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

Starting with the 2008 model year, Subaru changed to a new 5-door hatchback chassis for its flagship Impreza STI line.  Along with the new chassis design included a completely revamped suspension that promised to not only deliver better handling, but also a step above in ride quality over the previous model Imprezas.  The step up in ride quality cannot be questioned, however feedback from many new STI owners was that the car did not feel as responsive or crisp as the previous version STI.  With this in mind, EPIC Engineering sought to solve these issues, while still maintaining the crucial aspect of ride quality.

EPIC Engineering spent almost 10 months researching and developing a spring kit to suit the needs of the vast majority of 08+ STI owners.  This spring kit is geared primarily for daily drivers who want to get more out of their suspension, but not have to make sacrifices in daily drivability.  Multiple drivers with varying levels of driving experience helped test these springs to allow for a wide variety of viewpoints and opinions.  Lowering the car approximately one (1) inch all around with slightly less in the rear, the EPIC Engineering spring kit gives an aggressive raked stance to the car, yet still very much allows the car to clear speed bumps and steep curves with little to no problem.  The ride height is optimal for handling, which is improved through progressive spring rates and replacement bump stops.  These progressive spring rates allow for a nice and comfortable ride for the highway or daily commuting, but also provide proper stiffness and responsiveness when taking corners hard.  Body roll is all but eliminated, as is the understeer and softness of the stock setup.

For the customer who is looking for exact spring rates to match up with a custom race strut setup, these springs are not going to be the best choice.  However, for every customer who wants to push their car hard at the track, the number of customers who don’t go to the track vastly outnumber them, and that customer will find the EPIC Engineering springs perfect for their daily driven needs.  The EPIC Engineering springs inspire confidence in handling and do not make the compromises in ride quality that many other suspension setups do.  The difference is in the details.

You can purchase these springs from our website by following this link.

Couple more photos:

A customer came to pick up his special order wheels today.  The wheels are Work Meister S1 2-Piece, in 15×8 -2 4×114.3 with a special Matte Gunmetal finish for his Toyota Corolla AE86.  He had these air freighted from Japan and it took a little less than 1.5 months to arrive.  Awesome stuff!  We hope to have him back for more photos after the wheels are mounted onto his car.  We’ve also added these photos to our product photos section above.

Work Meister S1 2-Piece, 15x8 -2 4x114.3 Matte Gunmetal

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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 are pleased to announce that we are now carrying Harman Motive products! These include the brand new products they’ve released for the Nissan GTR, as well as the 08+ STI. For the complete listing of Harman Motive products we have on our website, please click here.

We’ll be adding more products soon, so please keep an eye out! In the meantime, here’s a video clip of the Harman Motive midpipes for the GTR:

All right, so you’ve got the full exhaust, you may or may not have an intake, and you’ve got some engine management that we mentioned in the previous blog entry, so what’s next? Before we actually dive into talking about replacing that snail under the hood, it’s important to mention the pipe that leads to the turbo itself from the headers. This is the uppipe, and for the 02-05 WRX, it is home to the third catalytic converter in the exhaust system. Due to this cat being there, it is important to replace this pipe whether or not you decide to go with an aftermarket turbo or not. There’s been more than a few cases of the high temperatures of the turbo heating up the material that makes up the catalytic converter, which then breaks apart and has nowhere else to go but into your turbo. Since the uppipe replacement is probably the most difficult and time-intensive exhaust part to replace, it’s wise to either do this or have it done when you replace your downpipe, and of course when you replace your turbo. Given the difficulty and time needed to do this replacement, we don’t normally recommend replacing an already catless uppipe in the STI or the 06+ WRX for example since the smoother exhaust flow of an aftermarket uppipe is usually negated by the cost and time required for replacement.

So now that you’re not putting your turbo in danger, let’s talk about your stock turbo itself. I’m going to try my best not to get hung up on names and specs, so please bear with me. The 02-07 WRX and Forester XT come stock from the factory with a Mitsubishi TD04L-13T turbo. For the 08 WRX, they changed this turbo to a Mitsubishi TD04-13T to match the new style intercooler from the Legacy GT, but then Subaru decided to change it again to the IHI VF52 for the 2009 and up since the 08 WRX was critiqued as not having enough punch. The 04-06 STI use an IHI VF39 turbo, while the 07 STI uses an IHI VF43 turbo, which is essentially a slightly modified VF39. By contrast, the newer 08+ STI uses an IHI VF48 turbo that is completely different. The 05-07 Legacy GT comes stock with an IHI VF40 turbo, but that has since changed to the IHI VF46 turbo for 08 and up. It’s most likely that the newer 08 and up Forester XT also uses this same turbo, but we haven’t had any at our shop yet to verify.

