World One Performance Blog

New from Element Tuning are the fully built Pro Comp block packages, available either in a short block or long block!  If you’re looking for a top-notch motor to drop in to your WRX or STI, look no further.  These motors have been tested and proven time and time again at the track and will set stand up to just about anything you can throw at them!  For more information, please follow either of these links:

Element Tuning Pro Comp Long Block for Subaru, 2.5L

Element Tuning Pro Comp Short Block for Subaru, 2.5L

The time has come for the final blog post in this series. In the last blog entry, we talked about turbo upgrades, and this blog will discuss the proper supporting modifications needed for a turbo upgrade, along with building up the motor. This of course is where all the basics end.

So you’ve got your exhaust, engine management, and you know what turbo you’d like to upgrade to, but you can’t just slap that bigger turbo on and call it a day. The reason why it’s not quite that simple is because the turbo adds much more air to the motor, thus you need to balance it out with additional fuel, cooling, air flow, and of course, a tune to balance everything out, since the stock ECU will not be able to compensate properly for the amount of air the turbo is going to need. Thus, after you’ve figured out what turbo you’d like to upgrade to, you also have to plan on upgrading the following (if you haven’t already):

• Fuel pump
• Fuel injectors
• Air intake
• Intercooler
• Engine Management

If you’ve been following our discussed mod path thus far, chances are you already have some sort of engine management, but probably not a larger intercooler or air intake. With an upgraded turbo, you’re going to need all of these, along with fuel system upgrades. We’ll go ahead and start with the fuel system upgrades first.

For most small to moderate-sized turbo upgrades, a simple Walbro 255lph fuel pump is more than capable of pumping out enough fuel for your needs. Walbro fuel pumps are pretty much a staple when it comes to fuel pump upgrades, and will be more than enough up to about 500 whp. If you decide to go with a turbo that’s going to put out more than 500 whp, then you’re going to need a fuel pump system capable of supporting your turbo’s thirst. There are a few options out there, such as dual Walbro pump, Bosch high flow pumps, and Aeromotive fuel pumps. Each of these is capable of doing the job properly, but we’ve had our best success with the Bosch and Aeromotive fuel pump upgrades. The thing to keep in mind however is that all of these options aren’t a direct replacement for your stock pump like the standard single Walbro pump, as you’re going to need additional lines, fittings, etc. As you can see, we’re definitely getting out of the basics now.

Of course, an upgraded fuel pump is no good if they don’t have the proper injectors to actually put the fuel into the motor. Stock WRX fuel injectors are 440cc, whereas stock STI fuel injectors are 560cc. However, this is further complicated because the WRX and the 07+ STI uses a top feed style injector, whereas the 04-06 STI uses a side feed injector. The jury is out on why Subaru decided to change this and then change it again, but it’s just another complication that you need to keep in mind. Thus, if you’re upgrading your WRX to use a VF39 off an STI, you can’t just swap in the stock STI fuel injectors unless you get the 07+ specific ones. They simply will not fit.

The size of your fuel injectors is going to depend on the size of the turbo they’ll be supporting, but generally it’s better to be capable of more fuel than to run out of fuel. On that same token, you don’t want to go too overboard either. For example, if you’re running a VF39 on your WRX, there’s absolutely no need to go with 850cc fuel injectors. This causes problems not just in the fact that there’s too much fuel available, but it’ll ultimately frustrate your tuner when they try to scale the injectors down properly. Generally, here’s what you’d be shooting for in terms of fuel injectors:

For 2.0L WRX

• 16G to VF34: 560cc – 740cc injectors
• 18G or larger: 740cc – 850cc injectors

For 2.5L WRX, STI, LGT, and FXT

• 18G to 20G: 740cc – 850cc injectors
• FP Green to GT35R (pump fuel, low boost): 850cc injectors
• GT35R (race fuel, high boost) and larger: 1000cc or larger injectors

Again, the above is all generalizations, since the amount of fuel you’ll need is also dependent on the amount of boost (and thus forced air) you’re going to be running. It’s also important to keep in mind that 850cc is pretty much the limit that the stock fuel pressure regulator will be able to handles, so if your car requires 1000cc injectors or larger, you’re going to have to replace your fuel pressure regulator with an aftermarket one, such as a Turbosmart or Aeromotive. On top of this, not every company makes direct swap-in 1000cc fuel injectors, so it’ll be important to make note if there’s anything you need to splice or add in order for the fuel injectors to function and install properly.

