Intercooler for stock AAN

[Timon]

J need change my intercooler , and J watching on ebay universal front mount ic, and j think take 2.25 (57mm) inlet and outlet, but my friend say to me, to J need a 2.5 (63mm) ic.... Engine is stock, and J need for help...

[Thuppu]

Hmm, I think this is wrong section for the question(was also thinking that what the heck is the "J" but it prapably stands for "I"..?). But I did it like this on my urs4:



It's a 300x450x75mm IC with 3" inlets. I leaved the stock IC in serial wit the new one.

[UrS4boy]

But I did it like this on my urs4:

It's a 300x450x75mm IC with 3" inlets. I leaved the stock IC in serial wit the new one.

I don't have the data to back this up but based on thermodynamic principles, it is very likely that running a side-mount OE intercooler in series with a front-mounted intercooler results in very little temperature drop but significant pressure drop due to the added core length, as conceptualized here:

[s2_bo]

looks cool any how

[UrS4boy]

J need change my intercooler , and J watching on ebay universal front mount ic, and j think take 2.25 (57mm) inlet and outlet, but my friend say to me, to J need a 2.5 (63mm) ic.... Engine is stock, and J need for help...

With a stock engine you do NOT need a front-mount intercooler. The OE side-mount is fine. However, if you want to replace your side-mount with a front-mount, you might want to review this audifans.net DIY:

http://www.audifans.net/modules.php?...highlight=fmic

[Thuppu]

Well, I couldn't notice any difference with the pressure and behavior when I added the front IC. I did also improve the stock IC breathing like this:



So, would it be any difference if I put a bigger front IC and remove the side IC? The stock IC is quite big after all, only the air breathing is poor...

[UrS4boy]

Well, I couldn't notice any difference with the pressure and behavior when I added the front IC. I did also improve the stock IC breathing like this:

So, would it be any difference if I put a bigger front IC and remove the side IC? The stock IC is quite big after all, only the air breathing is poor...

I wrote up a DIY for using a B5 S4 vented liner section in a C4 UrS wheel well back in 1999. Here is a link to a repost of the DIY in 2005:

http://www.s-cars.org/postnuke/modul...rticle&sid=154

The trick with intercoolers is the most heat transfer occurs when the temperature differential is the highest (that is why my graph is initially so steep). As the air flows through the core and the temperature drops, the rate of temperature drop decreases (law of diminishing returns). In contrast, the pressure drop is a function of the core configuration (passage-way design) and the length of the core. Assuming similar core designs between your FMIC and the OE SMIC, the SMIC-in-series is adding a lot of pressure drop but not very much temperature drop. You would probably be better with a thicker FMIC core but with a "Euro" spec bumper, I don't think you can go much more than 2.5" (65 mm) core. In NorthAmerica, our bumpers stand futher away from the radiator and A/C condensor and we can use 3" or 3.5" FMIC cores with out too much cutting and trimming of bumper plastic. Personally, with my NAmerican (Canadian) UrS4 bumper, I am now running an Apikol FMIC system (with Samco hoses) an no OE SMIC.

[Thuppu]

So, what does the pressure drop mean? Like I told, couldn't notice any drop on the boost gauge. The front IC is 3" thick.

[UrS4boy]

So, what does the pressure drop mean? Like I told, couldn't notice any drop on the boost gauge. The front IC is 3" thick.

The turbo cold side has to push air through the piping and intercooler(s) to the throttle body. Along this flow path there are restrictions and bends which "fight" the turbo from moving the air to the throttlebody. Just like water flowing in pipes from a reservoir to you kitchen tap, pushing the fluid (water/air) through these restrictions requires energy. The potential energy in the flow is measured by the pressure. When energy is used up pushing the fluid through the restrictions, including friction losses in the pipes, the pressure drops. The energy that is used up is turned into heat (not a good thing with an intercooler). As a result, a restrictive flow path will both decrease the pressure that is available at the throttle body and slightly increase the temperature of the fluid (compressed air in our case). In short form, this might mean that with the SMIC in series you might get 1.52 Bar relative at the intake manifold, but with it removed, you would get more, e.g. 1.65 Bar relative (numbers are made up for this example but they are likely pretty close to reality).