Air-To-Air vs Air-To-Liquid Intercooler

[MSGGrunt]

I am about to undertake a custom turbo build and need to know if an air-to-liquid intercooler would be easier to adapt in my situation. I am concerned about having the room in front of the radiator for the air-to-air cooler and all the assorted duct work that I would have to find room for. I was thinking that an air-to-liquid may fit where the windshield washer and radiator resevoirs are located. Any thoughts on this? Are their size/CFM considerations with the air-to-liquid type as well? These are what I am considering.

http://cgi.ebay.com/Spearco-Air-To-...DVWQQrdZ1QQcmdZViewItem?hash=item110042035513

http://cgi.ebay.com/Liquid-to-air-i...DVWQQrdZ1QQcmdZViewItem?hash=item120039605660

 

[motorsargeT]

Personally I prefer Air to Air intercoolers. With the liquid to air setup you still need a separate heat exchanger to cool the liquid that is cooling your intake charge. That exchanger would generally need to go where an air to air intercooler would fit in front of the radiator. In my experiance with these two setups it always seems that the exchangers are too small to adequately cool the liquid. I have built several 500+ HP STis and WRXs for customers. The 2 that wanted a liquid to air intercooler had numerous heat soak problems and were always battling high coolant and oil temps, all of which were solved by going to a front mount air to air intercooler.

 

[MSGGrunt]

Makes sense. I thought that the air-to-liquid was a stand alone system that wouldn't need a separate heat exchanger. Back to finding room in front of the radiator for the inter cooler and figure out how to plumb all the duct work without having to run in under the vehicle or eliminate my signal lights like Dusty did.

 

[turbocruiser]

Personally I prefer Air to Air intercoolers. With the liquid to air setup you still need a separate heat exchanger to cool the liquid that is cooling your intake charge. That exchanger would generally need to go where an air to air intercooler would fit in front of the radiator. In my experiance with these two setups it always seems that the exchangers are too small to adequately cool the liquid. I have built several 500+ HP STis and WRXs for customers. The 2 that wanted a liquid to air intercooler had numerous heat soak problems and were always battling high coolant and oil temps, all of which were solved by going to a front mount air to air intercooler.

Wow, very cool info, I would LOVE to feel a 500 HP WRX!!!

With your experience, can you give some guidance on whether and when to clean an air-to-air cleaner. What's the proper procedure, etc. Thanks.

 

[motorsargeT]

There is no set interval as to when to clean an itercooler that I know of. My thoughts on it, especially in an off road vehicle(landcruiser), would be to keep the outside clean so as that air can continue to travel through it. At work I have several customers that have over 150,000 miles on their factory installed intercoolers which have never been cleaned inside or out. A lot of it would probably depend on each truck. And in Subarus a bad pcv valve will fill the intercooler up with oil real fast. The average lifespan of a turbo car's pcv valve is about 15000 miles max and then they are gummed up.

 

[bjowett]

Personally I prefer Air to Air intercoolers. With the liquid to air setup you still need a separate heat exchanger to cool the liquid that is cooling your intake charge. That exchanger would generally need to go where an air to air intercooler would fit in front of the radiator. In my experiance with these two setups it always seems that the exchangers are too small to adequately cool the liquid. I have built several 500+ HP STis and WRXs for customers. The 2 that wanted a liquid to air intercooler had numerous heat soak problems and were always battling high coolant and oil temps, all of which were solved by going to a front mount air to air intercooler.

Good info, Josh. I'd like to add that in this case, we are speaking of a system that is not nearly as high strung as a 500 HP STI. If sized correctly, the liquid unit should handle this application quite well.... There is quite a bit more room for both exchangers on the Cruiser.

IMO, the air to liquid will be a cleaner install, and easier to fit, but will cost more.

 

[landtank]

I've recently read up on this and the air to air cooler is more efficient. It's also a simpler system without pumps and such to move the coolant. The big advantage to the air to water system is the ability to ice down the unit. This is common in drag applications where you only need the cooling for a short time.

 

[sleeoffroad]

Air to air can be done, but getting all the plumbing sorted out takes some doing. Seems like there is always something in the way. You have to decide on a inlet/outlet on the same size or flow through. Safari uses same side, AVO uses flow through. There is enough space, but you will likely have to move/replace the transmission cooler with another unit. I will post pictures later of the AVO system on the 80.

