World One Performance Blog

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.

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.