Thread: Dual intercooler set up

Seems to me that an important point that no one has so far mentioned is for an intercooler to work well, a decent volume of cooling air needs to go through it. Wind obstructers including large driving lights and especially air conditioner condensers in front of standard intercooler reduces this. Also, probably more important is what is behind it. The standard radiator shroud on 300 Tdi's looks like an aerodynamic abomination to me. I would expect that the tips of the fan blades would tend to partly push air back to behind the intercooler partly countering the intended effect of the fan. Also, the standard 300 Tdi needs a large fan to push air past all the obstructions behind and down the sides of the motor to underneath the vehicle.


I have vent holes on the rear of both front guards. Standard air conditioner condenser was removed a long time ago. For when I get around to replacing it, have one which just goes in front of radiator and not intercooler.


Note for the last 85.000 km over 6 years I have had not had the shroud on One advantage of this is to greatly increase the amount of cooling air down the left - exhaust manifold side of the motor. Have a temperature sensitive switch that opens at 105 degrees on the cylinder head which the wire to fuel solenoid on injector pump goes through. My fan normally lives behind seat in extended cab. (Bonus: Stops viscous coupling problems!) Have had to stop and put it on for three short periods. It will overheat with long periods of idling when stationary in warm weather. Solution - watch temp gauge and get moving or switch off motor first. Once fan was installed while dealing with characteristic split in original header tank, once when radiator blocked with rubbish from driving slowly through tall wild oats in paddock and once when had large wind obstructing loads on both vehicle tray and trailer on a hot day.


My original air conditioner condenser also had an electric fan in front of it. Looked to me like another significant wind obstructer. In severe conditions it should help but obviously often would need switching on just because it was there.


Would be interesting to do some comparative tests with various setups under different conditions with temperature gauges in the engine intake air stream exiting the intercooler. I tried this once using a capillary tube water temp gauge with the sensor on the air hose to the inlet manifold. Interesting to watch, but I removed it rather than persevere with trying to make a good seal that would last.

If you have an intercooler which covers the same area as your AC condensor, then the best position is AC condensor out front, then IC, then radiator.

The total air-flow restriction is exactly the same regardless of the order you put them in. But the difference is the temperature.
The AC condensor will add about 2 degrees max to the air temp. The IC can add 10 degrees or more.
The AC condensor is most sensitive to temperature, the IC less sensitive.

Putting the IC first will mean when the engine is working hard your AC will be useless.
Putting the AC first will make only 1-2 degrees difference to the IC temp but means your AC will work when your engine is. The engineers who design vehicles always do it this way as owners notice their cabin being 10C hotter a lot more than they notice IC temps 2C hotter.

Pusher fans are indeed useless, but they were the only way the factory could guarantee airflow over the AC condensor at idle when the main engine fan isn't doing much.
I went to decent electric puller fans (aftermarket fans are generally rubbish) and removed the pusher fans. the pusher fans themselves weren't much of a flow restriction. But the structure to hold them was and held all sorts of dirt, rubbish and dead insects against the cores. Blocking airflow.

I dont know how but this little jigger cools the air to less than ambient .No wires makes a sandblasting helmut bearable the exhaust air is bloody hot and the supply to the helmet cool Cant see it working in a intercooler system but did plant a seed of doubt

Originally Posted by Ancient Mariner

I dont know how but this little jigger cools the air to less than ambient .No wires makes a sandblasting helmut bearable the exhaust air is bloody hot and the supply to the helmet cool Cant see it working in a intercooler system but did plant a seed of doubt

Is that a compressed air feed?

If so, throttling air (or any gas) to lower pressure cools it. This is the principle behind refrigeration.

An air conditioner condenser in front of the radiator which slightly warms and restricts air flow through it should generally make no difference as there is considerable reserve cooling capacity under normal conditions. However, when motor is working hard, the more cool air passing through the intercooler the better. A fine cored air conditioner condenser in front of it is probably more counter productive by slowing the air flow than warming it. Also with condenser in front of radiator only makes it much easier to clean chaff, dead insects etc that also restrict air flow from the intercooler core. Full width aftermarket intercoolers in front of everything should be best, but unless motor is working a lot with heavy loads in hot conditions would involve considerable expense for marginal improvement

while you cant cool air to below ambient without some kind of refrigeration you can do it with just air.....

