Remote mounting STS turbo Camaro/Trans-Am

[desperado]

Ok, I assume that that heat has nothing to do with the motor even running. Heat is just a detrimental byproduct of combustion right???

[Trouble Maker]

Hey Eli, that V is volume.

 

For everyone else, this is where Eli got that from.

 

PV=NRT is the actual equation. This is called the ideal gas law.

 

P=Pressure

V=Volume

N=Number of Mols in the gas, One mol is Avogadro’s number of molecules of whatever, Avogadro’s number=6.02214199 × 10^23.

R=Constant

T=Temperature

 

I usually think about it like this, R won't change, for the same given sample, N obviously won’t change. So we lose temperature on the way back, what can change? Well Pressure and Volume. A given pressure across a cross sectional area will have a certain velocity. A lower pressure will have slower velocity. Both the Pressure and Volume will drop reducing the CFM of the air flowing through the exhaust side of the turbo making it spool up slower.

 

Side Note, Reducing the cross sectional area raises velocity and raising it reduces the velocity. This is why 'smaller, a/r' turbos spool up quicker, why putting a larger exhaust (all other things being equal) will give you more power up top and less down low, etc.

 

Ok, back to the original topic. Say you have a given sample of a gas; nothing can come out or in. It’s in an elastic box, or lets say a balloon, that nothing can move in or out of.

 

Our First situation is as follows

P1*V1=N1*R1*T1

 

Our Second situation is as follows

P2*V2=N2*R2*T2

 

Well, if the second situation is the same sample as the first, with just some parameters changed, there are certain things that cannot change. That once again is N and R.

 

So N1=N2 and R1=R2

 

So First equation:

P1*V1=N1*R1*T1

Or

P1*V1/T1=N1*R1

 

Second equation:

P2*V2=N2*R2*T2

Or

P2*V2/T2=N2*R2

 

Since N1=N2 and R1=R2, then N1*R1=N2*R2

 

So P2*V2/T2=N2*R2= N1*R1=P1*V1/T1

Or P2*V2/T2=P1*V1/T1

 

We can easily think about how the temperature is going to drop, and measure that (EGT gauge).

 

So that equation can be re written as T2/T1=P2*V2/P1*V1

 

If T2 is lower than T1 then T2/T1 is going to be something lower than 1.

 

And that kids, is your chemistry/physics class for the day.

And if I didn’t make any damn sense, here’s a better explanation. tongue.gif

http://wine1.sb.fsu.edu/chm1045/notes/Gases/IdealGas/Gases04.htm

[nathan]

Who cares about the efficiency of the turbo since the fact that they do not shield that turbo is what is going to kill it. That oil cooler line is only about 2 inches off the ground! The first train track or weird pothole that car hits is going to bust the line, release all the oil onto the road, freeze the turbo, then screw the block.

[Mowgli1647545497]

Neo's hit on it with the elastic balloon description. Thats a visualization made for people to understand whats going on with the gas to drive home its not any one parameter but all three.

 

In aero engineering we'd call that a chunk, or a pulse. In aero-ease it implies a mass of air moving downrange.

 

doggunracing is right: its mass flow - but I implied that when I said "pulse". But as it interacts with the impellor, if you don't take a shortcut and look at the whole turbo as a black box, you need to look at the blade - the interaction is at the surface of each impellor blade. And the 1st order parameter there is pressure. (surface not being a volume) And while the flow of the mass of air (the balloon) over the impellor is the mechanism for creating the pressure, the pressure on the impellor surface is the force that moves it.

 

So I'll say it again, as Neo also showed some of: heat is related to pressure. The gas equations show that relationship - but nowhere does it say that at x pressure you will always measure y temperature (and rightly so, because thats not reality).

 

Ergo, you can drive a turbo (or any other closed-system device) with ANY temperature gas (as long as its still gaseous) at the same kinetic energy.

 

Thermal efficiency and "Heat" is an M.E. fudge shortcut for describing the energy flow without actually understanding it or modelling it. Understandable since most M.E. curriculums don't actually teach true fluid flow beyond an introductory set. Hell most ME textbooks call a shockwave a "head" and then when that occurs they erase their design and start over instead of handling the shockwave. Why bother when you can just assume a closed system and then look at tables?

