Water-Air Intercooler

[geeky]

Hey Guys,

So i'm currently in the midst of the FT project and found a Saab 9000 FMIC that I Was planning on running, but the more I think about it with the 01 and the secondary air injection pump being right next to the bumper passenger side, I'm leaning towards a SMIC or even a water cooled setup.

I'm really interested in running a water cooled system and was wondering if anyone in the B5 A4 crowd has ever done it and how you hooked it up. I'd love to go with an apikol smic but those things are quite pricey to say the least or even an S4 Stage 3 SMIC but it's hard to find just one.

But if anyone has experience running a water-air intercooler and information on how you setup the plumbing I would really appreciate it. Thanks!

oh does anyone know what the dimensions are for the A4 smic (core, and then a separate measurement with endtanks) and same goes for the S4 oe smic

[xdewaynex]

I remember seeing a thread of a guy doing a VR6 build in an A4 I believe it was, that designed a water cooled intercooler. I could have gotten the measurements for smic, but I honestly just threw mine away this past weekend.

[geeky]

well i mean on a 1.8 application. Is it more efficient to run a SMIC or a water-air cooler.

[revolution337]

I could grab the dimension of the stock SMIC sometime this weekend if no one beats me to it.

[Seerlah]

I was looking into this a while back, and the info I got is an air-air is better for a dd. Air-water is more for if you have no choice, or drag situations. You also have to take in the consideration of the extra weight of the water. It's not really significant, but eh. I still have a pic saved on my computer to how someone set his up on a B5 A4, and I think a GT3071R.

What you would do is remove the SMIC, and place in your water cooler container there. Then run 2-2.25" piping from your turbo outlet to the water cooler. You can actually use the stock piping if you wanted. Not sure if you know how an air-water intercooler works or not, but I'll tell it anyways:

You have your water cooler. Your IATs gets cooled from this, by passages in it similar to an air-air intercooler (different design). The water cooler constantly has coolant/water pumping through it via pump, and this water/coolant gets cooled by an extra radiator (heat exchanger) you place on front of your vehicle. You run lines from this to your water cooler, with the pump incorporated in the lines that constantly work in motion. Along with this, you would ideally want to place on an electric fan over the radiator. Or even better, a high powered one to replace the belt fan (EFK) that pulls air to have it able to have fresh air cool both the radiator for your engine and the heat exchanger for the air-water intercooler. And that's about it. Air-water setups are very pupular in the VW crowd, but rarely seen on Audis.



You can see the heat exchanger placed in front of the radiator (top one is power steering cooler). But ideally you would want a fan for it also. And cheap ones work just as good as the high priced ones with it comes to air-water setups. Just be sure you have a quality pump (Bosch I think is most used).

If I am wrong with any of this information, please correct me. But I was looking into this heavy a while back. And really, got it sparked back up again.

[M-Hood]

well i mean on a 1.8 application. Is it more efficient to run a SMIC or a water-air cooler.

air to air is better for a street car, even the companies that make and sell air-water setups say that

Yes water can pull more heat out of the air but it is then harder to get the heat back out of the water, so as that water keeps heating up your IAT's just end up increasing.

[bw86]

Why not just get rid of the SAI pump?

I don't have a tape measure around, but by looking at the stock SMIC it's around 7x8x3 (core)

[Nateness]

air to air is better for a street car, even the companies that make and sell air-water setups say that

Yes water can pull more heat out of the air but it is then harder to get the heat back out of the water, so as that water keeps heating up your IAT's just end up increasing.

I would respectfully disagree. Air-to-water works just as well on the street. Just look at old Toyota Celica Alltracs, the old ST165's and the CS ST85 and the JDM/UKDM ST205's came with A2W from the factory. You need to make sure you have a properly sized HX to reject heat to once you pull it out of the charge air. On a hot day, you could even put ice in the water sump.... like if you were waiting in line at the drag strip or in between runs for AutoX.

Keep in mind that the convection coefficient of water is much higher than air. If you have degrading return water temperature, the heat rejection HX is undersized for the application.

Main downside of A2W is that you've got more parts/pieces that could fail. It's not as idiot-proof as A2A. I suspect that most cars come with A2A IC's from the factory because they may be less costly than an engineered A2W setup.

[spindoctor]

Main downside of A2W is that you've got more parts/pieces that could fail. It's not as idiot-proof as A2A. I suspect that most cars come with A2A IC's from the factory because they may be less costly than an engineered A2W setup.

^This. Also it does add a little more weight, ..you gotta factor in the liquid that circulates in the A2W setup.

Not a good thing for an autocrosser/circuit car considering a stock A4's weight distribution is already 60% more to the front and the engine pokes far forward past the front axle line.

[CCA4]

This is interesting info, I had never considered an A2W IC setup before. Sub'd!

[M-Hood]

I would respectfully disagree. Air-to-water works just as well on the street. Just look at old Toyota Celica Alltracs, the old ST165's and the CS ST85 and the JDM/UKDM ST205's came with A2W from the factory. You need to make sure you have a properly sized HX to reject heat to once you pull it out of the charge air. On a hot day, you could even put ice in the water sump.... like if you were waiting in line at the drag strip or in between runs for AutoX.

Keep in mind that the convection coefficient of water is much higher than air. If you have degrading return water temperature, the heat rejection HX is undersized for the application.

Main downside of A2W is that you've got more parts/pieces that could fail. It's not as idiot-proof as A2A. I suspect that most cars come with A2A IC's from the factory because they may be less costly than an engineered A2W setup.

