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Project WRX: Part V

Engine management without wires

Aug 15, 2003
0309_01z+subaru_wrx_sedan+rear_left Photo 1/6   |   Project WRX: Part V

With Project WRX cranking out 240 hp at the wheels, while wearing a highly adjustable DMS suspension, huge brakes, sticky tires and 17-inch wheels, we feel like we're approaching the end of a good run with an old friend.

However, being the neurotic car-modifying freaks we are, we can almost always find reasons to fix what's not broken. That's what we're doing this month. The last time we dealt with ECU changes on Project WRX, we installed the Xede piggyback computer from Vishnu Tuning to control engine parameters vital to the hardware mods we made. This month, we may have found an even more elegant solution.

2017 Subaru Impreza
$18,395 Base Model (MSRP) 24/32 MPG Fuel Economy

Vishnu now has an alternative for those who are less interested in tuning the car themselves. This alternative, known as ECUTEK, is actually a piece of software which allows Vishnu to "reflash" the stock WRX ECU using a laptop computer through the OBD-II diagnostic port. ECUTEK software allows control over every detail of Subaru's highly advanced engine management. The elegance of the system is multifaceted for the consumer.

0309scc_projwrx02_z Photo 2/6   |   Boost parameters
The WRX's stock boost control is a function of engine speed, vehicle speed, altitude and temperature. This screen shows the tuner the desired boost (top table) and the wastegate duty cycle percentage (bottom table) as functions of load and engine speed. Boost control this advanced means there's less chance of overspeeding the WRX's stock turbo at high altitude and provides an extra margin of safety over MAP-based systems.

ECUTEK is a smart solution for those who want big power as much because of what it doesn't do as what it does. Small nuances of engine calibration such as cold start, load compensation, hot restart and other difficult-to-tune or condition-dependent problems are virtually eliminated since Subaru has already done the job right from the factory. Vishnu tunes only the maps required for more power as determined by the many different upgrades customer's cars might have. In other words, every reflash is essentially a custom tune specific to that car's mods and the fuel used. Since Project WRX is fitted with Vishnu Stage 2 mods, tuning began from the Stage 2 baseline map for California's 91-octane pump gas. However, Vishnu has on file a sample pool of maps from cars with varying levels of modification and different octane (including 93- and 94-octane East Coast fuel), which streamlines the tuning process and allows ECUTEK software a huge range of application from mild, near-stock cars to 400-hp monsters. Project WRX is somewhere in between.

The tuning process begins with four or five dyno pulls on Vishnu's Dyno Dynamics chassis dyno to get the engine up to temperature and witness the adaptability of the stock ECU based on the car's mods. Once the range of adaptability has been verified, changes begin in the knock correction table to bring the engine as close to the knock threshold as possible. The base ignition map is fairly conservative, as Subaru's engine management is very adaptive and will advance ignition timing on its own. Therefore, most tuning changes are made to cells in the knock correction table. Power is maximized by manipulating the cells that tell the ECU how far it is allowed to advance ignition timing without reaching the knock threshold. This means the knock correction values are sometimes as high as 11 degrees advanced beyond base map values. According to Shiv Pathak, the owner of Vishnu Tuning, Subaru engines must operate as close to the knock threshold as possible to make maximum power. Therefore, allowing the ECU to determine the ignition timing is the best way to tune the engine. This results in a smooth power curve with immediate adaptability to heak soak, sustained thermal load or octane fluctuations.

Subaru's stock boost control is also highly advanced, relying on many sensor inputs to determine safe, yet effective, levels of boost. Unlike many aftermarket boost controls which are MAP based, Subaru's stock management determines boost based on engine speed, vehicle speed (which affects intercooler efficiency), altitude and temperature. MAP-based controllers can overspeed undersized turbos at high elevation, shortening their life. Multi-parameter based boost control is simply safer.

0309scc_projwrx03_z Photo 3/6   |   Complete parameter list
Here you can see all functions that ECUTEK tuners are able to manipulate. Tuning for maximum power realistically only involves a few parameters, but ECUTEK allows access to nearly every function of the WRX's stock ECU.

There are other benefits, as well. Subaru's stock ECU has several safety nets built in. Unlike many stand-alone systems that are only reactive, the stock Subaru ECU constantly observes average knock correction and can apply a global retard by switching fuel maps if average knock correction value reaches a preset limit (see the fuel tables screen capture ). In other words, if the ECU sees crappy gas, it will switch to a crappy gas map automatically. This adds an additional margin of safety for highly stressed engines against bad fuel or other problems.

Once tuned, Project WRX made 240 hp and 205 lb-ft of torque on the ECUTEK reflash--comparable to the 239 hp and 216 lb-ft it made running on the Xede piggyback. The reflash is also marginally less expensive at $750 vs. the Xede's $795. The primary difference between the two is tunability, although any results produced with the Xede can be duplicated through the ECUTEK software, if that's the goal. ECUTEK is essentially for enthusiasts who don't need the ability to do their own tuning. Xede offers most of the benefits of a full stand-alone system for those who do.

Delta Dash
Since we installed the ECUTEK on our car, Vishnu has begun selling a software bundle called Delta Dash, which allows reflash users limited access to boost, ignition and fuel and other maps. This software isn't designed for complete tuning, rather it's an enthusiast-friendly interface to select parameters. Delta Dash doesn't allow access to individual cells in each map. Instead, only global changes can be made to base fuel, ignition and boost maps.

More importantly, Delta Dash can be used in race or valet applications to change boost maps on the fly by pressing the throttle to its wide-open position and pushing the defroster button at the same time. This feature could also be activated as a safety margin by hot-climate users on 100-plus-degree days to alternate between low and high boost--especially those of us in California who must run on 91-octane fuel. Delta Dash uses the parallel port on a laptop computer for connection to the OBD-II port in the car. All changes are made in real time. It costs $325.

Previous Installments
June 2002
Vishnu Stage 0, Exhaust testing

September 2002
Big brake kit and testing

March 2003
Vishnu Stage 1 and 2, SPT suspension

August 2003
DMS suspension, Enkei RPF1 wheels, Kumho Ecsta MX tires

Sources

Kumho Tires
Rancho Cucamonga, CA 91730
800-445-8646
www.kumhousa.com
Progress Technology
Anaheim, CA 92806
800-905-6687
http://www.progressauto.com
Irvine Subaru
Lake Forest, CA 92630
800-970-5755
http://www.irvinesubaru.com

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