What's that sound? Is it a bird, a plane...? No, it's a Subaru! And...it's normal. If you have a Subaru, you've probably noticed it sounds a little differently than other vehicles. Maybe you even wondered if something was wrong. That's a common "new user" concern - which easily gets put to rest when they realize it's not just their Subaru, it's everyone's! Living in Seattle, Washington and along the Pacific Northwest, you probably hear the Subaru hum pretty often.
But have you ever been told WHY it has its own special sound? Read below to find out.
The Subaru Sound: Boxer Engine
That distinctive Subaru sound we have all come to know, is thanks to the vehicle's boxer engine, which is different than the engines in other vehicles. This 2.5 liter engine has a horizontal, flat design, with headers that are unequal in length. (Which, for those of you who are not car nerds - that's totally different than other designs with equal length headers.) The header piping from cylinders one and three are different in length from those from two and four. This means, the exhaust gas coming off the engine has to move through different lengths, as does the sound it produces, which creates an uneven tone (much like a rumble), instead of a smooth tone.
Subaru's Jessica Tullman offered the following explanation:
"The new engines, especially the four cylinders, are extremely efficient so they have very low friction. Because of that, this process assists the engine behavior at startup to help them warm up. When the engine coolant temperature is approximately 158 degrees Fahrenheit or below, the ignition timing map in the ECU is changed to retard the engine timing. This timing change is done in order to quickly heat up the exhaust catalyst to reduce emission gases.
This change causes part of the combustion process to occur as the exhaust valves are opening in the cylinder head. The release of the high pressure combustion gasses entering the exhaust system causes this noise. Depending on several different inputs into the ECU, such as engine coolant temperature and throttle opening angle, this noise could occur until the engine coolant temperature reaches the desired temperature.
The timing change logic is slightly different from model to model. This slight difference means that some vehicles have different noises. The noise is not harmful to the engine or exhaust system. "
With that said, drive your Subaru in peace and with pride! You have a beautifully, unique vehicle that is ready to take you from Seattle, to wherever adventure calls.
If you feel you have an abnormal sound at any time, let us take a look. We'll be able to ease your mind and help solve any possible disturbances. Click here to schedule an appointment at Suburb Service, or call (206) 705-8695 to reach our Seattle location. Show your Subaru some love.