Engine Management For Subaru WRX/STi

What are some specific types of engine management While this FAQ does not go into specifics for every type of engine management, this thread covers many types. This link offers several comparisons of different system features as well. There are some not covered in these threads though and may be considered as well.

Generally speaking, what engine management option will give me the most power? Custom tuned engine management solutions will always give you more power. Every off the shelf engine management solution has a built in safety factor. This depends on the manufacturer. This is because their “Stage 1” or “VF-30” map has to safely make power for someone living in Phoenix’s heat and 91 octane, to Denver’s high altitude, to Boston’s cold and 93 octane. The gasoline and geographic variances can leave horsepower on the table.

More specifically, what engine management option will give me the most power? This is one question without a correct answer. Let’s say that you research a very comprehensive stand alone engine management system such as a MoTeC unit and decide that it’s the “best” for your car. At the end of the day, it’s about what the tuner is most comfortable with. Some tuners may be able to extract better results from a “lesser” system simply because they understand the interface better.

For someone interested in tuning their own vehicle, they should match their tuning skills with an engine management solution that they are able to understand and use correctly. For someone interested in professional tuning, they should consult with their tuner for their recommendations. Both of these actions will ensure a good tune with a minimum amount of rework, guessing, and trial and error. While most tuners are capable of learning new or more advanced engine management systems, consider the benefits of an “older/worse system” your tuner is familiar with vs. your tuner learning a “newer/better system” at $200/hour plus possible dyno time.

I have a reflashed ECU and am not seeing their advertised HP, why? First off, have you met their criteria EXACTLY? The #1 cause of low HP with reflashed ECU owners is their lack of meeting the manufacturer’s requirements. If they require a full turbo back exhaust and you only have a downpipe and a cat back exhaust, 100% of the blame is on the end user. As well, if they require a full exhaust and you have a full exhaust, uppipe, headers, and a bigger top mount intercooler, this can cause problems as well.

Also realize that HP figures vary. You cannot compare (for example) a manufacturer’s Mustang Dyno HP figures to your local DynoJet HP figures. Even comparing identical dynos to each other is futile as dyno software set-up, altitude, temperature, humidity, and other factors do not ensure an equal result.

In addition, realize that a reflashed ECU still utilizes many of the stock ECU’s learning functions. This means that in a perfect world, you will see the advertised HP from your reflashed ECU. This may also mean that on the day of dyno testing, your octane, the temperature, humidity, and many other factors are considered by the reflashed ECU when determining total power output. If the advertised numbers aren’t there on dyno day, it doesn’t necessarily mean there is a problem, but rather, your ECU is protecting your engine from low octane, high temperature, high humidity, or other factors.

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