candymanjl

my air to water setup on my CRX worked well but would heat soak. you have to have a large heat exchanger and a large coolant reservoir to even try and keep up with the heat. at least when you run an air to air the air cooling the intercooler stays constant at ambient.

no system will be 100% efficient and you can't drive on the street with ice in the air to water system all the time, that's only something the drag guys can get away with for one run at a time. with an air to air say the charge air is 150 degrees and ambient is 100 degrees, if the system is 90% efficient you'll end up with 105 degree air going into the motor.

with the air to water setup there's two cooling systems that have to work well together, the intercooler itself and the heat exchanger for the coolant for the intercooler. if you have a really efficient intercooler but the heat exchanger isn't very efficient or doesn't have enough capacity you're just going to heat soak the coolant and the intercooler won't work as well. say when the coolant when the system is heat soaked it's 20 degrees over ambient (typical for the systems I've worked with) and ambient is 100 degrees. now that same 150 degree charge air with a 90% efficient intercooler is only getting cooled down to 123 degrees. if the coolant was 10 degrees over ambient then you'd get 114 degree air into the motor, still more than the air to air.

you'll never get the coolant in a air to water setup down to ambient since no system is 100% efficient. so while the air to water intercoolers themselves may be more efficient, they're relying on another system to cool the water that they need to cool the air. even if the air to air is only 80% efficient in this scenario it'll still get the air down to 110 degrees. that's cooler than a 90% efficient air to water with 10 degree over ambient coolant getting the air down to 114 degrees.

the main reason to run an air to water setup is to have a very small amount of charge piping to have to pressurize. just look at a VT setup next to a turbo setup, the volume of space that needs to be pressurized between the piping and intercooler is probably 1/3rd or less in the VT setup. that means the charger can compress all the air and pressurize the motor quicker but at the cost of higher intake temps.

s2000Junky

In a drag race scenario it really makes sense to have air to water for the simple fact that you can fill it full of ice. On the street you dont get that benifit so it just makes sense to run the best cooling method which is proven to be air to air. Your talking to a guy with an AC

MugenRioS2k

A properly designed a a2w system ( < I said system not just one of the HX exchangers) will not heat soak and will have the same approach as a properly designed A2A.


It comes down to packing constraints between the two setups and the necessary requirements for cooling the air charge.

s2mmkay

true and i'll take ambient/sub ambient temps with 90% shorter piping than an a2a intercooler pumping out ambient temps (ambient temps herein miami are about 82+ on average) so imsure water will be able to dissipate more heat than air.

try blowing on a glowing red pipe and see how long it takes to cool it off.. now get that same pipe and dip it in a bucket of ambient water. yeah.. i thought so too..

Sellout

In an air/water setup, you have to remove the heat from the water as well as remove the heat from the charge air. Neither of these heat exchangers is 100% efficient, which means that it is PHYSICALLY IMPOSSIBLE to cool as well with air/water as you can with air/air (unless, of course, you use ice or some other method to cool the water to well below ambient)

The trade off is that air/water has less pressure drop, so it's worth it if the system is designed well enough.

The few of you who don't automatically understand this make me sad for the state of our hobby...

MugenRioS2k

Either system be it a2w or a2a will perform equally.



is a2w has a complexity factor in exchange reduced pressure drop and increased response.


where a2a has slightly more pressure drop and slightly slower response in exchange for being passive.


In the case of a supercharger in most case a A2W is the better solution.

In a turbo application the a2a is usually superior because the turbo will spool up to compensate for the pressure drop.

then there is the cost issue.
A2W is usually more expensive then an A2A

s2000Junky

Best combination is AC for limited boost loss and water injection for maximum cooling beyond what any fmic will do alone.

And i agree an fmic is much more effective on a turbo set up versus SC. But either one will get the best results from water injection directly.

Sellout

You're a mechanical engineer aren't you? You know better than to say that they're equal. Both are good enough, and there are advantages and disadvantages to either side, but they're not equal.

MugenRioS2k

yes I am a mechanical engineer and both can be equal performers if designed properly.

in this case performance is not just defined by the final IATs there are other considerations.

yes in a a2w there are two HX transfer mechanisms but I can make a A2W have the same approach as an a2a with out using ice.

Sellout

Ahh yeah. I should have known you wouldn't be talking about just the cooling performance... It's pretty standard for me to only think about the cooling efficiency itself, since temperature transfer is my life, heh.

I think you and I agree, now that we're on the same page.

Please tell me you're talking about something interesting, and not just spraying water over the ambient HX for >100% efficiency...