compress the air, its heats up, hold it at pressure and let it cool down and then let it expand again. Same basic principle as normal airconditioning but without all the phase swapping from gas to liquid. This is how some aircraft AC systems used to work on ground running, but they had a massive advantage on things used to haul air around bleed air from an engine compression chamber was tapped off, let cool to ambient and then allowed to expand over a heat exhanger which cooled the cabin air. and then when it got to alttude the flow was changed so the heat exchanger copped the hot air coming off of the engine and the process reversed allowing the cab air to be heated.


problem is even tho its a total loss system because it involves dicking around with the laws of thermodynamics its still technically refrigeration.

the sand blaster jigger works on the same principle.

inside is a small cylinder that receives direct compressed air. the jacket outside the cylinder gets a total loss flow of air over it this cools the small cylinder, that small cylinder then delivers air to the helmet outlet through a small orifice and there you have cooled air through the principle of expanding a gas requiring some heat absorbsion.

From memory it should be good for 5 maybe 10 degrees below ambient.

Thanks Dougal I have a small understanding of how refrigeration works but usually think liquids turning to gas and not air to air as in a intercooler setup .I do have to take exception to your statement that pusher fans are useless The two 12" fans I have on my roof mounted condenser push out that much air thru the exhaust duct I have been able to dispense with the Hyclone

Originally Posted by mox

Seems to me that an important point that no one has so far mentioned is for an intercooler to work well, a decent volume of cooling air needs to go through it. Wind obstructers including large driving lights and especially air conditioner condensers in front of standard intercooler reduces this. Also, probably more important is what is behind it. The standard radiator shroud on 300 Tdi's looks like an aerodynamic abomination to me. I would expect that the tips of the fan blades would tend to partly push air back to behind the intercooler partly countering the intended effect of the fan. Also, the standard 300 Tdi needs a large fan to push air past all the obstructions behind and down the sides of the motor to underneath the vehicle.


I have vent holes on the rear of both front guards. Standard air conditioner condenser was removed a long time ago. For when I get around to replacing it, have one which just goes in front of radiator and not intercooler.


Note for the last 85.000 km over 6 years I have had not had the shroud on One advantage of this is to greatly increase the amount of cooling air down the left - exhaust manifold side of the motor. Have a temperature sensitive switch that opens at 105 degrees on the cylinder head which the wire to fuel solenoid on injector pump goes through. My fan normally lives behind seat in extended cab. (Bonus: Stops viscous coupling problems!) Have had to stop and put it on for three short periods. It will overheat with long periods of idling when stationary in warm weather. Solution - watch temp gauge and get moving or switch off motor first. Once fan was installed while dealing with characteristic split in original header tank, once when radiator blocked with rubbish from driving slowly through tall wild oats in paddock and once when had large wind obstructing loads on both vehicle tray and trailer on a hot day.


My original air conditioner condenser also had an electric fan in front of it. Looked to me like another significant wind obstructer. In severe conditions it should help but obviously often would need switching on just because it was there.


Would be interesting to do some comparative tests with various setups under different conditions with temperature gauges in the engine intake air stream exiting the intercooler. I tried this once using a capillary tube water temp gauge with the sensor on the air hose to the inlet manifold. Interesting to watch, but I removed it rather than persevere with trying to make a good seal that would last.

Sorry about quoting everything but it's hard to edit on the mobile.

The standard Australian installed Tdi/Td5 Defender condenser has a ridiculously fine fin pitch to get the required capacity (it's an if the shelf universal Sanden part) but unfortunately it tends to really block air flow to the rad ads I/C.

The difference in coolant temps between fitted and removed in winter is noticeable, there is almost 5 Kelvins difference climbing a small range on a sub 15°C day.
The added 10" Davies Craig fan is next to useless.
It must make a difference in peak hour traffic/low speed work otherwise it wouldn't be fitted, but I just found it blocked air flow at normal speeds so ditched it.

As you've found, the air flow through a Deefer engine bay is atrocious too. They really need that fan to force the air out of the engine bay even at cruising speed.
I still haven't vented my guards (and I have shears, electric shears, a nibbler, hole saws.....)
Pressure differential gauges are cheap these days, years ago when I intended to test it I was too cheap to buy a Magnahelic gauge. Maybe one day, but other things always take priority.

Interesting what you did with the shroud as I've contemplated similar, but was going to cut it short of the I/C and install separate electric fans on it for low speed work.
I've drawn up a larger face area/deeper core bar and plate I/C in the standard spot with radically different shaped tanks to try and get better/more uniform flow through the core. The standard tanks are ****.
Just have to do it.
Planning a road trip in June, maybe I can get it done prior to that? Along with everything else that needs attention!
Ha!