I have been searching but have not been able to find information relating to the difference in electrically operated fuel injectors.
I understand that there can be a difference in flow rate. (And I would love to find data which would allow identifying the flow rates of various injectors and/or manufacturer's specs)
Other than differnces in flow rate, I am a loss to explain why there are so many different injectors, why sometimes the same injector may be used on engines of different capacity and why similar or nearly identical engines may use different injectors.
What characteristics does an injector have other than flow rate and duration of opening (controlled by the computer)?
"Dirtroadie" wrote in news:1124551438.304651.130440 @z14g2000cwz.googlegroups.com:
flow volume, coil voltage, spray pattern and mounting differences is the only thing i can see as unique for applications. it would be nice if they were all the same but i have wanted that (generic except for length) on something as simple as wiper blades for years. it will NEVER happen. 'unique' keeps prices up..........kjun
Well, yes, feed pressure would be another variable, since most injectors for gas engines are little more than valves that open and close and feed a spray of lightly pressurized fuel (~40 psi)into a low pressure area (the intake manifold.
Diesel injectors, of course, operate differently since they must force fuel into a cylinder somewhere close to the point of maxiumum compression (~250-400 psi for typical diesels). So diesel injectors need not be a part of this discussion.
I guess ultimately what I am wondering about is how well a typical ECU (computer) can compensate for a change in injectors. In theory it would seem that such compensation would be very straightforward as long as the injecctor had (1)a sufficient flow capacity for the top end and (2) did not require too short a pulse at the low end.
Electronic fuel injection is what made fuel injection possible for the mass market. The last carburetors were actually electronically controlled also.
The problem has always been how to measure the exact amount of fuel to add to gasoline, which must be added to the WEIGHT of air entering the induction system. While there were a number of ways to measure the VOLUME of air entering a system, WEIGHT is much harder.
Carburetors in the fifties through seventies were marvels, actually containing fluidic computers to try to convert volume flow into weight (mass) flow, and they did a reasonable job, but not perfect by any means. To obtain full benefits of FI, one had to do a better job. Except in racing engines, which could be run very rich, this was very hard to do. The first electronic fuel injection systems actually had an analog computer as part of the system- very expensive.
When digital electronics became widely available at reasonable prices, it solved this problem reasonably well. Remaining carbs went electronically (digital) controlled, EFI went digital, and the rest is history. As EFI was becoming a consumer product, different methods of mass flow rate, oxygen sensors, cheaper temp sensors, etc. were developed too. Modern EFI does an amazingly good job at controlling mixture, with of course, feedback from oxygen sensors. So it is a closed loop, servo controlled system.
Room for improvement? Sure. Weak link is oxygen sensor. The so-called transfer function curve from existing ones is funny shaped, and not conducive to good servo control. People are working hard on that problem, or at least were when I retired, and I assume they are continuing.
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