All right, so now you figured out your turbo, your fuel upgrades, and probably your intercooler and intake too. Of course with most rotated turbo setups, the intercooler piping and intake are typically included with the kit, otherwise you’re off to do something custom on your own. Once all of your new parts are installed, all you need now is a good tune for your choice of engine management and you’re pretty much off to the races! But wait, what about building up the motor? Are you even going to need it? In our experience, building the motor is typically dependent on a few things: tuning, size of the turbo, amount of boost you’ll be running, and your choice of fuel. For 99% of the street builds we’ve done, which are all at or below 450 whp, there really is no need to build the motor at all with proper tuning. Even at this power level in a racing situation, a proper tune has shown to keep a motor happy and healthy. For example, throughout the entire 2007 Time Attack Race Season, Phil from Element Tuning competed and won races across the country with his 2006 STI with a bone stock motor. His car was consistently powered between 450-500 whp on race gas in one of the most punishing types of racing possible, yet it still held up great and he never had a problem. Since he decided to add more power to the car in the 2008 season, he eventually built up the motor, but for all of 2007, everything was great. This shows that proper tuning is key to making sure your motor stays healthy, especially since no matter what you decide to build a motor with, a bad tune will still make it pop. Like pretty much all shops, we have our preference in terms of cost, availability, and reliability, but as long as you follow the formula below and stick with a trusted brand, everything should work great.  Here’s what we recommend if you’re sure you’ll be above the 450whp level, based on our experience:

• Forged Pistons – The stock pistons tend to be the first thing to go given enough boost, since they are cast.  Forged pistons are typically the first and foremost part that we recommend replacing.
• Forged Connecting Rods – These are also a smart thing to replace if you’re going to be replacing the pistons anyway. Forged rods will stand up to more stress and thus keep your motor healthy in the long run.
• High Performance Main and Rod Bearings – The bearings are always smart to replace if you’re going to have everything taken apart to begin with.  We always replace the bearings when we have the motor apart.
• High Performance Camshafts – Building up the bottom end was the “easy” part, but building up the heads is a completely different story. The one thing to keep in mind about the cams is that all of them will shift your powerband toward the top end, thus we usually don’t recommend cams for someone who wants low-end/street power.
• High Performance Intake and Exhaust Valves – Valves will definitely help cams breathe, but aren’t always a necessary item, as it all depends on how big of a build you’re doing.
• Titanium Valve Springs and Retainers – If you’re going to replace the valves, you might as replace the valve springs and retainers too. This will help the valves perform properly and stand up to more power you throw at the motor.
• Oil Pump and Oil Pan – If there’s one thing that a build motor and big turbo needs, it’s proper lubrication of its parts. A high volume oil pump helps keep the oil flowing when needed, and most aftermarket oil pans not only hold more oil, but also act as a heatsink to help keep the oil cool. In our experience, external oil coolers actually tend to inhibit the flow of oil and since Subarus already come with an oil cooler from the factory, we usually don’t recommend any sort of external oil cooler.
• Headstuds – You want to make sure there’s a good seal when you put the motor back together. Thus, getting proper headstuds that can take the pressure are very important.

And with that, we pretty much have an awesome motor that can handle almost anything you can throw at it. Sure, you can go with a sleeved block and increase displacement, but if that’s really your goal, you probably wouldn’t stopped reading this a long time ago, since that’s WAY beyond the basics. In any case we’ve built cars that are capable of well over 650 whp with all of the above build motor mods, which is going to be more than enough to satisfy just about everyone. I hope you’ve enjoyed this series of blog entries, and I hope it’ll remain as a good reference to all Subaru enthusiasts out there. Happy modding!

We’re quite proud of this customer car The 1000cc injectors were maxed out, so hopefully with some larger injectors and full Q16 we’ll be able to break the 700 whp mark. Car was tuned with an Element Tuning Hydra by Phil from Element Tuning. I’ll let Phil contribute with his thoughts.

The car hit 649.3 whp on Q16/92 Pump 50/50 Mix, and 555.6 whp on 92 Pump + Water. Dyno and photos:

Major Modlist:

World One Built Motor
- CP Pistons and Rings, Standard Bore
- Element Tuning Rods
- Cosworth Cams
- Cosworth Main Bearings
- Cosworth Rod Bearings
- Cosworth High Flow Oil Pump
- Brian Crower Valve Springs and Titanium Retainers
- Brian Crower Intake and Exhaust Valves
- ARP Headstuds
- Moroso Oil Pan
- Rotated Intake Manifold

Element Tuning Hydra EMS
Element Tuning Hydramist
Element Tuning Catch Can
Forced Performance HTA GT3586R
Custom 3-inch Downpipe
Custom Twin Dump Uppipe
Custom 4-inch Intake with Filter
Custom Intercooler Charge Pipes
Greddy Evo2 Catback
Tial MSV 38mm Wastegate x2
APS DR525 FMIC
Turbosmart E-Boost2
Turbosmart 1200 Fuel Pressure Regulator
Ultimate Racing 1000cc Injectors and Fuel Rail Kit
Bosch High Output 72psi Fuel Pump
TiTek Equal Length Header

Hopefully, our previous engine management discussion didn’t overload your brain and just kept you coming back for more with this latest installment.  We pick up where we left off moving to the “Stage 3,” which typically involves an upgraded intercooler.  Just like with almost every modification we’ve discussed thus far, intercoolers carry with them some myths that many people believe to be true without ever having any personal experience to back up their claims.  But, before we get into those myths, it’s important to know what exactly the intercooler does in the first place.

