If I get a turbo for my car, will it affect my fuel economy?

I'm thinking about getting a Honda Civic si and in time I was thinking about putting a turbo kit in it just to have more fun but how would it affect my gas mileage?

Adding a turbo should increase fuel economy. Turbos don't increase fuel consumption they just allow you to use the fuel you have more efficiently by burning exhaust.

A properly engineered turbo kit will include new larger injectors and fuel pump. Your fuel consumption will increase unless you can keep your foot out of the floor board, which you can't.

The whole point of getting a turbo is to improve performance. The turbo is just a device that uses exhaust gases to power a turbine which in turn brings in more air for more combustion which requires more fuel. If you are concerned about fuel consumption and don't go into boost to save fuel, you've just defeated the point of getting a turbo. And boosting the high compression and high hp per displacement K or B engine in your car works against the engine design. The internals will need to be strengthened, making this an expensive modification. You might as well tear down the engine and install some high performance parts. People on the forums are claiming the performance K engines can gain around 40 hp from relatively simple bolt ons. The stock Si engine is already decent for what it is.

Of course. You get more power from more fuel burnt. But this will be short lived if you just bolt it on You need the head machined to lower the CR.

No, of course not.

A device designed solely for the purposes of pulling more air, and fuel, through an engine would never damage fuel economy.