80mm AFM's

[MidnightGTR]

Heyas

Just wondering are Rb20 80mm AFM's as good of an upgrade as Z32 ones or would I be wasting my time?

I understand they are both 80mm but I dont understand how the voltages work, I think the rb20 have a lower voltage or something?

Just asking as rb20 AFM's seem to be alot cheaper then Z32 ones.

Thanks

[MidnightGTR]

Forgot to mention the mods, I got a PFC and HKS 2540's and a few other little pieces going on soon.

[Cubes]

I measured the internal diameter of the RB20 AFM and its only 70mm.

I always thought they were 80mm also.

I've had a S1 RB25 AFM on my car, it ran perfect and was the same size side by side. (I didn't measure them at that time)

Reason I decided to measure the AFM is i've been having a few idling issues so I decided to slap the Mesh back in. And what do you know.. A Perfect idle at 600rpm, no more hunting or popping.

[MidnightGTR]

Yeah I think I read in a magazine or two that they were supposed to be 80mm, not to worry.

thanks anyway

[OREX]

yeah you're right the voltage on the RB20 AFM is lower than a Z32 unit. something like the impedence (ohms) of the afm being lower makes them melt internally when you wind up massive power. some crap like that. steer clear of them.

[Sydneykid]

Hi midnightGTR, RB20/25 and Z32 AFM's are all 80 mm OD, that's outside diameter, not ID that's inside diameter. There is no real difference between an RB20 and an RB25 AFM. On the other hand the Z32 AFM is calibrated differently, so at the airflow the RB20/25 AFM shows max voltage, ~5 volts the Z32 afm is only showing ~4 volts. This means when the airlfow gets higher the Z32 can still show voltage increases to the ECU.

Q45 (Infinity) AFM's are 90 mm (OD), so they have the same calibration advantage but they are also larger in diameter for less restriction.

Hope that helps.

[Roy]

yeah you're right the voltage on the RB20 AFM is lower than a Z32 unit. something like the impedence (ohms) of the afm being lower makes them melt internally when you wind up massive power. some crap like that. steer clear of them.

I think you will find they are a good upgrade for a GTR pumping out reasonable amounts of power. Basically the difference between the Z32 and RB20 AFM will be for a given cfm of airflow, the RB20 AFMs will read a higher voltage, which depending on your hp could be a problem when it comes to tuning. (if the AFM goes out of range then there is no way the ECU knows how much fuel to inject, but can still be tuned around)

So if you have the std crappy 65mm GTR AFMs then RB20 units are a much cheaper upgrade then Z32s, and equally as capable provided you arent running huge power (i suspect the power figure would be + 350rwkws but GTR owners would know better then me)

[Sydneykid]

Hi, I have posted this table a few times, but just in case you missed it.

Air Flow meters RWKW & Engine BHP

------ ---- OD ---- RWKW ---- RWKW ---- BHP ------ BHP

No of AFM's ---- ------- 1 -------- 2 -------- 1 -------- 2

RB26 ------ 65 ------ 149 ------ 299 ------ 271 ------ 474

RB20/25 --- 80 ------ 226 ------ 453 ------ 376 ------ 683

Z32 ------- 80 ------ 255 ------ 511 ------ 415 ------ 763

Q45 ------- 90 ------ 302 ------ 605 ------ 479 ------ 890

Please note that this is only an indication, every engine is different and tuning makes a big difference.

[jezzrrr]

Gary,

Are they the limts for each meter ?

Jeremy

p.s. the KW's are still bigger over here :-)

[crack]

it would seem to me that an upgrade to r32 afm's would be a good thing. on an r32, one 80mm afm was sufficient for reading airflow for six cylinders. on an rb26 that was upgraded with r32 80mm afm's, each afm is only measuring airflow theoretically for three cylinders. depending on how full on the rb26 is, i don't think you would ever max out the r32 afm's.

thats just my thoughts on how it might work.

[Sydneykid]

Are they the limts for each meter ?

