Quote:
Originally Posted by svxcess
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It would be most interesting video, almost an hour long. Poses many questions not often asked. The first of other videos to follow. He covers these topics:
Introduction: Who am I and what gives me the right? I will use analogies to make this easier to understand
1. General fluid dynamics and fluid body temperature
2. ATF fluid as a coolant- absorbing and storing energy, transferring energy, it’s own heat. What is the job of ATF as a coolant, how is the heat generated anyway?
3. What is the temperature supposed to be and why. Sounds like a familiar range, right?
4. What happens if it is too cold and what happens if it is too hot? What is too cold and too hot?
5. What is the flow of the ATF and why?
6. Where do I measure the temperature of the fluid body and why?
7. FAQ:
a. Why did the car not have a cooler from the factory? Were the engineers inept?
b. AT OIL TEMP light- Who thought that one up? Has anyone ever seen it come on?
c. So the car doesn’t need a cooler. I get it. But I want to add one anyway. It won’t hurt right?
d. The cooler is restrictive. I feel like the cooler should flow more.
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Temperature in respect of the SVX transmission has been given far too much emphasis on the network. As long as the fluid remains as such throughout the system, i.e. does not vaporise at any point, the system will operate correctly. Given that the overall viscosity is not significantly reduced, as would occur if water or whatever was to contaminate the system.
The fluid provides lubrication for the moving parts and very importantly, a vital means of hydraulically distributing power. Significantly, the latter absolutely depends on the level of pressure available and delivered, i.e. line pressure.
Heat within the System normally becomes generated as a result of friction developed within the various clutches as these gradually transfer and transmit torque. This heat is normally adequately dissipated via the fluid to the existing casing and plumbing.
The positive and direct closing of the clutches depends on correct line pressure. Low pressure results in clutch slip, extra abnormal friction and adverse heat. This to an extent which can not be overcome by means of an extra cooling facility. Damage occurs at the points where the heat becomes generated, i.e. locally at the clutch plate faces which as a result “burn out”.
The warning system should correctly be applied in respect of pressure, rather than heat and in respect of the SVX the temperature setting is too conservative.
When after purchasing an SVX I joined the network and was horrified to become instructed that transmission wise, I had a lemon on my hands. The confusion published soon became apparent. To be sure, I discussed the possible fitting of an external cooler with a local transmission specialist. Their reply - “All Subaru transmissions are considered suspect, but for good reason we only fit coolers to cars used as taxis or for towing. There is no point in adding extra plumbing as a further area of possible pressure leakage.”
I did not fit a cooler to my car, but sometime later, did fit a clearly visible line pressure gauge. At the time, this information was included within threads.
4. What happens if it is too cold and what happens if it is too hot? What is too cold and too hot?
The fluid can only be too cold if due to very abnormal conditions viscosity becomes affected such that flow is impaired. A highly unlikely scenario. However it has been stated here, that certain operations do not take place until fluid reaches normal temperature, but as I understand it this situation is confined to the torque converter.
If the fluid reaches its boiling point or even partially vaporises in pockets, this will upset effective line pressure. As a result clutches will slip unduly and become damaged.
6. Where do I measure the temperature of the fluid body and why?
There is no significant point in measuring the temperature. Line pressure is the decisive factor requiring analysis. However it would best be measured at a point within the transmission or externally close to the outlet. The sensor should be in direct contact with the fluid. A thermistor probe down the dip stick shaft would suffice.
7. FAQ:
a. Why did the car not have a cooler from the factory? Were the engineers inept?
Cooling was/is adequate, but the engineers were certainly inept in not specifying a solenoid valve rated for constant operatioln in respect of solenoid "A".