2 replies to this topic

[dead_eye]

Evening all, Im building an mr2 turbo setup at the minute and a conversation came up the other day with regards to fuel pressure and performance. Now i know a fair few motorsport teams run 10bar plus systems but my question is more towards what effect it has o.e why its beneficiall? allowing a smaller injector to flow more fuel or a similar size injector to flow the same fuel faster and atomize it better etc
Also is there a maximum level you can flow petrol fuel at with indirect injection? i.e could you take a cdi fuel setup and run petrol at 1500 bar?
Very up in the clouds question but this is a very odd up in the clouds engine

thanks,
harry

[dead_eye]

come on one of our resident geniuses must now the practical benefit of high pressure fuel injection

[J. Edlund]

For one thing, a higher fuel injection pressure decrease the sauter mean diameter; the size of the fuel droplets. It also increase the kinetic energy of the fuel droplets, thereby decrease the effect pulses in the intake can have on the fuel. The latter is most likely important for a F1 engine given the placement of their high pressure injectors (which most likely runs close to 100 bar these days).

The downside with high pressure injectors is the increased cost, increased weight and increased power consumption of the fuel pump (F1 engines, like all high pressure systems use mechanical fuel pumps).

A high fuel pressure together with a high precision injector also allow large amounts of fuel to be injected within a short time period. This means the time when the fuel is injected can be chosen more freely.

Of course, the advantages of higher fuel pressures are generally reserved for diesel engines, direct injected gasoline engines and HCCI engines, but it's not without effect even on production indirect injected gasoline engines. The effect do however greatly differ from engine to engine and the gains tend to decrease the higher the injection pressure becomes.