World One Performance Blog

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!

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]

Last week, we finished discussing the different downpipe options out there, but before we get started with intakes and engine management, I just want to make note of the title change of this particular blog series. The reason for this is that it was mentioned to me by a reader (thanks, Mike!) that this same advice will also apply to Legacy GT and Forester XT owners as well. While some of the designs of the exhaust components may be different, the motors all behave similarly since they’re almost exactly the same anyway. Thus, if you’re a Legacy GT and/or Forester XT owner, don’t fret: these same mods will work for you too!

Anyway, we’ve covered the turboback portion of the exhaust, so now let’s talk about the intake. Just like with some of the exhaust myths we previously discussed, the intake has many myths associated with it as well. Some people have insisted that any and all aftermarket intakes are bad for your car, and that your car will soon near explode if one is installed. This blatant generalization is really quite false, and while some aftermarket intakes do not work as well or are as properly-designed as others, putting on an aftermarket intake is not going to spell instant death for your Subaru. In fact, it was proven in the November 2008 issue of Subiesport Magazine that intakes do make a difference, and that certain intakes are definitely better than others, especially after tuning. Thus, if you’re afraid that getting an intake is going to hurt your car, as long as you choose wisely, everything should work out just fine. While the stock airbox is actually very efficient and is already by design technically a cold air intake, an aftermarket intake will provide a noticeable increase in throttle response, since the higher flow of air will help your engine rev faster. This higher flow of air however can pose some problems, especially the farther along you go in your power mod path.

These problems arise when choosing your engine management options. Unlike other cars, such as the Evo, the stock Subaru ECU (or “engine control unit”) can be very temper-mental, depending on the mods you put on the car before tuning. Just like how the myth propagated that an aftermarket intake will blow up your car, a similar myth has been attributed to the turboback exhaust system, with some claims that installing a turboback will void your warranty. This is absolutely not the case, and we’ve even fought a local Subaru dealership and won in a warranty fight, with Subaru of America themselves ordering the dealership to provide warranty service to our customer’s car. In any case, this “if you install this mod, you’ll blow up your car” nonsense ties in to engine management, since now the phrase has become “if you install this mod, you’ll blow up your car UNLESS you get some engine management.” The truth is, YES, your car will perform better when tuned properly with good engine management, and YES your car will be more reliable and safer when tuned properly with good engine management, but NO your car will NOT blow up just because you installed an aftermarket intake and an aftermarket turboback exhaust system. Obviously, this doesn’t take a person’s driving style into account, but the whole idea of instantaneous motor death is ridiculous at best. We still very much recommend engine management at this point, but more because it’ll truly bring out the full potential of the car (especially when tuned properly) and because the car will perform better and more reliably, but not because it casts some sort of protection charm over you motor.

So, if engine management isn’t absolutely and completely necessary at this point, at what point is it? The intake and turboback modifications we’ve discussed are still really basic bolt-ons, thus the temper-mental stock ECU can still do its job without too many problems. However, the additional airflow both into the motor and out of the motor does confuse the stock ECU a bit, hence why engine management at this point is definitely recommended to get the ECU back on the right path. Beyond this point, when you add even more air flow (such as a bigger turbo, intercooler, and intake) and also more fuel (such as larger fuel injectors), the stock ECU simply does not know what to do, and thus engine management is absolutely necessary. Often times, the car simply will not idle or run at all without engine management and these additional mods. Thus, to put it plainly: for an intake and turboback, you’ll probably be just fine, but for anything more than that, you’ll definitely want engine management.

