What did you do TO your Bronco Sport today?

[Mark S.]

“Components incapable of controlling current by means of another electrical signal are called passive devices. Resistors, capacitors, inductors, transformers, and even diodes are all considered passive devices”

Also from a description of "passive" electronic components:

Generally, passive components are not able to increase the power of a signal nor are they able to amplify it.

Using that definition, a turbocharger most definitely increases an engine's power.

We can argue about whether it's a passive device or not all day and I doubt we will change each other's minds. My primary dispute with your previous post was your claim that a turbocharger doesn't depend on engine power for operation. I don't believe that to be the case, and I don't think you do either given your statement that "at the end of the day, [the turbocharger] won't do much without a running engine."

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[Mark S.]

A turbine engine is only slightly related to what is happening in a turbo. The turbine engine does the compression, ignition, expansion, and exhaust. The exhaust of a turbine engine is somewhat similar to a turbo.

Turbine engines operate by harnessing the flow of hot, expanding exhaust gases to spin a turbine wheel. That wheel is connected via a common shaft to a large compressor which forces pressurized air into the combustion chamber. It's exactly the same principle as a turbocharger writ large.

How do you square these two comments?

The turbo isn’t using heat to make it work.

vs

...the reason for that is that if it loses temp it will also lose pressure. You want as much of the exhaust pressure to remain as you can get, so you want to keep that gas as hot as possible.

So is it using heat or not?

Physics tells us there’s a direct, linear relationship between absolute temperature and pressure, therefore the pressure inside the exhaust manifold is inextricably linked to heat. Exhaust gas flow results because there's relatively high heat (pressure) on the engine side and relatively low heat (pressure) on the exit side. In other words, the more heat in the exhaust gas the higher the flow.

Here's an interesting video explaining the physics behind turbo blankets based on a study by UT Austin in 2016. The upshot is there are performance gains to be had by containing exhaust heat in the turbocharger. A turbo blanket can also prevent heat-related damage to other nearby engine components. IMHO, for your ordinary, average daily driver, the benefits do not justify the increased wear a turbocharger will experience by using a blanket, but they explain why most race teams running turbocharged engines use a blanket on the turbocharger.

 

[delm]

Also from a description of "passive" electronic components:



Using that definition, a turbocharger most definitely increases an engine's power.

We can argue about whether it's a passive device or not all day and I doubt we will change each other's minds. My primary dispute with your previous post was your claim that a turbocharger doesn't depend on engine power for operation. I don't believe that to be the case, and I don't think you do either given your statement that "at the end of the day, [the turbocharger] won't do much without a running engine."

Turbos most definitely increase an engine’s power. But that is not the same thing as increasing electric current.

Correct - I could have been more clear and tried to clarify when I stated that it operates indirectly from the engine. The main point being, it is not operating off a belt, like a supercharger, which is not passive.

 

[IdahoDirtFarmer]

Not really something I did "to" my Bronco, but if anyone is wondering you can fit 3 whole hogs in the back of a Bronco. Forgot to take a pic. before I pulled two milk crates out though. 600 lbs. of pork fits just fine.

 

[Mark S.]

Not really something I did "to" my Bronco, but if anyone is wondering you can fit 3 whole BUTCHERED hogs in the back of a Bronco.

One slight correction. Unless you have a photo of three UNBUTCHERED hogs in your Bronco. Now THAT'S something I'd like to see!

 

[IdahoDirtFarmer]

One slight correction. Unless you have a photo of three UNBUTCHERED hogs in your Bronco. Now THAT'S something I'd like to see!

If they could jump high enough to get them loaded I might give it a whirl. Hard enough getting those assholes to step up into the stock trailer for their final road trip.

 

[Meanderthal]

Turbine engines operate by harnessing the flow of hot, expanding exhaust gases to spin a turbine wheel. That wheel is connected via a common shaft to a large compressor which forces pressurized air into the combustion chamber. It's exactly the same principle as a turbocharger writ large.

How do you square these two comments?



vs



So is it using heat or not?

