Air-con system to cool intake charge..

Was thinking about this earlier, do you think you could use an air-con system to cool the intake charge, better than a standard charge cooler?

Funny you should ask about this Stu. I was thinking about this the other day and I think I came up with the fact the amount of power required to run the air-con unit wouldn't give big enough gains to compensate?

What about actual refridgeration technology? Making the charge air really cold?

Well, I was just thinking of having an addtional 'jacket' around some ofthe pipework, post intercooler/chargecooler, to aid in the cooling. I would imagine that you couldn't use the air-con to do a great deal of cooling, as in it's normal application, it's taking air that is say up to 40degC and cooling it to 18degC. As you say it might be that the power required to run the compressor at full chat would be over the amount of power gained by cooling the charge that much, if indeed it was possible to cool it that much.

Also, I'm not sure if cooling the charge a LOT would be productive either. Perhaps a very cool intake charge would hinder fuel atomisation to much. There is no point having a dense charge if the fuel cannot atomise properly. mind you, I guess modern injectors may counter that.

I think the best way to use A/C would be to refrigerate chargecooler water. If that was kept at 0 degrees or lower, then you'd get some impressive condensation on the intake and chargecooler core

Now, that is a good idea. That wouldn't be too difficult to acheive either. What sort of temps do you see in your charge cooler reservoir, Kev?

There's no way A/C could cope with cooling compressed air from a turbo, but it *might* be able to keep water at a consistent temperature, well, just like a fridge

You can obviously shove ice cubes in tank which is OK for a 1/4 mile blast, but no good for a long road trip!

I've never measured the water temp in the tank mate. The hottest it's ever been was a little less than luke warm and that was after a lenghty spell on the dyno. Stealth's dyno fan is too high to get air onto my heat exchanger, otherwise it would have been lower.

Having 3 galls of chilled water would be awesome for cooling hot transient blasts from the turbo.

Perhaps the cooling effect of the air over the evporator/charge cooler rad probably has a much better effect than refridgeration. Maybe it may be possible to keep the water/alcohol below 0degC. Now that would be good.

Hmmmmm, food for thought I guess

I saw a chap at G-Werks who was using refridgeration technology in his inlet pipe to chill the air on the way in. However, personally I am not convinced by the efficacy of that (more power to run that you would make, restrictions to airflow in the pipe etc).

Water has a huge heat capacity, so needs lots of energy to cool it down. Presumably what you need is a cooling system that only takes power when you are on part throttle. So the refridgeration works when you are pootling around. As soon as you go full throttle, refridgeration switches off, there is less drain on the alternator, less drain of power, and you already have a chilled system. If you want to be really sneaky you use recovery of power during braking as with F1/Prius etc. You'd want to have a network of copper pipes round your inlet manifold as well, to provide cooling there, give the cold air as much chnace as possible to stay cold.

If you use a standard air/air intercooler many people use water spray systems on them which is the same principle as aircon. The water evaporating from the outside surface of the intercooler cooles it very effectively as it draws energy out.

A bit like when you get out of the swimming pool and you are covered in water when it's windy you get cold. As soon as the water has dried off you don't feel the cold again, this is because less heat is being drawn from your body. A washer bottle full of water spraying a fine mist over the cooler will last an hours journey or so on a hot day.

So, it would also be advantageous to spray water on the evaporator of a water to air cooler for additional cooling?

Yep that would work.

Another question, can you run water through an air-con rad? I know they're quite small bore etc, but as they are usually the size of the main radiator, or a little smaller, it has good surface area! I can get a genuine Rado VR6 a/c rad for £70 (normally 4 x that price) and was thinking of using it as a supplementary cooling rad.....with water spray

What if you used the air con in periods where you weren't using max power, just pootling, and then dropped the air con pump out at WOT, then you'd have a supply of cold air, but no additional load on the engine...

Flusted had a water spray system on his G60 with FMIC once I believe.

I think the pipework might be a little bit thin Kev... Not sure though. Often have quite compact but thick air con rads on tractors, perhaps a foot to 18 inches high, 6 inches wide and a couple of inches thick. with several cores running front to back. Also have similarly dimensioned oil cooler rads... Will show Mic and Stu next weekend....

kevhaywire wrote:Yep that would work.

Another question, can you run water through an air-con rad? I know they're quite small bore etc, but as they are usually the size of the main radiator, or a little smaller, it has good surface area! I can get a genuine Rado VR6 a/c rad for £70 (normally 4 x that price) and was thinking of using it as a supplementary cooling rad.....with water spray

I used to use an aircon rad for my chargecooled G60 in my avatar pic, it was quite good but as toad quite correctly pointed out the connections were a bit small, but if i'd used a better pump capable of higher pressures then I'm sure it would have been fine though, but I was young and skint at the time so i left it as it was

If you got a really thin one you could have a very big rad in there with a massive surface area, just sat right in front of the VR one. Then lots of room left behind for two massive 11" fans to pull lots of air through for effective charge cooling in traffic. If you then put an undertray on that only leaves a gap where the exhaust is, it creates an air flow over the exhaust, cooling that as it passes over it.....

oh yeah, when you've finished making an undertray, can I copy it please

Yeah I currently use 15mm ID hose for the chargecooler, but even if it dropped down to 10mm through the A/C Rad, the cooling area would make up for it in theory. The pump I've got is pretty powerful so should cope with that no trouble

I'll get right onto the undertray, LOL!

See, at first thought, you'd think an undertray would in fact increase under bonnet temps, as the air can't get out, but I 'get' why one with the gap by the exhaust would have the opposite effect. I suppose when you've got fast moving air past an orifice, the lower air pressure will draw the air out through the hole. I suppose that would be the reason for some vehicles having louvred bonnet

Sorry, going a bit OT there.....Carry on!

You need to be careful when evacuating a lot of heat through a small orifice though A small opening would be more harmful than no undertray at all as the heat would back up into the bay. A big opening would solve that though. That's why some folk tilt open the trailing edge of their bonnets as it's one big vent as opposed to small louvres.... heat can escape a lot faster, unimpeded.

Kind of reminds me of the Subaru 'interheater' problem. Some folk think it's air going over the top of the intercooler at high speed that is the problem, but the actual issue is 'air stalling' in the engine bay. What happens at certain speeds is the air pressure coming through intercooler equals the pressure of the air coming through the front and cancel eachother out. The result is the air can't 'flow' through the IC and it just hangs around heating up the IC