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post turbo air velocity?

Posted By: feets

post turbo air velocity? - 06/11/10 02:43 PM

What's a resonable upper limit of air velocity in the intake tube before the throttle body?
I read something about it years ago when I was laying out my stuff but I don't remember the details.

Obviously, subsonic velocities are going to be less turbulent but what kind of air speeds are you guys seeing?

I would imagine the type of intake and thottle body would make a difference.
A standard carbed intake would have the air splattering against the floor and distributing accordingly but what about an intake like mine? It's a front loaded plenum. What kind of air distribution issues will I run into when velocity starts getting too high?

I understand the plenum becomes a pressure vessel. Pressure everywhere will be equal. However, there is a difference between pressure and air movement.
Posted By: instigator

Re: post turbo air velocity? - 06/11/10 06:22 PM

Some of the guys making 2500+ hp are using a 3.5 inch inlet and 90mm throttlebody....I feel like a 3" and 75mm TB would be acceptable till 1500+ hp....The more boost pressure and smaller the motor per hp the smaller the intake tract should be able to be....I'm going top stick with my 75mm and hope to be in the 1400hp range with my new induction system.
Posted By: feets

Re: post turbo air velocity? - 06/11/10 07:55 PM

I'm running a 3" tube and calculated my velocity. It was much higher than I expected. I know there is plenty of room to grow with my car.
No doubt the velocity across the blades is down dramatically. I went from a 1000 cfm TB to a 1700 cfm blade.

I have seen some systems that were too small for my tastes.

I wonder if there is such a thing as too little velocity before the throttle blade.
Posted By: TRENDZ

Re: post turbo air velocity? - 06/12/10 02:06 AM

The inverse is true. Velocity drops with boost. Density increases causing more friction and making it harder to "bend" air around corners. I had an intake like yours on my original engine configuration. The front two cylinders would show rich plug readings until I extended the throttle body mount plate forward about 2" and put a "lump" in the floor before the 1&2 cylinder inlets. The lump causes a low pressure area to help turn the air. It made a suprising difference at lower boost levels.
In any case, increasing the tube/ throttle plate will slow the velocity and help make the turn, but it's not boost pressure that's creating velocity, it's your engines breathing characteristics.
Posted By: Duner

Re: post turbo air velocity? - 06/12/10 01:11 PM

How is this velocity calculated?

I am pushing boost thru a 50mm 2bbl throttle body. In NA form, I think it's supposed to provide roughly 600 cfm. Obviously with boost - that number increases. Does that sound like a restriction?
Posted By: feets

Re: post turbo air velocity? - 06/12/10 02:31 PM

Pressure and velocity are two separate things. Just because you have pressure everywhere doesn't mean you have velocity everywhere.
Air can move on one side of a pressure vessel and not on the other.

Velocity can be calculated (roughly) by figuring out the volume of air your engine consumes in one minute and comparing that to the area of your intake tract.

Pressure has NOTHING to do with volume. A 25 gallon air tank has 25 gallons of air regardless if pressure is at 5 psi or 125 psi.
Also, your engine only consumes half it's displacement per revolution.
Posted By: CW25

Re: post turbo air velocity? - 06/12/10 03:06 PM

Why don't you post this on the advanced tech section of TM. I can't think of anyone more qualified than Boostengineer to help answer this question.
Posted By: TRENDZ

Re: post turbo air velocity? - 06/13/10 07:13 PM

Pressure has everything to do with volume when we're talking about gasses. There's alot more volume of air in a 25 gallon tank at 125psi than there is at 5psi.
My point is this... Density is changed by pressure. Pressure creates more volume. Volume creates friction. Friction slows things down.
Try running out of the door of a burning building with a hundred other people trying to do the same thing. Its a lot faster by yourself(less volume). Alot of people will get through that door, but not at the speed you could get through by yourself(velocity).
Posted By: whiplash

Re: post turbo air velocity? - 06/15/10 03:15 PM

Quote:

Pressure has everything to do with volume when we're talking about gasses. There's alot more volume of air in a 25 gallon tank at 125psi than there is at 5psi.
My point is this... Density is changed by pressure. Pressure creates more volume. Volume creates friction. Friction slows things down.
Try running out of the door of a burning building with a hundred other people trying to do the same thing. Its a lot faster by yourself(less volume). Alot of people will get through that door, but not at the speed you could get through by yourself(velocity).



