Radiator relocation

[FOG]

I need to replace my transaxle in my mid engine sand car. Going from a Mega Sand to a 2d.
The radiator is behind the LS motor as shown in my drawing as current
and I have to relocate it to get the 2d to fit.
My first thought was to move it up and lay it down because of some other mods I want to make keeping the air flow in the same direction.
But then I thought it might be better to have the air flowing in the opposite direction. Pulling cooler air from the back of the car instead of pulling warmer air off the motor.
What do you cooling experts think?

 

[honEXduner]

Under most sandrail conditions, the backside of the radiator will be a low pressure region when driving. This low pressure will significantly reduce the effectiveness of your fan package as they have to constantly overcome this pressure delta to move any air through, if mounted as shown in the second diagram. While the logic of warm air rises and wanting to pull cooler air from below is reasonable. Those effects will be overshadowed by the increased air flow resistance for the fans when driving, likely lowering efficiency.

 

[Rockwood]

Under most sandrail conditions, the backside of the radiator will be a low pressure region when driving. This low pressure will significantly reduce the effectiveness of your fan package as they have to constantly overcome this pressure delta to move any air through, if mounted as shown in the second diagram. While the logic of warm air rises and wanting to pull cooler air from below is reasonable. Those effects will be overshadowed by the increased air flow resistance for the fans when driving, likely lowering efficiency.

This

Also, the angle of the radiator is asking a lot of airflow (air is lazy) to go through the radiator naturally. You’ll need ducting or something to encourage airflow. I’d try to keep it as high and vertical as possible.

To stop hot air from the engine polluting the radiator, the ducting can grab air from above the exhaust (I doubt the engine block will affect temps much). You really only need 1/3 of the radiator’s frontal area to feed it, assuming the ductwork is designed correctly:

As you can see, as long as the ducting has a gradual enough curve to keep airflow attached (no more than 15* is a good general rule), airflow through the radiator would actually increase compared to straight ducting since you're reducing air speed (which increases pressure, see Bernoulli’s Principle).

 

[Rockwood]

Something like this:



Thought the ducting near the engine would be helped a ton if you moved the radiator back

 

[Stinky]

I had a Honda w/the the direction of airflow reversed from your diagram....my radiator tilted forward at the top....Your new way won't work, as previously mentioned. AND, as previously mentioned, as high and as vertical as possible is best. BTW, this works best w/air, AND coolant flow. Your air is naturally going to want to rise as it warms....don't fight that.

To add on what HonEx said, your diagram has high-pressure in front of the radiator, you are going to try to push air against that....that ain't gonna work. Your fans won't do it....although it might work, if it ducts out into the air passing over (which is low pressure, the faster the air moves, the lower the pressure). IOW, you want the air to flow, in your diagram, from low pressure to high pressure....it naturally wants to go high to low.

My Honda ran hot until I made a duct that, on the bottom, came straight forward, horizontally from the lower edge of the radiator, as far forward as the leading upper edge (just like in the video, but more open on the front). On the side, a triangle, underneath the radiator, w/the upper edge of it following the side of the radiator, the lower edge is horizontal, and joins up w/the middle horizontal part (which naturally lines up w/the triangle, on each side). Additionally, the leading edge of the duct had a spoiler, that angled down to catch more air.

Soooooo, looking at it from the front, the walls of the duct looked like this... w/the radiator in the middle of the "U" L____I

Your old set-up is better. But, I bet that your fans were on a lot.

NO< NO< NO you'll be banging your head against the wall. Airflow front to rear and low to high (rises as it warms).

If ducted properly, your fans will hardly ever come on.

 

[FOG]

Thanks guys. I really appreciate all of your feedback. As I mentioned, it was my first thought to keep the air flow the same way. But then I started over thinking it and thought “what if “.
One of the reasons I love this site
is all of the experts that keep guys like me from getting into trouble with our “what if’s”.

 

[wesinls]

Figured I'd share since I have the same setup...I have a heat exchanger and an oil cooler as well (just for the oil) - but I've yet to see over 200 degrees. No windshield either, I'm sure that's a factor.

 

[Goatpoker]

Good comments on the pressure topic. My experience is that you can overcome anything with enough fan. If you are counting on natural air flow to cool you are going to end up with challenges.

I think the more you lay it down the less pressure has an effect on the fan efficiency so if you were ok with drawing #1 then you will be ok in #2. You are not getting enough natural air flow in that layout to matter. It's all the fans

 

[lincster]

Good comments on the pressure topic. My experience is that you can overcome anything with enough fan. If you are counting on natural air flow to cool you are going to end up with challenges.

I think the more you lay it down the less pressure has an effect on the fan efficiency so if you were ok with drawing #1 then you will be ok in #2. You are not getting enough natural air flow in that layout to matter. It's all the fans

100% agree with this.
My engine radiator has always set like the radiator in the drawing under "current".
At that angle and blocked by my back seat/fuel tank.

Old style fans, straight blade, I always ran 210-225F.
Went to new fans, curved blade, now I run at 180F, all the time.
Nothing else changed but the fans.

See the radiator in the below pix, tucked down?