Quote:
Originally Posted by Coyote X
I think most of the gains they got in mileage is from the gearing. The turbo just let the higher geared car drive more like a normal car. If they can find identical cars one with a turbo and one without there probably wont be any difference.
Adding a turbo to a car and not changing gearing or going to a smaller motor is not going to help anything but acceleration really. Kind of a similar problem of doing aero mods and not changing gearing. The engine load decreases but the rpms are high enough you are still using a lot more gas than you really need to.
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You can change mileage without changing gearing. The whole point of the article is to point out that a turbo will increase low end torque therefore the driver can upshift much earlier while maintaining the same acceleration. The 97 Volvo 850 is a good example of this. The non turbo 850 produces 168lb/ft at 4700rpm while the low pressure turbo produces 190lb/ft between 1800-5000rpm. While the fuel economy between the automatics is identical (LPT was only offered with auto in US) a manual trans car would give you the ability to upshift at much lower rpm.