[Cozz]

bluovalguy, If I understand correctly what you are trying to say is that more pressure in the intercooler at higher temps = less pressure at colder temps? I believe that the statement is not true. One thing people are forgetting is why there is 20psi in front of the intercooler to begin with.

[bhuff]

Originally posted by 67King:
NOw, another thing - volume kind of changes, but not really. If you have the same size pipes on the inlet and outlet, a cross section of each gives you the same volume.

Sorry, I wasn't very clear with the volume thing.
My assumption with the ideal gas equation was that "n" (the number of moles) remains constant. That means that volume is based on the number of moles you are considering. If you are saying 1 mole goes through the intercooler, then one mole will take up a larger volume before the intercooler than after.
Everytime I said volume, I was saying the volume which a certain mass of air takes up, which is the same as speaking in density.
I think we are in complete agreement here with just a few misunderstandings between us. :cheers:

[Rara]

Well, I started this reply last night, but was unable ot finish, due to some power problems in my neighborhood, so I'll see what I can do to finish it up . . .

first and foremost, I'm gonna ignore 92boostednotch, because I will just end up making fun of him too much, and he will take it way too personally, and try to start namecalling again.

I think 67king's post is prolly the best to respond to, as he covered things pretty well . . . (though, I think deep down, he and I are pretty well in agreement, right Harry? )

All of that is perfectly fine and repeatable - in an isolated system.

Yes, but not just in an isolated system, there are other cases where it will be applicable that are not isolated.

Guess what, fellas, we don't have an isolated system.

No we don't, but we do have a system that can be legitimately treated as a constant flow system, and things still apply (check a basic fluid mechanics textbook, c'mon, I know you saved yours)

THe fact that air is constantly moving in and out of the system means that a pressure drop will be caused by anything impeding flow.

Absolutely, positively 100% correct. Though, I might phrase it "The fact that air is moving at all, means anything impeding flow will cause a loss of flow energy, or, a pressure drop". Further, in a practical situation, most of the pressure losses encountered will be due to flow "friction" we are talking about here.

And the fact that the intercooler does not seal the two sides from each other means that they would be at the same pressure if there were no airflow.

Also true, but airflow at a given mass flow rate, and with everything else constant, except temperature, the pressure must drop with the temperature.

Anyway, I won't bother finishing that train of thought, because bluovalguy has done a good job covering it.

Cozz,
Yes, that statement is true, while in your application there may be other affects involved that may cloud seeing it clearly. Please, go take a basic thermo, or fluid mechanics class, and then come back if you still disagree. Its a simple matter of physics, that lowering the temperature of a given mass of air, while keeping it in the same volume (ie pipe size) the pressure must decrease by an amount directly proportional to the temp decrease.

and back to the original question, I also agree w/ 67king and bluovalguy on thier assesments, however, I would be far less willing to depend on a water/alky injection system on the street for detonation control, mostly because the complexity necessary when you make the system "fail-safe", and the inherently lower reliability of that far more complex system.

[Cozz]

Rara, You missed my statement so hear it is again, why is there 20 pounds of air before the intercooler? What I am trying to get at is you can't have 20psi on one side of a pipe without haveing 20 psi on the other side of the intake. You can heat one side of the pipe while freezing the other side but the pipe will share the same psi throughout.

[Rara]

Originally posted by Cozz:
Rara, You missed my statement so hear it is again, why is there 20 pounds of air before the intercooler? What I am trying to get at is you can't have 20psi on one side of a pipe without haveing 20 psi on the other side of the intake. You can heat one side of the pipe while freezing the other side but the pipe will share the same psi throughout.

I didn't miss your statement at all.
sure, but only if the flow can mix and equalize. If the air is flowing through the pipe, it can't eqaulize, and the pressure is different. One of the major components of how an airplane wing lifts is because of a high pressure area under the wing, and a low pressure area above the wing, simply because the airflow can't equalize because things are moving.
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.

[Cozz]

If the air is flowing through the pipe, it can't eqaulize, and the pressure is different.

So why is there 20 psi before the intercooler?

[Rara]

Originally posted by Cozz:
[QBSo why is there 20 psi before the intercooler?[/QB]

because you said there was.

seriously, because of resistance to flow. Pressure can only build if the air is being constrained into a smaller area than it wishes to be in, ie the turbo packs more air into the intake tract than there would otherwise possibly be.

Cozz, seriously, why don't we just chalk it up to you not understanding what's going on? because we could go on for years with me (and others obviously) explaining and re-explaining this stuff to you. Go study up on how air and other gases behave with respect to temp and pressure and density changes, then come back.
Really, I'm not trying to be a prick at all, it just seems to me we are gonna go in circles for a long time, wasting both of our time, becuase you don't understand the underlying principles. Beside the fact that its not terribly important of a discussion anyway, since most of the pressure losses in the intake are to due flow restrictions.

[damage]

I just wanted to add something....

Originally posted by 67King:
If it were as simple as pressure, there would be no benefit to using a larger turbo. I mean, a T3 will boost our engines well over 20PSI. Why bother with a hybrid? Because it increases the mass of air that can be flowed because it is cooler, and therefore more dense.

Mass flow increases, but it doesn't run cooler at the same pressure and inlet temps. The (Ideal exit temp will be the same if they have the same efficiency rating at the same pressure differential.

[Mike SVOR]

Rara, dude, your confusing people. lol

Just admit that there will be no pressure difference between one side of an intercooler and the other side of an intercooler if these rules are true:
1. your intercooler flows more air than what you need.
2. Your turbo can flow more air than what you need for the boost level you plan to run.

You said to go and prove you wrong, well I've already did it.
I put two boost gauges on my intercooler's inlet and outlet pipes. There was no difference in psi between the two gauges.

So, you've got to be saying either:
1. My intercooler doesn't work
2. Your wrong

Look, Everybody here knows that air shrinks in volume when cooled. Everyone knows that.
But your saying even with a straight pipe that there will be a difference in pressure between one side and the other. That's just wrong.

Mike SVOR

p.s. We're still cool right? Don't mean any dis-respect to you. :cheers:

[Cozz]

Rara I ask you a simple question and you could not even answer it correctly. I know how it works but I wanted to see if you knew but when somebody comes up with this....

The "what if the car runs out of gas" argument is ridiculous, because, if the car runs out of fuel under boost, the fuel flow just stops, and the car makes no more power, engine dies, and you roll off to the side of the road, you fill it up again, and you are on your merry way.

I figure he doesn't have a clue. But it's simple really, We have a pressurized system in front of us, A turbo building boost on one side because of the restrictive motor on the other side. And on the middle we have an intercooler. Rara is right about pressure dropping vs. temp. 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. Hey Rara should I take those basic thermo, or fluid mechanics classes? I'll go if you go to how does a motor work class after that no fuel at high boost post.