 

Its one thing to be able to read tables or formulas in a book - its another to understand whats going on. Fluid flow is messy, using heat tables just means someone else did all the work.

 

[ 14. December 2004, 12:08 PM: Message edited by: Mowgli ]

[Mowgli1647545497]

To make it easier for Desparado and Sunny D to see I'll give an example:

 

The shuttle fuel turbos. The turbines that pump the fuel to the engines. That flow is under higher pressure than you'll see on ANY street engine, and yet the turbo there is moving a flow that is cold enough to flash freeze a rose into shatterable brittleness. Entry and exit.

 

The engineers there never talk about thermal efficiencies in those turbos. We also don't talk about that in tubojet or turbofan engines. We model the actual compressor stage and turbine stage in the flows. The flow around and past the blades.

 

Heat is a concept for engineers to use in design when they don't understand the motion of the gas and don't need to, its a shortcut.

 

[ 14. December 2004, 12:05 PM: Message edited by: Mowgli ]

[Mowgli1647545497]

One last maybe easier example - stripping it all away:

 

Down in the Vacuum chamber laboratory - I can lay a turbo impeller under a heat lamp and warm it up all day long, giving it GOBS and GOBS of heat. The thing isn't going to spin at all.

[Mowgli1647545497]

Originally posted by desperado:

Ok, I assume that that heat has nothing to do with the motor even running. Heat is just a detrimental byproduct of combustion right???

Yes - its a byproduct of the reaction of the fuel and air. But you don't need that to drive a pressure engine. Ever played with those baking soda engines as a kid? There are alot of volume expansion reactions that don't increase temperature that are wickedly efficient. Heck some even LOWER temp as they proceed to completion.

 

Its wild to put your hand on pycone engine and feel it get cooler as it runs. That thing the temperature decrease of the gas reaction is so dramatic it actually overcomes the frictional heating of the engine and the whole thing cools down as it runs.

[rl]

Originally posted by Mowgli:

One last maybe easier example - stripping it all away:

 

Down in the Vacuum chamber laboratory - I can lay a turbo impeller under a heat lamp and warm it up all day long, giving it GOBS and GOBS of heat. The thing isn't going to spin at all.

LOL!

[desperado]

graemlins/doh.gif

what ever, I'm going back to watching the flying monkeys now.

[Nate1647545505]

Originally posted by Mowgli:

To make it easier for Desparado and Sunny D to see I'll give an example:

 

The shuttle fuel turbos. The turbines that pump the fuel to the engines. That flow is under higher pressure than you'll see on ANY street engine, and yet the turbo there is moving a flow that is cold enough to flash freeze a rose into shatterable brittleness. Entry and exit.

 

The engineers there never talk about thermal efficiencies in those turbos. We also don't talk about that in tubojet or turbofan engines. We model the actual compressor stage and turbine stage in the flows. The flow around and past the blades.

 

Heat is a concept for engineers to use in design when they don't understand the motion of the gas and don't need to, its a shortcut.

ahw thanks sweetie smile.gif

 

I've read quite a few of these heat/density/your mother pushes the turbine threads, and you probably had the best explanation.

 

But in practice, with all equations aside, why do all automotive turbo motors have the turbocharger off of the exhaust manifold, and not remotely mounted? My non-educated ass believes for the gas's velocity, but you’re welcome to educate me on that.

 

Another thing when remote mounting, you have to scale down your A/R to increase velocity, ok, that in turn has an effect on your upper-end power. I guess it all depends on what kind of power curve you want your motor to have, but I wouldn't want a smaller exhaust A/R(to a point), when I could have a bigger, and not have any spool issues.

 

Now tell me about compression ratios with relationship to exhaust gas velocity smile.gif

[Mowgli1647545497]

My guess is that they mount it close to the engine for a few reasons:

 

1) Complexity. Why design, find vendors to manufacture, (or manufacture in-house) all the piping, clamps, mountings and all the hardware required to relocate that turbo when you can just bolt it to the manifold and replace all that cost with the cost of the 4 bolts it takes to hold it on.