The intercooler is essential to making power and maintaining efficiency on a turbocharged motor. There are two main types of intercooler:  air-to-air and air-to-water.  Most factory turbocharged cars use an air-to-air intercooler, since it’s much less complicated mechanically (no need for a water reservoir for heat exchange), not as heavy, and typically not as expensive either.  Air-to-air isn’t quite as efficient as a good air-to-water intercooler, but the cost/benefit involved tends to make the air-to-air intercooler the top choice is most situations.  Nevertheless, both types of intercoolers do the same thing:  they cool down the charged (compressed) air from the turbo so that it’s more dense when going into the motor.  As air is compressed, it generates heat, and heat also expands.  With more heat involved, there are less oxygen molecules, and with less oxygen going into your motor, the less power you can make.  The intercooler helps this by pushing this heated air to the intercooler core, which looks and acts similarly to a radiator.  As cool air passes over the intercooler fins, it helps cool down this air and makes it more dense as it then gets pushed into the motor.  Cooler, dense air contains more oxygen molecules, and thus you’re able to make more power.

Since the intercooler core acts as a heat exchanger, the size of the core determines how well or efficiently it can cool down the compressed air. The location of the intercooler core also matters as well, since it can easily be affected by ambient temperatures and needs proper airflow to do its job.  This is where a lot of the debate and myths start to come into play.  Subarus come stock with a top-mount intercooler (TMIC).  The size of this TMIC depends on the model and year of your car, with the STI TMICs typically being the largest offered from Subaru.  Given the size of the stock turbo (depending on the vehicle), the stock TMIC is usually perfectly fine for cooling and efficiency.  You can put on a larger intercooler and it won’t hurt anything, but you will need to get tuned properly for it and in the end, it might not yield much of a significant difference over stock.  Seeing gains of maybe 10 whp maximum typically isn’t worth the $900+ you’d have to pay to reach that much of a boost in power.

The location of the intercooler is the next matter of contention.  While the stock intercooler is located on top of the motor (hence the name top-mount intercooler), it really isn’t the most efficient place for the intercooler, especially when upgrading to a larger one.  The main reason for this is the simple fact that it sits not just on top of the motor, but also on top of the turbo, which of course radiates quite a bit of heat.  While the stock heatshield helps with this, when upgrading to a larger turbo, you can’t reuse the stock heatshield (or really any other heatshield for that matter) and thus the TMIC suffers greatly from heatsoak.  This is much more apparent when the car is stagnant such as in stop-and-go traffic or in line at the drag strip, rather than when the car is actually traveling at speed on the road.  In the case of the car actually moving, the stock hood scoop, combined with the stock air splitter, actually does a good job of helping provide proper airflow to the TMIC as well as shielding it from the ambient heat from the motor.  However, the problem then is with a larger TMIC, because the stock air splitter is not typically compatible with a larger TMIC, and in the case of an aftermarket hood, there simply isn’t any air splitter whatsoever.  This isn’t to say that a larger TMIC won’t do a better job than the stock one, but simply that there are definitely drawbacks to keeping the intercooler on top of the motor.

By far the best location for the intercooler is at the front of the vehicle.  Front-mount intercoolers (FMICs) draw air directly from the front of the car, which helps not just when the car is moving with air flowing over it, but also at a stop since it has direct contact with the outside air.  However, some people have insisted that by putting the intercooler at the front of the vehicle, there’s too much of a drop in pressure because of the added piping, and thus you will suffer additional turbo lag.  With proper tuning, this is completely false, and is normally a complaint from people who install a FMIC and do not get properly tuned or even tuned at all.  Owning two Subarus, both with FMICs, I can say with full confidence that there’s no difference in turbo lag whatsoever thanks to proper tuning.  However, there is indeed a pressure drop nonetheless, and thus it’s important to choose the right size core.