I think your confusing mass flow and volume flow. Gallons is a unit of volume. If you said there is a higher mass of air in a tank at 125psi then at 5psi, then that would be correct. The volume is constant, mass increases.
Density is changed by pressure, pressure does not create more volume. Volume does not create friction, friction is caused by objects moving. A change in position.

I don't know if there is a practical limit to the velocity. The more mass flow, the higher your boost will be, to a point where you will start to lose efficiency in the turbo and just heating things up. Any reduction in flow resistance will be a reduction in boost and an increase in efficiency. Again, within practical limits
Posted By: TRENDZ

Re: post turbo air velocity? - 06/15/10 10:55 PM

If pressure does not create more volume, please explain how a balloon works.
A given volume, lets say a gallon sized container (since a gallon is a liquid measurement. Air is not liquid, though it is fluid), will hold twice the volume of air at twice the pressure.
Mass flow indicates movement, hence the word "flow". Flowing more means more friction.
You can try to disect my logic if you want, but the fact is, the speed of the air flowing through an engine does not increase with boost pressure, it drops.
Posted By: instigator

Re: post turbo air velocity? - 06/15/10 11:22 PM

well when charge piping starts to be made out of ballons then your therios may start to ring tru.....the ballon expands because it's wall strength is weaker than the pressure inside..an aluminum or steel pipe has the strength not to expand...a pipe with higher pressure has more mass of air than a pipe at a lower pressure, and that increase of mass is what generates power...also pressure drops will lower at higher pressure with equal mass.....
Posted By: 8valves

Re: post turbo air velocity? - 06/18/10 01:36 AM

Quote:


Pressure has NOTHING to do with volume. A 25 gallon air tank has 25 gallons of air regardless if pressure is at 5 psi or 125 psi.
Also, your engine only consumes half it's displacement per revolution.




If I went with that statement, then how would a turbo motor make any more power than an NA?

As in, you're forcing more volume of air (cfm increase with compressor wheel speed) into the same available space (either your intake manifold or your engine's displacement, whichever you prefer). That increases the pressure.

As you're well aware of, more boost in the intake waiting for the valve to open is just more CFM being pumped into the same given intake plenum.

Otherwise, everyone should stop building turbo systems and strap a 50 gallon air tank in the bed of their truck and feed their engine with a 1/4" hose at 300 psi and go enter into Pro Mod.
Posted By: feets

Re: post turbo air velocity? - 06/18/10 02:46 AM

Quote:

Quote:


Pressure has NOTHING to do with volume. A 25 gallon air tank has 25 gallons of air regardless if pressure is at 5 psi or 125 psi.
Also, your engine only consumes half it's displacement per revolution.




If I went with that statement, then how would a turbo motor make any more power than an NA?

As in, you're forcing more volume of air (cfm increase with compressor wheel speed) into the same available space (either your intake manifold or your engine's displacement, whichever you prefer). That increases the pressure.

As you're well aware of, more boost in the intake waiting for the valve to open is just more CFM being pumped into the same given intake plenum.

Otherwise, everyone should stop building turbo systems and strap a 50 gallon air tank in the bed of their truck and feed their engine with a 1/4" hose at 300 psi and go enter into Pro Mod.



You're confusing yourself.
With boost, you're not pushing a greater volume of air into the engine. You are pushing THICKER air into the engine. Big difference.
Again, a 25 gallon air tank holds 25 gallons. Period. 5 psi or 5,000 psi doesn't change it's volume. It's still 25 gallons.

The turbos/blowers move massive cfm. The engine is essentially a potato in the tail pipe. It can only move so much air volume. When the turbos push more than the engine can take it all stacks up as boost. That's the same thing as turning on your air compressor. It only holds 25 gallons. The stacked up air is denser than the outside air.

Now that you're running air with more density you need more fuel to make it burn.

CFM = cubic feet per minute.
Cubic feet is a measure of volume.
25 gallon tank is a measure of volume.

Notice it doesn't say anything about density? Cubic feet of air at what pressure? Below sea level? 30,000 feet?

A turbo inlet wheel is called a compressor. That thingie making all the noise in your garage with a 25 gallon tank attached is a compressor.
They both do the same thing. They shove more air into an opening than mother nature had in mind.

