Turbo question - pounds per square inch

[Deadly BlaZe]

So let's say a turbo is boosting 10 psi, how do you determine how many square inches there are for every 10 lbs??

 

[dieseltech]

Ummmm. This seems like an odd question. Im not sure if you're asking for an explanation of PSI? 10 psi means that there is 10 pounds of force per square inch of physical surface area in the system. And psi is the variable, not the surface area. I'm still puzzled to the relavence of this question, any insite would be helpful.

 

[Lordpaxin]

Perhaps he is curious about the "Volume" of air he is moving at 10psi.; CFM?

 

[dieseltech]

ahhhh, perhaps. good call Lordpaxin.

 

[GST98BIG16G]

hes the only one that knows the purpose of the question

 

[boostnhard]

hey i was just reading an article on modified mag which talks about that and it is exactly double as pounds
ex: 20psi = 40 sq inches

 

[TSG59_Steve]

hey i was just reading an article on modified mag which talks about that and it is exactly double as pounds
ex: 20psi = 40 sq inches

That doesn't make any sense at all...

PSI actually stands for Pound-force per square inch. "At 1 lbf/in2, a force of one pound-force is applied to an area of one square inch." - Wikipedia

So basically you don't measure the "inches" of psi, you need an area/volume to apply it to.

The answer to his question is 1.

 

[GST98BIG16G]

are we there yet? are we there yet?

 

[Defiant]

Where the hell's my beer?

 

[boostnhard]

Stevey i know what i read!!!!!!!!!!!!!!!!!!!!
i can prove it

 

[wret]

Sounds like the netflix commercials.
What's the square root of blue?

 

[Deadly BlaZe]

I don't think you guys get the question.

My question is if it's 10 lbs per square inch...how many square inches are you applying 10 lbs of force to? How would you determine something like that?

 

[wret]

My question is if it's 10 lbs per square inch...how many square inches are you applying 10 lbs of force to?

All of them.

When you put a volume of gas at x psi into a vessel half the size, you get twice the pressure. See Boyles law for more info.

 

[Deadly BlaZe]

All of them.

When you put a volume of gas at x psi into a vessel half the size, you get twice the pressure. See Boyles law for more info.

So then how many square inches are we forcing 10 lbs into a dsm? I'm assuming there is an answer to that, unless psi is just a measurement and there isn't really a certain amount of square inches that we're forcing 10 lbs upon.

 

[4pistons]

Here's the formula:

sq. in. = PSI/volume x air temp/cubic ft. of available airspace x Turbo size/your age x tire sidewall section width.

Seriously........

10 PSI means there is Ten Pounds of force pushing on every square inch of area. Doesn't state HOW many square inches, it could be one, could be 1000, it doesn't matter. The area is the variable. It is not a way to state the area, it is a way to state the pressure.

Rick - '91 GSX

 

[xveganxcowboyx]

hey i was just reading an article on modified mag which talks about that and it is exactly double as pounds
ex: 20psi = 40 sq inches

You're right. The earth has just under 30 square inches of surface area. I checked atmospheric pressure, I know!

Deadly, you'll need to measure the total distance of all your intercooler piping, cylinder size (well, we know that one...), intercooler, etc.. to find the total square inches.

Try this. Take a piece of paper and measure a long and short side. Multiply the numbers. (8.5x11). The paper has a total of 93.5 square inches. Now roll it in a circle so that the opposite ends are touching. Think of that as a section of intercooler piping or one cylinder.

Of course this is not at all important to...anything, but you asked.

 

[wret]

So then how many square inches are we forcing 10 lbs into a dsm? I'm assuming there is an answer to that, unless psi is just a measurement and there isn't really a certain amount of square inches that we're forcing 10 lbs upon.

You are confusing surface area with volume. Square units are two dimensional and used to measure surface area. Cubic units are used to measure 3D volume. When expressing the intake of quanities of air, it is necessary to use the fourth dimension; time. Typical maximum intake volumes for our cars are on the order of 400-500 cubic feet per minute (cfm), but it's assumed that the air consumed is typical atmospheric pressure.

Atmospheric pressure is close to 15 psi, so if you are boosting 15 psi, you are approximately halving the the volume of air and doubling the pressure as it is forced into the engine.

