CPT
02-06-2014, 04:07 PM
There seems to be quite a bit of differing thoughts and opinions about external (auxiliary) transmission coolers. What type, how to run them, and where to place them. Many years ago we did some comprehensive testing of external coolers to answer all the questions. These tests were initiated by a Grand National we had in the shop that kept overheating the fluid and blowing it out the vent. The first step was to make certain that it wasn't any type of internal trans pressure leak, so we actually swapped the whole transmission, but still had the same exact issue. Next, we installed a large "tube and fin" external cooler. The problem was still there. We then installed 2 external coolers, ran in series. The problem was still there. At that point, we decided to install temp gauges on the in and out cooler lines. What we found was disturbing. The fluid coming out of the cooler (s) was hotter than the fluid going in. The series of tests proved that only using one cooler didn't heat the fluid as much, and that running through the factory radiator provided substantially better cooling.
After spending a week, trying to figure this out, we were directed in the direction of a "stacked plate" cooler that was actually smaller than the first "tube and fin" cooler. The "stacked plate" cooler fixed the car, and actually cooled the fluid. We knew that effect, but were puzzled by the cause. Some research (and some common sense) led us to the reason. Think about a "tube and fin" design. It's basically a tube that has a series of 180 degree bends that run through series of fins. Now, think about fluid dynamics. Everytime fluid is asked to change direction rapidly, it produces more pressure. Pressure generates heat. This also explains why using a larger or double "tube and fin" style cooler generates even more heat.
As stated, the test also confirmed that running your cooler lines through your factory in radiator cooler first, provides better cooling. We have confirmed this countless times since . A "stand alone" cooler just isn't adequate to keep the fluid cool enough on a street driven car. I've proven this theory to many customers, via the use of a n infrared heat gun.
Cooler placement is also critical. We've seen people who place them in places "where air can pass through them while driving". The only time you can mount a cooler anywhere other than directly in front of the radiator/condenser is if you're using a dedicated electric fan. When a cooler is mounted directly in front of the radiator/condenser, it uses your stock fan (s) to pull air through the cooler while the car isn't moving. In a normally operating transmission, the torque converter produces the largest majority of the heat. It produces the most heat while it is stalling (slipping). The converter is stalling the most when the car is sitting still.
Testing an experience has led us to the conclusion that the Tru-Cool 4490 cooler (11"x12"x3/4"), ran in series, mounted directly in front of the radiator is sufficient to cool a streret/strip car with very high stall converters. Obviously, there are others whos results may differ. I can only suggest what I've learned from personal experience and testing on a high number of various vehicles.
Frank
After spending a week, trying to figure this out, we were directed in the direction of a "stacked plate" cooler that was actually smaller than the first "tube and fin" cooler. The "stacked plate" cooler fixed the car, and actually cooled the fluid. We knew that effect, but were puzzled by the cause. Some research (and some common sense) led us to the reason. Think about a "tube and fin" design. It's basically a tube that has a series of 180 degree bends that run through series of fins. Now, think about fluid dynamics. Everytime fluid is asked to change direction rapidly, it produces more pressure. Pressure generates heat. This also explains why using a larger or double "tube and fin" style cooler generates even more heat.
As stated, the test also confirmed that running your cooler lines through your factory in radiator cooler first, provides better cooling. We have confirmed this countless times since . A "stand alone" cooler just isn't adequate to keep the fluid cool enough on a street driven car. I've proven this theory to many customers, via the use of a n infrared heat gun.
Cooler placement is also critical. We've seen people who place them in places "where air can pass through them while driving". The only time you can mount a cooler anywhere other than directly in front of the radiator/condenser is if you're using a dedicated electric fan. When a cooler is mounted directly in front of the radiator/condenser, it uses your stock fan (s) to pull air through the cooler while the car isn't moving. In a normally operating transmission, the torque converter produces the largest majority of the heat. It produces the most heat while it is stalling (slipping). The converter is stalling the most when the car is sitting still.
Testing an experience has led us to the conclusion that the Tru-Cool 4490 cooler (11"x12"x3/4"), ran in series, mounted directly in front of the radiator is sufficient to cool a streret/strip car with very high stall converters. Obviously, there are others whos results may differ. I can only suggest what I've learned from personal experience and testing on a high number of various vehicles.
Frank