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Q45 AFM GTR Compatible?

ALL GTR

By ALL GTR,
in Engines & Forced Induction

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SLK-GTR Community Regular

SLK-GTR

Posted
Posted

i was looking at fitting a pair of Q45's to my GTR but i spoke to a few people about them and they said they were was to big and would be an asshole to tune, in stead i got a pair of nismo AFM's instead they fit straight up to the standard piping and plug straight in, there a little dear but a straight fit. 80mm same as z32

Sydneykid Grand Master

Sydneykid

Posted
Posted

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

Rule of thumb for 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. For example, I have seen a GTR equiped with twin Q45 AFM's make 1100 bhp.

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

pnblight Mentor

pnblight

Posted
Posted

sydneykid your on it ,to for application up to 450rwkw the rb20/25 are a better afm because of the better sensitive ie air flow to voltage change . Only once you need more hp does the z32 come into its own and really how many car are in this league ?

Sydneykid Grand Master

Sydneykid

Posted
Posted
So should I keep the Q45 for when I go a T51 or T88 or invest in a Z32.

What I want to really know is if this is goin to be alrite to tune or should I think about another angle??

If it's a GTR you really need 2 X AFM's to match the ECU requirements. So I take it you are asking if you should run 2 X Q45 AFM's or 2 X Z32 AFM's. Well the answer is in the table, if you are intending to run more than ~800 bhp then 2 X Q45 AFM's would be my recommendation. If you are intending to run less than ~800 bhp then 2 X Z32 AFM's would be my recommendation.

If you want to run the 2 X Q45 AFM's on the road, the engine will need vary carefull tuning. Two 90 mm AFM's do not have very much airlfow at low rpm to meter, so they are tricky to tune. If you have big cams they get even harder.

You should also be aware that getting a "Y" inlet (to connect 2 X AFM's to 1 X turbo) for 90 mm AFM's can be tricky. I have only ever seen one. On the other hand a "Y" inlet for 80 mm AFM's is relatively easy to get. Greddy, for example, have them off the shelf.

Hope that helps :D

Sydneykid Grand Master

Sydneykid

Posted
Posted
SK your table is not correct, Z32 afm is fine for 330rwkw

EDIT: I know you posted its only a guide but maybe the single afm hp rating for Z32 and Q45 could be bumped up a but?

Hi BU5TER, it is only a "rule of thumb" minimum. If the engine is not using its airflow efficiently then the AFM flow rates are accurate. An "efficiently" tuned engine, with the right parts balance, will exceed the minimum. But if I used that, too many cars wouldn't make it, so I would much rather be conservative. :D

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