Turbo Gods Needed: Which is better thicker/thinner intercooler?

[DamnedButDetermined]

Me and a friend are having a debate about which is better.

Here is the situation...All things the same...Which is better?
24" long x 8" tall x 5" thick
24" long x 8" tall x 2.5" thick
those are numbers puller out of my ass but you get the point!

He says thinner is better. Reason being, you won't have as large a pressure drop.

I say a thicker intercooler is better. Reason being, you will have more space to cram all that hot air, before it is used. And engine is only going to use a certain amount of air under a certain boost pressure, so the left over air will keep recirculating inside the intercooler continuing the cooling process. Now i don't think the loss of pressure in the intercooler is that big of a deal, because what is forced in one side of the intercooler must come out the other. So the boost pressure in the pipping before it gets to the intercooler will be the same as it is after it leaves the intercooler.

now a little background here...I am an idiot sometimes, so forgive if this answer is obvious!

[N1ceDrgn]

It comes down to the application and a little personal preference. If you are running with a smaller, stock-size turbo, a smaller turbo is all you're gonna need. Otherwise the amount of lag you are going to experience will be more of a handicap than an irritation. If you are using a larger turbine, be it a T04 or T67, then a larger intercooler would be a good move. I was running with a hybrid from Turbonetics and my engine after I got it bored over, the larger 3 core intercooler I have was needed, a little for what I had at the time. It is needed for the T04 and waste-gate I intend to use.
Now some favor a smaller intercooler for drag racing and drifting, with a smaller intercooler, the 'turbo-lag' is nearly eliminated for the most part. It is still there but it is reduced a lot because the amount of pressure is the same, 'under boost'. However with a larger one, you are filling a larger space, so the pressure lag will be more noticeable. Like I said though, there are compromises that need to be made. Less flow, and less lag, or more flow and more lag. Another way is 'some-what-restricted' air flow, or none. Take your pick...

[240racer]

actually if that is the only variable the answer is obvious. Thicker is better for a number of reasons. However, that isn't usually the only variable. First off, before I go any further I want to say that a thinner heat exchanger is more effiecient per weight or whatever.
The reasons that thicker is better, one there is more surface area available for the heat transfer to take place. Also, from the charge airs perspective there is more surface area for it to flow in, which reduces your pressure drop. This is also the reason that it is better to flow i through the 24x5" side rather then the 8x5" side. That is why side to side intercoolers have more pressure drop then top to bottom ones that are the same size. The air has more cross sectional area to flow through and doesn't have to flow as far through the turbulent heat exchanger.
You are wrong when you say the pressure is the same on both sides of the intercooler, in fact the pressure inside the intercooler is quite low. When the velocity is low, the pressure is low, and this is an inverse of cross sectional area. That is why large pipes flow more then small pipes, lower pressure per the same amount of flow. When the air enters the intercooler, it is flowing relatively smoothly, however, the fins in the intercooler and huge increase in cross sectional area make the air lose velocity and pressure quite fast, this causes turbulance. The air must then get back into the little exit hole and when it does this it will not be flowing very smooth as well as being colder, which means it takes up less volume as well, all of these things cause the pressure to be reduced.
Now, with all of the advantages of thick intercoolers and heat exchangers in general that I have given, the reason for thin intercoolers is this. When you increase the thickness from 2.5 to 5" you may only gain a couple percent in effiecency of the intercooler, but you doubled the thickness. It is definatly a case of diminishing returns. You probably would hardly notice a difference in temp drop between the two sizes of intercoolers you mentioned, but I bet you would notice a fair amount of difference in the pressure drop.
Your friends reason for thinner intercoolers and pressure drop doesn't make sense to me, unless he cares about the outside air flowing through the intercooler, which doesn't matter.

[240racer]

Originally posted by N1ceDrgn
It comes down to the application and a little personal preference. If you are running with a smaller, stock-size turbo, a smaller turbo is all you're gonna need. Otherwise the amount of lag you are going to experience will be more of a handicap than an irritation. If you are using a larger turbine, be it a T04 or T67, then a larger intercooler would be a good move. I was running with a hybrid from Turbonetics and my engine after I got it bored over, the larger 3 core intercooler I have was needed, a little for what I had at the time. It is needed for the T04 and waste-gate I intend to use.
Now some favor a smaller intercooler for drag racing and drifting, with a smaller intercooler, the 'turbo-lag' is nearly eliminated for the most part. It is still there but it is reduced a lot because the amount of pressure is the same, 'under boost'. However with a larger one, you are filling a larger space, so the pressure lag will be more noticeable. Like I said though, there are compromises that need to be made. Less flow, and less lag, or more flow and more lag. Another way is 'some-what-restricted' air flow, or none. Take your pick...

Yeah I forgot to mention turbo lag, this only applies if you are concerned with downshifting or taking off from cruising. The inside volume of the intercooler is all that matters here, so you would choose the thinner intercooler since it has half as much volume and probably 85% of the effiecency of the thicker one.

[N1ceDrgn]

Thanks for the tech add-in. I didn't do that good of a job explaining it as I should have but between your post and mine, I think the point was delivered. Again, thanks for the tech side of it.