There’s always been the idea that bigger equals better, but when it comes to intercoolers, this isn’t necessarily always the case.  With Subarus specifically, there are some intercoolers that are just too large for the turbo its supporting, which causes too much of a pressure drop and thus a car isn’t able to make as much power as it could have with a smaller intercooler.  For example, the APS DR725 you see to the left here on Bailey’s car is gigantic, so it really wouldn’t be the right choice for a smaller upgraded turbo such as an 18G or 20G, and definitely a bad choice for the stock turbo.  Plus, given the fact that smaller intercooler cores such as the APS DR525, TurboXS, and Perrin are more than capable of handling well over 600 whp, you pretty much have to get a matching gigantic turbo to take full advantage of the DR725’s size.  Along with the size of the intercooler core comes the change in weight distribution, since you’re essentially adding 35 or more pounds to the front of the car.  Many would argue that this alone is reason enough to keep the intercooler in the top mount location, but generally speaking, this is more of a problem for those who do lower-speed racing such as auto-x, rather than types of racing that require the full power output, such as time attack and drag racing.  Finally, the other problem with a FMIC is purely aesthetic, since in most cases you have to do quite a bit of cutting of your front bumper cover to fit the intercooler there, not to mention you lose your factory bumper beam as well.  Most kits will include a replacement bumper beam of some sort, but it’s still not the factory, government-approved, and crash-tested bumper beam, so more frontal damage than expected is likely to occur should you get into some sort of accident.

Despite its drawbacks, we normally recommend FMICs to anyone who wants to bring out the full potential of the car.  It’s just important to choose the right size and design to suit your needs.  Of course, since a bigger intercooler doesn’t really benefit you without a bigger turbo, we’ll be talking about the different aftermarket turbos out there in our next blog entry.

The boss gave the OK for some crazy exhaust sales going on. Just follow the links below:

All Invidia 35% off

All MXP 10% off and free shipping

Element Tuning Turboback for 02-07 WRX/STI 18% off

JIC 02-07 Spartan Type 1 WRX/STI Exhausts 12-15% off

Greddy Ti-C Catback for 02-07 WRX/STI 18% off

Greddy Evo2 Catback for 02-07 WRX 18% off

These crazy exhaust sales will not last for long. Purchase now to secure your order!

Continuing from the other day’s blog, you can see we’re obviously a day behind. But, let’s continue without delay!

The UTEC quickly became the go-to form of engine management between 2003 and 2004, but soon Cobb released their own AccessPort to compete with the UTEC. The AccessPort was a reflashing device instead of a piggyback ECU, which offered several advantages. Being a reflashing device, nothing needed to be installed between the stock ECU and the car (like how piggybacks are installed), and since it reflashed the stock ECU, it was similar to the ECUtek in terms of tuning resolution. Since this reflashing was done through the car’s OBD-II port under the steering wheel, the AccessPort could also be used to log and/or display types of data, such as RPM, throttle position, and more. The AccessPort also included pre-made basemaps for specific engine mods, which made it just as easy, if not easier to use, than the UTEC for those who are not interested in doing their own tuning. Cobb eventually released their own AccessTuner to allow users to do their own tuning, but it was a separate option and not included as part of the standard AccessPort package. For those who didn’t care to tune their own car, Cobb gave their dealers with AWD dynos the option to do “Protunes,” which allowed for professional tuning via the AccessPort at a shop. These Protunes could also be saved and distributed, so many Protuners released their own maps to match specific modifications as well. Despite some initial hiccups to get all of the basemaps working properly and safely for all vehicles, the AccessPort went on to become a huge success for Cobb Tuning, and it eventually overthrew the UTEC for the king of the hill in affordable engine management.

However, the basemaps that both TurboXS and Cobb supplied did have their disadvantages. In order to maintain safety, these maps were tuned for the lowest common denominator and were specific per octane level as well, to ensure that customers would not blow up their motors. While they still improved performance over being untuned and they kept the motor healthy, there was still always going to be room for improvement with a custom tune for each specific car. This still remains true today, although the margin for improvement has been able to shrink with some new engine management options available. The other problem (although not a problem for most people) is that you typically have to follow a specific mod path for the basemaps, and if you stray away from that, you have to get a custom tune for your car no matter what. While for big horsepower applications a custom map is a given, simply changing your intake away from the stock airbox is enough to warrant a custom tune, except for intakes specifically developed by TurboXS and Cobb Tuning respectively. As mentioned in the previous blog, the stock airbox is rather efficient so this may not be a big deal, but not being able to change the intake without a custom tune does put limits on your freedom of modification. Striving for more freedom of modification, other companies sought out to create another option for those people who wanted to not only wanted more freedom than he UTEC and AccessPort offered, but also get away from the limits of the stock ECU itself.

