why do turbos ALWAYS kill mpg? (& why not bypass)

[Baltothewolf]

Yes, while that may be the case, the manufacturer still runs more aggressive tunes and lower compression on turbocharged engines. It's a fact of life.

When I had the turbo on my insight, my MPG went up by 3mpg. This was measured at the pump, not going off the FCD.

Why are we still beating this over the head anyway, it's been proven when you add a properly sized turbo/supercharger to an N/A engine, it gains 10-20% MPG due to the increased VE.

[cRiPpLe_rOoStEr]

Originally Posted by Baltothewolf

Why are we still beating this over the head anyway, it's been proven when you add a properly sized turbo/supercharger to an N/A engine, it gains 10-20% MPG due to the increased VE.

It adds efficiency to the engine, but a ricer-rated transmission leads every improvement in combustion efficiency to be wasted

[NHB]

Originally Posted by Baltothewolf

Yes, while that may be the case, the manufacturer still runs more aggressive tunes and lower compression on turbocharged engines. It's a fact of life.

When I had the turbo on my insight, my MPG went up by 3mpg. This was measured at the pump, not going off the FCD.

Why are we still beating this over the head anyway, it's been proven when you add a properly sized turbo/supercharger to an N/A engine, it gains 10-20% MPG due to the increased VE.

Turbo has nothing to do with aggressive tune anymore. Here in Europe almost every model has a turbo. This includes plenty of eco models, MPVs and busses.

Turbocharging can increase or decrease MPG. If you use some home made installation, most like you will loose some fuel efficiency. Better turbo installations can improve FE. For example VW's new 1.5 TSI has a geometric compression ratio of 12.5 thanks to miller cycle, which would not be possible without high boost pressure. Turbo gives also good low end torque, which allows tall gearing.

[Baltothewolf]

Originally Posted by NHB

Turbo has nothing to do with aggressive tune anymore. Here in Europe almost every model has a turbo. This includes plenty of eco models, MPVs and busses.

Turbocharging can increase or decrease MPG. If you use some home made installation, most like you will loose some fuel efficiency. Better turbo installations can improve FE. For example VW's new 1.5 TSI has a geometric compression ratio of 12.5 thanks to miller cycle, which would not be possible without high boost pressure. Turbo gives also good low end torque, which allows tall gearing.

Allow me to further strike the deceased horse. Home made kits are installed 99% of the time for power, so more aggressive tunes are used, because the install is done improperly. Definitely agree with the low end Torque/taller gearing statement though.

[straight5]

There have been several comments about turbocharged engines being different internally with heavier rods, bearing and other parts. That may be generally true, I don't know.
fwiw During the mid to late 1990's, the turbocharged 5 cyl Volvo engine was mostly the same as the NA engine. Internally the only parts that I can remember being different were the piston (for lower compression of course) and the sodium filled exhaust valve. As for the transmissions and gearing - I have no idea if they were different.

I can tell you that I've been very happy with the mpg of my turbo car. My Saab 9-5 turbo has averaged about 32mpg over the last 13,000 miles. The odometer is showing just over 205,000 miles. As the OP and others have pointed out though, I have nothing to compare it to that would be a fair comparison.

[deejaaa]

Go back to the year: 1992. get a GM, 6.2 NA or 6.5 TD, same engine(bore diff isn't enough), exhaust, etc.... Turbo had more power AND ECONOMY! same thing for 93. 94 had (somewhat) computer control.