Crossflow vs down flow? (1 Viewer)

[1Fine40]

This may belong in chat, but I'll chance it. Is a crossflow radiator more efficient, and if so, why? Would a crossflow radiator of the same core size as a down flow unit be any better? Why?

Thanks, and Cheers

 

[FJ40Jim]

Crossflow better

Crossflow is better for a number of reasons.

My favorite reason is because in a downflow radiator, dirt and scale build up in the top tank, plugging the tops of the vertical tubes, rendering the entire radiator ineffective.

By comparison, the dirt in the crossflow radiator falls to the bottom of the sidemounted tank, only restricting the bottom tubes as the dirt builds up.

 

[Mark W]

n a cross flow radiator thre cap is mounted at the lowest pressure point of the system (after the radiator core, on the suction side). In a downflow it is mounted at the highest point (before the radiator core on the "push " side).

A cross flow actually maintains higher pressure thoughout the cooling system with the same cap.


Mark...

 

[1Fine40]

A cross flow actually maintains higher pressure thoughout the cooling system with the same cap.
Mark...

Is the increase of pressure throughout the system a good thing? Would you want to use a higher pressure cap with a crossflow? And, if it maintains more consistent pressure, does it offer therefore better (more efficient cooling) for equal size cores?

Cheers!

 

[Mark W]

Higher pressure means a higher boiling point. When everything is working normally, this is not much of a factor. But when things heat up a bit it helps.

You could use a higher rated cap with either system. The mechanics of the two means that the pressure in the engine will be higher in a system with a cross flow radiator than one with a down flow if both have the same cap.


Mark...

 

[1Fine40]

O.K., I understand that concept. I wonder why Toyota didn't use crossflow in the Cruisers? And, If you were going to replace the stocker with an aftermarket radiator (Mine is leaky...) would you go with a crossflow instead of the traditional downflow unit?

Cheers!

 

[mrgadget]

I was having overheating problems for years untul a mechanic friend said, what I need is a crossflow aluminum dual pass radiator, it brought the temps down 30-40 degrees, when running it's setting at about 195.
I had to move the battery back about 4" and come across from the drivers side to the pass. side to enter the radiator, made a simple shroud and done. I thunk I saw them on Summit for about $220.

 

[guammybear]

So if a cross-flow rad has the filler/cap on the inlet hose does this defeat the purpose of a crossflow?

 

[misterpepper]

I can understand the points about sediment or cap location in the system, but I'm not sure either really represents a clear benefit over the other. I would think that with radiators typically being rectangular in shape, having the flow run in the longer direction would give the coolant more chance to cool. Since an FJ40 radiator is pretty close to square flow direction probably doesn't make much difference. Maybe it was something like hose routing that was the deciding factor.

 

[reddingcruiser]

All things considered, both down-flow and cross-flow have advantages in certain applications. Cross-flow radiators have just become more prominent as car designers have reduced the frontal area of cars, requiring shorter, wider radiators.

In an engine conversion situation, IMHO, if you want the coolant system to perform correctly in the widest variety of applications you should try to duplicate, as close as possible, the arrangement the engine had in its OEM configuration with regards to coolant capacity, radiator surface area and air-flow requirements (including fan size and efficiency). Because, in the end, cooling is the ability to transfer the coolant temperature to the ambient air that is drawn through the radiator, and keep the coolant temperature (and pressure) within the operating limits of the system.

My aluminum cross-flow just fits between the fender wells and runs at whatever the thermostat temp is. I run the stock clutch fan and a shroud.