Enter the Element Tuning Hydra EMS. In 2005, Element Tuning entered the fray with their version of the Hydra EMS. The Hydra is a standalone ECU that completely replaces the stock unit. While standalone ECUs of the past required the user to tune every aspect of the car’s behavior from simply idling all the way up to wide-open throttle, Element Tuning took this difficult and time-consuming process out of the equation by taking care of all this programming already, as well as shipping the Hydra with basemaps specific to each car’s modifications, much like the UTEC and AccessPort. Moreover, Element also had maps available for a wide variety of different sized turbos, water/alcohol injection, and different sized intercoolers and intakes. The Hydra also had equal or better tuning resolution than the stock ECU, thus a basemap from a Hydra would typically be more accurate than that of a UTEC or AccessPort. This lowered the amount of custom tuning that would need to be done, but of course a custom tune per vehicle would also bring out the full potential of the car’s setup, which of course was easily possible with the provided software. On top of all this, the Hydra was also very adaptable to different environmental conditions, so the problem of having a map tuned for sea level and then needing a completely different map for mountain passes was effectively eliminated. Our own World One STI back in 2004 actually had a prototype Hydra EMS that helped it finish 2nd in its class and 6th place overall at the very first Primedia Time Attack. However, as good as this system is for tuning and adaptability, it also had its disadvantages, especially for daily drivers. The main issue is that because it’s a replacement to the stock ECU, it does not support OBD-II, and thus it will not pass emissions in just about every state in the country. The other issue, although it may be a very minor issue to some, is that you also lose your cruise control, however this is problem is apparently being fixed for the 08-09 STI. AEM soon followed up with their own plug-n-play Hydra EMS, but not until just in the past year, so support and available tuners aren’t quite as available at this time currently.

Since the release of the Hydra, both TurboXS and Cobb Tuning have updated their UTECs and AccessPorts respectively to add more features, but yet another option was introduced in 2006 that has since thrown the engine management market on its head. A group of computer-minded enthusiasts put their minds together and were able to connect to the stock ECU and then go on to start programming it. It took awhile to get things reliable and easier to use, but as it stands today, this Open Source style of tuning using the OpenECU software has become an easy entry point for customers to start tuning their own vehicles, especially since the software itself is free to download. The only purchase necessary is the Tactrix cable, that allows you to connect your laptop to your car’s OBD-II port (much like how the AccessPort connects). While OpenECU is always in a state of development, many tuners have embraced the software and use it as their primary form of tuning, allowing them to tune to the same levels as that of the AccessPort and ECUtek. Of course, the drawback is that you have to rely on user support rather than having any guarantees or formal support from a company, so in many cases, you’re on your own.

Overall, Subaru owners should be thankful that they have so many choices available to them. This isn’t the case with other makes such as Mitsubishi and Nissan. No matter what form of engine management you choose, it’s always important to understand that how well your car performs is going to depend on how the car is tuned, whether that’s strictly from a basemap or from a custom tune. If you go with a custom tune, be sure the you go to a reputable tuner that has experience tuning the type of setup that you have. After all, just because someone can tune a 300 whp car doesn’t mean that they won’t have any problems tuning a 600 whp car. As always, if you have any questions, please feel free to contact us or post a comment here. For our next part in this series, we’ll be talking about intercoolers, both top mount and front mount, and how they can affect your car’s behavior.

Yesterday, we discussed the choosing of an aftermarket catback system to the WRX or STI, not only for additional power, but also for aesthetic purposes. However, as much as we all love the boxer sound, in terms of actual measurable power, the catback alone really doesn’t do much. Thus, after the catback, the next power mod most people consider is an aftermarket downpipe. The downpipe is where the true power starts to be made, since as you can see from the photo to the right, the stock downpipe has 2 power-robbing catalytic converters, or “cats” for short. In this photo, the downpipe on the bottom is the stock downpipe, whereas the downpipe on the top is an Invidia catless downpipe. In comparing the two downpipes, you’ll also notice a few differences other than the cats: the stock downpipe is split into two pieces (some people and manufacturers only refer to the top-most section as the downpipe, and the second section as the midpipe), and the flange at the top that connects to your turbo has a flat plate. These two differences are clear examples of how different companies prefer to approach creating an aftermarket downpipe.

Before we go further however, we must make a disclaimer: removal of the stock catalytic converters is for off-road use only, and if caught using a catless system on the street, you may be cited and fined. In other words, you do have to pay to play, so make sure you’re well aware of this, especially in states like California where emissions laws are very strict and may involve impounding your car if violated. Now that that’s out of the way, most aftermarket downpipes have the following features that are geared as improvements over the stock downpipe:

• Removal of all cats or replacing 1 or 2 cats with high-flow performance cats
• Replace the flat flange at the turbo side with a “bellmouth” or “divorced wastegate” flange
• Change from a 2-piece pipe to a 1-piece pipe

Of course, just the same as with catbacks, not every downpipe is equal, and this is even more clear with the different designs out there. No matter the design though, the main thing that really should be considered is fitment. Some downpipe have problems fitting due to hanger location, but others simply have issues with fitting because they’re made to mate to their own proprietary exhaust system, so they might require a separate pipe for it to connect to the aftermarket catback of your choice. On top of this, most aftermarket downpipes will not bolt on directly to the stock catback for 02-07 WRXs and STIs, however this is completely the opposite for 08-09 WRXs and STIs, which don’t have any problem bolting to the stock catback. Why would you want to bolt onto the stock catback you might ask? Well, although you do sacrifice power by sticking with the stock catback (since it creates a bottleneck), you do get a significant power increase over stock and you don’t attract any unneeded attention from the authorities.

