Maxed AFMs in GTR - Alternatives to Z32s?

[Sydneykid]

So the smaller throat diam of the GTR AFMs makes no difference.

Another thing a friend did, that i also see on Jap cars is remove the hot wire sensor from wahtever AFM you are using and simply drill a hole in your inlet pipes to suit. Some good resin to seal it, onto the pipe, and away you go.  

If i go twin with RB26 head thats all i was going to do with the Z32 or Q45 AFM with the std RB20 Pfc.   But i was going to try and put the full AFM in the pipe from the intercooler to Inlet plenum, figured the AFM may even read more accurate as it is sensing the cooler air post intercooler...would have to extend the wiring though...ppls thoughts?

If you relocate the AFM hot wire sensor into a larger diameter pipe then it will show lower air speed (therefore lower voltage) for the same volume of air ingested. It isn't quite linear, but simplistically, if you take an RB20 AFM hot wire sensor and stick it in a 90 mm housing it will show around 4.0 volts at the same airflow that it showed 5.1 volts in the original 80 mm housing. The problem is at idle it will show 1.0 volts instead of 1.3 volts, and that may be too low for the ECU to use.

That is the main reason why the Z32 AFM upgrade is popular, they show almost exactly the same voltage at idle, the advantage is they tapper off as the airflow increases. As I said not a linear change.

I have seen a couple of cars with airflow meters in the pipework from the intercooler to the plenum. Most usually the 90mm Q45 AFM's. The problem with doing it seems to be mechanical as they are plastic and the inlet flange (where the airfliter box usually bolts on) is not very strong. They also seemed to have additional retaining methods (epoxy and bolts) holding the hot wire sensor in place. Obviously being under boost, you can't afford to have any leaks.

This is also quit effective if you locate the BOV before the AFM, that way you don't get the sudden spike of richness when the BOV vents.

Have I opened Pandora's box enough?

[pnblight]

you can buy z32 afms from REPCO and the like, cheap there a std bosch part and the plug is also std bosch part I would think you could get them around $380-390 ea(with plug)NEW, as i got two cheaper but only cos i know the guy.

the rb20/25 afm is an excellent upgrade an better than the z32 up to around 530rwhp

,its only if you are going to go more than 530rwhp would i suggest buying z32

(keep in mind i'm talking for a GTR)

[[[d a n n y]]]

so...

the RB20/25 AFM's have a bigger scale than the RB26 afm's?

is that right?

so two RB20/25 AFM/s are better than two RB26 AFM's?

[pnblight]

yes larger scale (std afms~400rwhp to rb20/25 540rwhp)

and larger size 80mm(std 65mm) less restriction then std afms

(same physical size as z32)

same plug as std so will plug straight in but you will need to change pfc setting and you should aways check on dyno for safe air/fuel ratios as it uses slightly different load points from the mapping

ps i de-screened mine as well to flow better

hope that helps

pete