dual radiators

rockcity

rockcity

everyday is a chance to get better
Joined
Apr 10, 2005
Location
Greenville, NC
Anyone have experience with having dual radiators on a trail rig or race buggy?


I know a lot of hot rod guys do it but I don't think I've ever seen it on a 4x4...


stacked or not?

parrallel or series?

there are a ton of options to consider....

I have done a lot of research on it but haven't tried it or seen it off road. why?

I need more cooling in the buggy but don't have room for a larger radiator and don't want to relocate to behind the seat...
 
One of the guys racing class C was telling me about dual rad's. White buggy that first came to the spartanburg race.

Edit: I belive it was #22 Scott Decker.
 
Yeah, Scott got the idea from Erik Miller's Twisted Customs race buggy. He has had good luck with the setup. I think it runs a 22x19 front and rear plumbed in series.
 
tw89yj said:
Yeah, Scott got the idea from Erik Miller's Twisted Customs race buggy. He has had good luck with the setup. I think it runs a 22x19 front and rear plumbed in series.
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If I'm not mistaken Erik had a little to do with Scott's build....
 
We shot a lot of temps on a pair of 11x7 stacked oil coolers (Same principle) on our Baja chase truck. We found a 50% reduced efficiency in the second unit. How ever, It did drop oil temps (durring hard running) by another 30 to 40 degrees. The second cooler looses a lot of air flow if you only use 1 fan. Scavenging pre-heated air through the second unit obviously limits it's thermal efficiency.

I wonder what the effect of a pusher and a puller fan on either side of the stack would do. It may pull cooler air from the gap between the the 2 units. Anybody tried that?
 
nctom said:
We shot a lot of temps on a pair of 11x7 stacked oil coolers (Same principle) on our Baja chase truck. We found a 50% reduced efficiency in the second unit. How ever, It did drop oil temps (durring hard running) by another 30 to 40 degrees. The second cooler looses a lot of air flow if you only use 1 fan. Scavenging pre-heated air through the second unit obviously limits it's thermal efficiency.
I wonder what the effect of a pusher and a puller fan on either side of the stack would do. It may pull cooler air from the gap between the the 2 units. Anybody tried that?
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Generally, a pusher + puller is less efficient than a puller only. The pusher actually increases the static pressure and negatively effects the puller (at least with a single core). I doubt that it would really pull that much cooler air from the sides if there was a small gap between the cores. If it did, the cooler air would flow through the edges of the core which have alot less air flow anyway, depending on the fan size/distribution.
 
FWIW, when we ran multiple rads on mining equipment, they were in-series and not stacked (but shared the same fan).
 
everyone mentions running them in series...

I've been considering running mine in parallel to reduce the amount of resistance for the water and to keep the efficency of each radiator at its peak.

I guess I'm looking for a setup that is somewhat stacked. I have room behind my current radiator but low down and spaced out about 4" or so. My primary radiator is leaned back about 20*, so there is a good amount of usable space at the bottom. I'd run it in mostly fresh air and with its own seperate fan, so there shouldn't be too much of a problem getting mostly fresh air
 
I would try an oil cooler with a electric fan tied to a thermostat first. B&M makes a nice one that comes with all you need. Also do you have your ATF going through the radiator? On my last buggy what helped the most was sealing up all the air gaps between the electric fan and the radiator. This forces the air that the fan was pulling to have to come through the radiator.
 
If they are in series then all the fluid will just take the path of least resistance and not be forced to go through both radiators.
 
rockcity said:
everyone mentions running them in series...
I've been considering running mine in parallel to reduce the amount of resistance for the water and to keep the efficency of each radiator at its peak.
I guess I'm looking for a setup that is somewhat stacked. I have room behind my current radiator but low down and spaced out about 4" or so. My primary radiator is leaned back about 20*, so there is a good amount of usable space at the bottom. I'd run it in mostly fresh air and with its own seperate fan, so there shouldn't be too much of a problem getting mostly fresh air
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Rob your diverter will be your limiter. You will most likely end up with a dead pocket and one system sit dormant with static coolant. You would be better up toi stall a very large expansion/ tmp drop tank than to use a parallel system. To have both branches pressure exactly equalized is damn near impossible.
 
Can you get a single, thicker core unit? as noted I would ensure oil/trans coolers are separate.

There really should be no issue with flow unless the plumbing is stupid and odd-sized for parallel hx's, however if you mount one in front of the other you pretty much lose a lot of the benefit because the delta-T across the second radiator would be lower


EDIT: after reading you above post, you are suggesting a smaller unit below... yeah, that could cause flow issues. I was originally referring to duplicate sized units
 
Barnes 4wd said:
On my last buggy what helped the most was sealing up all the air gaps between the electric fan and the radiator. This forces the air that the fan was pulling to have to come through the radiator.
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This is much more important than most people think.
 