Now, I know I’ve mentioned a plethora of letters and numbers that probably don’t mean anything to you at this point, but the main point out of all this is the pure and simple fact that choosing an aftermarket turbo for your car is no easy, quick and dry process. The reason why Subaru has gone to different lengths to use such different turbos in each model and model year is to provide a driving experience that is responsive, quick, and satisfying. If Subaru just wanted to go balls out with the power, they could’ve easily slapped on a larger turbo for more high-end kick, at the expense of low-end response. Mitsubishi did this with their FQ-series Evos and while they were fast on the top end, just about every automotive journalist could make a sandwich by the time the car hit boost. In choosing the right turbo for your needs, being able to make a sandwich before boost is probably something you’ll want to avoid for the vast majority of the people out there. Thus, it’s important to set goals for yourself, do your research, and if possible, go for a ride in a fellow Subaru owner’s car so you can actually feel how a certain turbo affects the car’s drivability.

We’re lucky at this point in time because there’s a wide variety of turbo upgrades available for Subarus to match just about every person’s needs, from upgrades for daily drivers all the way to full-on drag racing turbos. This wasn’t always the case however, and there was a time early in the age of the 02-03 WRXs that it was almost unfathomable that a WRX could run a quarter-mile in the 10s, much less the 12s. Back in 2002, just about every turbo upgrade consisted of a take-off turbo from a Japanese-model STI (since there was no STI in the US until 2004). These turbos were all IHI turbos, and ranged anywhere from the VF29 from the Version 6 STI to the VF34 from the Version 7 STI Spec-C. While these turbos were definitely larger than the stock WRX turbo and provided a very good and responsive upgrade, they lacked top-end power. Larger and older IHI turbos such as the VF23 and VF22 added some extra oomph, but even the modified versions of these such as the Power Enterprises PE1818 and PE1820 (respectively) would push a WRX into the 310 whp range with an aggressive tune. However, since these turbos came off of different models of WRX or STI in Japan, they were a direct bolt-on fitment, which still to this day is a big plus. Thus, combined with the limited engine management options at the time, the IHI VF-series turbos and their modified variants were pretty much the only upgrades available in the early years of the WRX in the United States.

Soon though, turbo manufacturers and modifiers started to experiment with different housings and brands. Both HKS and Greddy offered some of their own turbo upgrades, but they tended to be cost-prohibitive at the time, thus they were a rare find. Nonetheless, Greddy’s bolt-on turbo upgrade was their version of a Mitsubishi TD05-18G, and it’s possible that their use of this turbo style drew the attention of US turbocharger companies such as Forced Performance. In late 2003 and early 2004, Forced Performance (FP) began experimenting with taking Mitsubishi turbos and modifying them with housings so that they could easily bolt on to the WRX’s intake and exhaust paths. They would use different housings, different turbine compressor sizes, different sized compressor wheels, clipping the fins to supposedly help with spool, and even polishing and porting to help with airflow. After many experiments, FP ended up with a TD05-16G and a TD05-18G that bolted right into place, yet carried equal or greater punch than the IHI VF30 or VF34, which were the go-to turbo upgrades at the time. FP touted its 16G as being able to give as much power as a VF34, yet spool faster and in the end be cheaper to purchase. Their 18G consequently touted as the new big turbo upgrade for a WRX, capable of producing numbers in the 320 whp range with the right combination of parts, build options, and race fuel. The first models came out as being oil-cooled only, so turbo timers had to be used for proper cool-down after driving, but eventually FP added the stock water lines as well, making them just about as good a turbo swap as the IHI turbos.

While the new FP turbos gained popularity, the advent of the 2004 STI brought a new IHI turbo into the mix: the VF39. Similar in size and power potential to the VF29, the VF39 was often seen as a good upgrade for the pure and simple fact that you could buy one used for quite cheap. However, where would the new STI owners go for an upgraded turbo? The 18G was a possibility, but it wasn’t a huge leap in power over the stock VF39 thanks to the extra 1/2 liter of displacement. FP started to produce a few 20G variants, both with a TD05 or a larger TD06 housing, but STI owners wanted more. During the time that FP was experimenting with WRX upgrade options, they took one of their DSM upgrades, the FP Green, and modified it to fit a WRX. The FP Green is essentially a TD06-20G turbo with a larger compressor wheel, but this large size ended up being just a little too big for the 2.0L WRX and produced quite a bit of turbo lag. On the other hand, the FP Green seemed to be a perfect match for the new 2004 STI, and soon the Green became the go-to turbo for the STI. The 2004 World One STI used an FP Green with the then prototype Element Tuning Hydra EMS, which propelled the car to 440 whp on race gas and resulted in a 2nd Place Class Finish at the first Primedia Time Attack in November 2004. The FP Green was a good upgrade since there wasn’t much turbo lag and it had a decent amount of punch.

