pre-rad size for chargecooler?

jupilerman · 01-21-2007, 08:39 AM

Hi all,

I am planning to boost my little 1.8litre engine with a mere 6-7 psi.
air/air didn´t work out as it is mid engined. Bought a small charge cooler.
However, I couldn´t find information about sizing of a pre rad for cooling the charge water. I´v read about people using oil coolers and even airconditioning condensors. These seem to be more effective doing their job than regular water coolers. I am not into all the different fin types that exists in these coolers, so was hoping to get some info on here.
cheers,
david

2.2 Straight six · 01-21-2007, 01:43 PM

something like an ~8x6" Setrab oil cooler mounted where it can get ambient air (possibly under the car, maybe with a scoop to catch more air) would be good to cool the water, of course the bigger the cooler, or the more of them, the more efficient the charge cooler will be.

don't forget you'll need a water reservoir in the system, so water comes out of the chargecooler, into the pump and then into the reservoir. most of the cooling for the water is done in the delay between it leaving the chargecooler and going through the rest of the system, so by the time it's out of the reservoir and back to the cooler it's at a reasonable temperature again.

UncleBob · 01-21-2007, 01:54 PM

its a question of how much heat you need to disapate, and how quickly you need to do it. The larger the tank is, the less you can get away with, as far as cooling capacity.

At 6-7 psi, you won't need much, since that produces very little heat. I personally would use something larger than an oil cooler. They are too restrictive, same goes for condensors. Heater cores work very well, if you want something on the smaller end. Even better, a motorcycle radiator

jupilerman · 01-21-2007, 02:07 PM

Thanks for the swift replies guys. Appreciate it.

Since the charge cooler will be on the highest point in the water circuit, I also have a filler neck attached to it.

Basically there´s two kinds of pumps. The impeller one and the magnetic.
The magnetic loses quite some flow when headloss gets higher, but then it doesn´t leak. The impeller gives higher flow at higher headloss, but then breaks down easier. Since this is sortoff a weekend/holliday car, I´ll go for the impeller ones. Easily found cheap on fleabay. Mostly from standheating systems in Merc end BMW (cold countries like germany, austria or Northern US). They flow 13-19 l/min (3.43 - 5 gal/min).

So the coolant reservoir should be after the rad? right? this is the buffer of cooled water. It could turn out to be a heat soak though? But then, at 3l capacity, it wouldn´t soak that much in a minute ;-)
cheers

Black Lotus · 01-21-2007, 08:18 PM

You are looking for a radiator to dump the heat from the CC water back into the atmosphere?
My Lotus Esprit has a stock (sorta) Charge Cooler system and has a separate 8" by 33" radiator for it at the very front of the car. It is important that this radiator gets first crack at the cool air and is as big as possible. If you are going to be driving twisty roads in this car, avoid reservoir tanks (despite what Corkey Bell says) and go with big radiators. On my car, there is a small expansion chamber--maybe 10 ounces-- that receives the bleed water at the top of the CC. No reservoir tank is used because the tubing going to the front of the car is so long that it holds quite a bit of water anyway. It takes about 30 seconds for the water to make a "lap" of the system. See my photos on this site for reference. I now have a double size CC, but other than that the engine compartment is the same.
Cheers,
Brian

jupilerman · 01-22-2007, 03:12 AM

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