Heat Exchanger Question

Rauq

Goblin Guru
I don't think there's an IN and OUT on the HX, but if you're not mounting parallel to the ground, you will want to put the inlet closer to the ground to ensure it's full of coolant and not air.
 

JBINTX

Goblin Guru
Does it matter which port is IN and which port is OUT in the heat exchanger?
Depends if DF sent you a left handed one, or a right handed one.


Just kidding. No it does not.
Route your hoses as direct and as short as possible.
typically "in" is on the bottom and "out" is on top - if there is such. So air isn't trapped. Dang it. Rauq beat me to this post....
 

Gtstorey

Goblin Guru
I don't think there's an IN and OUT on the HX, but if you're not mounting parallel to the ground, you will want to put the inlet closer to the ground to ensure it's full of coolant and not air.
I would have said that you don't want air on the outlet of the heat exchanger/return to motor. Aren't most car radiators top hose hot/from the motor and the bottom cool/return to the motor?
 

Rauq

Goblin Guru
I would have said that you don't want air on the outlet of the heat exchanger/return to motor. Aren't most car radiators top hose hot/from the motor and the bottom cool/return to the motor?
haha I was so confident and proud in my answer, and in an instant you've brought me back to my great consternation

I am confident in saying you don't want the inlet and outlet both facing towards the ground. I can't imagine how that results in anything except for an air bubble across the top of the HX.

I think radiators tend to have the outlet mounted below the inlet as they have enough volume to actually allow for the cooler fluid to sink to the bottom in low-flow scenarios.

But for a small heat exchanger, as in our application, I think filling from the bottom allows trapped/entrained air to escape through the outlet better than flowing top to bottom. This might not be an issue if can bleed the system of air really well while the pump's not on, but still suffers in instances where air is picked up from the small pocket at the fill point as in a stock Cobalt HX system.
 

Robinjo

Goblin Guru
Currently, my heat exchange is mounted in the stock flat location with both ports on the same plane. I'll keep the top/bottom orientation in mind if/when I move it somewhere else.
 

Desert Sasqwatch

Goblin Guru
These come in various sizes and can be installed at places in the cooling system that would tend to trap air, like up front at the radiator which has no filler cap. Just a suggestion. :D
 

Gtstorey

Goblin Guru
haha I was so confident and proud in my answer, and in an instant you've brought me back to my great consternation

I am confident in saying you don't want the inlet and outlet both facing towards the ground. I can't imagine how that results in anything except for an air bubble across the top of the HX.

I think radiators tend to have the outlet mounted below the inlet as they have enough volume to actually allow for the cooler fluid to sink to the bottom in low-flow scenarios.

But for a small heat exchanger, as in our application, I think filling from the bottom allows trapped/entrained air to escape through the outlet better than flowing top to bottom. This might not be an issue if can bleed the system of air really well while the pump's not on, but still suffers in instances where air is picked up from the small pocket at the fill point as in a stock Cobalt HX system.
I started to go into the trapping of air, but I'm not sure how much it matters whether it's top or bottom fill. If the HE is the highest point in the system it will trap air either way. If it's not the highest point air will still try and leave the system to reach it. But if the system gets low on coolant you want to still suck fluid gathering at the bottom instead of air at the top. At some point the pump will loose it's prime. Of course this is all a general discussion and will depend on the details of where it's mounted.
 

finazzoty

Well-Known Member
Potentially silly question related to this topic - if I’m using the heat exchanger duct kit and mounting the heat exchanger below the radiator (as it’s shown in Adam’s photos), would the fan still be used? Assuming it would be as there is a wire in my harness for it, but I do not see one depicted in Adam’s picture
 

Chubbs

Well-Known Member
Potentially silly question related to this topic - if I’m using the heat exchanger duct kit and mounting the heat exchanger below the radiator (as it’s shown in Adam’s photos), would the fan still be used? Assuming it would be as there is a wire in my harness for it, but I do not see one depicted in Adam’s picture
No, the fan is not used. The duct shroud takes the place of the fan. Just tie the wire up out of the way somewhere.
 

finazzoty

Well-Known Member
No, the fan is not used. The duct shroud takes the place of the fan. Just tie the wire up out of the way somewhere.
Figures - So now of course I'm brought to the question of: Which option is more effective? I don't particularly love the look those nostrils in the sides of the hood, but I also feel like the area where the heat exchanger will be mounted will harbor quite a bit of heat from the radiator...and then you just have a fan blowing hot air over the heat exchanger. Thoughts?
 

snirtman

Well-Known Member
Figures - So now of course I'm brought to the question of: Which option is more effective? I don't particularly love the look those nostrils in the sides of the hood, but I also feel like the area where the heat exchanger will be mounted will harbor quite a bit of heat from the radiator...and then you just have a fan blowing hot air over the heat exchanger. Thoughts?
The heat exchanger fan is a puller (or at least mine is), so it'll pull air from below the car adding some downforce :)

There was a racecar in the 70's that used this concept to such great effect that it was banned. He used two military grade fans that together could pull almost 10,000 cfm. He mounted them at the rear of the car and ducted them to draw air from beneath the car and blow it out the rear. Claimed he could generate almost 2000lb of downforce at any speed. Here's an article about it.
 

Sluggonaut

Goblin Guru
I'm running just the naca ducts on my LSJ-T and had no problems with IAT temps last year.