A compressor shoves more air in than your tools can use. It stacks up in the tank as pressure.
A turbo shoves more air in than your engine can use. It stacks up in the engine as boost.
Posted By: 8valves

Re: post turbo air velocity? - 06/18/10 03:11 AM

Quote:

Quote:

Quote:


Pressure has NOTHING to do with volume. A 25 gallon air tank has 25 gallons of air regardless if pressure is at 5 psi or 125 psi.
Also, your engine only consumes half it's displacement per revolution.




If I went with that statement, then how would a turbo motor make any more power than an NA?

As in, you're forcing more volume of air (cfm increase with compressor wheel speed) into the same available space (either your intake manifold or your engine's displacement, whichever you prefer). That increases the pressure.

As you're well aware of, more boost in the intake waiting for the valve to open is just more CFM being pumped into the same given intake plenum.

Otherwise, everyone should stop building turbo systems and strap a 50 gallon air tank in the bed of their truck and feed their engine with a 1/4" hose at 300 psi and go enter into Pro Mod.



You're confusing yourself.
With boost, you're not pushing a greater volume of air into the engine. You are pushing THICKER air into the engine. Big difference.
Again, a 25 gallon air tank holds 25 gallons. Period. 5 psi or 5,000 psi doesn't change a thing. It's still 25 gallons.

The turbos/blowers move massive cfm. The engine is essentially a potato in the tail pipe. It can only move so much air volume. When the turbos push more than the engine can take it all stacks up as boost. That's the same thing as turning on your air compressor. It only holds 25 gallons. The stacked up air is denser than the outside air.

Now that you're running air with more density you need more fuel to make it burn.

CFM = cubic feet per minute.
Cubic feet is a measure of volume.
25 gallon tank is a measure of volume.

Notice it doesn't say anything about density? Cubic feet of air at what pressure? Below sea level? 30,000 feet?

A turbo inlet wheel is called a compressor. That thingie making all the noise in your garage with a 25 gallon tank attached is a compressor.
They both do the same thing. They shove more air into an opening than mother nature had in mind.

A compressor shoves more air in than your tools can use. It stacks up in the tank as pressure.
A turbo shoves more air in than your engine can use. It stacks up in the engine as boost.





I'm well aware of how a forced induction system works. Please refrain from repeating your statement multiple times, it just makes for uselessly long posts.

Let's make this far simpler and see how it goes for you. We'll even use your air tank example.

Your statement, "pressure has NOTHING to do with volume".

Your 25 gallon air tank has no outlets. One inlet only. At atmospheric pressure, it is already holding 25 gallons of air at whatever altitude you want as it's open to atmosphere.

The only way to increase pressure in the tank to above atmospheric is to introduce more air, beyond it's capacity, into the tank. It doesn't have to be pressurized air, just more air period (CFM, which is a measurement of volume)and not let any out.

Voila. Pressure increased based on volume.
Posted By: feets

Re: post turbo air velocity? - 06/18/10 03:18 AM

Quote:

Voila. Pressure increased based on volume.



Adding volume from outside the system will increase pressure.

You're not increasing the volume inside the engine.

The volume disappears once it enters the turbo. It's now thicker air.

I can fit an entire Goodyear blimp worth of air into a smaller vessel.
What happened to that million cubic feet of volume?
*poof*
It's now stuffed into a 25 gallon tank.

Hey, what's the volume of that tank? Lookie there! It's 25 gallons. Granted, it's at a heck of a lot higher pressure than the blimp.

You can't mix volume and pressure. They are two separate things.

Do I need to repeat that or did you get it this time?
Posted By: 8valves

Re: post turbo air velocity? - 06/18/10 10:19 AM

Quote:

Quote:

Voila. Pressure increased based on volume.



Adding volume from outside the system will increase pressure.

You're not increasing the volume inside the engine.

The volume disappears once it enters the turbo. It's now thicker air.

I can fit an entire Goodyear blimp worth of air into a smaller vessel.
What happened to that million cubic feet of volume?
*poof*
It's now stuffed into a 25 gallon tank.

Hey, what's the volume of that tank? Lookie there! It's 25 gallons. Granted, it's at a heck of a lot higher pressure than the blimp.

You can't mix volume and pressure. They are two separate things.

Do I need to repeat that or did you get it this time?



Haha! No, not needed at all, but I will certainly try to make it simpler yet for you.

But you did get it up there, I put it in bold just in case it got missed.

This is a matter of physics. Things don't "dissapear".

The volume is still there, it's just condensed, exactly as you were onto with the density topic.

