Supercharger Vs Turbocharger

[sirbob]

Ive head a lot of people try and tell me that a turbocharger is more efficient than a blower. I dont believe them...


My opinion is...


Both are compressing the same amount of air, say 6psi, then both are doing the same amount of pump effort, which equates to the same amount of horsepower loss from the motor, they just do it in different ways.

A blower gets it pumping effort from the motor directly, a turbo gets it from pushing exhaust through a turbine (creating turbulence, drag, back pressure and exit losses on the way, all of which take power away from the motor)

So both are as efficient as eachother...

What do you think?

[Babalouie]

I think the reason the supercharger is less efficient is because it soaks up engine power in driving the supercharger. The drag is quite a lot, I think something in the region of 30hp.

There is a loss of efficiency in that the exhaust gasses are restricted by the turbo but it's not anywhere near as much as what the supercharger soaks up.

[Matty]

A big \"it depends\"... (and Steve, that latter book has nothing about forced induction... better to read Maximum Boost by corky bell)

For starters, there are different types of superchargers. Roots and twin screw are naturally lower in thermodynamic efficiency, by nature of their design. Instead of boost pressure, they'll be wasting energy creating excess heat.

Centrifugal superchargers have higher efficiency, but will only generate full boost at maximum revs, not much you can do about it at low revs...

In any case, a SC will be drawing power off the crank, and wasting any exhaust gas energy.

Sure, a turbo puts some backpressure on the exhaust, but it uses this backpressure to put energy back into the motor! Which ever way you look at it, from simple thermodynamics the turbo will be more efficient.

As for power, well the turbo isn't limited to making a set pressure at a given rpm. The boost can be brought on early and controlled as you desire.

[kitkat]

the way i see it... a turbo is the better option.
Look at the best cars out there... Rally cars all use turbos, if the supercharger was better im sure they would use it.
the bugatti veyron, that car relies on power and they chose the turbo obviously because it can deliver more power.
Easiest way to chose between something is look at what the best use.

its like saying AWD handles better than RWD, if they did then F1 cars would be AWD.

[glen73]

Ive head a lot of people try and tell me that a turbocharger is more efficient than a blower. I dont believe them...


My opinion is...


Both are compressing the same amount of air, say 6psi, then both are doing the same amount of pump effort, which equates to the same amount of horsepower loss from the motor, they just do it in different ways.

A blower gets it pumping effort from the motor directly, a turbo gets it from pushing exhaust through a turbine (creating turbulence, drag, back pressure and exit losses on the way, all of which take power away from the motor)

So both are as efficient as eachother...

What do you think?

one is a lot more cheaper than the other.
plus a supercharger has power from idle.
i really dont understand why you would post this as you seem to answer your own question......

[Benny]

Contrary to popular opinion, turbochargers do not produce boost because the exhaust gas is passing through it. Otherwise, you could get full boost when you rev it in neutral.
If you have ever watched a boost gauge on a turbocharged car, you will notice that when reving in neutral, no boost is produced.
Boost is produced by loading the engine and the increase in temperature of the gasses is what actually makes it work.
Just like a gas turbine engine.
Because of this fact, turbocharged cars can be far more economical than supercharged cars, because the supercharger is always drawing its power from the engine.
Supercharged engines don't really produce any worthwhile boost from idle either. In fact, most supercharged motors won't get going until they have around 4,000 RPM spinning them around.
If you did have a supercharger that produced useable boost from idle, it would draw so much power, that half of the horsepower would just be for driving the supercharger.

You've seen those big superchargers sitting onthe top of dragsters, did you know that one of these monsters (like a GMC 71 for example) can draw as much as 500hp out of the engine? Sure, they make the engine produce 5-8,000 hp, so it doesn't really miss the other 500hp and they don't care about fuel comsumption either considering they use about 40 litres to cover 400m.

