injector question


Active Member
May 25, 2001
When injectors are listed at 72lb, or 50lb, At what fuel pressure is this determined?, and where can i find a chart with these numbers?
As always Thanks
3 bars differential pressure across the fuel injector.

In our application, the differential pressure (upstream pressure minus downstream pressure) across a fixed restriction (represented by the fuel injector opening) determines the flow rate.

We have europeans/those on the SI or metric system to thank for the 3 bars reference. Ummm, like Bosch and Lucas...

Bar is a standard unit of metric pressure, equivalent to 14.504 psi, which is nominally the barometric pressure at some nominal altitute ASL (above sea level). Like the top of the tower in which Big Ben resides, or something - j/k...

When the vacuum line is off the FPR the downstream pressure is atmospheric (barometric). When it's on, it's nominally the pressure after the throttle blade.

I'm bored... lol!

what the hell is all that crap lol , on or off would have been a suficiant answer!

The pressure you read when you attach a pressure gauge to the fuel rail is the pressure upstream of the fuel injectors. This pressure increases (under pressure or boost) or decreases (under vacuum) based on the reference pressure. The reference pressure comes from the vacuum/pressure line (harness or hose) after the throttle blade.

The fuel pressure regulator, which is actually a back differential pressure regulator, opens and closes to maintain the differential pressure you set with the reference pressure vacuum/pressure line off.



BTW, when we say, for example, 50 lb injectors, we mean 50 PPH, or pounds of fuel per hour. Since gasoline weighs about 6 pounds per gallons, 50 lb injectors flow about 8 gallons (each) per hour...

OK, I'm still bored...