What did you do TO your Bronco Sport today?

[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.

 

[Kraken23]

Added Curt trailer hitch and installed hitch cover.

 

[wireman]

Added the Aeroskin II deflector and a flag decal on the tailgate. Decal is excellent quality.

 

[AndyMac204]

But you had fun, right?

honestly it was a pretty good time, and unusually warm weather for this time of year.

 

[Mark S.]

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.

You're right, sorry! You can read the continuing debate here.

 

[jhnvan]

I love a good debate and technical info so I'll follow the new thread though

 

[Mrmike]

I installed Redline hood struts about 1 month ago. Today I removed the factory hood support rod. Makes for a much cleaner look and could be re-installed if needed.

 

[mikeyncc]

New floor mats today.

First thing I bought....Cross Bars coming tomorrow!!!
Oh Yea

 

[davidb1841]

Its Pine Pollen season in NC....Washed it!

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