I noticed a fuel cooler(i think thats what it is) on my truck just past the fuel tank. What purpose does this serve? does diesel really need to be "cooled"? Ive owned several ford diesels and medium duty diesels, but this is the first one I'v ever seen.
Bosch HPCR injection pumps the fuel rails up to 30,000 psig. That puts in a LOT of heat of compression. Bypassed fuel also cools the injectors - this hot return fuel is cooled before returning to the tank. Like Keith said, when the injection pump pulls fuel from the tank it flows through both Fuel Injection Control Modules (FICM) to cool their electronics packages that produce the high voltage for operating the injectors and a lot of heat. Then it goes through the filter head and on to the pump to repeat the cycle.
I think LB7 fuel runs "hotter" than all other Dmax's because LB7 injectors operate on 96 volt solenoids...LLY's are 48 volts IIRC...and then the 2006 LLY/LBZ just use 12 volt solenoids (I think)...which is why the EDU/FICM is/can be integrated right inot the Bosch A35 ECM with not as much of a need for a fuel cooler. No voltage stepping-up, so theres no transformers or anything to create heat. The high press fuel that does not get used tho is returned to the tank fairly warm tho because it was just pressurized to ~26000 PSI.
Although the ECM is capable of commanding fuel pressure up to 160Mpa under high loads or WOT, fuel pressure is constantly being manipulated depending your partitcular conditions and is generally much less than 160Mpa. When cruising at 60mph I'm seeing fuel pressure between 60-75Mpa, fuel temps ranging between 95-130, with ambient air temp in the 40's. I thought the increased pressure/heat compounded with the fact that the pump is located in the lifter valley of the 200deg engine???
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