RANGE ROVER - renowned for fuel economy, I think you'll find.
Just a thought, given that 99% of modern diesels and an increasing number of petrol engines have a turbo, could there be a benefit to a manufacturer
supercharging instead?
I'm figuring that "off boost" periods (steady speed) wouldn't really exist with a supercharger, but that would be counteracted
with needing less throttle to begin with. With the advantage of no turbo lag surely supercharging is the way to go, or am I missing something?
If there were a benefit, then why are they not all doing it?
I think the argument against supercharging are all to do with fuel economy.
Modern turbos are more efficient than superchargers, its as simple as that.
I would think that more turbos are used because most normal driving is done below the boost threshold for economy, with the higher revs and power available when needed. Best of both worlds in a petrol engine.
Possibly cheaper aswell?
Remeber the BMini was SC and then changed to turbo. They must of done it for a reason.
Not a highjack but maybe a little bit of fun game.
What BRAND NEW PRODUCTION cars still offer a supercharged model?
Jaguar - Various
Mercedes - Various
Audi Seat - A1, leon and others are twin charged
Any other?
Yes we do!
RANGE ROVER - renowned for fuel economy, I think you'll find.
quote:
Originally posted by liam.mccaffrey
I would think that more turbos are used because most normal driving is done below the boost threshold for economy, with the higher revs and power available when needed. Best of both worlds in a petrol engine.
I think one of the main differences is that the energy required to spin a turbo is effectively "free" from exhaust gases whilst a
supercharger is more of a parasitic load on the engine as it's crank driven like an alternator.
I think a turbo charger is always going to be more fuel efficient although a supercharge may give a better power delivery and response. But the gap
is narrowing with variable geometry turbo chargers etc.
Using an engine with the throttle more closed makes it less efficient thermodynamically. There is a lower limit on the fuel air ratio, meaning you
can't run super leanunlike a diesel.
Fundamental differences I'm the two engine techs mean what works on one doesn't on the other.
There is one big thing in a superchargers favour.....................
They sound ace
I seem to remember someone mentioning that turbo's are easy to get through type approval emissions tests while maintaining decent numbers. With the emissions tests based on low revs (just above idle) they leave the turbo 'inactive' to make sure there are minimal emissions. Then when the turbo spins up later in the revs they get the BHP numbers that sell the cars. It's a salesman's wet dream, and in a market based on profit it's money that rules.
You could probably have an ECU controlled magnetic clutch so the supercharger doesnt take any load below (say) 5% to get good emissions, or even one
where the magnetic resistance increases with throttle position so the supercharger doesnt fully engage until you get to (say) 30%+ of WOT, but then
that adds even more cost! I guess you wouldn't for our sort of car as the complexity would outweigh the fuel gains.
Hugh
quote:
Originally posted by Ninehigh
Just a thought, given that 99% of modern diesels and an increasing number of petrol engines have a turbo, could there be a benefit to a manufacturer supercharging instead?
I'm figuring that "off boost" periods (steady speed) wouldn't really exist with a supercharger, but that would be counteracted with needing less throttle to begin with. With the advantage of no turbo lag surely supercharging is the way to go, or am I missing something?
The main advantage is that a turbo recovers a certain amount of heat energy from the exhaust that otherwise would be wasted. This means that the parasitic loss for a given amount of useful work output is less, and efficiency is therefore greater.
Aren't the VW TFSI engines turbo and supercharged?
quote:
Originally posted by JC
Aren't the VW TFSI engines turbo and supercharged?
quote:
Originally posted by JC
Aren't the VW TFSI engines turbo and supercharged?
quote:
Originally posted by PSpirine
quote:
Originally posted by JC
Aren't the VW TFSI engines turbo and supercharged?
Yes but VAG aren't known for the simplicity of their systems.
That's what £65bn of engineering spend budget gets you.