PFC Readout (pic) I guess I need a bigger AFM?

[The Mafia]

Well, I was wondering why the engine light was coming on at 6500 RPM for a half a second so I consult to the PFC manual, and it says that detonation is 3 quick flashes.

Reading a little further and it reveals that the air flow meter is maxing out if it comes for a half a second at and part of the RPM range.

heres the pic (taken with my phone in the dark, sorry about the lack of quality)

As you can see, I have half then fully nailed it, changed gears, then backed off. The Left hand side of the graph is 5.0 (5.0 volts) and that little bar scraping along the bottom is the knock level.

Don't you just love the monitoring of the powerfc?

I think its awesome for diagnosis.

Ok, so apparently when the stock airflow meter hits 5.0 volts, it maxing out?

Do I need a bigger one like a Z32?

My car -

FMIC

Custom split Front and Dump pipe all on one

3.5 inch exhaust with high flow cat and 4inch cannon

NGK irridium tip plugs (.8mm) (these are pretty damn good, they don't get dirty)

And of course, a Power FC.

[Birnie]

I'm no expert, but if you haven't even boosted the car up a bit, a can't see how your are maxing out the airfow meter????

Nearly everyone is boosted to around 10-12psi (I'm on 10) and I haven't heard of upgrades for that for those levels.

Is there some sort of set up within the Power FC for which meter you are using, maybe u picked the wrong one???

Guessing of course bt doesn't seem right to me.

[The Mafia]

I'm no expert, but if you haven't even boosted the car up a bit, a can't see how your are maxing out the airfow meter????

Nearly everyone is boosted to around 10-12psi (I'm on 10) and I haven't heard of upgrades for that for those levels.

Is there some sort of set up within the Power FC for which meter you are using, maybe u picked the wrong one???

Guessing of course bt doesn't seem right to me.

I am running 10psi... Should the stock AFM be able to handle that?

Weird.. ?

Anyone else

[Sydneykid]

Hi Mafia. boost is really irrelevant, it's increased airflow that causes the AFM to exceed its maximum voltage (5.1 volts). My rule of thumb is 240 rwkw, that's where I start looking at upgrading the RB20/25 AFM, the Z32 AFM is good to around 320 rwkw. It's the same size (80mm) as the RB25 AFM, so it isn't really "bigger". It is calibrated so that it shows around 4 volts at the same airflow as the RB25 AFM shows 5 volts. So you have another 1 volt to tune with.

You don't have too much of a problem yet as it isn't sitting on 5 volts for long rpm durations. If you have higher power asperations, then its time for an AFM upgrade.

Hope that helps

[The Mafia]

thats weird, cause I have only about 150 rwkw at the moment.

I wonder why the hell its maxing out?

I have a pod filter (k&n) and an inceased turbo to pod pipe (stainless with partition)

Maybe there needs to be a correction set in the powerFC ?

[Birnie]

Hi Mafia. boost is really irrelevant, it's increased airflow that causes the AFM to exceed its maximum voltage (5.1 volts).  My rule of thumb is 240 rwkw, that's where I start looking at upgrading the RB20/25 AFM, the Z32 AFM is good to around 320 rwkw.  It's the same size (80mm) as the RB25 AFM, so it isn't really "bigger".  It is calibrated so that it shows around 4 volts at the same airflow as the RB25 AFM shows 5 volts.  So you have another 1 volt to tune with.

You don't have too much of a problem yet as it isn't sitting on 5 volts for long rpm durations.  If you have higher power asperations, then its time for an AFM upgrade.

Hope that helps  

I was going to try hard at contradicting this thread and then i saw "Sydneykid" :Oops:

...anyway, sureley the more you boost, the more air the engine is chewing etc. therfore more airflow. I mean, how do you get to 240 rwkws anyway...and then 320. probably by boosting it to 15psi and then 25psi or something and needing more airflow, and bigger airflow meter.....thats what i thought anyway.

:headspin:

[Birnie]

or better calibtrated meter i should say..oops

[Sydneykid]

I was going to try hard at contradicting this thread and then i saw "Sydneykid"  :Oops:  

...anyway, sureley the more you boost, the more air the engine is chewing etc. therfore more airflow.  I mean, how do you get to 240 rwkws anyway...and then 320. probably by boosting it to 15psi and then 25psi or something and needing more airflow, and bigger airflow meter.....thats what i thought anyway.

:headspin:

Ahh no, an example might help. We have 2 race GTR's, one Production, the other Improved Production. The Production GTR has Group A turbos running 2 bar and makes 305 rwkw. Obviously to comply with the the regs it has std cams, std head (no porting) etc. The Improved Production GTR has Garrett GT28R's and makes 385 rwkw at 1.4 bar. But it has 272/280 cams, ported head, polished combustion chambers, higher compression ratio, forged rods, forged pistons etc.

A turbo is not simply an air pump, you have to think of both the compressor and the turbine as they are solidly linked. If you increase the boost (at the compressor) then you must also increase the restriction (at the turbine). There is a point at which increasing the boost actually adds even more restiction at the exhaust, and the engine looses power.

Hope that makes sense