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ALS · 04-09-2017, 11:44 AM

OK lets jump back a few years to the early to mid nineties and we're looking at a Volvo 940. They came with either a NA 2.3 liter inline four or an intercooled turbo charged version. The NA was rated at 114hp and the Turbo motor was rated at 160hp.

The big difference was at highway speeds the fuel mileage difference between the two motors was dramatic. The Turbo version topped out at a max of maybe 27.5-28 at 55 mph. The NA 2.3L on the other hand would easily pull 32-33 mpgs at speeds of 60-65 mph.

Driving a Turbo for mileage takes some skill, one is you want to keep the turbo out of boost as much as you can. The issue is the computer tosses in extra fuel under boost, one for more power, and for another reason to cool the incoming compressed air to avoid detonation (Knocking). That is why Turbos appear to not get the best fuel economy even though they have smaller engines. You may have a 2.0 liter motor but under mid boost you're burning fuel like you have 2.5L-2.7L and under heavy boost probably more like you're driving a car with a 3.0L to 3.5L motor.

I modified a 87 2.3L Turbo Volvo wagon for fuel mileage years ago. I dropped the Cd by lowing it and removing the roof rack. Pulled the automatic and replaced it with a five speed manual. Swapped out the 3.90 automatics rear gears for 3.31's. Highway mileage jumped from 325-340 miles per 15.8 gallon tank to 425-440 miles per tank. The biggest factor was replacing the non locking torque converter automatic transmission with a manual.

If you can drop the Cd and weight of the car you can easily increase the fuel mileage of a turbo car. Less air resistance and weight to haul around the less need for you have to force the turbo into boost.

The biggest issue especially with highway mileage in a modern manual transmission turbo car is the manufactures are always lowering the OD gearing for better performance instead of fuel mileage. Most of the manuals are running 300-400 rpms higher than the same car with an automatic. Same applies most of the time to the NA version over the Turbo version.

04-09-2017, 11:44 AM	#10 (permalink)
ALS EcoModding Apprentice Join Date: Jun 2008 Location: Pittsburgh Posts: 119 Thanks: 2 Thanked 26 Times in 18 Posts	OK lets jump back a few years to the early to mid nineties and we're looking at a Volvo 940. They came with either a NA 2.3 liter inline four or an intercooled turbo charged version. The NA was rated at 114hp and the Turbo motor was rated at 160hp. The big difference was at highway speeds the fuel mileage difference between the two motors was dramatic. The Turbo version topped out at a max of maybe 27.5-28 at 55 mph. The NA 2.3L on the other hand would easily pull 32-33 mpgs at speeds of 60-65 mph. Driving a Turbo for mileage takes some skill, one is you want to keep the turbo out of boost as much as you can. The issue is the computer tosses in extra fuel under boost, one for more power, and for another reason to cool the incoming compressed air to avoid detonation (Knocking). That is why Turbos appear to not get the best fuel economy even though they have smaller engines. You may have a 2.0 liter motor but under mid boost you're burning fuel like you have 2.5L-2.7L and under heavy boost probably more like you're driving a car with a 3.0L to 3.5L motor. I modified a 87 2.3L Turbo Volvo wagon for fuel mileage years ago. I dropped the Cd by lowing it and removing the roof rack. Pulled the automatic and replaced it with a five speed manual. Swapped out the 3.90 automatics rear gears for 3.31's. Highway mileage jumped from 325-340 miles per 15.8 gallon tank to 425-440 miles per tank. The biggest factor was replacing the non locking torque converter automatic transmission with a manual. If you can drop the Cd and weight of the car you can easily increase the fuel mileage of a turbo car. Less air resistance and weight to haul around the less need for you have to force the turbo into boost. The biggest issue especially with highway mileage in a modern manual transmission turbo car is the manufactures are always lowering the OD gearing for better performance instead of fuel mileage. Most of the manuals are running 300-400 rpms higher than the same car with an automatic. Same applies most of the time to the NA version over the Turbo version. Last edited by ALS; 04-09-2017 at 12:06 PM..