[damage]

Originally posted by Cozz:
... but any pressure drop is quikly filled by the surounding higher pressure untill there is even pressure around.(THIS IS HOW WE MAKE MORE HP) The only way to get a pressure drop after the intercooler is when the intercooler drops in efficiancy and produces back pressure.

Dude, intercooler efficiency has little to nothing to do with pressure drop.

Intercooler efficiency is only an inlet to outlet temp ratio. Efficiency is only reduced by removing the cooling outside medium or the intercooler itself is a huge flow restriction causing loss of turbulenent airflow inside, i.e. a probe I/C on a 502 quad-turbo big block.

[Rara]

Mike, Cozz,

You guys obviously have some fundamental misunderstandings about the way air behaves, and can't seem to comprehend. You both need to start over from the beginning, and get a real understanding of how things actually work. Heck, it seems both of you still think its the extra pressure that makes the power on a turbo motor, and not the extra mass flow . . .

[Cozz]

by damage:

Dude, intercooler efficiency has little to nothing to do with pressure drop.

Intercooler efficiency is only an inlet to outlet temp ratio. Efficiency is only reduced by removing the cooling outside medium or the intercooler itself is a huge flow restriction causing loss of turbulenent airflow inside, i.e. a probe I/C on a 502 quad-turbo big block.

damage I was talking about cfm effiecency. Spearco intercoolers are rated at flow numbers that are equal to 1.5 pressure drop. Meaning the Spearco 2-174 that is 4.5 X 16.4 X 8.75 (I like this one) flows at 1050 with a 1.5 pressure drop(restriction). You can flow more but only to get a higher pressure drop.

Rara, I think you "have some fundamental misunderstandings about the way air behaves" because you are saying that the air before and the air after equal each other but this is not so. If they equal each other, how do you make more HP with an intercooler? But with your math an intercooler is not needed because there is no gain. Right math wrong formula. :crazy:

[bhuff]

Originally posted by Rara:
Mike, Cozz,

You guys obviously have some fundamental misunderstandings about the way air behaves, and can't seem to comprehend. You both need to start over from the beginning, and get a real understanding of how things actually work. Heck, it seems both of you still think its the extra pressure that makes the power on a turbo motor, and not the extra mass flow . . .

You obviously have a fundamental misunderstanding of dynamic systems.
Yes, you are right that a decrease in temperature decreases the pressure, but that is for a constant volume container.
You are assuming V is constant (flawed assumption for this dynamic system). Since you volume isn't changing, you still have the same number of molecule of air in each liter of volume. To increase power, you must increase the MASS flow of air. Buy keeping the volume constant, you are keeping the number of air molecules in each liter of air constant!
Here is a vivid example...
P1V1/T1=P2V2/T2 (a version of the ideal gas law with n and R constant).
now you say V is constant.....
P1/T1=P2/T2
solving for P2 (pressure after intercooler, we have:
P2=P1*T2/T1
If you go from 300F to 150F (422K to 339K) starting at 15 psi (30psi absolute)...
P2=30*339/422=24.1psi converting back to gage pressure, you have 9.4psi! All of these number are resonable number, but in real life, the pressure drop across the intercooler is NOWHERE NEAR THAT. That is a 5.6 psi drop!
Don't tell me that you don't assume a constant volume. I have it in writing right here...

A better way to try your example, take two enclosed spaces of equal size, and containing the same mass of air (same temp and same pressure in both) then heat one "box" and cool the other "box", you will most definately find that the hot box has a higher pressure than you started with, and the cold box has a lower pressure than you started with. same exact idea as the airflow through the intercooler, since the air in front of the IC and the air in the back of the IC cannot mix, because the air is flowing.

You "box" is a constant volume. This a static system, NOT A DYNAMIC INTERCOOLER.
I am not trying to be rude, but just trying to teach you something.

[Scepter86]

I have a great idea....
First step: Get a lot of money
Second step: Buy the most expensive I/C you can
Third step : Install it
Forth step: Drive around town and be happy.
Fifth step : Pop the hood, look at it, and be happy
:thumbup:

[damage]

Originally posted by Cozz:
damage I was talking about cfm effiecency. Spearco intercoolers are rated at flow numbers that are equal to 1.5 pressure drop.

CFM efficiency? WTF is that? Once again, I state, I/C efficiency is only a ratio of temp inlet to outlet.

Don't confuse efficiency to pressure drop. I know you aren't, but don't even mention it in the same sentence.

blue88mustang:
P1V1/T1=P2V2/T2 (a version of the ideal gas law with n and R constant).
now you say V is constant.....
P1/T1=P2/T2
solving for P2 (pressure after intercooler, we have:
P2=P1*T2/T1
If you go from 300F to 150F (422K to 339K) starting at 15 psi (30psi absolute)...
P2=30*339/422=24.1psi converting back to gage pressure, you have 9.4psi!

