Calculated load value refers to a comparison of the present airflow to the peak airflow, with the peak airflow, if known, corrected for altitude. With wide open throttle as 100%, this definition offers a dimensionless value that is not engine-specific and gives the service technician a clue as to what percentage of engine capacity is being used;
First, let’s think about typical aspiration. Let’s examine the formula in detail: divided by the maximum airflow possible at that rpm. Using a 3.0L engine, we’ll assume the following:
- At WOT at 700 pm and 100% volumetric efficiency (VE).
- This 3.OL engine could theoretically produce 20.7 grams per second at a flow rate of: 700 -2 x 3.0L x 1.18 grams per liter 60 seconds.
- In reality, most engines are only 50% volumetrically efficient at this speed.
- As a result, our maximum airflow value is 10.35 grams per second, or half of the 20.7 grams per second.
- The amount of atmospheric air pressure that is available to the engine is only around one-third (10 in. MAP), assuming a sea level BARO of 29.9 in.-Hg and an intake vacuum of 20 in.-Hg.
- Now that we have calculated the idle closed-throttle airflow for this 3.0L engine, we can see that it is equivalent to 3.4 grams per second (10.35 grams per second divided by 3).
Why Use a Calculator?
Ever wonder if a sensor is a MAF? I am aware that I have, but how do you know that further testing is warranted? You can find the answer by taking a short look at grams/second.
Using the 1:1 ratio, you can make an educated prediction. It is one gram per second for each liter of engine size. However, it’s been said that Kia/Hyundai don’t function with it very well or at all.
Use the calculator below and contrast the results with the data pid from your scan tools to obtain a more accurate comparison.
How to use calculator
- Enter engine RPM at Idle
- Enter engine size in liters.
- The calculated load is approximate with a +/-10%.
- Grams/second is approximate with a +/-10%.