madprofessor
"Loose Cannon Creations"
Linking below a Walbro page that explains lots of things I've wondered about their common 3-fittings plastic pulse pumps like the ones I'm accustomed to. There's enough info that it's certain some other folks can learn from it also, so sharing it here. Here's some of the notable HIGHLIGHTS:.............
...............Not exactly plastic, it's an engineered composite. Typical applications: to 25 hp. For 2-strokes the pulse comes from anywhere exposed to straight crankcase pressure, for 4-strokes it's supposed to be on the intake (manifold) due to the oil in the crankcase. Fuel flow gph is completely dependent on pulse inlet's pressure differential. A 2-stroke could have a pressure differential greater than 8 psi (crankcase), a 4-stroke usually has less than about 2 psi (intake manifold) so a built-in spring assist helps it out. Fuel pressure is nearly the same as engines' pressure differential (including with a 4-stroke's spring assist), so a 2-stroke will have greater fuel pressure and flow than a 4-stroke.
Read the page for more info. NOTE: It does not say anything about us hooking up the pulse to the crankcase pressure (valve covers) on the 4-strokes we most often work with, but my guess is the fuel pressure and flow would be the same as on a 2-stroke. At least I found out enough about the main thing I was looking for, the gph on a 4-stroke engine. No numbers for it, but "Typical applications: to 25 hp." tells me enough. Won't starve a hotrod 212.
Walbro_FPC_pump_PS_EN.pdf
...............Not exactly plastic, it's an engineered composite. Typical applications: to 25 hp. For 2-strokes the pulse comes from anywhere exposed to straight crankcase pressure, for 4-strokes it's supposed to be on the intake (manifold) due to the oil in the crankcase. Fuel flow gph is completely dependent on pulse inlet's pressure differential. A 2-stroke could have a pressure differential greater than 8 psi (crankcase), a 4-stroke usually has less than about 2 psi (intake manifold) so a built-in spring assist helps it out. Fuel pressure is nearly the same as engines' pressure differential (including with a 4-stroke's spring assist), so a 2-stroke will have greater fuel pressure and flow than a 4-stroke.
Read the page for more info. NOTE: It does not say anything about us hooking up the pulse to the crankcase pressure (valve covers) on the 4-strokes we most often work with, but my guess is the fuel pressure and flow would be the same as on a 2-stroke. At least I found out enough about the main thing I was looking for, the gph on a 4-stroke engine. No numbers for it, but "Typical applications: to 25 hp." tells me enough. Won't starve a hotrod 212.
Walbro_FPC_pump_PS_EN.pdf