When Cold Case first was introduced, all our radiators were dual and 3 pass. The 3 pass can only be used with offset/offset downflow radiators Through customer data obtained over time, we had some higher temps than we had expected with downflow units using the 3 pass method. Turns out when the fluid had to be pushed up through the middle of the radiator, some cavitation occurred. Cavitation is 'bad'. So we then switched to dual 1 1/4" cores and eliminated the multi pass units with the downflows. The increased fluid volume did way better than the 3 pass method and we've stuck with that ever since.
We stayed with dual pass on the crossflow radiators because this has already been tested and used by major auto mfg's. Since there is not the need to 'push' the fluid uphill, we are not seeing any of the cavitation issues noted on the downflow units.
