Fooling Air Flow meter

[the phantom]

Yes!

[Sydneykid]

Hi Enrico, 5.1 volts is it, so I would say it's time for a Z32 or Q45 AFM. In order to use either of these with the standard ECU, the tuner would need to be able to get access to the AFM voltage table inside the ECU. If they can get access, then they need to input the voltages that the AFM sees for the various amounts of air flow.

For example the RB25 AFM might show 1 volt at 10 pounds of air flow per minute. The Z32 AFM would then maybe show 0.8 volts for 10 pounds of air flow per minute. The RB25 AFM might then show 2 volts at 15 pounds of air flow per minute. The Z32 AFM would then show say 1.2 volts for 20 pounds of air flow per minute.

The airflow and voltage changes are not linear and so the tuner needs to know the ratios to input into the table. The theory is if you could get these ratios correct, you wouldn't have to retune the car everywhere. Only the bit past the rpm where the RB25 AFM was reaching 5.1 volts would need retuning. The reality is no one (not even Apexi) get the table perfectly correct, so they pretty much always need a retune in quite a few places.

Can your standard ECU AFM voltage table be accessed and changed? That's the question you need to ask your tuner. I haven't ever tried, but maybe someone else on here has.

With a Power FC you simply go into the AFM menu and select the type of AFM you are using. The PFC changes the voltage table to the preset values worked out by Apexi, which as I said above aren't exactly correct. I know this because when I upgrade an AFM and select the correct one, we still have to retune the car (both fuel and ignition) in areas where we shouldn't have to if the table was correct.

Hope that helps.

[Busky2k]

Well the thing is, if you reach 5V on the AFM then you basically have reached the end of the mapping capabilities of the stock ECU and the Unichip will not make a difference. Time for an PowerFC Dean.

[EnricoPalazzo]

I just got this email from Air Power Systems (Unichip):

Dean,

Even if the MAF is max’d out, there are a number of solutions. – We deal with this issue on WRX’s all the time. - John / David should know how to handle this.

Best Regards,

David

APS