More Fuel Injection Confusion

[frankendat]

I may have asked similar questions before, for some reason the information isn't sticking. Thank you for your continued tutelage.

 

There are times, between all the part hoarding, manual skimming, internet believing bullshit, which is the breadth of my Nissan/Datsun fuel injection knowledge, I return to understanding fundamentals, or more to the point, where a misunderstanding of fundamentals could create unnecessary grief. As mentioned often, I attempt my first MPFI build, modifying a Z24 to MPFI or basically, KA24E the hard way.

I still do not have a firm grasp on how this will work. My primary reason to MPFI the Z24 is to make use of oxygen sensors and throttle position sensors and fuel/air ratio sensors and knock sensors to keep the fuel/air ratios, lean but not dangerous, and operating the engine as efficient (mpg) as possible, given circumstances at the time. Auto makers are incorporating low boost turbos and/or supercharges into higher compression (around 9) engines to increase efficiency. Based on this, I have acquired a turbo and manifold to incorporate a low boost turbo. For purposes of this post, turbo details are not essential, I mention it, as it impacts fuel/air.

I assume (and assuming is often where I misstep) keeping fuel/air in the best position, the additional air from the turbo and porting the head, will require additional fuel. This guy: https://www.autospeed.com/cms/a_0349/article.html

Makes the claim that stock injectors can be run +20% by increasing fuel pump pressure. I like this idea because I already own 8 stock injectors, but thinking about the injectors, starts the mind avalanche.

By CC’ing the combustion chamber and knowing the volume of fuel introduced by the injectors, and the volume of air (forced or otherwise) fuel/air ratio is born. In theory, this process it trackable and understood by an ECU. The ECU, then adds/subtracts fuel or air intake, to keep operation, as efficient as possible. HOW IS THIS ACCOMPLISHED or HOW IS FUEL/AIR MODIFIED DURING OPERATION? I have gone over the parts in detail and have found no armatures or electronically controlled orifices, that would provide a method of increasing or decreasing fuel flow. For air flow, it seems if boost is set to 5lbs, if under 5lbs it is regulated by the engine speed and  if over 5lbs boost is reduced by blowoff or forced recirc. But, mechanically controlling boost, in that matter, seems inefficient and analog compared to ECU control. My last thought is that injector production is tied to electric current flow, which is controlled by the ECU. Is this also true, and if so, is it also true for the pump?

What am I missing?   

[Z23T]

Knowing what type of ECU and components you are planning to use will help people answer your questions with more accuracy. 

 

In the most basic of terms electronic injectors change the amount of fuel they flow by the ECU altering the pulse rate, or the time the injector is open. Many other factors will change the amount of fuel injected, like the flow rate of the injector, the amount of fuel pressure the regulator allows in the fuel rail, and the ECU taking input from the various sensors, like temperature, airflow rate, a throttle position sensor, etc. 

 

I suggest you buy a book like the one listed in the link below and educate yourself on fuel injection systems. I know it says Bosch fuel systems, but most car manufactures use systems that are basically the same as what Bosch has developed.

 

https://www.amazon.com/Bosch-Fuel-Injection-Engine-Management/dp/0837603005

 

 

 

[frankendat]

11 minutes ago, Z23T said:

Knowing what type of ECU and components you are planning to use will help people answer your questions with more accuracy. 

 

In the most basic of terms electronic injectors change the amount of fuel they flow by the ECU altering the pulse rate, or the time the injector is open. Many other factors will change the amount of fuel injected, like the flow rate of the injector, the amount of fuel pressure the regulator allows in the fuel rail, and the ECU taking input from the various sensors, like temperature, airflow rate, a throttle position sensor, etc. 

 

I suggest you buy a book like the one listed in the link below and educate yourself on fuel injection systems. I know it says Bosch fuel systems, but most car manufactures use systems that are basically the same as what Bosch has developed.

 

https://www.amazon.com/Bosch-Fuel-Injection-Engine-Management/dp/0837603005

 

 

 

Excellent information, thank you

[datzenmike]

The ultimate arbiter of fuel/air ratio is the O² sensor input to the ECU. For part throttle or cruise, stylometric and even lean is the order of the day and if throttle is closed under deceleration conditions there is no need for fuel at all. Part throttle lean isn't near as dangerous as full throttle lean. Stock ECUs have built in parameters that guesstimate the injector pulse and this is confirmed by the 0² and additional adjustments added if needed. Under full throttle, the economy fuel map is thrown out the window and richer is preferred to protect the engine and give the best power.