Physics tells us there’s a direct, linear relationship between absolute temperature and pressure, therefore the pressure inside the exhaust manifold is inextricably linked to heat. Exhaust gas flow results because there's relatively high heat (pressure) on the engine side and relatively low heat (pressure) on the exit side. In other words, the more heat in the exhaust gas the higher the flow.

Here's an interesting video explaining the physics behind turbo blankets based on a study by UT Austin in 2016. The upshot is there are performance gains to be had by containing exhaust heat in the turbocharger. A turbo blanket can also prevent heat-related damage to other nearby engine components. IMHO, for your ordinary, average daily driver, the benefits do not justify the increased wear a turbocharger will experience by using a blanket, but they explain why most race teams running turbocharged engines use a blanket on the turbocharger.

Warning, lot’s of thinking out loud here:

Is it using heat? Not to any real extent. Let’s try a thought experiment. Let’s supply pressurized air at room temperature to the “exhaust” side of the turbo. There is a change in pressure as the air passes through the turbo, which does lead to a change in temperature as well. Does that mean the turbo used the heat, or did it use the pressure? The turbo would work basically the same no matter the temperature of the air used to drive it.

When you compress a gas, the temperature will rise. The reason for that is you have taken the same amount of energy (heat) and put it in a smaller space. When you let that gas expand again, the temperature will go down but you still have the same amount of energy (heat). No heat was used in the process. There are some losses in the real world but let’s not make this too complicated.

There is a hot gas involved here but the turbo isn’t using that heat for anything. The turbo works off the change in pressure. My point about losing heat and the use of turbo blankets and other devices is that you don’t want to lose heat energy to the outside environment because that would lower the pressure. Essentially, if the turbo does start to “use” heat it then looses pressure, which we don’t want. We want as much of the energy as possible to go into the pressure drop. There is going to be some energy loss due to changing temperature but we want to minimize that because that loss reduces the useful energy we have to turn the turbo.

The leap here is that a change in temperature is not the same as a change in heat for this system. The temperature increases when the pressure increases but the heat is the same.

On the intake side of the engine, we do try to lose heat. That is in the intercooler, where we want to shed heat energy. We would prefer to keep all the heat in the exhaust gas until it gets through the turbo. That is why the turbo is as close as possible to the exhaust side of the head. Probably also the reason we don’t mind having a long passage for the intake side. We lose some due to friction but we are also shedding heat in all that piping along with the intercooler.

Maybe this is another potato/potatoe debate?

 

[AndyMac204]

summer and winter shots on lake winnipeg, same spot.

 

[AndyMac204]

sucked into a ditch. 1.5 hours of shovelling and tugs from a 2wd f150 got us out. good reminder to carry a tow rope and shovel in the truck.

 

[Mark S.]

Maybe this is another potato/potatoe debate?

I don't think so. Without heat there is no expansion to create pressure, ergo without heat there is no flow. A turbo works on the basic principle that hotter the gas the greater the flow. That's why you get better turbo performance by wrapping it and keeping the heat in the gas.

 

[Mark S.]

sucked into a ditch. 1.5 hours of shovelling and tugs from a 2wd f150 got us out. good reminder to carry a tow rope and shovel in the truck.

But you had fun, right?

 

[Meanderthal]

I don't think so. Without heat there is no expansion to create pressure, ergo without heat there is no flow. A turbo works on the basic principle that hotter the gas the greater the flow. That's why you get better turbo performance by wrapping it and keeping the heat in the gas.

The expansion in the turbo is because of the pressure in the exhaust manifold. It doesn’t need heat to work.

This is why I am saying that the turbo is not the same as a turbine engine. The turbine engine requires the addition of heat (burning fuel) to make it work. In our engine the pistons create the pressure to drive the turbo. The heat does not add anything to the power output of the turbo.

As I said above, you could create the pressure to drive the turbo with air of any temperature. It’s the pressure that drives it, not the temperature. You want to limit heat loss because the loss of temperature will also cause a loss in pressure.

 

[Mark S.]