Transfer the 25 gallon air tank at 5000 psi to a 5000 gallon air tank. It's no longer at 5000 psi, yet it fills the tank. The volume didn't "dissapear".

That's how a boosted engine makes power. That's why I've put together several 122 CID setups that make more power than your car, or any of mine for that matter. The cylinder pressure increases exponentially, yet the 1200 HP 122 CID motor is still moving X CFM, just like the 1200 HP 500 CID motor. Same CFM. Just a different pressure to get it.

Once more: CFM is a measurement of volume. It IS DIRECTLY effected by pressure.

This still has nothing to do with your original post/question, but I figure someone ought to stand up in a thread where people are discussing calculating airflow velocity theories and ideas, when this basic principal was jumped right over.
Posted By: Duner

Re: post turbo air velocity? - 06/18/10 01:49 PM

It's all over my head.....
I'm just going to put a bigger spring in the wastegate and let it ruin all of my velocity while I keep my volume the same but increase the pressure.

Velocity. We don' need no stinking velocity. We gots boostage!
Posted By: furious70

Re: post turbo air velocity? - 06/18/10 03:10 PM

Quote:




Haha! No, not needed at all, but I will certainly try to make it simpler yet for you.



That's how a boosted engine makes power. That's why I've put together several 122 CID setups that make more power than your car, or any of mine for that matter. The cylinder pressure increases exponentially, yet the 1200 HP 122 CID motor is still moving X CFM, just like the 1200 HP 500 CID motor. Same CFM. Just a different pressure to get it.

Once more: CFM is a measurement of volume. It IS DIRECTLY effected by pressure.

This still has nothing to do with your original post/question, but I figure someone ought to stand up in a thread where people are discussing calculating airflow velocity theories and ideas, when this basic principal was jumped right over.



I'm not sure why anyone coming across as a self appointed turbo expert would be talking in terms of volume instead of mass???
Quote:

Once more: CFM is a measurement of volume. It IS DIRECTLY effected by pressure.


While not untrue, this is a very confusing statement to make as the formula for cfm has no ability to describe this effect.

lbs/min makes a lot more sense than cfm to me when trying to accurately describe the air being consumed by an engine with a turbo on it. I would like to see your math laid out that shows the 2 engines you describe above consume the same cfm (in order to do so I believe you are going to have to make a whole host of assumptions- the very crux of the problem here- trying to use a unit of volume measure when a unit of mass measure is required)
Posted By: feets

Re: post turbo air velocity? - 06/18/10 03:23 PM

He's talking about cfm. I guess he plans on bragging about consuming all of earth's atmosphere in his 122 CID engine.

What does all the air in the world outside the engine have to do with the air that's in the engine?

CFM = cubic feet per minute

25 cubic feet of air at 5,000 psi take up EXACTLY the same VOLUME as 25 cubic feet of air at 5 psi.

The 5,000 psi will have a much higher DENSITY than the 5 psi but the VOLUME (cfm) doesn't change.
Posted By: feets

Re: post turbo air velocity? - 06/18/10 03:46 PM

Quote:

Transfer the 25 gallon air tank at 5000 psi to a 5000 gallon air tank. It's no longer at 5000 psi, yet it fills the tank. The volume didn't "dissapear".




This is beautiful!

Gallon = unit of measure

25 is less than 5,000

25 gallons is less volume than 5000 gallons.

Disappear was a bad term for both of us to use. Convert is appropriate. Perhaps even disperse.

You are talking about MASS not VOLUME.

The mass of air that was contained in a vessel with a volume of 25 gallons has been transferred to a vessel with a volume of 5,000 gallons.
The mass is the same. Volume is greater. Pressure is decreased.

It's simple physics man.
Posted By: 8valves

Re: post turbo air velocity? - 06/18/10 05:19 PM

Quote:

It's all over my head.....
I'm just going to put a bigger spring in the wastegate and let it ruin all of my velocity while I keep my volume the same but increase the pressure.

Velocity. We don' need no stinking velocity. We gots boostage!



Funny, but lots of people would be far better off if they ignored math that may or may not be fully understood and go with that method!
Posted By: 8valves

Re: post turbo air velocity? - 06/18/10 05:26 PM

Quote:

Quote:




Haha! No, not needed at all, but I will certainly try to make it simpler yet for you.



