Head flow rating....

[JoshPeters]

Ok guys... . here's what I'm wondering.



If I was to take a mass air flow sensor from a car. Put 12v power, ground and hook up the signal to an O-scope seal it to the head face surface. Take an Air regulator and air hose seal it to the... . lets say intake side of the head. Take the intake valve out and leave the exhaust valve in. Then add lets say 40psi of air to the intake side. You can now measure in voltage how much air is passing through. Disconnect... . lets say, start porting that intake runner. Hook everything back up and do the same test again. Couldn't you achieve the same results as a much more expensive flow bench?



The Mass air flow sensor uses a hot film, that changes resistance when air passes over it, as the resistance changes, so does the voltage. If only so much air can pass through the port, then you should get A: voltage. After modification it should pass more air giving it B: voltage.



Am I thinking this through properly, or am I missing something?



Josh

 

[RDupree]

the way you flow a head is with the valve in,you check flow at different lifts,100,200,300,400 thousands etc. you want to make sure you have a good balance,just because it flows good at . 200 don't mean it will flow good at . 400... get it?

 

[JoshPeters]

Gotcha! That's easy enough to do.



Thanx!



Anything else I should know?

 

[KBennett]

It sounds like a great idea but I think you need more electronics. The way I understand a MAF to work is that the temperature of the heater(film, wire, etc. ) is constantly being measured by the ECU. If the temperature drops the ECU supplies more current to the heater to keep it at the same temperature. The flow is calculated on the amount of current needed to keep the heater at temperature. Remember that the incoming air temperature will affect this measurement so the ECU is probably factoring this in.



You probaby won't need an oscilloscope to take the measurement. A good digital meter with a high input impedance should do the trick.

 

[JoshPeters]

Good point. When I do testing at work, all Benz asks for is a straight voltage reading. There is a temperature sensor built into the sensor, but I'm not sure if or how it would change the reading. Being it would be a constant in this experament, I don't think it would be a factor.



Josh

PS, now that I think about it. The sensor I have sitting on my tool box is a changing voltage type sensor. I can read the output with my DVOM. I was thinking my O-scope would be more accurate, but you are correct a DVOM would work just as well.