The FSD Cooler provides more than enough cooling capacity for the Fuel Solenoid Driver module if the surface pressure is at its proper value (mounting screws remain at the proper torque). The heat transfer pad material we include in our FSD Cooler kits is identical to that used by Stanadyne. This heat transfer pad has excellent properties, but as mentioned above, thermal transfer performance is surface pressure related. In general, a higher clamping pressure produces a higher heat transfer efficiency.

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The chart below illustrates the thermal performance/surface pressure relationship for the Stanadyne heat transfer pad:

Pressure - PSI	10	25	50	100	200
Thermal Performance ° C/W	2.44	1.73	1.23	1.05	0.92

Note: A lower value means more heat transfer capacity. Thermal Properties and Testing

Grade-8 screws have always been supplied in our FSD Cooler kits. Grade-8 screws are normally not available in a plated version - only the lower grades are. To be able to supply plated grade-8 screws, we originally had them plated locally. Plating our grade-8 screws caused some FSD kit buyers to assume these screws were of lower grade quality. Because of this, we have stopped plating the grade-8 screws supplied with our FSD kits in order to avoid any confusion.

The FSD Cooler is heat-treated to T6 condition, the threads are rolled (not cut), and the final product is anodized to improve its resistance to corrosion and make the thread surface less load sensitive. The screw thread length used in the FSD Cooler aluminum is 1.5x screw diameter. The combination of T6 heat treatment, anodizing and the 1.5x screw depth helps to ensure that the screw threads will not fail, given the forces applied.

Introducing washers underneath the screw-heads reduced the surface pressure on the plastic by approximately 60% when compared to screws without washers. We have not seen any tendency for the screws to sink into the plastic when using washers. However, clamping pressure can relax somewhat over time and after many thermal cycles. This problem is due to a small amount of compression of the plastic material in full depth, which can reduce the clamping force applied by the four screws. Approximately 3000 miles after replacement, we recommend owners re-torque the screws to maintain the clamping force and the thermal transfer performance.

I understand that some customers are using thermal compound (grease) instead of the heat transfer pad supplied with each FSD Cooler kit. We have tested Dow 340 grease (often used as a reference compound), and the following heat transfer properties were discovered:

Pressure - PSI	10	25	50	100	200
Thermal Performance ° C/W	2.67	1.48	0.60	0.56	0.52

Dow 340 is a high quality grease, which can outperform the thermal transfer performance of the original heat transfer pad, but not all heat transfer compounds perform as well as Dow's. Its performance, as with the heat transfer pad, is directly related to the surface roughness, surface flatness and clamping pressure applied. As with the original heat transfer pad, clamping pressure must be maintained, or thermal transfer performance declines.

The grease should be applied in a very thin layer, to the FSD only. Do not use the heat transfer pad and the grease combined, and don't fill up the cavities around the transistor with grease as some people recommend. Radiation and convection from the FSD transistors will transfer heat at least as effectively. This is one reason why the heat transfer pads in our kits incorporate openings for the transistors.

The following chart illustrates the heat transfer properties for a new and soon to be released heat transfer pad material:

Pressure - PSI	10	25	50	100	200
Thermal Performance ° C/W	0.95	0.94	0.92	0.91	0.90

As you can see, this new material maintains thermal transfer performance over a wide range of clamping pressures, unlike both the Stanadyne heat transfer pad and Dow 340 thermal compound, where clamping force variations produce a large change in thermal transfer performance. The secret is that this material is solid until it reaches 55° C, then it makes a phase change and turns into an expanding jelly compound. With these new heat transfer pads, there is no need to periodically re-torque the mounting screws.

Tests have shown that a thermal performance value of approximately 1.00 is the ideal. Values below 1.00 will not extend the service life of the FSD module, but values greater than 1.00 will reduce the FSD life, with an increasing ratio. This means that it's not possible to take advantage of the Dow 340 thermal compound's higher capacity, with its required higher clamping forces.

The FSD Cooler was designed to be mounted to the intake manifold. Airflow over the cooler in this location is sufficient to offer proper cooling of the FSD module. If you move the FSD Cooler to another location, you might increase its cooling capacity, but may not necessarily extend the service life of the FSD module.

If you would like to improve the overall heat-dissipation performance of the FSD Cooler - install the new heat transfer pad when it becomes available, and keep those screws properly torqued in the meantime.

Best Regards,

Christer Lindstrom, BETA

Beta Maskin AB
Hogboleden 28
774 61 Avesta, Sweden
Phone no: 011 46 226 54070
Fax no: 011 46 226 50757
e-mail: mail@betamaskin.se

Please note: The new heat transfer pad will be released before the end of July 2003, and will be supplied by DSG and their dealer network. It will attractively priced and will be included in the FSD Cooler kit once it's available.