That's how a boosted engine makes power. That's why I've put together several 122 CID setups that make more power than your car, or any of mine for that matter. The cylinder pressure increases exponentially, yet the 1200 HP 122 CID motor is still moving X CFM, just like the 1200 HP 500 CID motor. Same CFM. Just a different pressure to get it.

Once more: CFM is a measurement of volume. It IS DIRECTLY effected by pressure.

This still has nothing to do with your original post/question, but I figure someone ought to stand up in a thread where people are discussing calculating airflow velocity theories and ideas, when this basic principal was jumped right over.



I'm not sure why anyone coming across as a self appointed turbo expert would be talking in terms of volume instead of mass???
Quote:

Once more: CFM is a measurement of volume. It IS DIRECTLY effected by pressure.


While not untrue, this is a very confusing statement to make as the formula for cfm has no ability to describe this effect.

lbs/min makes a lot more sense than cfm to me when trying to accurately describe the air being consumed by an engine with a turbo on it. I would like to see your math laid out that shows the 2 engines you describe above consume the same cfm (in order to do so I believe you are going to have to make a whole host of assumptions- the very crux of the problem here- trying to use a unit of volume measure when a unit of mass measure is required)



Does an engine use mass efficiency, or volumetric efficiency?

As I said above half kidding, if people thought outside of the math that can become quite overwhelming they often get alogn pretty well just on logic alone.

But, here.

V(cu.ft./min) = n(lbs/min) x 10.73 x T(deg R)/(29 x P(psia))


That is why I'm speaking in CFM. Because it's a function of lb/min. I was trying to make this as simple as possible. Since most engine builds calculate in CFM (head flow, for instance) instead of turbo guys calculating compressor flow in lb/min.

Furthermore, Feets, if math is all we're going to argue with here then the proof is there for you. Pressure is directly involved in the equation to find volume.

What more can I offer?

I'm not getting riled or mad or anything, just trying to point out some things since people around here respect your opinion and look to it as truth. To make the statement "pressure has NOTHING to do with volume" is wrong, however you want to argue it.

This isn't a d*ck measuring contest either. The small engine comparison was for demonstration purposes. No braggign needed, I'm not looking for a pick-me-up. If anything this should be a good read for some.

And as a final note to ponder, lets make this very simple, once more.

A throttle body flows 600 CFM at 28" depression on a flowbench. Does it change how much it flows if it is done at 10" depression. How about 10 psi? 30?
Posted By: Shaker223

Re: post turbo air velocity? - 06/18/10 05:45 PM

Quote:

Quote:

It's all over my head.....
I'm just going to put a bigger spring in the wastegate and let it ruin all of my velocity while I keep my volume the same but increase the pressure.

Velocity. We don' need no stinking velocity. We gots boostage!



Funny, but lots of people would be far better off if they ignored math that may or may not be fully understood and go with that method!



That's the way I think!!
Posted By: instigator

Re: post turbo air velocity? - 06/18/10 07:09 PM

CFM don't mean squat..throw an A or an S before it and then we may be able to help out.....
Posted By: 8valves

Re: post turbo air velocity? - 06/18/10 07:23 PM

Should I ask what correction, smoothing, and dyno type your sig is based off of as well, then?



Oh, and let's move to measuring in psia too!

PS- Badass car, looking forward to seeing how the new setup responds. I would think quite well.
Posted By: instigator

Re: post turbo air velocity? - 06/18/10 07:35 PM

Don't remember the details..was a dynojet....whatever it was it was enough to go 128mph in the 1/8th at 3500lbs!...

will the friction loss stay the same with a proportional increas of mass due to a proportional increase of pressure as long as temp stays the same????this is the question.
Posted By: feets

Re: post turbo air velocity? - 06/18/10 07:56 PM

Quote:

A throttle body flows 600 CFM at 28" depression on a flowbench. Does it change how much it flows if it is done at 10" depression. How about 10 psi? 30?



A pressure differential across a restriction will increase flow rates.

If a throttle body is fed pressure at 10 psi on a flow bench it isn't seeing pressure under it, assuming my impression is correct.

An intake manifold is different than a flow bench. The flow bench sucks the air out and it's out of the equation after it passes the blades and get measured.

In a boosted engine, you have pressure above and below the throttle body. The throttle body is still a restriction.

Assume the there is 12 psi above the throttle and 10 psi in the manifold. The throttle body can't flow enough cfm to accomodate the full capacity of the induction system. This results in a 2 psi restriction.

