richardlillard1
SILVER Star
The viscosity of the fluid is totally dependent on the design of the fan clutch. The general rule of thumb is that the more shearing area for the fluid, the less cst you need, but valve design also plays into it heavily.
For the 80, there are three main clutch types:
The Aisin black hub, which was installed by the factory on 93-95 models and has a lot of shearing area, in addition to what I would call a more aggressive valve design. These generally don’t need to go above 15k, sometimes as high as 20k, but that’s rare. The clutch will pull air hard from the moment it comes “on” given the little boot-shapes design of the valve opening.
The Eaton, which I’ve seen on most OBD II (95-97) 80s has a lot of shearing area, but a more refined valve design. The valve slowly comes on, leaving it’s largest opening for the very last and thus having probably the most desirable characteristics if you’re looking to avoid a loud roar. The two valve openings are also next to each other, versus 180° out as on the Aisin clutches. These clutches seem to like somewhere between 20k and 30k at the high end and adjusting the valve temperature is a bit trickier because it involved bending the bi-metal spring instead of adjusting a plate with two screws. Still, I’ve seen them work with fantastic results.
The Aisin blue hub is the most common, the only one of the three which can be purchased new and has the least shearing area of the bunch. The valve design, while slightly different and updated compared to the black hub, still comes on more aggressively than the Eaton which equates to a very strong clutch when the viscosity of the silicone is further stepped up. These seem to do well when given 25k at the low end, up to 30k+ on the high end.
I’ve tuned all three clutches with good success.
I’ve done a few Aisin clutches for the hundy and 4runners and have found that the design falls into one of the two Aisin categories above, so I tune accordingly, usually setting the valve on any clutch to ~120° for the first opening, using a thermocouple.
For the 80, there are three main clutch types:
The Aisin black hub, which was installed by the factory on 93-95 models and has a lot of shearing area, in addition to what I would call a more aggressive valve design. These generally don’t need to go above 15k, sometimes as high as 20k, but that’s rare. The clutch will pull air hard from the moment it comes “on” given the little boot-shapes design of the valve opening.
The Eaton, which I’ve seen on most OBD II (95-97) 80s has a lot of shearing area, but a more refined valve design. The valve slowly comes on, leaving it’s largest opening for the very last and thus having probably the most desirable characteristics if you’re looking to avoid a loud roar. The two valve openings are also next to each other, versus 180° out as on the Aisin clutches. These clutches seem to like somewhere between 20k and 30k at the high end and adjusting the valve temperature is a bit trickier because it involved bending the bi-metal spring instead of adjusting a plate with two screws. Still, I’ve seen them work with fantastic results.
The Aisin blue hub is the most common, the only one of the three which can be purchased new and has the least shearing area of the bunch. The valve design, while slightly different and updated compared to the black hub, still comes on more aggressively than the Eaton which equates to a very strong clutch when the viscosity of the silicone is further stepped up. These seem to do well when given 25k at the low end, up to 30k+ on the high end.
I’ve tuned all three clutches with good success.
I’ve done a few Aisin clutches for the hundy and 4runners and have found that the design falls into one of the two Aisin categories above, so I tune accordingly, usually setting the valve on any clutch to ~120° for the first opening, using a thermocouple.
