12 replies to this topic

[racean69]

anyone had anything to do with "Aussie Desert Cooler" radiators in perticular the triple flow radiator. they sound good but i have a mate who thinks putting "walls" inside of a radiator would create turbulance/ cavitation or air locks etc which may produce pockets of steam any comments on this one?

[Struggler]

Look at it this way.....

Your water pump will push water at a certain speed at a given engine RPM,

If your radiator is a triple flow then the water will have to move thru the radiator 3x as fast as normal, encountering 3x the friction, this places 3x the stress on your water pump impeller, which in a 308 is a fairly poorly designed unit at best.

Realistically it won't help much at cruise, and is a hinderance at RPM, causing cavitation earlier than would normally be encountered.

My advice, stick with a 3 row. The radiator in a Holden V8 isn't the limiting factor, the water pump is. If you want the best radiator then fit a cross flow unit such as WB or C/dore.

Just my opinion.

[shanegtr]

cavitation is a problem for pumps(any type of pump) and is caused by a pump being able to discharge more than what it can suck. What happens is the liquid tha is being pumped "stretches" in the suction side(from low pressure) and creates airbubbles. Once the liquid reaches the impellor the air bubble implode due to positive pressure. These implosions can be very damaging and chew out impellors and pump housings. That is the case with most pumps I work with, but on a car water pump cavitation is more than likely caused by poor impellor design/clearances. A triple flow radiator shouldnt create a noticable restriction to water flow as the water is still flowing throught the same amount of tubes. Air pockets should stay at the top of a radiator, but is not always the case. I've just ordered a triple flow so I can let you all know how it goes once in and running.

Edited by shanegtr, 16 November 2005 - 10:45 PM.

[antelopeslr5000]

The best investment I ever made was to purchase a PWR aluminium radiator (crosss flow) that I had custom made for my 308 LX combined with a Davies Craig 16" thermo fan. I can sit in traffic in 40 degrees and the engine doesn't even look like getting hot. Expensive outlay, I know, but in the end you get what you pay for.

[Redslur]

I have fitted one to my 308 recently. It made a huge difference in both cruise temperatures and especially low speed driving. I rate them highly..

[shanegtr]

to find out exactly how good(or bad) they are you would have to setup 2 radiators, standard and triple flow with the same temp water going in and measure what temp comes out. Sounds like a job for the mythbusters As for having more friction and loading up the impellor, it actually works in reverse. We start all of our big cooling water pumps with the discharge valve only open about 15% max. Any more than that and the motors trip out from overload. So we basically deadhead the pumps for startup because there is less load

[Struggler]

Sorry, I opened my mouth before checking all the facts. Here is the correct pressure increase figures......

Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.

To read the whole article go to http://www.stewartco...Tech_Tips_5.htm

Without getting into an argument with anyone.....

cavitation is caused by a pump being able to discharge more than what it can suck. What happens is the liquid tha is being pumped "stretches" in the suction side(from low pressure) and creates airbubbles. Once the liquid reaches the impellor the air bubble implode due to positive pressure.

I am not arguing with your definition, but the cause is more poor design of the impeller rather than the pump being able to discharge more than what it can suck.

The quote above is a little fuzzy, the water pump isnt going to suffer like described. In most systems now the water pump is moving large volumes of water courtesy of the thermostat bypass arrangements anyway.

I didn't dispute the capacity of the pump to move volume, just its ability to push water through a radiator with much higher internal friction. Once the wheezy 308 impeller has to force water through the greater restriction its design fails it, causing the earlier cavitation. Basically what I am saying is the 308 pump is an average unit by design of its impeller, yes some are better than others but overall, compared to other manufacturers, it is poor. Forcing it to work harder by pushing water through a triple pass radiator is not a great idea.

[shanegtr]

poor impellor design can cause cavitation also. My definition is based on my trade and the type of pumps I work with. Just a thought, wanst there someone who was making a better designed impellor for water pumps? Cant remeber who but Im sure they where mentioned in street machine

[shanegtr]

there is an easy way to find out how much restriction it has by seting up a couple of pressure gauges, but Im not going to do that, so I'll just have to see how the radiator goes