Injectors to big?

VicS

Well-known Member
Location
SE Il.
426 allis naturaly aspirated. What is the down side of having inj to big. This is in a D17 antique puller.
 
Adding more fuel will make more black smoke,probably with very little gain in HP especially if your rpm's drop.Kinda like running a gasser with the choke partially closed.
 
My question for the diesel experts would be, what determines the shot of fuel, the pump or the injector?
 
High pressure diesel pumps must pressurize, time, and meter the fuel to each injector for each cylinder. While indirect injection engines work well with single hole injectors, direct injection engines usually have at least three, and some newer engines have seven or eight smaller holes for better air/fuel atomization. For years most had four or five holes, and opening pressure was about 2500 PSI for non turbo engines, and 3000 PSI was used for turbocharged engines. Most newer engines now are at least 3600-3800 PSI, and some are 4400-4600 PSI on direct injection engines. Common rail electronic systems are much higher than that even..
 
So, are you saying that pump meters the fuel & injector is the atomization factor? Just trying to learn something here, since subject caught my eye.
 
Lots of construction work around here. Lots of old rock buckets making the trips back and forth. Lots of them (black) smoked because somebody turned the pumps up higher than the engine could process the fuel-air mixture. I know Texas and the EPA have been after diesel smoking and since retired, not on the road much, so don't know what's out there today.
 
More smoke. There is only so much oxygen in the air charge so that there an upper limit on fuel delivery. Increasing fuel delivery above cylinder capacity just wastes fuel.
 
The injector is just a pressure switch. It stays open as long as there is 2500 psi or whatever the number is for that injector is for the engine in
question, with fuel pressure against it. The pump determines how long that will be. So turning up the pump turns up the volume.
 

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