Nevertheless, STI owners still wanted more power. FP released their Red turbo, was had an even larger compressor wheel than the Green, but required a 3-inch turbo inlet tube for installation. Not satisfied with the stock-location bolt-on turbos, the demand grew for larger turbos that required the fabrication of special piping, since these turbos were simply too large to directly bolt on to the stock location and oil/water lines. Since turbos were going to be bigger, many companies started to release pre-fabricated kits using Garrett GT-series ball-bearing turbos. The theory behind the ball bearings was that they would help the turbo spool faster, especially given the much larger size compared to stock. These new “rotated mount” turbo kits typically utilized a Garrett GT30R or a GT35R, with the GT35R capable of well over 450 whp with the proper supporting mods. For those going for real big power, the Garrett GT40R and GT42R turbos were available for use with these rotated mount kits, sacrificing spool for big top end power and sub-10 second quarter mile times. Other companies such as Element Tuning also released rotated mount turbos to compete in this arena with faster spool but equal power numbers to the GT35R, but by in large the Garrett turbos were still definitely the most widely used. Although these new rotated mount turbo kits produced great power numbers, they did have a few drawbacks. First and foremost was the cost of these kits. Since new piping had to be purchased which often consisted of a new intake, downpipe and uppipe, along with an external wastegate, everything just added up to becoming quite expensive. Moreover, since the turbo was now rotated, a front-mount intercooler was an absolute requirement, so those people who wanted to retain the top-mount intercooler in exchange for a few less horses were completely out of luck.

Of course, the whole problem with the stock location turbos at the time was the simple fact that they couldn’t be large enough to produce the same power that the rotated mount turbos did, even if they spooled faster. Element Tuning helped solve this problem with their GT52 turbo, which provided the power of a rotated mount GT30R, but also spooled faster. On top of this, since it’s a direct bolt-on turbo, no extra piping needs to be purchased. This differed from the FP Red which produced similar power and spool, but required the 3-inch turbo inlet tube. Eventually, more turbo manufacturers followed suit to compete. Element Tuning then released the direct bolt-on version of the GT65 turbo, which is able to produce GT35R power in a bolt-on configuration, although requiring a 3-inch turbo inlet like the FP Red. ATP soon came out with their own direct bolt-on GT35R turbo, and for awhile, turbo technologies remained a bit stagnant.

Earlier in 2009, Forced Performance came back into the fray with their new HTA-series of turbochargers. Through their R&D processes, they were able to improve both the spool speed and also the power potential of their already venerable 16G, Green, and GT35R. For example, the HTA 68 kept the fast spool of the 16G, but put out power levels equal or greater than that of the 18G. Here at our shop, we’ve already seen great success with the HTA GT35R, as seen in our customer Luke’s 649 whp 05 STI.

So there you have it: the history of turbo upgrades for your Subaru. So which of these is going to work best for you? The most important thing to keep in mind is that generally speaking, the bigger you go, the slower the turbo will spool, but the more top end power you’ll have. It’s also important to remember that the same boost level for one turbo is going to put out a different amount of power than another turbo. By this, I mean that 18 psi on an STI’s stock VF39 is going to produce less power than 18 psi on a FP Green on the same vehicle. Remember, boost is all about the amount of air going into your motor, so with a bigger turbo, you thus are forcing in more air, and if you have more air at the same amount of boost, the pressure is much stronger, which of course leads to more power. To sum it all up, here’s a general listing of some of the turbos I’ve discussed here and their potential power levels (given the proper supporting mods and fuel):

For 2.0L WRX

• Mitsubishi TD04-16G: 210-230 whp
• IHI VF29 and VF39: 250-270 whp
• IHI VF30 and VF34: 260-280 whp
• TD05-18G and Forced Performance HTA 68: 280-320 whp
• TD05-20G: 290-330 whp
• Forced Performance Green and Element Tuning GT49: 300-350 whp
• Forced Performance Red, Forced Performance HTA Green, Element Tuning GT52, and Garrett GT30R (rotated and bolt-on): 350-400 whp

For 2.5L WRX, STI, LGT, and FXT

• IHI VF39: 280-300 whp
• TD05-18G: 300-340 whp
• TD06-20G: 330-370 whp
• Forced Performance Green and Element Tuning GT49: 350-470 whp
• Forced Performance Red, Forced Performance HTA Green, Element Tuning GT52, and Garrett GT30R (rotated and bolt-on): 375-500 whp
• Garrett GT35R (rotated and bolt-on), and Element Tuning GT65: 400-530 whp
• Forced Performance HTA GT35R: 550-700 whp
• Garrett GT40 and GT42R: 700+ whp

That should do it for this blog. In the next blog, we’ll talk about the supporting mods necessary to support the turbos I’ve talked about above, including having to build the motor to support these power levels. This will ultimately end the series, since we’ll no longer be talking about basics. As always, if you have any questions at this point, please don’t hesitate to contact us!

Many thanks to everyone who made it out to the BBQ!  Big thanks to Robert from MySubie.com again for helping organize.  We had a great turnout for a MUNday night and some really nice cars came out as well!  Here’s the gallery for my photos.  Enjoy!

[View with PicLens]

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.

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