Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Turbocharged Saab hit 99.9 Mpg highway, 51 Avg after fill.

Drive Stick · 08-26-2010, 09:10 AM

I typically get in the mid 40's with mixed city / highway. The key to my success here has everything to do with a low compression engine staying out of boost, and spending just as much time coasting with the engine off, as I do with the engine on. 51 mpg is my record high for this car, last fill was 359 miles / 8.119 gallons of fuel = 44.21 mpg. Prior to that was 423 miles / 11 gallons of fuel = 38.45 mpg.

I take trips upstate NY every few weeks, so of course I will report back next time I return home with new results. I believe If traffic conditions remain the same, I could potentially pull of another 50 tank.

The common misconception most people seem to have is that if you have a turbocharger, you can't get good gas mileage. When in fact, turbocharged engines are more economical off-boost in most cases. 8.4:1 compression requires much less fuel consumption than my Subaru with 9.5:1 naturally aspirated.

Staying out of boost is as simple as not going more than 40% throttle in the first 2 gears, and less than 50% throttle in 3-5 gears. In essence, when I'm driving for fuel conservation, I'm driving only as though the engine were naturally aspirated. I let the 5 speed transmission gearing do the uphill work for me by downshifting to 4'th gear keeping the rpms at 2,600 where this engine makes peak torque - but I stay out of boost as I try to never exceed 10 in/hg of vacuum. At 65 mph on the highway the engine is very near peak efficiency from what I've observed thus far from my records.

The vehicles mpg calculation is not an instant reading, it doesn't fluctuate quickly at all, it climbs very slowly. On this particular occasion I was able to coast for a few miles at a time many times in a row as I rolled through the mountains.. climbing back up-hills was a breeze achieved by my downhill speeds. Now, if one were to discredit the factory gauge reading and call it instant, regardless of any error.. the final fill / math shows that at over 50 mpg the car was getting plenty of time with infinite mileage as I coasted with the engine off.

08-26-2010, 09:10 AM	#3 (permalink)
Drive Stick Weight Reduction Join Date: Mar 2009 Location: NJ Posts: 113 Celica GTS - '02 Toyota Celica GT-S 90 day: 36.32 mpg (US) Thanks: 0 Thanked 3 Times in 3 Posts	I typically get in the mid 40's with mixed city / highway. The key to my success here has everything to do with a low compression engine staying out of boost, and spending just as much time coasting with the engine off, as I do with the engine on. 51 mpg is my record high for this car, last fill was 359 miles / 8.119 gallons of fuel = 44.21 mpg. Prior to that was 423 miles / 11 gallons of fuel = 38.45 mpg. I take trips upstate NY every few weeks, so of course I will report back next time I return home with new results. I believe If traffic conditions remain the same, I could potentially pull of another 50 tank. The common misconception most people seem to have is that if you have a turbocharger, you can't get good gas mileage. When in fact, turbocharged engines are more economical off-boost in most cases. 8.4:1 compression requires much less fuel consumption than my Subaru with 9.5:1 naturally aspirated. Staying out of boost is as simple as not going more than 40% throttle in the first 2 gears, and less than 50% throttle in 3-5 gears. In essence, when I'm driving for fuel conservation, I'm driving only as though the engine were naturally aspirated. I let the 5 speed transmission gearing do the uphill work for me by downshifting to 4'th gear keeping the rpms at 2,600 where this engine makes peak torque - but I stay out of boost as I try to never exceed 10 in/hg of vacuum. At 65 mph on the highway the engine is very near peak efficiency from what I've observed thus far from my records. The vehicles mpg calculation is not an instant reading, it doesn't fluctuate quickly at all, it climbs very slowly. On this particular occasion I was able to coast for a few miles at a time many times in a row as I rolled through the mountains.. climbing back up-hills was a breeze achieved by my downhill speeds. Now, if one were to discredit the factory gauge reading and call it instant, regardless of any error.. the final fill / math shows that at over 50 mpg the car was getting plenty of time with infinite mileage as I coasted with the engine off. __________________