Now that you found a need for engine management, either because you’re going with big power mods or because you just want your turboback to perform to its fullest potential, what’s the best engine management choice? This is where things could potentially get complicated. There are three main forms of engine management available for Subarus:

ECU Reflash

• Cobb Tuning AccessPort
• OpenECU
• ECUtek

Piggyback ECU

• TurboXS UTEC
• Dastek Unichip

Standalone ECU

• Element Tuning Hydra EMS
• AEM EMS
• Tec3
• LinkECU
• MoTec

While each of these forms of engine management accomplish the same basic principles, they each do it in different ways, and ultimately to different levels of success as well. An ECU Reflash uses the stock ECU, but loads different maps on it to control the motor, allowing the stock ECU to still control other functions such as the HVAC and cruise control. Piggyback ECUs are small computer devices that act as a middle man between the stock ECU and the rest of the car, with one end plugged into the stock ECU and the other end plugged into the car’s wiring harness. Finally, standalone ECUs completely replace the stock ECU with a new one.

Back when the WRX first made its way across the Pacific in 2001, the two main engine management solutions available at the time specifically for the WRX were the ECUtek reflash and the Dastek Unichip, which was offered by TurboXS and Vishnu Performance. The ECUtek reflash worked and still works well, but the license to be an ECUtek programmer was/is on the very expensive side, so typically these reflashes needed to be performed by a shop every time. The TurboXS and Vishnu Unichips on the other hand had a pre-installed basemap to suit specific level of car modification right out of the box, and could be further programmed by an authorized tuning shop specifically for each vehicle. The difference between the different company’s Unichips was how the basemaps were programmed and how they would connect to the car, either via a wiring harness or if they had to be hard-wired. It was from TurboXS’s “Stages” that we get the Stage 1 to 4 levels that we still use to this day: Stage 1 was for a Unichip and catback only, Stage 2 was for a Unichip and Turboback, Stage 3 was for an added larger intercooler, and Stage 4 was for an added larger turbo, injectors, and fuel pump. Anything more than that was simply considered “Stage 4+”. Since both Unichips came with a preloaded map to match your level of modification and it was a relatively easy install, the Unichip was by far the more popular option at the time. However, one problem with these preloaded basemaps is that they were designed specifically for the airflow of only the stock intake airbox, and thus aftermarket intakes were not compatible with the preloaded basemaps, and therefore required custom tuning. This caveat has been an issue with many later forms of engine management, including the Cobb Tuning AccessPort we all know and love today. Nevertheless, people (myself included) happily removed the aftermarket intake they purchased and reinstalled the stock airbox to ensure that the Unichip was happy and performing properly. Standalone ECUs such as the Tec 3, LinkECU, and MoTec existed, but since they did not have the same plug-n-play functionality of the Unichip, they were often only used by more hardcore WRX modifiers. After all, the last thing most customers want to do is spend hours tuning their ECU just to get their car to idle correctly, let alone actually increase performance over stock.

Over time, the Unichip started to show some problems. For one thing, certain Unichip owners would find that the pre-loaded basemap on their Unichip would either simply be erased over time, or the stock ECU would actually override the Unichip, rendering it completely useless. The Unichip’s tuning resolution (the actual increments and scale of tuning certain things such as air/fuel ratio and ignition timing at specific RPM) was also nowhere near that of the ECUtek, so even the custom tunes did not end being as good as they could have been with better resolution. Given the problems they were having, TurboXS went on to develop and release the User-Tunable Engine Computer, or “UTEC.” The UTEC was a big step forward in not only tuning resolution, but because it allowed the user themselves to actually tune their car, rather than requiring a shop to tune it for them. TurboXS still provided basemaps to start from, and the user could load them onto their UTEC via laptop or taking the UTEC out of their car and plugging it into their home computer. This opened up a world of possibilities for many people, some of which are now prominent tuners who first started out tuning on the UTEC. Vishnu attempted to answer TurboXS’s ante with their own “XEDE,” but the XEDE proved to not be quite as versatile or as easy to use as TurboXS UTEC, and soon Vishnu abandoned Subarus and moved on to the brand new Evo market (which they also eventually abandoned).

See as this blog is starting to get quite lengthy, we will conclude this discussion on engine management in tomorrow’s blog.