Intercooling: Air/Water or Wally style
 

Hi all,

Please read before you vote! Sorry its long, but I'm interested to hear your thoughts.

After a full season of beating this car fairly hard (see link below for some build thread pics and details, in short: turbo subaru 2L) I need a better intercooler. Right now if I turn it up to 14-15 psi I can watch the intake temps shoot up to 70C. Plus it is very restrictive.

http://www.germanlook.net/forums/sho...?t=9599&page=2

For some reason I had it in my head that I wanted to have an air/air unit and fit it in the engine bay (what I've done already), and the notion/challenge of doing this somehow distracted me from the fact that no matter how much airflow (3-300cfm fans) goes passed the stock WRX intercooler its not big enough, AND not to mention the routing is terribly restrictive.


http://www.magix-photos.com/mpfw02/1...1.jpg~original

http://www.magix-photos.com/mpfw01/1...6.jpg~original

http://www.magix-photos.com/mpfw01/1...6.jpg~original

The criteria behind this car was that I wanted to keep the exterior as clean as possible with minimal signs of 'theres a 300hp turbo subaru in the back'. So I bought a Spearco 500hp A/W intercooler for a deal I couldn't pass up, but I'm stuck between two thoughts now:

A/W - I could mount the IC in the rear parcel tray so there would be ZERO heat soak, have a resevoir back there and a big 'ol radiator in front of my current radiator to cool the IC fluid. This option adds a pump, tank, radiator, BUT is still completely unnoticeable outside the car and actually cleans up the engine bay a lot. (no ice here just antifreeze/water mix)

A/A - copy Wally's setup (see pic below). To me this is the most simple, robust, proven solution, however although I'm typically a function>form kind of guy this would completely transform the look of the car IMO and not for the good. If this was a track car then I wouldn't hesitate. However I plan on putting 3-7000km on this a year and drive it to work everyday in all weather (no snow though) and its not supposed to 'look' like a race car.

http://i174.photobucket.com/albums/w...9.jpg~original

I'll also be making a cold air intake setup sort of like Wally's in this pic (behind licence plate)^.
Mike

I say if you want to keep it a sleeper go for the air/water setup. Water is more efficient and shouldn't heat soak to badly even in the worst traffic.

My Ghia doesn't really have great airflow over the decklid that could be used for an air-to-air and be efficient by getting good airflow. I've researched the A/W coolers extensively and decided that it would be the best way for me to fly in spite of potential drawbacks. Plus...

Our latest Touareg and Cayenne Hybrids use a pair of A/W unit for packaging and efficiency purposes.

The supercharged V6 in the latest Audi's use one (2 actually)

The LS9 in the Corvette uses one (pair)...

The RUF 4300K supercharged Cayman uses one(pair)...

The new turbocharged Segway uses one....

http://www.bellintercoolers.com/page...FAQ.html#FAQ_5



http://www.frozenboost.com/product_i...roducts_id=219



So I vote for the A/W unit.

I don't think either setup would heat soak they way I have it planned, but the worry I have it with the air/water not being able to cool the water fast enough on long pulls. It will have 'surge' capacity but you need a ton of cooling up front to even come close to good steady state performance it seems.

Surely, the A/W method is just a system to transfer heat to the external air. Therefore the water rad will be not be bigger than the A/A intercooler. Obviously the A/W intercooler will have to be sized\to ensure the transfer rate is sufficient. When Porsche were forced into A/W intercooling on their 935 there was no drop in power only extra complication and weight. Porsches A/W intercooler was relatively compact and coped with big numbers of ponies.

It's about delta T between sides of the heat exchanger. The intercooler is cooling 100C+ air with 30-40C water, the heat exchanger up front is cooling 40-50C water with 25C+ air, therefore more surface area is required to get the same kW or heat transfer. But more to your point, you now have two heat exchanger efficiencies to deal with instead of just one.

I'm still leaning towards air/water just spending the extra time now to try and get the numbers to make sense.

Hi

Is there much heat around your air filter intake?

I have PWR a2w inter cooler for my bug, have you looked at these people https://www.plazmaman.com/shop/?acti...Items&catId=23

I also read an interesting article about a fusion inter cooler, basically its wax filled, the wax is heated by the intake charge and heat is removed from the intake charge. If you cant read this link I have PDF files of it I can email to you.

Steve

I voted air 2 air.

Regardless of which path you choose, you'll need to fit all of the components based on your packaging restraints.

Wally's solution obviously works for him, and the results cannot be disputed. He has published the temp deltas for all to see, so you can come to your own conclusions.

My old air to water system worked great ( pwr 4" barrel ) and I could get the intake temps to below ambient with ice, but that only lasted about 30 mins on the street. When parked outside during the afternoon, I had intake temps above ambient because of heat soak, and the water took some time to cool while driving.

