A/C Air to water intercooler? - PeachParts Mercedes-Benz Forum

Cervan · #1 05-29-2008, 11:20 PM

Ive been thinking about it, why not just get an air to water intercooler and use the hugmongous ac condenser as a radiator for the intercooler? all you have to do is run a small flow pump and antifreeze. What do you guys think?

#2 05-29-2008, 11:49 PM

Its been done here before by a forum member.

It was what I was going to do before going with air-air.

bgkast · #3 05-30-2008, 01:07 AM

Why not use a radiator designed for water? I used one from a Honda goldwing, but the junkyards are full of small cars with tiny radiators that would be perfect.

Cervan · #4 05-30-2008, 02:08 AM

Quote:

Originally Posted by bgkast

Why not use a radiator designed for water? I used one from a Honda goldwing, but the junkyards are full of small cars with tiny radiators that would be perfect.

for one this one is much larger than any other radiator you could fit into the mercedes. And its before the engine radiator as well, Killing two birds with one stone? and if you have innopperable a/c (wich most of us do) It may be the best way to go.

bgkast · #5 05-30-2008, 02:10 AM

It's worth a shot, but I think you would get better efficiency with a real radiator. Little Toyotas have radiators that are about 1" thick and about 1.5'x1.5', they seem like they would be perfect to me.

#6 05-30-2008, 03:02 AM

Size is only part of the puzzle, you need one with the hose fittings in the right locations. It won't be much use to get a radiator with hose fittings that are pointing straight into your coolant radiator.

If you are up to the job, you can buy a custom radiator and have the tank ends split to have part for coolant and part for the intercooler. International does its trucks kind of like that with the radiator and intercooler side by side instead of one in front of the other.

babymog · #7 05-30-2008, 12:32 PM

I like the idea of an air-air if possible, but the water-air makes sense for packaging. I've looked at a bunch of them and discussed the applications for them at length with other Engineers and Sales Engineers at the SAE conference/show, and have these concerns:

By the time you get a water-air aftercooler small enough to package in the 124/603 compartment, will there be enough airflow through it to not restrict full-boost full-rpm operation significantly? Also, will there be enough contact time with one pass for the water to really pull much heat out of the air? If the answers aren't both yes, then the water-air solution won't work for the 124/603 application. Anyone have any pressure and temp delta numbers?

bgkast · #8 05-30-2008, 03:06 PM

I am not familiar with the W124, and I don't have any numbers off hand, but an air/water intercooler unit will always be way smaller and have way less of a pressure drop through it than an air/air unit that provides the same amount of cooling. This is due to the higher thermal conductivity of water vs air. The intercooler I am using is WAY oversized for my engine, it is roughly 1' by 1' by6" including the end tanks. The core is approx 1'x 6"x 6".

winmutt · #9 05-30-2008, 04:52 PM

Dont forget the down side of AWIC, heat soak.

bgkast · #10 05-30-2008, 06:18 PM

Heat soaking should not be an issue if you have designed a system with a proper volume of water in it.

babymog · #11 05-30-2008, 08:38 PM

Volume of water doesn't do it, area of radiator is what's needed to maintain acceptable water temperature.

I'm still not convinced that the A/W has enough contact time with the air to reduce the temp adequately, but it is the easiest system to package, and I'm only hoping for ~230hp (engine/SAE) so the area necessary should be fairly easy to calculate.

Anyone with an aftercooled 124 here?

#12 05-30-2008, 10:49 PM

Quote:

Originally Posted by babymog

I'm still not convinced that the A/W has enough contact time with the air to reduce the temp adequately

Thats why the flow rate is important, Too slow and you heat soak the water, too fast and the heat transfer rate will be low.

1.5-2gpm is the target range, IIRC.

bgkast · #13 05-30-2008, 11:11 PM

The reason heat soak is not an issue boils down to this:

The turbo produces the most heat when under "heavy" boost
The turbo is only producing "heavy boost" during hard, full load acceleration
bursts of full load acceleration do not last very long
If you have an adequate water tank and flow rate of water through your system your acceleration burst will be well over by the time all of the water begins to heat up

This is why it important to have a proper water flow rate and water volume in the system.

To quote Corky Bell "The front cooler is the least important part of the IC system, as it is doing most of its work when the vehicle is not operating under boost. At the start of a boost run, the entire system will be at approximately ambient temperature. As boost rises, heating the water in the main core, this heated water must get to the front core before it has any temperature difference with which to drive the heat out This time delay can be as longs as 7-8 seconds, depending on the size of the reservoir. That amount of time is typical of a boost application, It is clear, then, that the front cooler will do most if its work after the boost run... The font core does not need to be as big as it may seem at first glance, because the relative cfm rates through the two cores (IC and Radiator) will usually be heavily biased toward the front cooler. For example a forward velocity of just 60 MPH could potentially pit 5280 cfm through a cooler of 1 sq. ft, of area."

babymog · #14 05-30-2008, 11:36 PM

I remember the lesson that the Whittington Brothers taught the rest of the field in their 935 K2 cars around 1979. The rest of the turboed Porsches in IMSA were running water/air, the Whittington Brothers air/air, so they pushed the field until the water/air cars were heat soaked and had to back down, slaughtered them.

But I digress.

Water/air might be the ticket, since I have no space for an air/air aftercooler in front of the radiator with the condensor there. Plumbing is easier for water lines than for hot air also.

Will a spare aux-pump work for a circ. pump? I've got a spare from a VR6 Vanagon-Syncro project.

bgkast · #15 05-30-2008, 11:41 PM

I am using a MB Aux water pump.