techanical maf/injector question/theory

[Brandon11010]

technical maf/injector question/theory

Alright so heres what i know, im running 344 horse 360 torque on my 89 5.0.. Now according to the math for fuel injectors im running at over 90% duty cycle on my 19lb injectors which isnt exactly ideal.. Now my maf which is after market 75mm i believe,calibrated for 19lb.. I got ahold of a set of 24's which would be a bit better for my application, but heres where i lose my understanding.. If im not mistaken a stock maf is 55mm.. now when i installed my 75mm maf i then changed the velocity in which the air flows over the hot wire, the less velocity of air passing over the hot wire changes the voltage needed to maintain the correct temprature of the hotwire which would send a different signal to the pcm for load calculations and fuel delivery correct? and that bring me to the injectors, even if i installed 24lb injectors with a maf calibrated for 19lb, wouldnt they oxygen sensors adjust duty cycle on the injectors to get the correct air fuel ratio? providing that fuel trim isnt maxed that is..I know iv read everywhere that maf and inj need to be calibrated but i kinda wanted to dig a little deeper..

 

[ID89GT]

Just because the opening is bigger don't mean the electronics are any different. You will need to buy a maf calibrated to 24's if you decide to upgrade to 24 pound injectors.

 

[Brandon11010]

But if you have a change in air velocity over the hotwire it would change the signal sent to the pcm from the hotwire, and thats what i read all they time.. but do you know the details? such as why wont the o2 sensors have the pcm change the duty cycle of the injectors to get the correct a/f ratio reguardless of the flow they are rated for.. if your o2 is reading a lean condition they are going to send a signal to the pcm to increase the injector on time to get the right ratio..right?

 

[ID89GT]

Haha you are confusing me with all the technical stuff. I just know the mafs are bigger in diameter so they don't serve as a bottleneck for air travelling to the engine. But the electronics is what makes it calibrated for the injectors.. but after thinking I remember the whole thing with the sampling tubes and such that you change.. Gah now I am second guessing myself lol

 

[Brandon11010]

lol yea i get all the basic stuff about restrictions and calibrations and everything i can read on here, but it doesnt add up when i really think about how the system as i know it works

 

[Mustang5L5]

Yes, the o2's will technically adjust. The prob is over 3000 RPM, when the EEC ignores the o2 inputs and you will start to run rich.

Compensating with sample tubes is the incorrect way to do it these days anyway. It was great in the 90's when that's all we had, but the proper way to adjust for injectors is with a chip, or through the computer (93 cobra ECU).

 

[HISSIN50]

This is one reason why meter electronics and housings should be thought of as married pairs. A meter tags a given volume of air flow with a voltage, and this dynamic is tuned and calibrated for each meter family.