 

[Deadly BlaZe]

Ok thanks for the answers guys. It just boggled my mind one day. People say xx psi, then i was wondering, ok we know how many pounds, now how many square inches? But I think i got it now.

 

[boostnhard]

Wret that would make it double right?
10psi + 20 sq inches

 

[xveganxcowboyx]

Wret that would make it double right?
10psi + 20 sq inches

Did my sarcastic ass post not make this clear? Or the other posts that clarified square inches VS volume (cubic inches)?

Square inches is unimportant. What Wret was saying is that if you double the pressure of a gas the VOLUME is reduced to half. Essentially the molecules are squished closer together meaning the same amount of the gas will take up less space. Space being a three dimensional term, not two dimensional.

 

[Deadly BlaZe]

Wret that would make it double right?
10psi + 20 sq inches

Yeah honestly, that makes no sense.

 

[TSG59_Steve]

Stevey i know what i read!!!!!!!!!!!!!!!!!!!!
i can prove it

Prove it then...

 

[wret]

Wret that would make it double right?
10psi + 20 sq inches

Double the pressure, half the volume. Anything within the pressurized area receives the pressure in proportion to its surface area (square inches). Yes this means that a small object or small surface is exposed to less force than a large surface.

When everything is exposed to the same pressure, inside and out, the force has little effect, such as what we experience under atmospheric pressure. That's why we often think of (and refer to) atmospheric pressure as zero. It's when there is a pressure differential that things get interesting. Exposed surface area starts to get a little more meaningful. Think of the tiny, thin tube you use for a boost control gauge. Because of the low surface area, it is not exposed to a great amount of force and can easily handle 30 psi of boost pressure. Now think of how much more robust tubing is required for an intercooler pipe that is 2 or 3 inches in diameter.

 

[TSG59_Steve]

Double the pressure, half the volume. Anything within the pressurized area receives the pressure in proportion to its surface area (square inches). Yes this means that a small object or small surface is exposed to less force than a large surface.

When everything is exposed to the same pressure, inside and out, the force has little effect, such as what we experience under atmospheric pressure. That's why we often think of (and refer to) atmospheric pressure as zero. It's when there is a pressure differential that things get interesting. Exposed surface area starts to get a little more meaningful. Think of the tiny, thin tube you use for a boost control gauge. Because of the low surface area, it is not exposed to a great amount of force and can easily handle 30 psi of boost pressure. Now think of how much more robust tubing is required for an intercooler pipe that is 2 or 3 inches in diameter.

I think the "double the pressure, half the volume" thing would be easier with an example: I'll just use surface area. 100in^2 at 10psi = 200in^2 at 5psi. 10psi is double the pressure, and 100in is half the area. 10psi on 100in^2 would be 200lbs of force and 5psi on 200in^2 would be as well.

10psi on a surface area of 20in^2 would be a total of 200lbs of pressure.
So... Boostnhard, I think what you read, and are trying to say... which was not really related to the original question was: 20psi on 40in^2 = 10psi on 20in^2, which is also wrong. It should be 20psi on 40in^2 = 10psi on 80in^2.

 

[wret]

I think the "double the pressure, half the volume" thing would be easier with an example: I'll just use surface area. 100in^2 at 10psi = 200in^2 at 5psi. 10psi is double the pressure, and 100in is half the area. 10psi on 100in^2 would be 200lbs of force and 5psi on 200in^2 would be as well.

10psi on a surface area of 20in^2 would be a total of 200lbs of pressure.
So... Boostnhard, I think what you read, and are trying to say... which was not really related to the original question was: 20psi on 40in^2 = 10psi on 20in^2, which is also wrong. It should be 20psi on 40in^2 = 10psi on 80in^2.

Becareful not mix up volume and surface area units or you will confuse people even more.

In³ or cubic inch units are used to indicate volume. 3D
In² or sqaure inch units are used to indicate surface area. 2D

Although pressure is expressed as pounds per square inch (surface area) the volume of a substance at X psi would still be represented by cubic units.

If you want a real world example, think of a standard scuba tank. The most common size contains 80 ft³ of air at atmospheric pressure, crammed into a container of about 0.5 ft³. The starting volume is 160x the tank volume. Boyles law says that at the same temperature, the pressure would be 160x greater in the tank. 160 x 15psi (atmospheric) is 2400psi.