The expansion in the turbo is because of the pressure in the exhaust manifold. It doesn’t need heat to work.

This is why I am saying that the turbo is not the same as a turbine engine. The turbine engine requires the addition of heat (burning fuel) to make it work. In our engine the pistons create the pressure to drive the turbo. The heat does not add anything to the power output of the turbo.

As I said above, you could create the pressure to drive the turbo with air of any temperature. It’s the pressure that drives it, not the temperature. You want to limit heat loss because the loss of temperature will also cause a loss in pressure.

I think we're talking past each other. Let's see if we can find where we agree and work from there.

For one thing, I'm not saying it's ONLY heat that drives the turbocharger. I agree that it's pressure differential that causes the turbine to spin. My point is it's not possible to get the pressure differential required to produce boost on the compressor side without heat.

Here's a thought experiment: What happens if you spin the engine without combustion, using an external means? The pistons will still go up and down in the cylinders and the valves will still open and close. During the exhaust stroke for each cylinder the exhaust valve will open, and the air in the cylinder will be forced into the exhaust manifold by the piston moving upward. What happens with the turbocharger in this situation? Will it spin at the same rate as if the engine is running?

The answer, of course, is no. It requires the heat from combustion to generate enough pressure to spin the turbine side of the turbocharger fast enough to develop meaningful boost on the compressor side.

The same goes for a turbine engine. You can use an external air source to spin up the compressor wheels—modern airliners use a small turbine engine installed somewhere on the aircraft called the APU (auxiliary power unit) to provide air to spin up the main engines during start—but it isn't until you add the heat of combustion that you get the required pressure differential across the turbine wheels to generate enough power to turn the compressor wheels fast enough to produce meaningful thrust.

So, yes, pressure differential is what powers the turbine side of the turbocharger, and you don't get that differential without heat. The more heat, the greater the differential.

 

[jhnvan]

Maybe you guys should start your own thread about turbos so you stop polluting the what did you do to you bronco sport today thread with your debate.

Less arguing.... more pictures of mods!!!

 

[Meanderthal]

Here's a thought experiment: What happens if you spin the engine without combustion, using an external means? The pistons will still go up and down in the cylinders and the valves will still open and close. During the exhaust stroke for each cylinder the exhaust valve will open, and the air in the cylinder will be forced into the exhaust manifold by the piston moving upward. What happens with the turbocharger in this situation? Will it spin at the same rate as if the engine is running?

The answer, of course, is no. It requires the heat from combustion to generate enough pressure to spin the turbine side of the turbocharger fast enough to develop meaningful boost on the compressor side.

The same goes for a turbine engine. You can use an external air source to spin up the compressor wheels—modern airliners use a small turbine engine installed somewhere on the aircraft called the APU (auxiliary power unit) to provide air to spin up the main engines during start—but it isn't until you add the heat of combustion that you get the required pressure differential across the turbine wheels to generate enough power to turn the compressor wheels fast enough to produce meaningful thrust.

So, yes, pressure differential is what powers the turbine side of the turbocharger, and you don't get that differential without heat. The more heat, the greater the differential.

The combustion that happens in the cylinder goes toward driving the pistons. It does not do anything for the turbo. You are correct about the turbine engine requiring the combustion.

The pressure delivered to the turbine side of the turbo is delivered by the pistons. The air happens to be hot, but it doesn’t add anything to the work coming out of the turbo. If the hot air was adding work it would have to lose a significant amount heat to add work to the turbo.

Your thought experiment on turning the engine with an outside source, at the same rpm the engine would be spinning using combustion, is exactly what I was proposing. The turbo would spin at the same rate, whether that air is hot coming from the engine using combustion or cold coming from the engine being spun by an outside force.

Essentially, what happens on the intake side of the turbo is the exact opposite of what is happening on the exhaust side. Yes, there is a change in temperature in both cases but that change in temperature is driven by the change in pressure. That temperature change is also relatively small, not the kind of change needed to do any real work.

Since we are starting to annoy the community with what I would think is an educational conversation, we can take this offline or open a new thread.

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