Efficient diesel running temperature
Discussion
Does anybody know what temperature the diesel should be for best performance in the modern cars.
My golf 130 PD tdi has a factory fitted cooler on the return diesel line, so I'm guessing the pressure in the lines gets it hot.
My car is set up with a heat exchanger from the engine coolant to run veg oil, but I have realised that when running diesel it will also run through this exchanger.
The car has done 60K with this system without issue, but I'm wondering if the diesel economy will be lessened if it's hotter than ideal.
Coolant is 90degC so if the diesel runs at say 150degC normally then the heater would not actually heat it, but if it were 50degC normally, then there may be an issue.
What are the normal effecient tempertature perameters for diesel going through the engine?
My golf 130 PD tdi has a factory fitted cooler on the return diesel line, so I'm guessing the pressure in the lines gets it hot.
My car is set up with a heat exchanger from the engine coolant to run veg oil, but I have realised that when running diesel it will also run through this exchanger.
The car has done 60K with this system without issue, but I'm wondering if the diesel economy will be lessened if it's hotter than ideal.
Coolant is 90degC so if the diesel runs at say 150degC normally then the heater would not actually heat it, but if it were 50degC normally, then there may be an issue.
What are the normal effecient tempertature perameters for diesel going through the engine?
It doesn't make any difference to economy for two reasons:
1) most ems systems will measure fuel rail temperature to correct for fuel density, and so will inject the correct volume regardless
and more importantly:
2) diesels are unthrottled. Fuel mass = torque. So the driver will simply push the accelerator until the car is travelling at the speed they want to go. With hotter, slightly less dense fuel, you will need to push the accelerator a tiny fraction more to get the same torque that you would have with cold fuel, but you do that automatically and instinctively as a driver anyway!
BTW: the std fuel cooler is fitted because the HP fuel pump adds significant heat to the fuel, and the injector spill back fuel flows can also be quite hot (as the injectors are hot, especially at high loads/rpms).
1) most ems systems will measure fuel rail temperature to correct for fuel density, and so will inject the correct volume regardless
and more importantly:
2) diesels are unthrottled. Fuel mass = torque. So the driver will simply push the accelerator until the car is travelling at the speed they want to go. With hotter, slightly less dense fuel, you will need to push the accelerator a tiny fraction more to get the same torque that you would have with cold fuel, but you do that automatically and instinctively as a driver anyway!
BTW: the std fuel cooler is fitted because the HP fuel pump adds significant heat to the fuel, and the injector spill back fuel flows can also be quite hot (as the injectors are hot, especially at high loads/rpms).
Chears for that. Thats put my mind at ease and Its good to understand how things work. From what I've heard elsewhere the fuel will also be hotter than coolant due to the pump pressure, so the returning fuel will actually be cooled by the heat exchanger as well, so all makes sense now.
Thanks again
Thanks again
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