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Message: [QUOTE="Charles, post: 1566198, member: 103"] I was doing some blunt pressure vs flow calculations as a reality check for a second, and if you imagined a 7 holer with 0.012" holes....oh, say.... a 200 nozzle.... and you used the specific gravity of diesel fuel, applicable orifice shapes for a nozzle hole, an in-cylinder pressure of say 2400psi.... so on and so forth and you took some random flow rate of say, 300cc (per thousand) with a pw of 3ms, you could see what sort of injection pressure is being achieved there. I realize that a HEUI has an on time delay that cuts into the commanded pw.... but I also realize a HEUI has an OFF TIME delay that isn't intuitively accounted for. If not for the off delay, a huge nozzle could idle just like stock.... but alas.... even with the slightest pw that will actually fire the injector, they tend to want to over fuel and run ragged with big nozzles..... because..... they don't just snap right off... you have a MINIMUM injection time determined by the time for the magnetic gauss to fade away and the poppet to fight the icp and drop back down, shut down the oil and the pintle to reseat.... I think the on and off delays are very similar in length, and the off delay gets worse as rpm and commanded fuel go up because ICP is climbing and opposing the poppet... Anyway.... If you just assume the on vs off delays cancel one another, and you actually get 3ms.... For the 7 x 12 nozzle, if you ran it for 3ms and actually acheived 15k psi injection pressure, it would move 433cc. A distant dream. Ok... what if it hit 12k psi? 370cc. What if it were 11k? 352cc in 3. Ok, hell, 9k psi? 308cc in 3ms.... NINE...... thousand psi.... That's a 200 EDM moving 300cc in 3ms. Hardly a wild, hyperbolic example... Contrast that with say, a unit pump, mechanically locked to crank delivering fuel at 25k psi on that same orifice nozzle. In 3ms that would move 569cc. At 25k psi to inject 300cc would take 1.6ms. 400cc takes 2.11ms. But the unit pumps are running that pressure stock, at sub 2000 rpm. At 3k, 4k+ rpm they would be trying to fatally exceed those pressures. The Bosch EUP system is listed as being capable of 30k psi, so if you let it go there, it should live fine. At 30k psi 400cc takes 1.9ms...... or 1900uS as CR folk would say... Aside from the ability to radically alter the injection window in terms of crankshaft degrees, let's be honest about how wildly different 400cc at sub 9k psi burns compared to 400cc at 25k+ psi! Cut the injection window in half, and turn the fuel into vapor.... welcome to CR pressures.... [/QUOTE]