Tuning wrx for economy rather than performance

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Remove the turbocharger.

Why should there be? This is a car you buy for performance, not economy. Of course, performance improvements will usually make the car more efficient.....and therefore more economomical if the extra performance is not used. What's the point of performance enhancements if you don't use them, though?

David Betts snipped-for-privacy@motorsport.org.uk

Or don't push down on the go pedal very far.

zero

If you drive gently the turbo won't do much, which will increase your MPG. Shift early, anticipate stop lights, and don't get into drag races with Hondas. Air resistance starts to get important around 50 MPH, so stay in the

30-40 MPH range. Pump your tires up a bit harder. Use synthetic 5W-30 oil instead of regular 10w-30. Use synthetic oil in the transmission and axles. Keep the windows rolled up. Don't run the A/C. Put on skinnier tires...

Or, trade it in on a hybrid.

You could run a vacuum hose from the turbo compressor outlet to the wastegate actuator. This would prevent the wastegate solenoid (aka "bleed solenoid") from increasing boost above wastegate spring pressure. The result would be a reduction in max boost from about

13.5 psi to around 7-8 psi. It's completely safe for your engine, and you will see better fuel economy, assuming that you sometimes got into the boost before this change. Lots of people have run their WRX like this, some for extended periods of time, but it's usually the result of a vacuum plumbing error, not a desire for economy.