Once you’ve sorted out fitment issues, the next thing to consider is going catless or staying green-friendly with a high-flow cat. It has been argued that a good high-flow cat will not hamper power at levels below 400 whp, but in our experience, this has not been the case whatsoever. Moreover, running catless helps with throttle response and faster turbo spool since there’s no back pressure in the exhaust system to slow down the exhaust flow. It has also been argued that running catless creates a bad exhaust smell in the cabin, but while this may be the case when a catless downpipe is initially installed, the smell does go away over time, so long as the downpipe was installed properly with no leaks. And, since catted downpipes are typically almost twice as expensive as catless downpipes, unless you absolutely need a catted downpipe for emissions or racing restrictions, we always recommend a catless downpipe. Catless? But what about the check engine light? Well, certain forms of engine management will turn off this check engine light for you, but we will get into that when we talk about engine management in a future part of this blog series.

After deciding on whether to go catless or catted, the next big decision is in regards to the downpipe’s flange at the turbo side. Here are a few examples of the available options, other than stock downpipe’s flat plate design. First up is the “bellmouth” design, which looks like this on the TiTek downpipe:

Next up are two variations of the “divorced wastegate” design. The idea behind the divorced wastegate is that a stock style turbo has exhaust gases the escape from the turbo’s internal wastegate, and since that might cause turbulence when mixed in with the ordinary exhaust gases that exit the turbo, it’s better for these gases to exit out separately so that the exhaust flow is not interrupted. The first one is Invidia’s version, which is essentially just a flat divider plate that diverts the gases, but the gases still go down the same exact pipe further along:

In contrast, here is Element Tuning’s take on the divorced wastegate design. This downpipe actually features a completely separate pipe for the wastegate gases, which then meets up later on with the rest of the piping. The theory behind this is that it’s a true divorced wastegate and the extra smaller piping creates a venturi effect which makes the wastegate gases not only flow faster, but also create a suction effect that makes the rest of the exhaust gases flow faster as well:

In our experience, we definitely recommend either of the above styles. It’s best to stay away from the stock downpipe’s flat plate style, which can be found on a few downpipe brands out there. However, between a bellmouth and Invidia’s divorced wastegate style, we have not seen or felt a significant difference in power. On the other hand, Element Tuning’s divorced wastegate style has proven to produce more power over the other styles.

Finally, you’ll notice that Element Tuning’s downpipe is a 2-piece design, whereas the Invidia design is a 1-piece. Generally speaking, a 1-piece tends to be better when avoid exhaust leaks, but a 2-piece design gives the option to change from a catless race pipe to a catted pipe at your discretion. Not every 2-piece downpipe has an option for a catted downpipe however, so it’s best to do your research (as always) before purchasing. Nevertheless, if you have any further questions, again please don’t hesitate to contact us. For the next blogs, we’ll change gears a little bit and highlight some products and feature a customer car, but next week we’ll come back to the power mod path with a discussion about intakes and engine management.

Continuing off from yesterday’s wheel offsets discussion, since the vast majority of our clients are Subaru Impreza owners, it only made sense to discuss wheel sizes and options that fit on the Impreza, and the potential problems that might arise. As mentioned yesterday, heels have to clear 3 main things in order for them not only to fit on the car, but also roll freely: fenders, suspension, and brakes. To add complexity to this, the wheel diameter, width, offset, and even spoke design come into play. For example, even though a wheel might have a diameter, width, and offset that works fine, another wheel with the same exact measurements but a different spoke design might not clear the brakes. And of course, this depends on the brakes being used, whether it’s the stock STI Brembos, a StopTech BBK, or the 06-07 WRX calipers. The good thing though, is that we’ve installed a number of different wheel and tire setups here at our shop, so we can speak with confidence on the combinations I’m about to mention. I’ll also include the necessary suspension and/or fender modifications required for these wheels to fit without any rubbing.