The first column is RWKW for 1 X AFM, the secomd column is RWKW for 2 X AFM's, the third column is (engine) bhp for 1 X AFM, the fourth column is (engine) bhp for 2 X AFM's. :idea:

Hi Crack, as per the table, 1 X RB26 AFM is good for 149 RWKW. whereas 1 X RB20/25 AFM is good for 226 RWKW.

[Sydneykid]

Are they the limts for each meter ?

The first column is RWKW for 1 X AFM, the secomd column is RWKW for 2 X AFM's, the third column is (engine) bhp for 1 X AFM, the fourth column is (engine) bhp for 2 X AFM's. :idea:

Hi Crack, as per the table, 1 X RB26 AFM is good for 149 RWKW. whereas 1 X RB20/25 AFM is good for 226 RWKW.

[MidnightGTR]

Thanks for that info guys

So I would be better off going to rb20 afm's then sticking with the factory ones. Then if i ever maxed em out I could go to the Z32

[MidnightGTR]

Oh what are the Q45's from? Ive never heard of them before... can they be sourced second hand or a bit harder to find?

[Sydneykid]

So I would be better off going to rb20 afm's then sticking with the factory ones.

Only when you have reached the standard AFM's limits, ~300 rwkw.

Oh what are the Q45's from

A Q45 is a Nissan Infiniti, 4.5 litre V8, only has 1 X AFM so its a biggy. :aroused:

www.infiniti.com

Doughboy has some for sale I think, check his trader add in the "for sale" section.

[The Alchemist]

Hi guys, to elaborate a bit further on Sydneykids post, with a power FC you can simply "change" AFM at the press of a button. You only really need to do this once you past the max power rating Sydneykid stated on the above posts. Going for a "too big" an AFM like a 2x Z32 meters on a GTR with no other mods can lead you to be using less of the load map and therfore less tuning resolution than if you stuck with the std GTR meters. Also as far as a "restriction" goes has anyone ever measured the GTR turboes std compressor inducer? Its certainly much smaller the a Z32 AFM or even the std GTR meters.

Even an HKS 2530 only has a 47mm inducer so putting on huge AFM ain't going to make more power as far as restrictions go.

But like Sydneykid says 300kw or a bit more going to a set of RB25 meters will give you that extra mapping resolution that you need at higher CFM's without going overboard.

Mike

[GTRgeoff]

Considering alternative AFM's, I recently discovered that SR20 non turbo throttle bodies are larger than the SR20DET. The guy bought one from the wrecker I was at for about $80 and understood it was worth a few kW on his S14 SR20DET.

Getting to the piont though, is the SR20 AFM also larger, or is it the same as SR20DET which I would assume is close to RB20DET/25DET?

[DoughBoy]

At 300rwkw the Q45 was only at lvl 16 on the PowerFC map, so I'd say they've got a fair bit more resolution in them.. .more like 350-400rwkw.

[Penfold]

Just wondering what the whole process of installing Z32 or the RB20 in a GTR is. Obviously changing the size 65mm to 80mm will require filter adaptors and the adapted plugs. Tried to find some info but couldn't track it down in the forums. Say you had the HKS pods do you need diff piping??

Cheers,

Penold

[Sydneykid]

Just wondering what the whole process of installing Z32 or the RB20 in a GTR is.  Obviously changing the size 65mm to 80mm will require filter adaptors and the adapted plugs.  Tried to find some info but couldn't track it down in the forums.  Say you had the HKS pods do you need diff piping??

Cheers,

Penold

Hi Penfold, the rubber pipes from the turbos will stretch over the 80 mm, just be careful and use some lubricant. The best way to fit airfilters is to buy a pair of 80mm PODs, since that is RB20/25 size, they are easy to get. Then sell the 65 mm ones and get some of your money back. The plugs are different so make sure you get the 80 mm AFM's with plugs. I wire the 80mm AFM's connectors in parralel with the standard 65 mm AFM's connectors, as it is easy to swap back to the 65mm AFM's if you have any problems.

Hope that helps:cheers: