D-Jet Fuel Pressure Regulator, How high should it go? Options

[GregAmy]

What should be the maximum capability of the stock D-Jet pressure regulator? Mine only goes to 36.

If that's normal, is there another similar-format regulator that can go up to around 45psi?

Background: Microsquirt project. Was hoping to use the stock regulator, but now need something that I can easily mount in the same location, if possible. Injectors I'm using are rated at 43.5psi.

Discuss!

[barefoot]

Many years ago I had a project to design automotive fuel injectors working with then the Bendix company who did the initial patents on the D jet type system before Bosch got into the game.

Solenoid operated injectors take about 1.7 milliseconds to open before any fuel is delivered and an engine operating at 6000 RPM goes one full revolution in 10 milliseconds. the 10 ms is typically the 100% duty cycle for these injectiors.

Looking at the entire flow range of this system or "turn down ratio" you have about 2 to 10 ms flow range for the injector itself plus the trigger points range from idle speed of say 800 RPM to 6000 RPM max yields 8 to one for the injector and 7.5 to one for triggering interval for a total of 60 to 1 flow ratio for the system, that's pretty good.

Modern direct injection engines cannot use anything like 10 ms time as all injection has to occur in the compression cycle. new piezo injectors do not have any initial lag, so are a must for direct injection

As previously mentioned, flow rate is not linear with pressure, but varies with the square root of pressure. So if you've got to larger bore cylinders and want to match with more fuel flow, that can be done by adjusting pressure:
For a 10% larger displacement, in theory you want 10% more fuel flow. to achieve this you need 1.1 squared pressure increase ar 1.21 pressure increase.
So if standard pressure is 28, you'll need 33.9 psi. Hopefully the pressure regulator can be adjusted by this much.

Barefoot