please educate me on lb rating of fuel injectors

E28 technical advice asked and given! Troubleshooting, modifications and more.
gadget73
Posts: 1253
Joined: Nov 22, 2017 10:30 PM
Location: New Jersey

Re: please educate me on lb rating of fuel injectors

Post by gadget73 »

yeah Ford ECMs don't have the dead time parameter but they do have stuff that effectively covers it. Also handles the rise and fall time for the open and close commands.

but yes if its not correct, the tables end up whacky and it just doesn't run quite right. That last bit they mention at the end is another issue people run into when they think "bigger is better". Massively over-sized injectors do very poorly at extremely low pulse widths. The engine in mine originally specified a 19# injector and it was running in the mid-high 90% duty cycle range at full load. I bumped them to a 24# and its in the mid 80% now. Right on the edge of safety, it should probably be one size larger but I don't drive it in such a way that its really a serious concern so they probably aren't changing any time soon. Friend of mine with a fairly similar engine config that dynos within single digit horsepower to mine has 80# injectors. Apparently that specific one is well behaved at low pulse width, but it seems overkill to me. At full go he's at something like 45% duty cycle.
gwb72tii
Posts: 732
Joined: Sep 21, 2021 4:58 PM
Location: The Great Pacific Northwest

Re: please educate me on lb rating of fuel injectors

Post by gwb72tii »

ok, ok, but is there any down side or reason to not use the newer 4 pintle design from Bosch?
turbodan
Posts: 9217
Joined: Jan 09, 2007 10:19 PM

Re: please educate me on lb rating of fuel injectors

Post by turbodan »

They're fine. Motronic fires injectors in batches, against closed intake valves. Most of the fuel injected pools up until the valve opens, regardless of which injector is used.

A wider dispersion of finer droplets may pool a little less. Don't expect a big difference though.
gadget73
Posts: 1253
Joined: Nov 22, 2017 10:30 PM
Location: New Jersey

Re: please educate me on lb rating of fuel injectors

Post by gadget73 »

The later Fords ran those, but using sequential injection. They tend to have slightly smoother idle but its not a major difference. Batch fire I suspect you'd never notice.
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