How much radiator is needed?

[DORIGTT]

In looking at doing the Subaru swap a question comes up for me. How much actual radiator cooling area is needed to tame the heat?

I see people installing a variety of radiators in their cars and I wondered if there is a specific amount necessary to cool these down.

Thanks in advance.

Kev

[ricola]

Just fit the biggest you can get away with. The size of the donor car's rad is always a good startign point but pay close attention to intake/exhaust of cooling air too

Rich

[DORIGTT]

Hey Ricola,

Did you have any cooling issues with your Ghia project?

My biggest concern is getting enough fresh air for cooling while not having to butcher my nose. I'm sick enough to want to maintain a 'stock' outward appearance while uprating the mechanicals quite a bit.

Thanks

[ricola]

The rad in the Ghia was much bigger than needed, you could tell when the thermostat opened as the temp dropped suddenly! My brother has the car now and it will be getting an EJ20t at some point...

Rich

[Steve C]

Hi

Go as big as you can, remember the air flow is usually not as good in your car as it was in the donor car, also make sure the path for the air flow is well sealed so that all the cooling air gets forced through the radiator, try to look at other successful transplants.

Steve

[tom'72]

make sure the path for the air flow is well sealed so that all the cooling air gets forced through the radiator,

Very wise words, after I did this the cooling capacity increased a lot and almost never have to use the fan (only in very heavy traffic)

[GeorgeL]

Originally Posted by Steve C

Hi

Go as big as you can, remember the air flow is usually not as good in your car as it was in the donor car, also make sure the path for the air flow is well sealed so that all the cooling air gets forced through the radiator, try to look at other successful transplants.

Steve

Good point. Engineering cooling systems is not simple, particularly when you are trying to put one into a vehicle that wasn't designed for it.

Since you can't depend upon the airflow being as good, you need to compensate by increasing the radiator size.

The general idea is that you want to take the air flowing past the car and slow it down on the inlet side of the radiator. This increases the pressure which causes the air to pass through the radiator. The ducting on the exhaust side of the radiator is also important. It should exit to an area of high speed airflow, which will have the lowest pressure. Above all, you have to prevent recirculation through the radiator. That means that the radiator has to be well sealed to the ductwork and the exit of the ductwork need to be well away from the inlet.

Don't depend upon electric fans to move the air. They are not made for continuous usage and you create another failure mode if you depend upon then. Fans should only come on when vehicle motion is insufficient to move air through the radiator.

George