I just don’t have enough information on this. I was running a Afco dual pass and of course it was a lot better than my KB unit but it was also twice as thick at least. The question is if the coolers are the same size does the dual pass have an advantage over the single pass and if so how much?
My built in logic tells me that the dual pass can’t be much better than a single. With a dual pass (pretend we are working with 2x 1” core) you run the coolant through a 1” tube then turn it around and run it through another 1” tube. With a single pass you run it through 2 1” tubes but just I one direction. I can see where there could be an advantage, but nothing earth shattering.
The reason I ask is for my new heat exchanger setup I am thinking of going one of two ways. First way would be to get 2x 03-04 Cobra Afco dual pass exchangers and stack them. I would run one right into the other. This would give me a cooler about 22”x 18” and dual pass. Downside is that I would be spending over $700 on it.
Or
I can get one Be Cool exchanger with two 1” cores and size it at 22”x 18”. The Be Cool option would be about half the money.
How much better would the dual pass cool? Anyone have any speculation?
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I work with heat exchangers in the HVAC industry. An intercooler is nothing but a heat exchanger so I think this will apply here. I would think the dual pass is more efficient. Most of the multiple pass heat exchangers that I deal with have smaller internal tubes than the single pass units. This allows for more heat transfer at the same GPM than in a single pass. There is more surface area for heat exchange to take place. I would think that intercoolers work the same way. The greater the temperature difference between the coolant and the air, the more efficient a dual pass becomes over a single pass design. In a dual pass the heat transfer is greater because the coolant is subjected to more surface area within the coil. That is how it works in industrial heat exchangers. I'm not for sure if this is true in automotive intercoolers but I can't see why it would not be. If you are getting the heat transfer you need with a single pass in an automotive application, I wouldn't think there would be any advantage by going to a dual pass unit. However, if elecricity were driving the pump that pushes water through the tubes and a compressor was pumping the air around the outside of the tubes, like in the applications that I deal with, the dual pass would have a big advantage. I think your second option would yield the same results and also save you some money. Just my thought on it.
I asked myself the same questions (and vendors/manufacturers). I never got solid figures to back up the claims but this is the theory that I came up with:
My Whipple came with a Fluidyne heat exchanger with diminsions of approximately 22"L X 10"H X 1.5"W with relative small tanks on both sides. I purchased the Afco to replace it. The Afco is a dual pass dual core unit measuring approximately 22.25" L X 9"H X 2.5" W.
On the single pass single core Fluidyne I had more surface area but look at it a little deeper. Coolant enters the top driver's side corner. Passes one time from the driver's side heat exchanger tank through 1 of 25 tubes and dumps into the passenger's side tank before continuing to the charge cooler. So at any given time I have the volume of fluid in 1 tube exposed to cool air for approximately 22" before returning to the blower.
I gave up some surface area to the Afco since it is 1" shorter but gainined in overall system volume due to its much larger tanks and width. The Afco also has larger cooling fins between tubes which Afco claims allows for superior efficiency. Coolant now can travel through 1 of 2 tubes across (32 total if I remeber correctly) 22.25", turn and travel another 22.25". I now have coolant that has been exposed to cool air for a total distance of 44.50" and a heat exchanger that can process more GPM in comparison to the Fluidyne.
Spent some time reading whatever I could find on radiators/heat exchangers since I posted. There is some decent info out there. Found a few things that were not car related which was cool (pardon the pun) because there was no confusing the cooling issue based on application. It seems as if a dual pass system is the way to go as long as you are dealing with a system with restrictions which the intercooler is. It’s not the best way to go for a radiator because they move much more coolant faster. Some people had all the math posted up and a few tests to back it up. That being said going with a dual pass over a single pass is not going to be twice as good. In fact it looks like unless you did some crazy flow study on your particular setup and designed it to be perfect a dual pass will get you about a 10-15% cooling increase. Not earth shattering but certainly notable.
I was incorrect when I posed earlier. I only have 13.5” of vertical room for a heat exchanger, not 22”. I don’t know what I was thinking. And now that I know I am going dual pass I’m probably going to have to go with something that already has an application. From what I can tell from what I see offered I want to go with Afco again. Going with Afco leaves me with three different choices.