But like I said, for the street the air-air is just more efficient over the long run. Air-water is better in the short run or when using something like ice in the tank to make the water even colder. But I dont think someone that drives the car is going to be stopping at every store they pass to keep adding ice to the tank. lol

Here is what Bell Intercoolers has to say right on their web site.

How can an air-to-air intercooler be more efficient than a water based intercooler?
There is an overwhelming quantity of ambient air available to cool an air-to-air core relative to the charge air thru the inside of the intercooler (The iced down water intercooler is the only exception to this argument.). At just 60 mph, with a 300 bhp engine at full tilt, the ambient air available to cool the intercooler is about ten times the amount of charge air needed to make the 300 hp. Whereas the water intercooler largely stores the heat in the water until off throttle allows a reverse exchange. Some heat is expelled from a front water cooler, but the temperature difference between the water and ambient air is not large enough to drive out much heat. Another way to view the situation is that ultimately the heat removed from the air charge must go into the atmosphere regardless of whether it's from an air intercooler or a water based intercooler. The problem with the water intercooler is that the heat has more barriers to cross to reach the atmosphere than the air intercooler. Like it or not, each barrier represents a resistance to the transfer of heat. The net result; more barriers, less heat transfer.

[Nateness]

^This. Also it does add a little more weight, ..you gotta factor in the liquid that circulates in the A2W setup.

Not a good thing for an autocrosser/circuit car considering a stock A4's weight distribution is already 60% more to the front and the engine pokes far forward past the front axle line.

You could always put your water sump and HX in the rear of the car. Laying a HX flat under the trunk may actually work out pretty well... just look at the MR2 guys (althought they usually put an A2A in/under their trunks, but you get the picture). There's an orange subaru that also did something similar with their radiator system. Adding 30lbs of water to the middle or rear of the car is a fair trade off for lower/more consistent charge air temps.

[Nateness]

But like I said, for the street the air-air is just more efficient over the long run. Air-water is better in the short run or when using something like ice in the tank to make the water even colder. But I dont think someone that drives the car is going to be stopping at every store they pass to keep adding ice to the tank. lol

Here is what Bell Intercoolers has to say right on their web site.

Big picture, Bell's statement has some merit. Unfortunately, there are a lot of assumptions that go into that statement that I'm not sure everyone who is interested in this discussion is aware of. The big benefit of an A2W is that you can put in a core with a low pressure drop and compact shape in the engine bay to cool the charge air (both very good qualities) with better heat transfer than an A2A core of the exact same dimensions. You can then run the water lines and reject heat to a larger core somewhere else on the vehicle.

Consider this: the convection coefficient of water is many times greater than air.

http://en.wikipedia.org/wiki/Heat_transfer_coefficient

Water can have a value of ~500 to 10,000 W/m^2*k
Air can be around ~10 to 100 W/m^2*k

Using Q = h*A*dT, you can see that even when you compare the higher end of the spectrum for air and the lower spectrum for water, water will be about FIVE times more effective at convective heat transfer. (There are three primary modes of HT, but convective HT is going to drive what's going on in a FMIC.... no pun intended lol).

With a conservative ratio of 5, an A2A FMIC will need to have ~5 times the surface area of a A2W IC for the same application (at the point of heat transfer with the charge air... the exterior HX will still be limited by air, just like an A2A). If we were to evaluate this using real world figures, that ratio could become much bigger than 5. What this means is that you can use a low pressure-drop core that is easy to locate in the engine bay and then run water lines to a nice, thin HX with lots of surface area and little volume that you could tuck behind an A4 bumper and come out with the same effect as someone who had to buy an S4 bumper to cram in a huge A2A core. Lower pressure drop and none of the worry over "lag" from having lots of volume in the IC core.

I'm not saying that A2W is the best way to go for everyone, everyday, everywhere, but there are definitely some up sides that can be properly applied to many situations, including daily driven cars. For what it's worth, I went with a nice 3" ER FMIC, so I'm not nay-saying A2A, but want to point out the merits of A2W.

[geeky]

woo. Well what it comes down to for me is I had the FMIC setup in the past and I really dont want to hassle with the check engine code after removing the SAI. And in pure honesty I prefer not having to hack my bumper up again like last time.

[Seerlah]

If going FT, have the tuner write it out. You can actually code it out yourself. k0mpresd was so kind as to make a write up for us.

http://www.audizine.com/forum/showth...njection-dtc-s

Ok, I noticed that the pics no longer work. But maybe send him a PM for the pics. There were 2 screen shots. Original coding on one pic, and what he changed on the second pic. Also, he has a DIY on how to build your own bench flash.

http://www.audizine.com/forum/showth...r-your-me7-ecu

[M-Hood]

woo. Well what it comes down to for me is I had the FMIC setup in the past and I really dont want to hassle with the check engine code after removing the SAI. And in pure honesty I prefer not having to hack my bumper up again like last time.

The go with a good size aftermarket SMIC. Other option would be to go with a S4 bumper and relocate the SAI.

[geeky]

The go with a good size aftermarket SMIC. Other option would be to go with a S4 bumper and relocate the SAI.

that's what Im' currently contemplating, if I really want to dump cash into another S4 front end. I've become a huge enthusiast of the shaved A4 fronts that almost mimic the S4 front but dont hang as low.

[bmarshall]

Just go SMIC and water meth