Good idea or a complete lack of mechanical knowlege
Discussion
Mave said:
But if the piston is working against the pre-turbine pressure, then isn't that taking away expansion you could otherwise use in the piston? Isn't the work available from expanding from the pre-turbine pressure down to ambient the same, irrespective of whether you do it using a turbine or a piston?
If you could do it with a piston you would, but you can't, or at least you can expand it to a lower pressure with a turbine than you can with a piston, so you get more work out with both on the job than only one - team effort, you see!Err, I'm not sure where exhaust back pressure, scavenging and the like come into this. I'm sure they have some significance to efficient turbo system design, but they are not a significant source of the extra power produced by a turbo engine.
Correct me if I'm wrong, but a turbo just compresses the air drawn into an engine cylinder, making it denser, thus allowing more air (oxygen) to fit into the cylinder. Because there is more air you can add and burn more fuel for the given cylinder volume. Burning more fuel gives you more power.
An always on turbo will just use more fuel all the time (and get rather hot), so your fuel economy will go out of the window (along with your reliability I'd imagine).
You might as well have a larger capacity normally aspirated engine (as long as it isn't too much heavier), although I do appreciate that the turbo system does have some other minor side benefits.
Back in the day turbos never used to focus on economy. They were about getting more power (and thus using more fuel) for a given engine capacity and weight.
We now see that they can be used to make a poxy, gutless, but relatively economical small capacity engine actually perform when needed (as long as you work it). Economy is sacrificed when on boost though. The economy with more power claim is a bit of a cheat in that respect really.
Keeping the turbo spinning with electric motors and the like to keep on boost (like an electric anti-lag) is all very clever, but you still have to get the power for the motor from somewhere.
Using exhaust gas to spin the turbo is effectively recycling wasted energy, so ideally your electric motor would want to be getting its energy in a similar way. But how much energy would you need?
If you start having to add heavy batteries to feed this thing then you’re wasting your time.
Correct me if I'm wrong, but a turbo just compresses the air drawn into an engine cylinder, making it denser, thus allowing more air (oxygen) to fit into the cylinder. Because there is more air you can add and burn more fuel for the given cylinder volume. Burning more fuel gives you more power.
An always on turbo will just use more fuel all the time (and get rather hot), so your fuel economy will go out of the window (along with your reliability I'd imagine).
You might as well have a larger capacity normally aspirated engine (as long as it isn't too much heavier), although I do appreciate that the turbo system does have some other minor side benefits.
Back in the day turbos never used to focus on economy. They were about getting more power (and thus using more fuel) for a given engine capacity and weight.
We now see that they can be used to make a poxy, gutless, but relatively economical small capacity engine actually perform when needed (as long as you work it). Economy is sacrificed when on boost though. The economy with more power claim is a bit of a cheat in that respect really.
Keeping the turbo spinning with electric motors and the like to keep on boost (like an electric anti-lag) is all very clever, but you still have to get the power for the motor from somewhere.
Using exhaust gas to spin the turbo is effectively recycling wasted energy, so ideally your electric motor would want to be getting its energy in a similar way. But how much energy would you need?
If you start having to add heavy batteries to feed this thing then you’re wasting your time.
AER said:
Mave said:
But if the piston is working against the pre-turbine pressure, then isn't that taking away expansion you could otherwise use in the piston? Isn't the work available from expanding from the pre-turbine pressure down to ambient the same, irrespective of whether you do it using a turbine or a piston?
If you could do it with a piston you would, but you can't, or at least you can expand it to a lower pressure with a turbine than you can with a piston, so you get more work out with both on the job than only one - team effort, you see!
Instead of all the complexity of an electric motor and batteries, why not have a small compressed air cylinder which is released into the intake manifold when the driver comes onto the throttle and is recharged by the turbo when it's running at constant boost and/or load (or by a small electric compressor)?
kambites said:
Instead of all the complexity of an electric motor and batteries, why not have a small compressed air cylinder which is released into the intake manifold when the driver comes onto the throttle and is recharged by the turbo when it's running at constant boost and/or load (or by a small electric compressor)?
or a nozzle that blasts compressed air onto the vanes to spin them up.http://www.youtube.com/watch?v=zD9Ha0qsYuU
kambites said:
Instead of all the complexity of an electric motor and batteries, why not have a small compressed air cylinder which is released into the intake manifold when the driver comes onto the throttle and is recharged by the turbo when it's running at constant boost and/or load (or by a small electric compressor)?
Have you seen the size of the compressor for an air cyclinder?hairykrishna said:
xRIEx said:
...I'd assume not.
A model turboshaft engine, like the one on the hillclimb car in the video linked earlier, that seems to work.
The one on "Manic Beattie" isn't from a model - it's an air start unit from a helicopter. A model turboshaft engine, like the one on the hillclimb car in the video linked earlier, that seems to work.
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