Is that going to be different than pushing air on top of the throttle body at 2 psi and having no pressure in the intake manifold? Will the rate of flow be significantly different?

I haven't got a clue. I never played with a flow bench.

If the flow rate (cfm) of the throttle body is the same at 10 psi as it is at 40 psi the same volume of air will pass in the same amout of time. The thing that changes is the mass of air that has moved.

Gaseous compression is a fickle mistress. You have to make sure you maintain the same unit of measure. Mass and volume are two totally different measurements.

I would hate to see the pressure (and resulting temperature) required to compress air into a near solid form.


Saying pressure and volume had nothing to do with one another was a little too generic. When dealing with the typical street engine induction system the differences between absolute flow rates should be negligible.

This discussion started by talking about the velocity of air moving between a turbo and an intake manifold.

Naturally, a tiny throttle body will kill performance and create a nightmare of turbulence.
I seriously doubt that I'll be able to get a higher flowing thottle body for my application so that's a fixed restriction.
Posted By: feets

Re: post turbo air velocity? - 06/18/10 08:04 PM

Quote:

will the friction loss stay the same with a proportional increas of mass due to a proportional increase of pressure as long as temp stays the same????this is the question.



When you cool the compressed air don't you lower the pressure? If you can cool a higher pressure to the same temperature you're making good improvements. I think friction would still increase due to the increased mass.
Considering the pressures we are dealing with I doubt the increase in friction will be significant.
Posted By: TRENDZ

Re: post turbo air velocity? - 06/18/10 10:40 PM

Technical shmechnical.
My main point was to enlighten people to the fact that a turbo or supercharger does not have a positive effect (more speed) on velocity.
I always think about an imaginary dyno room, where the atmosphere is 100% under my control. I could remove the throttle plate on the engine, and control idle speed by (my word) "de-densification", or max power by pressalizin.
Think about what a throttle plate actually does. It changes the density in the manifold.
An engine ran in my fantasy dyno room would have a very similar torque CURVE at all levels of pressure(including vacuum) just at different levels. This would indicate similar air speeds through the engine at similar rpms.
Go ahead beat me up for living in a fantasy world
Posted By: feets

Re: post turbo air velocity? - 06/19/10 01:31 AM

My original question was about air velocity between the turbo and engine. The size of the intake tube will determine velocity. Is there a point where the air is moving too fast?

We kinda got sidetracked on semantics.
Posted By: Duner

Re: post turbo air velocity? - 06/19/10 04:20 AM

I guess one of the "non-math" but experience based question/answer would be: What if anything changes by going to larger or smaller boost tube from the blower or turbo to the intercooler then airhat. Quicker response? Loss of response? Temperature/density change? What does changing this do positively or negatively?
Posted By: furious70

Re: post turbo air velocity? - 06/19/10 12:25 PM

Quote:

My original question was about air velocity between the turbo and engine. The size of the intake tube will determine velocity. Is there a point where the air is moving too fast?

We kinda got sidetracked on semantics.



My copy is buried somewhere in our den, but Corky directly addresses this with some guidelines in Max Boost, no?
Posted By: Twostick

Re: post turbo air velocity? - 06/21/10 10:56 AM

Quote:

My original question was about air velocity between the turbo and engine. The size of the intake tube will determine velocity. Is there a point where the air is moving too fast?

We kinda got sidetracked on semantics.



According to a friend of mine who is way smarter about this stuff than I am, and if I understand him correctly, once it goes supersonic, flow will stall, that is it wont flow anymore CFM no matter what pressure is behind it.

I think a turbo map (hieroglyphics to me ) kind of explains that theory ie once the compressor wheel reaches a certain speed efficiency drops off a cliff. I'm pretty sure that speed equals or approaches supersonic. Or not .

Kevin
Posted By: whiplash

Re: post turbo air velocity? - 06/21/10 04:04 PM

Quote:

CFM don't mean squat..throw an A or an S before it and then we may be able to help out.....



Absolutely correct....

CFM is NOT a measure of Volume. It is a measure of FLOW....

This whole post is riddled with gray areas of physics.

It would be a lot easier if we all talked in terms of Mass flow. That's what auto engineers do. It takes a lot of the CFM SCFM ACFM PSI PSIG PSIA BS out of the equation. CFM is only "so" imporatnt because most people can't get their heads around grams/sec or lb/hour.
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