I can just use another 03-04’ Cobra heat exchanger which is what I had. They are 22 x 6 x 2.5” (132sq in of surface area). $370
I can use their new GT500 heat exchanger which is 22 x 9 x 2 (198sq in of surface area). 50% taller but a bit “thinner” (which may be a positive as far as airflow goes). $420
Or I can go crazy and use 2 03-04’ Cobra exchangers and have them welded together to end up with a monster 22 x 12 x 2.5” unit (264sq in of surface area). $750
On paper the dual Cobra exchanger setup looks fantastic. The question is how much more cooling will it provide. Doubling the surface area does not double the cooling ability. There is a curve to the gains and it curves toward the point of diminishing or no returns. I’m going to have to call the Afco guys tomorrow and see what they have to say.
As far as pumps goes the Bosch is one popular unit indeed. It seems as if people are using it in a LOT of applications. But if I were to go with the double exchanger route and run the lines to the trunk to a 2-3 gal “overflow tank” it looks like I would be at the limit of what could be expected from the Bosch. With a setup that big from what I can tell using a 20gpm pump would be the way to go. Maybe the Afco guys will have some input as far as what to do about a pump and what they think about a in trunk tank.
The downside, which is sort of an upside, is that if I go the double exchanger, big pump, trunk mount setup is there is no way I would do it without going with braided line and AN fittings. Very cool, very reliable, easy to work on, etc. But expensive. It seems as if there are really two choices. Either go simple (stock supercharger type setup with an upgraded exchanger) or go completely insane and over the top, probably have more cooling than can be used and spend quite a bit more money. There doesn’t seem to be a “middle ground” option. I don’t know what I want to do and I hate not having a plan! I hope the Afco guys can sort me out. I don’t want to do ay R&D next spring. And don’t even get me started on the way the radiator hoses run! Arrrrrrgggghhhhhh! I just pulled all of that stuff off and it’s just a jumble of mess. There is way too much going on there, too many hoses, too many loops, bla, bla, bla. I see how I could make a billet thermostat housing and re-rout the way the lines go while maintaining Fords stupid “only send 66% of the coolant through the radiator” setup. I could run some hard aluminum lines I spots and clean it all up, make it easy to work on, get it out of the way, etc. But again it would be a ton of work and there would certainly be some R&D to do when it was time to get the car out. And radiator/cooling R&D sucks. I want to “fix” it but I don’t want to open that can of worms either. Man I hate being a techno dork sometimes. I drive myself insane!
If anyone has any input I am all ears. I’m curious if anyone has ideas about the whole project. Sure beats talking about oil, CAI’s, what gear to get and what is the biggest tire you can put on a stock rim.
__________________
Under Construction. Better, Stronger, Faster than it was before.
I work with heat exchangers in the HVAC industry. An intercooler is nothing but a heat exchanger so I think this will apply here. I would think the dual pass is more efficient. Most of the multiple pass heat exchangers that I deal with have smaller internal tubes than the single pass units. This allows for more heat transfer at the same GPM than in a single pass. There is more surface area for heat exchange to take place. I would think that intercoolers work the same way. The greater the temperature difference between the coolant and the air, the more efficient a dual pass becomes over a single pass design. In a dual pass the heat transfer is greater because the coolant is subjected to more surface area within the coil. That is how it works in industrial heat exchangers. I'm not for sure if this is true in automotive intercoolers but I can't see why it would not be. If you are getting the heat transfer you need with a single pass in an automotive application, I wouldn't think there would be any advantage by going to a dual pass unit. However, if elecricity were driving the pump that pushes water through the tubes and a compressor was pumping the air around the outside of the tubes, like in the applications that I deal with, the dual pass would have a big advantage. I think your second option would yield the same results and also save you some money. Just my thought on it.
Thanks! Outside the car world applications are sometimes the best way to study something like this. In your situation the systems are designed as a system ad to work very well for the time/money spent. With the cars we are dealing with a bunch of variables we don't know. Having something outside the box to think about helps a lot.
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Dual Pass vs. Single Pass 