[Garry]

Mercedes and BMW (Mini) are shifting from superchargers to turbo's. There could be a message there.

[Matty]

Contrary to popular opinion, turbochargers do not produce boost because the exhaust gas is passing through it. Otherwise, you could get full boost when you rev it in neutral.
If you have ever watched a boost gauge on a turbocharged car, you will notice that when reving in neutral, no boost is produced.
Boost is produced by loading the engine and the increase in temperature of the gasses is what actually makes it work.
Just like a gas turbine engine.

I'll agree that it's a lot like a gas turbine, but contrary to the above statement, it's not as simple as heating the exhaust gas. Pressure, temperature, and flow rate all play a part.

Adiabatic expansion of the exhaust gas through the turbine (dropping both the temperature and the pressure in a related fashion), multiplied by the mass flow rate of gas, is where the energy to spin the turbine comes from.

The reason the boost gauge never registers when you're free-revving is because it takes bugger all energy (time and air flow into the engine) to spin the engine up to speed with a throttle blip, and the turbine has too much inertia to accelerate to operating (ie boost producing) speed in this time.

[tk421]

But if you want the best possible results, a supercharger is the way to go. But it will be more work to install and more expensive.

As far as a turbo being cheaper is concerned I think thats true if you have an NA, but if you have an NB the super is going to be cheaper at least for the intial fitment. The stage one AVO kit is nearly 6 grand for a box of bits as I understand it. You can have a stage 1 tuning MP62 supercharger box of bits from the states for under $4500 in the country, and at 170hp at the wheels it has more hp than the stage one AVO kit, and they say it takes 6hrs to fit.

That said If someone knows of bolt on turbo kit for the NB for 3k aussie then I'm all ears but I don't think there is one. I vote the super, after all they have the whhhine .

TK

[green_comet]

i have been looking at getting a jackson racing supercharger kit for my clubman, i didnt know that it made more power than a stage one avo kit.. just more reason for me to get one now. Although the BRPerformance ones have really caught my eye..

As for the debate the most reliable one would suite me the best, dont like spending all my free time under the bonnet of my car with different problems.. not looking at chasing huge power figures, just something that gives it that lil bit of oomph.. I think sc will do me just fine.. plus they sound awesome..

but thats just my opinion..

[Sean]

Shall I take this opportunity to throw a spanner in the works?

A few have mentioned a turbo will not produce boost in neutral....

If anyone cares I'll go out and video my car producing double digit boost while standing still and in neutral?

[glen73]

Shall I take this opportunity to throw a spanner in the works?

A few have mentioned a turbo will not produce boost in neutral....

If anyone cares I'll go out and video my car producing double digit boost while standing still and in neutral?

yes please, i already know you can i'd just like the video lol

[Sean]

Shall I take this opportunity to throw a spanner in the works?

A few have mentioned a turbo will not produce boost in neutral....

If anyone cares I'll go out and video my car producing double digit boost while standing still and in neutral?

yes please, i already know you can i'd just like the video lol

A quick scoot to the local industruial estate for this one....

A tad noisy, but proves the point

http://undercovercastle.com/auscartalk/boostneutral.AVI

Right click, save as...

[glen73]

Shall I take this opportunity to throw a spanner in the works?

A few have mentioned a turbo will not produce boost in neutral....

If anyone cares I'll go out and video my car producing double digit boost while standing still and in neutral?

yes please, i already know you can i'd just like the video lol

A quick scoot to the local industruial estate for this one....

A tad noisy, but proves the point

http://undercovercastle.com/auscartalk/boostneutral.AVI

Right click, save as...

very good mate, excuse me for my dumbass but when does the BOV kick in

[Sean]

very good mate, excuse me for my dumbass but when does the BOV kick in

When the pressure on either side of the throttle plate is uneven.

The wastegate was set to ~11psi for that little vid, just to prove double figures Can get it to make upto 17psi in neutral. It might be possible to get more, but really there's no need.