I had a similar equation done based on real numbers. Converting units to mmHg & K° and the General Gas Law which is based on Rara's Ideal Gas Law.

16PSI=827.4389mmHg
outlet temp 104.85F=313.62K
inlet temp 256.23F=397.72K

P(2)=P(1)* [T(2)/T(1)]
P(2)=652.472563 or ~12PSI

See Rara, the numbers don't jive. A loss of 4PSI isn't going to happen but with the worst of intercoolers.

I am not argueing that there isn't a loss in pressure due to temp drop. But pressure to temp is really almost independant, and can only be calculated by some other complex formula that I have yet to find in any standard textbooks or the Internet.

Frictional losses is what causes the pressure drop. I personally don't believe it is because the intercooler is a restriction as in CFM. But I haven't found any formulas (and don't have money for the books) to find the exact reason why.

[Rara]

let's step back, all I said was, a temperature drop will have a corresponding drop in pressure for a given volume. (for sake of analysis, a dynamic system can be treated as a static system, as long as you assume a constant flow rate, which I thought I made pretty clear)

In a practical application there are too many other factors to consider to see the effect clearly. Pipe size changes (ie volume changes), flow restrictions, non-constant mass flows (how long can you keep the mass flow rate exactly constant under boost in a turbo car . . . especially when the turbo is controlled by the boost, and not mass flow)
I thought it was quite obvious that I was using ideal conditions to describe how Pressure, Volume and temperature were related, and I apologize for not being clear enough if some of you missed that.

I made a statement that a temp drop would have a corresponding pressure drop all else being equal, and I was defending that statement, nothing more.

[bluovalguy]

OK guys, look at it this way...suppose you were to double displacement of the engine, (or maybe i should say the average volume at any given time between the turbo outlet and/including the cylinders) the boost pressure with the same turbo, spinning the same rpms would be halfed. now suppose we keep this same setup but somehow drop temperatures at the turbo outlet by half. the pressure would again be drastically reduced assuming the same mass of air was still flowing through the turbo inlet.

so why then is it so hard to picture pressure drops when an intercooler comes into play and effectively cuts hundreds of degrees out of the total air mass in the engine at any given point in time? pressure has to be equal throughout the system at all times? :bs: you guys have admitted that it's not the case as you say restrictions to flow can cause pressure differences from either side of the IC. if this is the case, why is it so hard to believe that an instant massive temperature drop couldnt cause a pressure drop that (just like a flow restriction) could not be equalized by the systems pressurization?

the speed at which the pressure can overcome potential differences is a mystery though. but even if you guys are right that pressures equalize so fast that differences are not measurable (i still dont buy it)...at least admit that with mass flow through the turbo inlet being held constant, pressure throughout the ENTIRE SYSTEM will drop with the use of an intercooler that can cause a reasonable temperature decrease.

[Cozz]

bluovalguy, check the Spearco website. HERE . Look at the flow # on the right then read the fine print on the bottom. It's not like from one second to another it drops 30degs. In order to to drop 2degs, it first has to drop 1deg. As the air moves through the intercooler it gets cooler by one deg. Any higher pressure will over come lower pressure within that 1deg change. It doesn't wait untill it drops a certain degs. or waits untill it leaves the intercooler. In order to produce 20 psi before the intercooler, you must have 20 psi after the intercooler or the 20psi would not be there in the first place.
Again, the best way to do this is one pipe with a blower on one side and a wall on the other with holes and freeze the center. You will see equal pressures at both sides but you'll have more air after the frozen side.

damage, sorry but CFM efficiency is the ability of how good an intercooler flows. I think I got it from such books like THIS ONE . I know it's confusing so I won't mention it again. :crazy:

[damage]

Originally posted by bluovalguy:
...(or maybe i should say the average volume at any given time between the turbo outlet and/including the cylinders)....

That is severe faulty logic. Only a change in VE or displacement will reduce boost pressure.

you guys have admitted that it's not the case as you say restrictions to flow can cause pressure differences from either side of the IC.

flow turbulence....

if this is the case, why is it so hard to believe that an instant massive temperature drop couldnt cause a pressure drop that (just like a flow restriction) could not be equalized by the systems pressurization?

I agree with that. However,

the speed at which the pressure can overcome potential differences is a mystery though. but even if you guys are right that pressures equalize so fast that differences are not measurable (i still dont buy it)

Buy it or not, it (temp drop causing pressure drop) is nearly immeasureable accept with the proper equipment.

Again, we are missing some formulas.