 

[SUMOTOY]

IC comments

Air to water is more efficient, if designed right. The problem is that you are adding another cooling system that has capacity. Air to Air is more convenient, not more efficient. Air to water efficiency gets really high because the IC can be placed directly in the plumbing from the turbo to throttle body.

Regarding single pass vs dual pass IC's. The trick to IC plumbing is the least amount of bends in the ducting system has the least amount of restriction for a given intercooler size. Add up the angles, the dual pass adds 180* quickly, but many times the total angles is less. BTDT.

Cleaning IC's. I dont' really see any benefit to cleaning it internally. If you have PCV, you will have it full of oil within minutes of cleaning it. A *LOT* of benefit can come from cleaning the external fins, however, and in fact, I've taken many IC"s to the spray wash with over 2/3 restricted.

Watch the pressure drops across the IC as well. At 10psi, you probably can do just about any IC and have a benefit, but you need to do some calculations here. IC's have a flow rating, you can do the math in Corky Bell's book to give you a guideline as to what size core will yield how much airflow. Most IC manufacturers also give a flow rating on the cores they sell, I usually shoot 20% higher than the max demand to account for the end caps.

Corky Bell's IC section in Maximum Boost probably gives more good information on IC sizing and calcs, than any of his words on the turbos themselves. Worthy of reads.

Several folks have also added misters to the front of the IC with good success. In the humidity of Chicago, the benefits are minimal, but in AZ, this is worthy of consideration.

Make sure you get the air to go thru the IC core. I've seen a lot of front mount IC's that have no airflow control. You want the air to go thru the IC, not around it.

HTH

ST

 

[landtank]

this is an excerpt from my research based on which intercooler to use:


This depends on the circumstances. These circumstances are; street use, drag racing, or endurance racing (more than two minutes).

Street use: The air-to-air intercooler will prove superior in efficiency when sized properly.

Drag racing: The short spurt of power allows the iced water to cool the charge air to below ambient temperature.

Endurance racing: The air-to-air intercooler is clearly superior due to the shorter route of getting the heat out of the air charge and into the atmosphere. Endurance racing would preclude the use of ice water, thus negating the singular advantage of the water intercooler. Further, the air-to-air intercooler is (virtually, see comments below) maintenance free.

 

[Darwood]

There is no set interval as to when to clean an itercooler that I know of. My thoughts on it, especially in an off road vehicle(landcruiser), would be to keep the outside clean so as that air can continue to travel through it. At work I have several customers that have over 150,000 miles on their factory installed intercoolers which have never been cleaned inside or out. A lot of it would probably depend on each truck. And in Subarus a bad pcv valve will fill the intercooler up with oil real fast. The average lifespan of a turbo car's pcv valve is about 15000 miles max and then they are gummed up.

So what you are saying is I need to replace the pcv in my Subaru?

 

[SUMOTOY]

this is an excerpt from my research based on which intercooler to use:


This depends on the circumstances. These circumstances are; street use, drag racing, or endurance racing (more than two minutes).

Street use: The air-to-air intercooler will prove superior in efficiency when sized properly.

Drag racing: The short spurt of power allows the iced water to cool the charge air to below ambient temperature.

Endurance racing: The air-to-air intercooler is clearly superior due to the shorter route of getting the heat out of the air charge and into the atmosphere. Endurance racing would preclude the use of ice water, thus negating the singular advantage of the water intercooler. Further, the air-to-air intercooler is (virtually, see comments below) maintenance free.

Air to air is the simplest to install, it's not the most efficient. What decreases intake air charge efficiency? Pressure drop from bends in the pipe, end cap design, and placement in the airstream. What makes A2W IC's efficient is they are normally placed in line with the charge air ducting. This allows the exchanger radiator to be placed in the optimal position for heat exchange, not the optimal position for end cap design and piping.

A low pressure system will get the most benefit from A2W, since it's likely not going to heat soak at low pressure, will have very little lag, and the heat exchange properties will be very good (read, charge air temps aren't as high at low pressure ratios).

ST

 

[landtank]

Air to air is the simplest to install, it's not the most efficient. What decreases intake air charge efficiency? Pressure drop from bends in the pipe, end cap design, and placement in the airstream. What makes A2W IC's efficient is they are normally placed in line with the charge air ducting. This allows the exchanger radiator to be placed in the optimal position for heat exchange, not the optimal position for end cap design and piping.

