Originally Posted by hcompton
Using Some plex in a 4 or 5 inch circle. With the head on top and the shop vac under neath. Then you can use strings and smoke to tell how things are flowing. Strings are really important for flow bench testing. And you dont need an expensive meeter and test unit that will not be acurate from day to day.
If you use the maf be sure to use a regulated power supply that can produce the same 12 v everytime. If it delievers more volts when it gets more volts it will screw the readings. Everytime you wife turns on the dryer you port work will be better. One of the main reasons home made flow benchs dont really work cause ypu need lots of tech equipment to support the meeter and reading of the meeter.
String always works if a little low tech. Also works great with smoke.
thanks for pointing that out osmetimes i forget not everyone will know what i know and how to check stuff
with the maf style flow bench ur readings can very well channge from day to day so its important if u dont finish in one day to go back and re measure a port u have done so ur ports u still have to do come out to the same number.
the 12 volt supply isnt as importnant as the 5 volt , the 5 volt is what gives the readings , normally the cars ecm supplys the 5 volts to the maf this way if it reads a lil high or low on the 5 volt line the ecm can compensate
in the case of a flow bbench if u have 5,2 volts one day and then 5.4 volts the next day ur results will read artifically high . so each day of testing or when changing from port to port its just as important to stick the dvom on the 5 volt line to make sure voltage is the same from port to port.
if not u can just see what the difference is and add/sub it from the reading u get when taking the flow measurements.
u can always buy 2 cheap vlt metters as well and ties one into the 5 volt feed line permantly and then the second onto the 0-5v output of the maf so u have constant readinsg of both lines
the 12 volt feed is used for the heating of the maf, the 5volt side is were the actual readings take place