Stark Performance Automatic Transmission Cooler Kit
 

Stark Performance is pleased to present our automatic transmission cooler kit for the BRZ and FR-S. This cooler kit was designed and tested to ensure that the factory transmission is kept cool during spirited driving or lapping sessions at your local track. Our testing showed the cooling circuit has sufficient flow and pressure to allow the addition of an auxiliary air/oil cooler without the need or expense of an additional pump. Our kit includes a Setrab Series 6, 19-row cooler core and comes pre-assembled with fittings and lines, brackets, hardware and instructions to install in an afternoon.

For pricing information, please check out our thread in the Vendor Classifieds area here: http://www.ft86club.com/forums/showt...59#post2035859

Development

We wanted to see how well the factory transmission cooler circuit performs under various conditions in the real world. So we set about splicing in pressure and temperature sensors to the factory transmission cooler circuit. On the FR-S there is an external heat exchanger that transfers heat from the transmission fluid to the coolant. The coolant that circulates through the heat exchanger is also part of the heater core circuit and is therefore at a lofty 200 degrees Fahrenheit. Fortunately, the FR-S uses Toyota WS transmission fluid which is a synthetic fluid and is capable of withstanding much higher temperatures than traditional mineral based fluids that start breaking down at 180 degrees.

Steady state testing at idle showed the transmission fluid to stabilize at 189 degrees. Once on the highway, steady state cruising yielded 194 degree transmission fluid temperatures. City driving with its stop and go pattern had elevated temperatures, but even with moderate acceleration, they were by no means alarming at 205 degrees. Overall, the factory system works as intended for daily driving duties.

Driving up a mountain pass enthusiastically, however, reveals that the factory heat exchanger is unable to shed heat fast enough to maintain reasonable temperatures. Within 2 minutes of spirited driving, the temperatures shot up to 235 degrees. While the synthetic transmission fluid can withstand high temperatures, the other components in the transmission cannot. Generally, seals will start to harden and crack over 260 degrees and the clutches will start to slip at 295 degrees. Therefore, we really don’t want temperatures to exceed 240 – 250 degrees for longevity.

Track testing with the factory setup naturally showed how woefully inadequate the system is for that kind of stress. While the car is advertised as being able to carry a set of track wheels and tires in the trunk with the rear seat folded down, it is not truly designed for track duty. In 8 minutes of track driving, the transmission temperatures climbed up to 244 degrees. In short, an automatic equipped car needs to have additional cooling if it is to be driven on a track.

Once we had established the need for additional cooling, we set about selecting a cooler core from Setrab. Setrab is well known for making high quality competition level heat exchangers used in everything from Baja 1000 Trophy Trucks to OEM applications from Jaguar, Mercedes, Ferrari and more. While we could have selected a less expensive core, those cores are generally not designed to flow air well at the high speeds seen on a race track. Most of the less expensive cores are designed for towing (high thermal loads at low vehicle speeds). As such, they are designed to increase turbulence to maximize heat transfer. At high speeds, however, they are restrictive to airflow and unable to cool as efficiently. Setrab cores, on the other hand, have a straight through fin design that balances turbulence with high speed efficiency. In addition, the tubes themselves have brazed turbulators that ensure excellent heat transfer between the fluid and the walls of the tubes.


Notice that the alternative core requires the air to be diverted at an angle in order to pass through the core. While this is great for low speed efficiency, it is not the best for racing.

With the Setrab core installed, the transmission maintained normal operating temperatures for a solid 30 minute enthusiastic run up the mountain. We are pleased to say that this works very well for spirited driving up a mountain pass. Track testing showed a marked improvement over the factory cooler setup, but has a little room for improvement. While temperatures peaked out at 233° Fahrenheit and below our established threshold, we would like the temperatures to be more in the 220° range. Therefore, we did some airflow modifications to the front fog light cover and fender liner to get air in and out more effectively.


With the airflow modifications, track performance was precisely where we wanted it to be with transmission temperatures peaking out at 221° Fahrenheit. During the last session, the temps stayed steady at 210° and only started to go up once we slowed down.

Overall, the cooler works well and does what we need it to do. For cars that do not see track time, the airflow modifications are not necessary as the cooler gets enough air to do the job extremely well during spirited driving.

Here is a picture of the kit and what it looks like installed:


With cooler weather rolling into Southern California this winter we noticed that the transmission temps were a bit cooler than we'd like to see with our transmission cooler installed. While we plumbed it so that the fluid goes from the transmission to our auxiliary cooler to the factory heat exchanger and back to the transmission, the factory heat exchanger can't quite add enough heat back to the fluid to warm up sufficiently. In some cases of cruising on the highway in 40 degree weather we saw transmission fluid temps drop as low as 127 degrees at steady state. Considering that our initial testing indicated that the OEM engineers designed the system to run at higher temperatures (189 - 200 degrees) and viscosity is affected by temperature we started working on a thermostat option for people that drive their cars in cooler weather. Here is a diagram of how the thermostat gets plumbed:


We started by adding an off the shelf, inline thermostat rated at 180 degrees to the system. Initial testing showed that the thermostat actually started opening at 160 degrees. Since thermostats are generally rated by their opening temperature, we thought that was a little odd. After discussing with the manufacturer of the inline thermostat we opened up the housing to swap out to a higher temperature wax motor. Low and behold it was equipped with a 160 degree wax motor as the temperature was stamped onto the housing. Apparently, this is common practice with the oil thermostat manufacturers for some reason.

While we tracked down a suitable replacement wax motor rated at a higher temperature, we did a little long term testing with the 160 degree thermostat installed. It did help bring the temperatures up a little higher, but they were generally in the 158 - 163 degree range cruising on the highway and up in the 169 - 177 degree during extended street driving. Obviously, the transmission cooler is more effective at highway speeds at shedding heat.