A low pressure system will get the most benefit from A2W, since it's likely not going to heat soak at low pressure, will have very little lag, and the heat exchange properties will be very good (read, charge air temps aren't as high at low pressure ratios).

ST

I can point you to countless web sites, some who sell intercoolers and they all say the same thing. Take it up with them.

 

[SUMOTOY]

I can point you to countless web sites, some who sell intercoolers and they all say the same thing. Take it up with them.

I take it up as just a myth based on a single fact. The thermal heat exchange coefficient of aluminum to water is higher than aluminum to air. Period. All else being equal, A2W is more efficient. I use the example in my shop all the time. Heat up a piece of aluminum and blow ambient air on it to cool it, or flow ambient temp water over it. Which cools faster?

It has some other benefits as well, less plumbing (= less pressure drop), less heat soak in stop and go traffic, and quicker throttle response due to less plumbing length. It's harder to install, but A2A in the 80 isn't a cakewalk either, you are speaking to several feet of plumbing in A2A.

ST

 

[landtank]

I don't know why I'm responding but I will.

In an air to water system you are still cooling by air.

First you cool the compressed air by water and then you are cooling the hot water by air.

You are still cooling the compressed air by air, there is just a middleman involved.

So in the end you are still transferring the heat in the compressed air to the atmosphere and the more layers in that process the less efficient the system will be.

 

[SUMOTOY]

I don't know why I'm responding but I will.

In an air to water system you are still cooling by air.

First you cool the compressed air by water and then you are cooling the hot water by air.

You are still cooling the compressed air by air, there is just a middleman involved.

So in the end you are still transferring the heat in the compressed air to the atmosphere and the more layers in that process the less efficient the system will be.

Sounds good, it's just not true. Air to water coefficient of aluminum heat exchage is just too much of an offest...

The difference is that the water to air intercooling will have a heat exchange coefficient some 100 times higher than air to air. And if you math out water to air, 1 qt of water absorbs the same amount of heat as 4000 liters of air. I think you oversimplified your example, remember air to water and water to air are the two exchanges in the A2W intercooler, either still more efficient than any A2A system. The advantage is that the radiator in the A2W can be mounted anywhere, doesn't have a massive pressure drop since the intercooling exchanger can be smaller, it has capacity all the time, and is exponentially more efficient at cooling the intercooler charge and the heat exchanger (it's radiator).

Like I said, the heat exchange of the water in the water radiator doesn't have to be really high in a low boost pressure system. The intercooler efficiency however, is much higher in a properly sized A2W system.

You can choose to do either one with good results, that doesn't change the physics of thermal transfer rates.

ST

 

[Lockd97]

Sounds good, it's just not true. Air to water coefficient of aluminum heat exchage is just too much of an offest...

The difference is that the water to air intercooling will have a heat exchange coefficient some 100 times higher than air to air. And if you math out water to air, 1 qt of water absorbs the same amount of heat as 4000 liters of air. I think you oversimplified your example, remember air to water and water to air are the two exchanges in the A2W intercooler, either still more efficient than any A2A system. The advantage is that the radiator in the A2W can be mounted anywhere, doesn't have a massive pressure drop since the intercooling exchanger can be smaller, it has capacity all the time, and is exponentially more efficient at cooling the intercooler charge and the heat exchanger (it's radiator).

Like I said, the heat exchange of the water in the water radiator doesn't have to be really high in a low boost pressure system. The intercooler efficiency however, is much higher in a properly sized A2W system.

You can choose to do either one with good results, that doesn't change the physics of thermal transfer rates.

ST

This completely counters everything you just said;

"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."

 

[SUMOTOY]

This completely counters everything you just said;

"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."

You confused even me on that one. Look, water and aluminum has more heat exchange efficiency than air and aluminum. It doesn't matter which side the water is on, it transfers heat better. What this means is, that the aluminum A2W intercooler will shed more heat to the water than the A2A intercooler. That water will then go to the radiator (the intercooler water circuit radiator) where it will have a higher radiator temperature than the A2A. So the W2A heat transfer will be higher as well.

The efficiency of this coefficient of A2W is somthing like 100times that of air to air. That can account for a lot of "resistance to transfer of heat", whatever that means.

ST