no bov, afm on i/c piping ?

[Bo0sT_JuNkY]

I used to have a turbosmart bov on my car with the spring set to "hard" i used to get a fluttering noise when backing off under low loads.I now have a stock bov which runs better but has a gay shhh to it.Now if i blank off the stock bov and run the afm on the i/c piping will i get the vl sound of "po po po".Ive heard that running the afm on the i/c is better as it gets a reading of the air flow ,temp after the effects of the intercooler.But mainly i want a more aggressive noise for the cool factor .Mods are 14psi,pod,large fmic,safc on a rb25.

[Sydneykid]

Hi Bo0sT_JuNkY, what you are describing sounds like no BOV at all. If that's the case then where you have the AFM is irrelevant. You can test this by disconnecting and blocking off the boost feed line to the BOV. If you like the noise, then that's it.

[browny]

From Warspeed:

O/k guys, there seems to be some confusion here about how these things actually work.

The proper name for one of these devices is "a hot wire anemometer" and they measure air velocity.

There are actually two hot wires, but you can only see one. One is mounted near the middle of the moving air-stream, and a second one is mounted within the mounting stalk. The second hot-wire is immersed in the air-stream, but is located in still air.

An electric heating current flows through both wires, and this current heats both wires. Now as the wires become hot the electrical resistance of the wire changes.

If there is zero airflow, both wires will reach equal temperatures, and the voltages and currents in both wires will be identical. The electronics senses this, and outputs a zero flow signal voltage.

Because there are two wires, they will always be at the same temperature, even though the ambient temperature may vary very widely. That is why there two wires to cancel changes in ambient air temperature.

Now when there is air movement through the flow-meter, the wire in the air-stream cools down slightly, because the moving air carries away some heat. This causes the electrical resistance of the wires to be different (because one is now hotter than the other).

The electronics senses the difference, and feeds more heating current into the colder wire to force the temperatures back to being the same. The amount of extra power fed to the cooler wire (located in the moving air-stream) is the actual flow-meter output signal.

There is a very sensitive amplifier to detect even minute differences in the wire temperatures, so air velocities over a very wide range can rapidly bring the wire temperatures back to equilibrium.

Now if you place the hot wire anemometer in a tube of known cross sectional area, it becomes a flow-meter. A known flow will create a known flow velocity, which equates to a certain signal output voltage.

...and...

Another interesting characteristic of these things, is that they are sensitive to air density. At high altitude where the air is thinner, less heat will be removed by the flowing air from the hot wire. So the flow-meter automatically shows less airflow when the air is thinner. A useful characteristic.

The crux is that the Nissan AFM's give a reading that is independant of temp and pressure and from a flow measuring perspective it shouldnt really matter where it goes. Consider tho that the AFM is plastic and so you may want to be careful about putting hot pressurised air through it.