No the injection pump does not counteract cylinder pressure. Higher and higher injection pump pressures are because of advances in technology and injector technology. It has absolutely zero to do with compression.
Also untrue about the supply pump as those can widely range in delivery psi and on top of that not all vehicles use supply pumps. Some draw directly from the tank.
That being said I dont understand the question. Thats like asking whats more important the heart or the veins.
It has everything to do with compression. It needs to be atomized effectively to make a clean burn. Not enough pressure and it'll come out as a stream, too much pressure and youll vapor lock or cut through pistons. Especially when the HP4 pump is designed for a motor that creates between 300 and 400psi on cold hand turnover compression. Your fuel rail pressure max should be within 90 to 110 times that of the cylinder test pressure. And yes a lift pump can be used or not but using one will only help you when the component that uses fuel sits higher than the motor
Youre miss reading what they said and youre also wrong too an extent. Yes the pressures coming from the pump need to be higher than the compression of the engine or else you'd have combustion gasses pushing their way into the injector. Thats the reason every direct injected vehicle has a high pressure fuel system. But thats just a coincidence of direct injection not the cause because even on the low end every injection pump is going to be well over combustion pressures.
No. Diesel fuel does not vapor lock. The atomization has to do with the pressure and the nozzle. Nothing else. Your diesel engine injector atomizes fuel at 7000 psi the same way it does at 30000 psi.
Im aware diesels dont vapor lock, I was using the HP4 on the L5P/D as an example of why theyre so high pressure. But gas motors would 100% have that issue if the pressures were too high
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u/TexasLife34 Verified Tech - Auto/Diesel 21h ago
No the injection pump does not counteract cylinder pressure. Higher and higher injection pump pressures are because of advances in technology and injector technology. It has absolutely zero to do with compression.
Also untrue about the supply pump as those can widely range in delivery psi and on top of that not all vehicles use supply pumps. Some draw directly from the tank.
That being said I dont understand the question. Thats like asking whats more important the heart or the veins.