Basically the stock AFM will max out around say, 250hp.. which is pretty crummy.. with a larger turbo, exhaust, intercooler etc, I find it was being maxed out at 12 psi.. sure you can just get the ECU's 'boost cut' removed, but its just guessing how much fuel to put in after its being maxxed out.. plus its a flow restriction in itself, in terms of the size of the thing..

So I went about replacing mine with a 76mm RB20DET AFM.. its only a wee bit smaller than the 300ZX unit (which is capable of reading a flow up to 550 hp apparently), I'm not interested in going anywhere near 550 hp at this stage.. plus the RB20DET AFM is more than suitable for the purpose and is about a third of the price of a 300ZX AFM.. simply because the 300ZX AFM's are in high demand.. (I've seen them sell quickly for $350)..

Yes.. replacing the AFM requires alot of re-tuning.. and dyno time etc.. its an expense and a half.. thankfully I'm rather good for a novice when it comes to tuning.. and I've got my car running with the new AFM on my own.. about a day's work of getting the mixtures right and running the car around the block.. numerous times..

My next plan of attack is to get the car down on a dyno and get it all perfect.

I beleive the Wiring of the RB20DET unit to be exactly the same as the 300ZX, as I used 300ZX AFM pin assignments to get things going..

Basically, on the new AFM, the pins are like this
 

Pin	Assignment
A	Nothing
B	Air Flow Signal
C	Ground
D	Ground
E	Positive

Note: C and D have continuity between the two, they're the same thing..)
(The only wires worth worrying about are B,C,E.. only three out of 6 pins!)

On the CA18DET AFM, its like this..
 

Pin	Assignment
A	Independant Ground
B	Positive
C	Ground
D	Air Flow Signal

(The only ones we'll need to worry about with wiring it up to the new AFM, is B,C,D)

So it went like this.. Pin A on BOTH is IGNORED.

Pin B on the current feeds E on the new.
Pin C goes to either C or D on the new.
Pin D goes to B on the new.

Btw, if you buy a new AFM, the bloody plug to connect to it would be handy.. I'm still looking for one!

These two pictures are to try and compare the size of the two.. the RB unit is on the right of course..

Sure it took a bit of fucking around to fit it.. but hey.. works a treat.. I scratched off the rb20t labelling later :-)

Check out the EPROM page for how to adjust the computer to suit.

If you have any further questions, I might be able to help - Reach me here - Boostcruising.com Forums