FrontPorchFab said:
This is much more important than most people think.
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x2!
I work at Volvo/Mack trucks, and they take it to another level. The cooling system on our trucks have a typical rectangular plastic/fiberglass shroud that tapers down to a circle right in front of the engine fan. The shround at the back face of the radiator covers the entire surface area of the radiator. There is a large aluminum ring that surrounds the engine driven fan with a very small gap between it and the ends of the fan blades. The aluminum ring is bolted to the engine block with brackets so it moves with the engine/fan. A rubber ring/flap is attached to the aluminum ring, that bridges the gap between the aluminum ring and plastic/fiberglass shroud. The purpose of all this is to ensure that when the fan is turning, it is creating as large a vaccum as possible on the back side of the radiator thus creating the highest air flow possible.


Here is a picture of the radiator on my cab truck. It is a Taurus fan cut out from its shroud, and fit to a custom aluminum shroud I made that covers the entire radiator surface. Foam tape seals all the edges of the shroud to the radiator, and the Taurus fan has silicone around where it is mounted to the aluminum shroud. That setup ensures that 100% of the useable radiator surface has air being pulled across it, and when that fan is turning, damn near 100% of the air it moves is coming across the radiator coils and not leaking in anywhere.

ai34.photobucket.com_albums_d117_drkelly99_Cab_20truck_rear_20c6ba51c59c1221650d41cab19394bfc8.jpg
 
yeah, the shroud covers the entire area of the current radiator. at most, there is maybe a 1/32" gap at a couple areas where the shroud mounts to the radiator.

ATF cooler is not part of the current radiator.

I thought about the flow being different in one versus the other which would almost make the problem worse.

Maybe just install a thermostat at the second smaller radiator to operate at higher temperatures...


don't get me wrong, the cooling during any trail riding has been fantastic. The only time I've had issues is when I was pushing it really hard (like hauling ass up trail 10 at Harlan up to the PITS :D ) or while racing, so the need for it is minimal at this time since I don't race a lot but would like to build it a little more universal so I can race and be OK
 
Barnes 4wd said:
On my last buggy what helped the most was sealing up all the air gaps between the electric fan and the radiator. This forces the air that the fan was pulling to have to come through the radiator.
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VERY important, without building a shroud, the area affected by the air moved by the fan would only be the size of the fan. A shroud will utilize every square inch of the core.
Barnes 4wd said:
If they are in series then all the fluid will just take the path of least resistance and not be forced to go through both radiators.
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I think you have series and parallel mixed up...if it is in series it must go through both radiators before returning.
 
GCncsuHD said:
VERY important, without building a shroud, the area affected by the air moved by the fan would only be the size of the fan. A shroud will utilize every square inch of the core.
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However, you still ahve to have an appropriate air gap between the fan itself and the radiator to draw from the coolers...else you will have a funky circular-esque temperature gradient emanating from the center of the radiator
 
Hurley said:
However, you still ahve to have an appropriate air gap between the fan itself and the radiator to draw from the coolers...else you will have a funky circular-esque temperature gradient emanating from the center of the radiator
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Absolutely.
 
GCncsuHD said:
I think you have series and parallel mixed up...if it is in series it must go through both radiators before returning.
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You are right, the problem would be if they were in parallel
 
I have a setrab oil cooler on mine, and it would still run hot. The largest radiator I could find, mounted up in cleaner air behind the headrests, finally solved all issues, under any conditions.
 
tw89yj said:
I have a setrab oil cooler on mine, and it would still run hot. The largest radiator I could find, mounted up in cleaner air behind the headrests, finally solved all issues, under any conditions.
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Good deal, glad you solved your issue. Sounds like you needed to move your radiator anyway. A properly sized oil cooler is part of a total cooling solution, not a band aid for the undersized, misplaced or poorly shouded radiator. If my comment sounded that way, my bad. The oil cooler keeps your oil at the steadier acceptable temp. When you water is too hot the oil is much hotter and doing damage. You need a smaller radiator when the oil temp is being kept in check. That was my point.
 
raven mad said:
OK, Ill bite on this.... what is the propper distance for the face of and electric fan to sit off the face of the core of a radiator ????
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The pros like Flexalite and Spal set them at what looks like 1-3 inches. I have one of each out in the shop. I will measure in the morning. All the race trucks I see in Baja are that or more.
If it is properly shrouded, you could enlarge that. The factory stuff looks like as much as 8 inches. I would imagine there is a point of deminishing returns if you go too far away.
 
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