For 02-09 WRX and 04 STI

The WRX and 04 STI are plagued by the 5×100 bolt pattern. This pattern is the actual distance that the lugs are spread apart on the wheel hub. While you wouldn’t think that a 14.3mm difference between the WRX and STI is a big deal, as it turns out, the wider the wheel and the lower the offset you go, the more stress you put on the wheel bearings in this bolt pattern. For this reason, many of the wheel manufacturers that we carry do not even make certain wheel fitments for 5×100. Here are a few examples that we have personal experience with:

• Volk TE37 17×8 +44 5×100 (clears STI Brembos)
• Volk TE37 18×7.5 +48 5×100 (does NOT clear STI Brembos)
• Volk CE28N 17×7.5 +50 5×100 (does NOT clear STI Brembos)
• Volk CE28N 17×9 +43 5×100 (clears STI Brembos, may require fender rolling depending on tire)
• Volk CE28N 18×8.5 +44 5×100 (clears STI Brembos)
• Volk GT-V 18×8 +46 5×100 (clears STI Brembos)
• Volk GT-S 18×8 +43 5×100 (clears STI Brembos)
• Gram Lights 57 Maximum 18×8.5 +45 5×100 (clears STI Brembos)
• Gram Lights 57 Optimise 18×8.5 +43 5×100 (clears STI Brembos)
• 57Motorsport G07WT 17×9 +45 5×100 (clears STI Brembos)
• Advan TC-II 18×7.5 +48 5×100 (does NOT clear STI Brembos)
• Advan T6 18×8 +45 5×100 (clears STI Brembos)
• Advan RS 18×8.5 +48 5×100 (clears STI Brembos)
• Advan RC-II 18×7.5 +48 5×100 (does NOT clear STI Brembos)
• Prodrive PWRC1 18×7.5 +46 5×100 (clears STI Brembos)
• Prodrive GT1 18×7.5 +53 5×100 (does NOT clear STI Brembos)
• Enkei RPF1 17×8 +45 5×100 (clears STI Brembos)
• Work Emotion CR Kai 18×7.5 +42 5×100 (clears STI Brembos)
• Work Emotion XD9 18×8 +45 5×100

As far as tire sizes go, you are of course limited to the width of the wheels that are even available to 5×100. In most cases, you can run a 245/35/18 tire no problem without any rubbing issues, but you can also run a 245/40/18 if your car isn’t lowered very much. However, a 255 tire will definitely require fender rolling and/or cutting.

For 05-09 STI

The change to the 5×114.3 bolt pattern opened up a plethora of wheel options to STI owners. Since 5×114.3 is a more universally-available bolt pattern, just about every wheel manufacturer had varying sizes of wheels that would fit. 8 and 8.5 wide fitments were almost always safe without any risk of rubbing, so long as you didn’t roll with a 245 or larger tire size. A 235 tire size is almost a sure-fire perfect fit with no rubbing issues. However, with more wheels available in 9 and 9.5 inch widths, the trend moved toward these wheel and tire sizes, which almost always require fender modification. Specifically for 9.5 inch widths, coilovers were required for suspension clearance along with rear camber bolts in order for the wheels not to rub on the fenders, which of course needed to be rolled anyway. Again, a few examples, each of course clears STI Brembos:

• Volk CE28N 18×8.5 +52 5×114.3
• Volk RE30 18×8.5 +52 5×114.3
• Volk RE30 18×9 +50 5×114.3
• Volk TE37 18×8.5 +50 5×114.3
• Volk CE28N 18×9.5 +40 5×114.3 (requires fender rolling, coilovers, and rear camber bolts for 05-07 STI only)
• Gram Lights 57 Maximum 18×8.5 +45 5×114.3
• Gram Lights 57 Optimise 18×8.5 +43 5×114.3
• Gram Lights 57F 18×8.5 +45 5×114.3
• Advan RG-II 18×8 +45 5×114.3
• Advan RS 18×9 +45 5×114.3
• Advan RZ 18×9 +45 5×114.3
• Prodrive GT1 18×8.5 +53 5×114.3
• Prodrive GC05F 18×8.5 +44 5×114.3
• Prodrive GC010G 18×8.5 +46 5×114.3
• Prodrive GC05F +44 5×114.3 (requires fender rolling, coilovers, and rear camber bolts for 05-07 STI only)
• Prodrive GC010G 18×9.5 +44 5×114.3 (requires fender rolling, coilovers, and rear camber bolts for 05-07 STI only)
• Prodrive GC010E 18×9.5 +44 5×114.3 (requires fender rolling, coilovers, and rear camber bolts for 05-07 STI only)
• Prodrive GC06H 18×9.5 +44 5×114.3 (requires fender rolling, coilovers, and rear camber bolts for 05-07 STI only)
• Enkei NTO3+M 18×9.5 +40 5×114.3 (requires fender rolling, coilovers, and rear camber bolts for 05-07 STI only)\
• Work Emotion XD9 18×9 +43 5×114.3
• Work Emotion CR Kai 18×8.5 +43 5×114.3

Obviously, with wider wheels, you can run wider tires. As mentioned above, just about everything 255 and up will require fender rolling, but we’ve managed to fit 265/35/18 and 275/35/18 after fender and suspension modification as mentioned above. The Element Tuning Time Attack Race Car pictured above runs on Prodrive GC05Fs in 18×9.5 +44 5×114.3 and 275/35/18 Hankook race slicks.