Imagine sitting under the sun at a show all afternoon, and then hitting the highway on the way home, trying to battle a tuned Jetta, and wondering why the engine does not feel strong.

I've got temp data from my air / water system, but Wallys solution is better overall at keeping temps in check, from data that he has freely provided.

Sandeep

There is, but I'll be making an airbox this winter to pull air from a hole I'm going to cut underneath the popes nose to get ambient air. Also will be heat wrapping the turbo and all the piping to get the heat out of the engine bay.

You've hit the nail on the head there, my resevoir and intercooler will be in the interior not in the engine bay so heat soak from sitting won't be AS bad, just as hot as it is in the car. Also having cooler intake air will help cool the water while not on boost.


How big were the radiator/heat exchangers that you guys were using and where were they mounted?

G'day

I run a stock Subaru WAIC that has an alloy radiator up front. I use a small Davies Craig water pump that is hard wired to the ignition so it's constantly on flat out at all times.
My intercooler sits in the stock subaru position behind the rear seat.
Although I'm only running 8 pounds boost, which is alot lower than yours, it does get up to 11psi on long straights on the track due to the air intake in the guard pressurising the air box.
But, even on a 35d day at the track, 6 x 2 minute laps, the highest I've ever seen intake temps is 55d. I think thats pretty good.

This setup has just had it's 6 year anniversary this Xmas Eve, 173'800klms (108'000) miles so to me it's proven itself.

Hope this helps
regards
Jak

Hmm, difficult one...:D

Armin runs air-air also and his intercooler is inside the engine bay AND runs trackdays (vids are all over this forum), so it IS possible.
The extremely quick action respons of the outside air-air version would be hard to beat wrt temps and low temps is what keeps our old design aircooled engines alive. As you have a jap 16V OHC watercooled engine, higher temps may not be as knock hazardous as with our head design, but the hp gains will always be with the solution with the lowest intake temps...

Choose your poison ;)

My first suggestion would be to leave the intercooler & get that air intake (pod filter) out of the engine bay. U will notice a huge improvement just in that alone.

have it so that it only gets air from outside only, & preferably not from under the car as it will only pick up warm air from the radiator & the road itself. I noticed big gains when I made this air intake in the guard.

Also, do u use decklid lifters on the track, this would also help get air forced into the intercooler. maybe try simple things first.

regards
Jak

The main problem I see is the way you have the wrx intercooler routed.It´s not a smooth transition into the cooler.If you were to go with an air-air set up,then I think Wally´s set up is the best solution because there is fresh air flow to the cooler.Armin´s set up is inside the engine bay,but it is hard to determine if it is as effective as Wally´s because Armin injects water at around 1 bar boost.In Armin´s case,I believe it´s due to the cooler position rather than the cooler itself.Still as Wally correctly said,it is an effective cooler.Another thing to consider is if you are to go with a water-air cooler, then it would be wise to keep the water circuit seperate from the engine water circuit.

I don't think I have ever seen a setup where the engine coolant also cools the intercooler. They run at such different temps, it would make the WAIC useless.

Even after a run on the track, I put my hand under my car & touch the return line from the radiator to the engine & it's very hot, but the return line for WAIC is below room temperature & I can even hold the back of my hand as it's relatively cool.

regards
Jak

I've heard of Air to water using engine coolant in industrial engines but not for an automotive application.

Jak you have some very good points, I also believe that if I clean up some little things it will make a big difference, but overall I'm not happy with the charge piping/routing and if I'm going in there anyway I might as well do a complete redesign rather than change a few things trying to make it work with possible future changes.

On the list is cold air intake, raise the intake manifold up 3/4" to acheive a straight inlet to the turbo (with cold air too) and also thermally isolate the intake manifold from the block, heat wrap/polish ex mani's, heat wrap turbo and down pipe.

The fuzion intercooler is a very neat concept but I think having a heat sink instead of a more steady state approach I would constantly be checking temps and generally be paranoid about it.

I think I might be sold on the air to water, mainly because I'm not running huge boost (for this turbo/combination) meaning I should be in the higher efficiency range of the turbo and don't need mega cooling. For the front coolers I was thinking of using two aluminum motocross bike radiators stacked one in front of each other just because they fit the size perfectly (like pic below), but its hard to find any data on what is big enough for a front exchanger. Most just say 'biggest you can fit'. I've done some calcs but only testing would prove anything.

Anyway, Ii'll hopefully be starting tearing it apart in a month or so and I'll update my build thread with pics.

http://img1.classistatic.com/cps/kj/...981dfl_20.jpeg