend to like the Recaros or the Sparcos. Stay away from the no-name seats that some folks sell - these are a safety item and the STi will go fast enough to get you into trouble. The back seat weighs around 10lbs. A roll bar is a VERY good idea and will add significant torsional rigidity.
- ECU Flash
An after market down pipe coupled with a ECU reflash will get you another 50hp or so. Total cost will be about $1000 depending. Folks tend to refer to this as a Stage 2 upgrade. Well worth the money, and reliability will not suffer that much.
There are several choices to reflash your ECU:
Each works, I have listed them in the order I prefer. I don't think that the Open ECU folks have quite the level of adjustability that the other two have.
Once you decide to trade off reliability for speed then you have bigger turbos, bigger intercoolers, a fuel system that needs to grow, better pistons, cams, etc. Just a question of how much you want to spend.