We finally were able to source a 195 degree wax motor that works in the thermostat housing, installed it and started doing some testing. Steady state cruising on the highway is now closer to OEM at 170 - 180 degrees. While one would expect the temperature to be closer to the opening temperature of the thermostat, approximately 10% of the fluid flowing through the thermostat does go out to the cooler circuit when the thermostat is closed. This is to prevent thermal shock when the thermostat opens as well as keep the cooler circuit pressurized.

In addition, we did some quick track testing to verify that the thermostat does not adversely affect the cooling ability of the system. We were fortunate enough to get 4 runs in our session (1 more than when we did the initial track testing). We are happy to report that the transmission outlet temperature stabilized at 223 degrees at the end of the 3rd run and did not exceed that temperature during the 4th run.

In conclusion, we are now offering a thermostatic option as an add on for those who drive their cars in cooler weather and would like their transmission temperatures to be closer to stock when adding our cooler kit. The thermostat housings are modified with new higher temperature wax motors with the fittings installed and pressure tested to ensure a leak free installation.

:clap: :clap: bravo. Very pleasing to see another auto trans cooler on the market.

Likewise !
 

I love the side mount !

How is the rad size in comparison to any others ?

ALSO - Is the wheel well grate included ?

:cheers:


http://i628.photobucket.com/albums/u...ps9793f959.jpg

CERBERUS

Thank you. The Setrab Series 6 19-row core is 11.14" wide while the Series 1 19-row core is only 6.42" wide. The core we use has 73% more surface area and 81% more volume than the smaller core.

The cooler kit does not include the vented fender liner. The vented setup was not necessary for spirited driving, but was helpful in keeping the temps nice and low on the track. I would recommend a transmission temperature gauge and if you find that you need more airflow for your car to keep temps down, then go for it. Otherwise it will add some drag.

We are currently looking for a test vehicle near San Bernardino, CA. The car needs to have forced induction already installed: centrifugal supercharger or turbocharger kit with a front mount intercooler that has one of the charge pipes routed through the passenger side. The qualifying car will get free installation as well as a discounted kit. This is so we can verify fitment and/or develop an alternate mounting solution.

Will there be an alternate side mount at the left hand side of the car? Currently my setup have the oil cooler mounter on the right hand side of the car and the intercooler in the center. And will this fit the BRZ as well?

It is possible to work on an alternate mounting solution on that side. It will be a bit of a challenge though due to the windshield washer reservoir taking up most of the space. If I'm not mistaken, there are a few turbo kits that actually delete it or require a smaller reservoir to clear their piping. That compounds the challenge.

Will this fit the BRZ as well?
Thanks.

It should fit the BRZ just fine. The only relevant difference between the FR-S and BRZ is in the front fascia design. Since there is an engine oil cooler on the market that also mounts in the same location as our transmission cooler, and it fits the BRZ, I don't anticipate any issues with fitment of our kit whatsoever.

Update: With cooler weather rolling into Southern California we've been noticing that the transmission temps are a bit cooler than we'd like to see with our transmission cooler installed. While we plumbed it so that the fluid goes from the transmission to our auxiliary cooler to the factory heat exchanger and back to the transmission, the factory heat exchanger can't quite add enough heat back to the fluid to warm up sufficiently. In some cases of cruising on the highway in 40 degree weather we saw transmission fluid temps drop as low as 127 degrees at steady state. Considering that our initial testing indicated that the OEM engineers designed the system to run at higher temperatures (189 - 200 degrees) and viscosity is affected by temperature we started working on a thermostat option for people that drive their cars in cooler weather.

We started by adding an off the shelf, inline thermostat rated at 180 degrees to the system. Initial testing showed that the thermostat actually started opening at 160 degrees. Since thermostats are generally rated by their opening temperature, we thought that was a little odd. After discussing with the manufacturer of the inline thermostat we opened up the housing to swap out to a higher temperature wax motor. Low and behold it was equipped with a 160 degree wax motor as the temperature was stamped onto the housing. Apparently, this is common practice with the oil thermostat manufacturers for some reason.

While we tracked down a suitable replacement wax motor rated at a higher temperature, we did a little long term testing with the 160 degree thermostat installed. It did help bring the temperatures up a little higher, but they were generally in the 158 - 163 degree range cruising on the highway and up in the 169 - 177 degree during extended street driving. Obviously, the transmission cooler is more effective at highway speeds at shedding heat.

We finally were able to source a 195 degree wax motor that works in the thermostat housing, installed it and started doing some testing. Steady state cruising on the highway is now closer to OEM at 170 - 180 degrees. While one would expect the temperature to be closer to the opening temperature of the thermostat, approximately 10% of the fluid flowing through the thermostat does go out to the cooler circuit when the thermostat is closed. This is to prevent thermal shock when the thermostat opens as well as keep the cooler circuit pressurized.

In addition, we did some quick track testing to verify that the thermostat does not adversely affect the cooling ability of the system. We were fortunate enough to get 4 runs in our session last night (1 more than when we did the initial track testing). We are happy to report that the transmission outlet temperature stabilized at 223 degrees at the end of the 3rd run and did not exceed that temperature during the 4th run.

In conclusion, we will be offering a thermostatic option as an add on for those who drive their cars in cooler weather and would like their transmission temperatures to be closer to stock when adding our cooler kit. Stay tuned for more on that.

Do you still need a boosted twin for testing?

Yes. PM sent.

I just need some location/contact info to add you to the R&D thread here:

http://www.ft86club.com/forums/showthread.php?t=5520

EDIT: Done

I have one of your coolers ready to install this spring when the weather is better. Since I drive mine year round and although it does not get too cold, we do have 20 and 30 degree days. I want one of the thermostat kits once developed so I can install it this spring.