how much power does a turbo make

[jamesqf]

Originally Posted by ChazInMT

Well James. It looks like to me you just said you need energy to run the turbocharger in the form of burning fuel. So, the turbine side of the turbocharger you admit needs power. I understand we burn fuel in our engines, pretty basic stuff. But when it leaves the engine on a normally aspirated engine, it just goes out the exhaust pipe fairly freely. Lets for grins say that it is at 1psi at the exhaust manifold. If there is a restriction in the exhaust system like say...A Turbocharger....then the pressure is going to rise in the exhaust manifold to say 3psi. This pressure and restriction WILL place a load on the engine, requiring more power from the engine in order to operate. That is where the power is coming from, our engines are big air pumps, and if you restrict the flow on the outlet, it needs more energy to overcome that.

Well, no. Remember your ideal gas law from physics? PV = kT, right? So the turbo extracts heat energy from the incoming exhaust gas, lowering its temperature and hence the pressure in the exhaust system.

it is a misconception that turbochargers run for free, as if they don't require energy to operate. They do, you admitted yourself that you need to use "a stream of hot gas generated by burning some sort of fuel" which makes my point exactly, turbochargers need energy to run.

Of course they need energy to run. The "for free" comes from the fact that the energy they use - the heat of exhaust gas - is energy that would otherwise go right out the tailpipe.

[mechman600]

The temperature delta across the turbine housing inlet to outlet is negligible. I have measured it on a dyno. Therefore, how can you say that wasted heat is being converted into useful energy? If heat was being converted by the turbocharger, the delta-T would be significant.

[ConnClark]

Originally Posted by ChazInMT

Could you explain how this works please, or point me to a website that says this and explains it.

You do not burn the engine. You burn the fuel which gives up energy that was stored in it. The engine is just a device that converts energy from one form to another. It does not create or destroy energy. No engine is 100% efficient at converting one form to another so you can sometimes recover energy that is lost with another engine. Regardless the energy to drive both comes from the fuel.

I'm guessing you think that all the energy to spin the turbine comes from the piston pushing the exhaust out of the cylinder. That contributes some energy to driving the turbine but the vast majority of the energy comes from residual pressure in the cylinder at bottom dead center. The exhaust valve opens here and all this left over pressure escapes (known as blow down).

If you read what I wrote, I said the turbocharger improves the efficiency of the engine several times. So why do you write this?

Probably because you keep stating that a turbo bogs down the engine and if it were there would be no net gain.

[ChazInMT]

Originally Posted by ConnClark

You do not burn the engine. You burn the fuel which gives up energy that was stored in it. The engine is just a device that converts energy from one form to another. It does not create or destroy energy. No engine is 100% efficient at converting one form to another so you can sometimes recover energy that is lost with another engine. Regardless the energy to drive both comes from the fuel.

I'm guessing you think that all the energy to spin the turbine comes from the piston pushing the exhaust out of the cylinder. That contributes some energy to driving the turbine but the vast majority of the energy comes from residual pressure in the cylinder at bottom dead center. The exhaust valve opens here and all this left over pressure escapes (known as blow down).


Probably because you keep stating that a turbo bogs down the engine and if it were there would be no net gain.

Originally Posted by jamesqf

Well, no. Remember your ideal gas law from physics? PV = kT, right? So the turbo extracts heat energy from the incoming exhaust gas, lowering its temperature and hence the pressure in the exhaust system..........

Of course they need energy to run. The "for free" comes from the fact that the energy they use - the heat of exhaust gas - is energy that would otherwise go right out the tailpipe.

Well then, It appears I don't know what I'm talking about.

You two have this all figured out so I'll just leave it at that, as I've stated before it is just a nuance and not a big deal. You just go ahead and think that there is no energy required from the engine to spin the turbocharger.

In fact, I'll give you an idea to run with, you'll both be billionaires in short order, and I'll just sit here and gloat that I should have done something with this idea myself.



Here it is, Since the turbocharger does not require power from the engine, why don't you invent a HUGE turbocharger to put on the exhaust of an engine and run a generator off the turbocharger capable of 50HP, since the turbine is just running off waste gas, you get 50HP for free! Use a 3HP Honda generator for an engine and then you can use the electricity from the 3HP generator too! Now you have a 53HP Electric generator, hook this up to a motor and you have a car using 3HP worth of gas, but getting 53HP output.



PLUS



EQUALS



Elon Musk...Watch your back! I smell Nobel Prize here! This is what you're saying will work so go for it!

Good luck.

[jamesqf]

Originally Posted by ChazInMT

Well then, It appears I don't know what I'm talking about.

You said it, not me :-)

Since the turbocharger does not require power from the engine, why don't you invent a HUGE turbocharger to put on the exhaust of an engine and run a generator off the turbocharger capable of 50HP, since the turbine is just running off waste gas, you get 50HP for free!

Been done. For instance here TIGERS A search will find many others, starting with the mechanical turbo-compounding of WWII-era aircraft engines, and apparently even a commercial truck engine, the Detroit Diesel DD1:

By inventing a new type of turbo compounding system, the DD15 engineers found a way to add 50 hp and still improve fuel economy by 5 percent. The system works by using a conventional Holset HX55 turbo without a wastegate that feeds into a unique "turbo compound axial power turbine" that transfers power directly to the engine flywheel. By scavenging exhaust heat that would normally fly out of the tailpipe, the "axial power turbine" is able to spin a small gearbox that helps create up to 100 lb-ft of torque when the engine is under a full load.

Detroit Diesel DD15 Diesel Engine - Diesel Power Magazine

Of course you can't get 50 HP out of a normal car engine, since you can only get out what's there (and even that's limited by thermodynamics).

[freebeard]

One you've captured this energy (as much as 40hp?) doesn't it make sense to use it in the most efficient manner possible?
plusplus

I could Photochop this, but that would slow down my response time (I'm busy). Can anyone connect the dots?

Maybe a one-way clutch so when you lift the throttle the propeller can freewheel. Sort of a less extreme version of this:


A better engineered example, although I doubt it is powered by a turbo. This could do wonderful things for the base pressure.

[Frank Lee]

I think the answer to OP is 42.

[mechman600]

I want that Beetle.