eyecandy

iTrader: (19)

I am looking at maybe adding an aftermarket intercooler to the list of my mods. I would like a V-mount setup, mainly because I do not want to have a mile in IC plumbing, nor do I want any extra radiator blockage. Plus I think it is kickass.

Anways, what is the largest size to use with the stock S4 or S5 turbo (I have a S4 turbo right now). What do I need to look for in and intercooler? I found one with a core size of 15x8x3 (w/ an overall width of 19") is that too big, to small, or just right?

As for boost I will probably be running an average of 10psi, sometimes under and sometimes over, prolly more under.

eyecandy

iTrader: (19)

~

Evil Aviator

You are going to need to determine the intercooler size on your own because you are attempting a custom project. I recommend making a cardboard mock-up to make sure it will fit. Make sure you compensate for the plumbing.

If you want a generalized statement about intercooler sizing:

1) The thermal efficiency is mostly related to the area (square inches) of the face of the intercooler. A long and narrow intercooler isn't as good as a more square (tall) intercooler. For example, given two intercoolers with a 100 sq in face, one that is 10x10" is better than one that is 20" long and 5" tall.
2) Don't use anything over 3.5" thick on a street car because the car will never get up enough speed to force a decent amount of air through the core. This statement isn't exactly correct, as there are a lot of factors like fin count, tabulator size, etc., but it's a good rule of thumb.
3) The more internal volume in the intercooler, the better it will work, but the more it will reduce the response (measured in hundredths of a second). Choose your poison.
4) Proper ducting works wonders. A divergent duct works best. You can use carbon fiber, aluminum, fiberglass, or just about anything somewhat rigid for the duct.
5) The bends, not the length of the pipe, are what cause the most pressure drop in the plumbing. The more degrees of bends, and the tighter the radius of the bends, the more pressure drop. BTW, pressure drop means lost boost.

eyecandy

iTrader: (19)

Is there a way to determine pressure drop?

When measuruing boost pressures is that from the turbo or the intake manifold? Because therotically if I want say 10psi of boost and the intercooler and piping drops 2psi I would set it at 12 psi.. Does sthat make sense?

j200pruf

iTrader: (4)

Evil why is the 10x10 intercooler better than the 20x5. Everything that I have read stated that they will have the same thermal efficency, but the one that has less distance for the charge air to travel would have less pressure drop, IE the 20x5. I am guessing this is probably something you have found out after a few years of messing with this stuff, and I wan't to know as much as possible.

Evil Aviator

Yes, with two boost gauges. Tap one near the compressor outlet (we will call this Pc), and tap the other into the intake manifold (we will call this Pm, which is where you would normally have a boost gauge). The pressure drop = Pc-Pm.

Note that this determines the pressure drop between the two boost gauge sensors, which will include the intercooler, plumbing, BOV, throttle body, etc. If you want to isolate a certain section of the intake system, then simply tap the boost gauge sensors on each side of the desired section, and the difference between the gauges will show the pressure drop.

You can measure it anywhere you like. An engine management system works best when the boost is measured in the intake manifold, which is known as "manifold pressure", or "manifold absolute pressure" if it is measured in absolute pressure rather than gauge pressure.

Your boost gauge should be tapped into the intake manifold so it reads the manifold pressure, and this would be your best reference pressure for setting your boost level. Yes, if your boost was set at 10psi manifold pressure, and you had a 2psi drop between the compressor and the intake manifold, the compressor would have a 12psi output. Therefore, setting your boost at 10psi manifold pressure would be setting your turbo at 12psi pressure if you had a 2psi drop in the intercooler and plumbing.

Yes, this is generally true, but the less pressure drop is due to the increased number of tabulators that result in increased internal volume, rather than the shorter distance. My #1 statement actually had two concepts lumped together, and I used the word "better" because I wanted to keep things simple. Sorry for causing confusion among the more educated readers of this thread.

As for my years of messing with this stuff, I have determined that Corky Bell's intercooler formulas have never once corresponded to an actual intercooler core, lol. Oh well, his other stuff is still good. I am sure that there is a better way to determine this type of thing, but it is currently beyond my education level because I am a pilot and not an engineer. The Spearco charts are the best thing I have found so far.