Someone crammed a fan in there with their duct, but I don't have the link handy. Mine was tight so I'm not sure how easy it is to squeeze the fan in there too, but I haven't felt the need to run anything other than the ducts so far.
 

Chubbs

Well-Known Member
Figures - So now of course I'm brought to the question of: Which option is more effective? I don't particularly love the look those nostrils in the sides of the hood, but I also feel like the area where the heat exchanger will be mounted will harbor quite a bit of heat from the radiator...and then you just have a fan blowing hot air over the heat exchanger. Thoughts?
The answer here depends on the circumstances. At higher speeds, the NACA ducts will be more effective. Ramming air directly into the nostrils at 100 mph is pretty darn effective at cooling. Sitting at a traffic light, those nostrils do nothing, and the fan is far more effective. So, when do you need to cool the intake charge? For me, it's at 100 mph. I don't care about intake temps while idling.

All that said, I definitely get heat from the radiator, even at speed, and even with the NACA ducts. My IAT2 temps seem to hover right around 150-160 degrees under load. Even with my auxiliary heat exchanger behind the passenger seat, it's still right around 150's. I think I'm getting a lot of recirculating heat in the engine bay though.
 

Fozda

Goblin Guru
I ran the NACA ducts in conjunction with the fan because I wanted to get fresh air over the heat exchanger but I also wanted to move air while sitting still. It was a tight fit but it does fit!
 

finazzoty

Well-Known Member
The heat exchanger fan is a puller (or at least mine is), so it'll pull air from below the car adding some downforce :)

There was a racecar in the 70's that used this concept to such great effect that it was banned. He used two military grade fans that together could pull almost 10,000 cfm. He mounted them at the rear of the car and ducted them to draw air from beneath the car and blow it out the rear. Claimed he could generate almost 2000lb of downforce at any speed. Here's an article about it.
The good ole fan car. I always thought that was the coolest thing (no pun intended lol). Shame they DQ'id
 

finazzoty

Well-Known Member
I ran the NACA ducts in conjunction with the fan because I wanted to get fresh air over the heat exchanger but I also wanted to move air while sitting still. It was a tight fit but it does fit!
So this was my exact thought as well - I would also like to have air flow while I'm not moving, but fresh air at speed. How did you deal with the fact that the fan pulls air in the opposite direction of the duct flow? I was thinking maybe there is a way to flip the fan blade around.
 

Fozda

Goblin Guru
So this was my exact thought as well - I would also like to have air flow while I'm not moving, but fresh air at speed. How did you deal with the fact that the fan pulls air in the opposite direction of the duct flow? I was thinking maybe there is a way to flip the fan blade around.
I flipped the blade and swapped polarity to make it a pusher fan. I also have a floor up front to keep the air from dumping under the front of the car.
 

Sluggonaut

Goblin Guru
I ran the NACA ducts in conjunction with the fan because I wanted to get fresh air over the heat exchanger but I also wanted to move air while sitting still. It was a tight fit but it does fit!
What is the benefit of moving air while sitting still? Is there a concern of heat soak from the engine raising IATs while sitting idle?

I can't think of a use case where I'd be raising IATs sitting still or any issues with leaving from a stop with IATs a few degrees higher that wouldn't immediately drop once I start moving.

I'm thinking about it from the standpoint of being a few degrees cooler at a stop versus running a few degrees warmer under load due to the fan impeding airflow from the NACA ducts. I could be underestimating how much IATs rise sitting still or overestimating the drawbacks of a fan in the path of the ducts, but it seems that the numbers I've seen posted in various threads show that NACA duct setups have lower IATs than those with just fans.

Maybe we can chart intercooler configs and IAT temps like we did with tire setups.
 

Ross

Goblin Guru
The heat exchanger fan is a puller (or at least mine is), so it'll pull air from below the car adding some downforce :)

There was a racecar in the 70's that used this concept to such great effect that it was banned. He used two military grade fans that together could pull almost 10,000 cfm. He mounted them at the rear of the car and ducted them to draw air from beneath the car and blow it out the rear. Claimed he could generate almost 2000lb of downforce at any speed. Here's an article about it.
There is a modern version of a fan car here. The McMurtry Speirling is a carbon fiber car with 1000hp electric drivetrain. Active suspension is able to keep the vacuum box close to the ground, so it only needs 70hp to get 2000kg of downforce for the 1000kg car.
40137
40139

Now to add a 1 meter ^2 vacuum box to the bottom of a goblin....
 
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finazzoty

Well-Known Member
What is the benefit of moving air while sitting still? Is there a concern of heat soak from the engine raising IATs while sitting idle?

I can't think of a use case where I'd be raising IATs sitting still or any issues with leaving from a stop with IATs a few degrees higher that wouldn't immediately drop once I start moving.

I'm thinking about it from the standpoint of being a few degrees cooler at a stop versus running a few degrees warmer under load due to the fan impeding airflow from the NACA ducts. I could be underestimating how much IATs rise sitting still or overestimating the drawbacks of a fan in the path of the ducts, but it seems that the numbers I've seen posted in various threads show that NACA duct setups have lower IATs than those with just fans.

Maybe we can chart intercooler configs and IAT temps like we did with tire setups.
This is also a good point about the fan impeding airflow. I may actually start a chart as soon as I get mine finished up - I can post it when that time comes and we can get others' info in there.
 
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