 

2) Noise management.

 

3) Packaging. You protect the turbo and other mechanics underhood.

 

4) Maintenance costs - everything in one compartment instead of spread all around the car. Spread any system over the body of a vehicle and you also spread all the parts of hte vehicle it can (adversely) affect.

 

5) Proximity. You harness as much of the exhaust gas's energy as possible by locating your turbo as close to the point at which the gas has its highest energy (for combustion engines thats the point of combustion). Locating it farther back you not only have to worry about keeping all that piping pressurized, but you also lose energy along the way as the gas pulse travels down the piping: the boundary layer of the inside of the pipe will be stealing energy from the flow thru friction, the air charge will be cooling as it travels along the pipe, thus losing that thermal energy also, etc. Also, you're forcing the engine to move 6-10ft of high pressure gas as opposed to 2-10inches of high pressure gas.

 

Car exhausts aren't like designing a house HVAC system where you just put a big ass motor/fan on one end and then say the whole system is "pressurized". One really should look at it as a flow. You're paying for pressurizing that piping afterall. And whereas in a house or office building the engineer doesn't give a crap, in a car any power thats not used to drive the wheels is wasted power. So one really should think of it like a flow and not a pressurized static system.

[cloead]

http://i.b5z.net/i/u/1473169/i/hot_turbo2_ezr.JPG

 

I'd rather have it under my hood rather than under my gas tank.

 

Talk about turbo lag. I get full boost by 2k.. I wonder what people using that system see 13psi by.. 5 grand?

[Nate1647545505]

Originally posted by cloead:

http://i.b5z.net/i/u/1473169/i/hot_turbo2_ezr.JPG

 

I'd rather have it under my hood rather than under my gas tank.

 

Talk about turbo lag. I get full boost by 2k.. I wonder what people using that system see 13psi by.. 5 grand?

It wouldn't nearly get that hot placed remotely, that looks like its in the stage of making lots of power. Keep in mind thats right off the cylinder head, so its real close to all them explosions.

 

They see boost late because it doesn't harness all of the exhaust gas pulse energy, like Mowgill pointed out. Plus you have to pressurize all of the piping, delaying spool.

 

By the way, Is this BallJoint? or Anyone that goes up to the N. Olmstead lot?

[Mensan]

Mowgli, you missed the entire point of what I was saying. Here it is nice and simple:

 

The pressure of the gas is driving the impellor, true. However, when the air that is supplying that pressure is cooled, the pressure will drop. The longer you make that transition from the manifold to the turbo, the more the temperature will drop. Also, on a smaller scale, in a pipe that long the gas will be compressed slightly, resulting in a longer spool time. To keep the gases flowing smoothly, and to keep the pressure at an ideal value, the turbo should be mounted as close to the exhaust port as possible, providing the flow path is optimal.

 

I got my training on gas turbine engines, I used to work on GE LM2500 engines, and also Allison 501K17's. I started training on them in 1995.

[Mowgli1647545497]

I obviously agree mensan, see my last post

[cloead]

I know it wouldn't get that hot under the tank.. but still. And yeah.. talk about turbo lag... all that piping to pressurize.

 

-no this isn't balljoint.. but I'm good friends with him. I do goto the n. olmstead lot tho.

 

(he's auto lol.. he put down 310rwhp tho.. to my 290. tongue.gif )

[Nate1647545505]

Originally posted by cloead:

I know it wouldn't get that hot under the tank.. but still. And yeah.. talk about turbo lag... all that piping to pressurize.

 

-no this isn't balljoint.. but I'm good friends with him. I do goto the n. olmstead lot tho.

 

(he's auto lol.. he put down 310rwhp tho.. to my 290. tongue.gif )

cool, welcome to the board, I'm the guy with the black grand prix that moseies on up there.

 

Me, balljoint, and the red supra are pretty even these days, but who knows about next season smile.gif

 

Welcome to the board

[cloead]

thanks..

 

i raced mike with the red supra.. and i beat him up untill 120mph when he started to walk on me..

 

so i guess that means i lost or whatever but oh well =/ next season ill be faster.

[gillbot]

http://popularhotrodding.com/tech/0411phr_sts/