Supercharger vs Turbo MPG ?

[jamesm]

One thing to note is that most modern twin screws (like the one innovate uses) have an internal bypass that equalizes pressure across the sc, negating much of what I wrote about above (additional load required to compress the intake charge when cruising). That said, on systems that do not have this, that load is a whole lot more than you'd imagine. It can take hundreds of horsepower just to run the (huge) blower on an alcohol dragster. Not so bad on a street car, but it is significant in any case where there is no bypass mechanism.

[Fast_Freddy]

There are many things that can be argued in the super vs turbo charger debate but mpg isn't one of them.

Has anyone noticed that no top tier OEM is currently using a supercharger to augment power output from lower displacement, higher mpg engines? They're all replacing V6 engines with turbo 4 cylinders. The VW/Audi 2.0T is already legendary. Most of the energy used to drive a turbo would otherwise be wasted heat expelled out the exhaust pipe whereas a supercharger places a much more consistent and greater parasitic drag on the engine. This has been common knowledge since the 50's for crying out loud...

[Foobar]

Originally Posted by jamesm

One thing to note is that most modern twin screws (like the one innovate uses) have an internal bypass that equalizes pressure across the sc, negating much of what I wrote about above (additional load required to compress the intake charge when cruising). That said, on systems that do not have this, that load is a whole lot more than you'd imagine. It can take hundreds of horsepower just to run the (huge) blower on an alcohol dragster. Not so bad on a street car, but it is significant in any case where there is no bypass mechanism.

Centrifugals take advantage of the same concept. The Vortech system, for example, bypasses the compressor except under heavy load.

[sw20kosh]

As stated in the Innovate Twin Screw thread... I am getting 31 mpg on the highway cruising at 70-80 mph with supercharger installed. These things come with bypass valves that allow the motor to breathe air from a more direct route (ie not through the rotors).

[jamesm]

Originally Posted by sw20kosh

As stated in the Innovate Twin Screw thread... I am getting 31 mpg on the highway cruising at 70-80 mph with supercharger installed. These things come with bypass valves that allow the motor to breathe air from a more direct route (ie not through the rotors).

It still breathes through the rotors so to speak, it just open a port between the top and bottom of the housing. This equalizes the pressure and reduces the effort required to drive the screws because it no longer has to compress anything. It's just spinning the screws, which consumes a bit of power, but not nearly as much as compressing the air does.

[sw20kosh]

Originally Posted by jamesm

It still breathes through the rotors so to speak, it just open a port between the top and bottom of the housing. This equalizes the pressure and reduces the effort required to drive the screws because it no longer has to compress anything. It's just spinning the screws, which consumes a bit of power, but not nearly as much as compressing the air does.

Yes this.

[radroach]

@Adeets I think the effective efficiency of FI vs NA depends on where you apply it. At sea level, the GT86 performs just fine but at over 500-1000m you'll probably want more efficient power throughput per mpg. NA + tune is probably the better choice at sea levels but once you get up in the mountains (considering europe, maybe austria) i'd think a supercharger would be more efficient.

[Robftss]

Depends on the engine's HP and vehicle drag. If you only have a 150 HP peak, you would be into boost @ 90 mph. If you have 300 HP peak, you may be running in vacuum or 'off boost'.

If you can sustain 90 mph off boost and steady state and all things being equal...

Worst: belt driven centrifugal supercharger and twin screw, they internally compress regardless of bypassing.

Roots type: bypassed. So only belt, up gearing losses and inertia.

Turbo: back pressure due to exhaust constriction @ turbine housing. (Turbo aircraft have a manual wastegate override, to decrease restriction and improve economy when boost is not required) Some OEM's have incorporated logic actuated wastegates to 'open' at cruise (Porsche).

Turbos have a slight advantage in 'off boost' drain, but they all consume power.

[surfuxalot]

i would think a turbo would increase mpg. turbos are way more efficient than supers. Supers add more stress to the engine, causing for the use of more gas. Turbos are also more reliable, if maintained well. Supers are not as reliable because the dependability of the power is on a belt, meaning if the belt break ur screwed unless ur remove it.

[Dream20b]

Why are you continually bumping old threads, I mean, seriously?