For 08-09 STI

The wider track and fenders of the 08-09 STI definitely allow for even wider wheels and tires, with much less risk of rubbing. This is partially due to the fact that the 08-09 STI comes with 18×8.5 wheels straight from the factory. All of the above wheels fit perfectly fine on the 08-09 STI, however 265 and wider tire sizes may require fender rolling, depending on how low of an offset you decide to run. Generally speaking, staying with a 05-07 STI safe offset will not require any fender modification on the 08-09 STI, and any of the 18×8.5 wheel sizes can simply reuse the stock Dunlop 245/40/18 tires. Fitment examples:

• Volk CE28N 18×9 +35 5×114.3
• Volk RE30 18×9 +35 5×114.3
• Volk TE37 18×9.5 +40 5×114.3
• Volk TE37 19×9.5 +43 5×114.3
• Advan RS 18×9 +35 5×114.3
• Advan RZ 18×9 +35 5×114.3
• Work Emotion XD9 18×9 +38 5×114.3
• Work Emotion CR Kai 18×8.5 +37 5×114.3

Again, I should stress that these are all just examples that we’ve tried here at our shop, and there are very many other wheels and sizes that will fit just fine. Just remember to do your research and if all else fails, contact us and we’ll be happy to make a recommendation!

Phil from Element Tuning just recently posted up some results from a car that he tuned. The car featured an Element Tuning GT65 bolt-on turbo, Element Tuning Hydra EMS, Element Tuning Hydramist, and supporting mods. This combination helped the car reach 494 whp and 445 wtq! More information on this can be found here on NASIOC.

The GT65 bolt-on is actually the turbo we’re planning to put in our own 08 STI. Since it is a direct bolt-on turbo, there’s no need for extra piping or an external wastegate setup. You get the power of a rotated GT35R (as proven by Phil in the link above) without all the hassle of custom this and custom that. This turbo makes proven power, and can be yours for $2099 including shipping.

With many turbo choices out there, Subaru owners are fortunate to have such a wide variety of sizes and power ratings available to them. However, with so many different names and numbers flying around, it’s easy to be confused as to what turbo works best. In the near future, we’ll have a post on choosing the best turbo to suit your needs, but this time around we’d like to highlight our best-selling turbo for 04+ STI owners: the Element Tuning GT52.

Unlike many other turbos out there that start relatively inexpensive, and then allow you to do your own customization in terms of housings, compressor wheels, porting, and polishing, Phil over at Element Tuning decided to do away with all the guesswork and actually create a turbo design that maximizes all possible potential given its size. Months of research and development went into the ultimate design of the GT52 turbo (as well as its smaller sister, the GT49 turbo). The final product ended up becoming our best-selling turbo, with countless happy customers both nationwide and internationally. Here’s how Phil himself describes the GT52 turbo:

This turbocharger is very similar to many other 7cm TD06 20G framed bolt-ons but that’s where the comparison ends. In this particular turbocharger we use a Garret GT30R 52 lbs compressor wheel, Garrett turbine wheel and shaft. The compressor is a GT30R rated at 52 lbs utilizing an internal wastegate.

Typically we see 20 psi by 3600-3800 rpm tuning with the Hydra with pump gas power in the 375-400 whp range. Both housings are completely ported for increased flow and wastegate performance. Race gas power is in the 475-500whp range.
Expect to achieve full boost with the proper modifications and a quality tune between 3500-4000rpms. Fuel upgrades for this turbocharger and proper engine management are required.

The Element GT52 has been recently updated to increase internal wastegate performance. Increased port work, larger wastegate port, and a larger wastegate valve has been utilized to ensure boost creep free performance.

Element GT bolt-on turbochargers include extensive porting of the turbine housing inlet, outlet, and wastegate passages. The wastegate passage is also enlarged and the turbine wheel modified to improve internal wastegate performance and creep free running.

All Element GT bolt on turbochargers are water cooled and come complete with water lines and an OEM oil drain line so installation is a direct bolt-on.

In our personal experience, we have been able to confirm all of Phil’s advertised numbers. This turbo does indeed hit about 20 psi by 3600 rpm and Patrick’s 07 STI hit 475 whp on race gas, which is well within the range that Phil described for horsepower numbers. Thanks to this turbo’s consistency and good availability, the GT52 has become our go-to turbo for any STI owner who wants a good balance of street power and track dominance. Since this turbo is a direct bolt-on, no extra piping or modification is required, although we do recommend replacing the turbo inlet pipe and switching to a Big MAF style intake. We also recommend Element Tuning’s stainless steel oil feed line for best results and to keep the turbo healthy.

You can purchase the Element Tuning GT52 Turbo for $1899 including shipping by clicking here.