Air Flow Meter?

What is an air flow meter in a gt-r? What are they for, and when should they be replaced and why?:confused:

The air flow meters measure the amount of flow of air between the intakes (or intake box stock)
and the turbines. It tells the computer (in conjunction with a plenum temp sensor) how much air you are
trying to shove in the engine....and directly controls how much fuel the computer decides to push into the
cylinders. The GTR meters use a voltage to heat the tip of a sensor, which is then cooled by the flow of air.
How much the tip is cooled determines (theoretically...but very close) how much air is being drawn through.
It's recommended they are changed every 30-45000 kilometers on a tuned car. If you don't change them and they go
bad here's what happens..(it happened to me:)) If only one fails, the computer gets confused and cuts the fuel it
sends to the engine....so the car sputters (it doesn't die because USUALLY the sensor has partial failure...ie the
signal is sporadically sent). This really sucks because the car doesn't put out enough power to go anywhere....and
you have to keep your foot on the gas to keep it running....if you let off....it dies. If BOTH meters go, it's a little
better situation in my mind.....the computer goes into protect mode and it cuts fuel above 3450 RPM (or 3250...something
like that). So you'll accelerate but as soon as you hit 32/3450 the fuel will stop, but when it drops below 3200, it comes
back. So you just have to accelerate slowly (but at least the car still moves and it doesn't die on you when you let go of
the gas.

As an addendum, if you're buying new ones...you might as well buy the AFM from the TT 300ZX. They're bigger and allow more HP!

Thanks for the detailed descripition. How much would it cost to get replacements for my gt-r. Gt-r AFM's or 300ZX ones? My car has around 36,00 km on it now. I would like to replace them here in japan before I bring my car to the states. Also, I have been thinking about some used HKS 2530's (the internals have been replaced with new ones). I'm not looking for nothing big in power gain, I just will feel better having steel turbo's vice the ceramic ones. I would hate to have the ceramics break someday and get injested into my engine! Thanks again!

If you are not looking forbig power gain, IMHO, you should not put in the 2530s. It will just induce lag and reduce low end torque considerably. The stock ceramic turbos are strong enough to withstand 1 bar (14.5 psi). I had used it before at 1.02 bar for everyday driving with track duty once a month (when the car was always at full boost!) and there was no problem at all! When they were replaced with 2540s later, there was no apparent damege at all. Just take care of it well - allow it to cool down before switching the engine off and replace the engine oil every 5000km - I think they will be okay!

....if you REALLY want aftermarket turbines...you're better off going with the HKS 2510's...which are "Stock replacements"...