Hi
I was wondering how to calculate the airflow rate,without knowing the VE of the engine.I know that Airflow Rate=(RPM*VE*MAP)/Temperature.Since the VE is the actual amount of air being pumped by the engine as compared to its theoretical maximum and actually i'm trying to calculate the actual amount,i don't get how can i use the formula above?.Any ideas?
Only through empirical measurement or very advanced mathematical and physical modeling. The empirical measurement I'm talking about is what you'd usually call "tuning" :-)
Also note, VE is not a number, it's a curve depending on many factors.
.I was thinkig,that would be easy but...Perhaps the easiest way for this task is to use a MAf with known characteristics, i mean output voltage versus airflow ,or i'm wrong again?
I use a formula I found in a tuning book of mine to calculate mass flow at certain rpm and load percentage. I mainly use it for idle but so far its been very close to what I've seen.
To expand on what I stated also that is at 100% load
at idle one is not gonna be near 100% load
normally depending on engine and whats being used, AC\heater\etc
Load will be between 14% to 25%
so I said 7.01lb\min at 100% load
take the airflow and mutiply it by your load %
7.01 * .14 = .9814
.9815 lb\min = 6.94298721 grams a second
so around 7 grams a second you will see with a 300 cubic inch ( 4.9l ) motor at a 14% load around 1000 revs at idle.
I found using this I get very close to tuning maf based setups
showMANiak wrote: .I was thinkig,that would be easy but...Perhaps the easiest way for this task is to use a MAf with known characteristics, i mean output voltage versus airflow ,or i'm wrong again?
You can try that but its very hard to do it properly without actually using it as well for the fueling in the system. They are highly dependent on how they are setup due to airflow past the sensor. Changing a pipe to a smaller or larger one or any bends before and after effect the output of the sensor a lot.
So without knowing for sure the best way is to use it with the ecu. so if you set fuel at lambda 1 and air measurement is 3 grams at idle and your o2 sensor is reading lambda 1 you know are pretty much right at 3 grams at idle at that load %.
.I was thinkig,that would be easy but...Perhaps the easiest way for this task is to use a MAf with known characteristics, i mean output voltage versus airflow ,or i'm wrong again?