G50: Mass Air Flow to Voltage Out Signal

[lino]

Found something online. Sometimes the link doesn't work so I'll post what's there and provide the link below:

Infiniti Q45 MAF Sensor



The Infiniti Q45 MAF sensor, which apparently flows more air than any other stock MAF sensor has an clear inside diameter of 3.19 inches (80mm) and is voltage-out (not frequency).



In OEM wiring harnesses, the wires are usually:

* Signal - White, pin "B", * Ground - Black, pin "D", * 12V - Black/White, pin "E"





There is a full output curve for this (and other) Nissan MAF sensors in this spreadsheet http://www.diyautotune.com/meg...s.xls

Source: http://www.diyautotune.com/meg...p.htm

[Q45tech]

If you extrapolate the numbers on a Q45 MAF you will find the difference netween 4.32 volts and 4.24 volts near redline is enough air to change horesepower by 18 HP.

Hopefully members see why I always ask for 2 decimal places in voltage.

Convert to grams per second and divide by 1.2 to get airflow vs potential HP. Pretty accurate on Q45.

I have never seen a MAF voltage above 4.40 volts [except near 32F ambient] most top out at 4.32.

Always log inlet temperature and barometer as 11F is 1% change and each 1000 ft is 3.3%....................................so ATL sucks in July but not as much as driving up a 5,000 ft mountain [-16.5% but temp also drops by 17F so the net is ~ 15%].

If you have 360 grams per sec of air and want a 12:1 A/F ratio divide by 12 and you need 30 grams per second of gasoline flow out of injectors [combined] and a return type fuel pump needs to produce 3 times that for regulation so [30/454] x 60 x 60 = 237.88 pounds per hour

[Q45tech]

If you look at the Mustang vs Q45 MAF you will see at exactly 4.0 volts on both the Mustang will be flowing 118 HP worth LESS AIR so you must have exact data on each MAF.

Every MAF will vary a lot from an identical one. DEPENDING on how much dirt, grease, oxidation is found on the elements. SO even if you flow bench analyse your MAF it may be a little different next month or next year.

Luckily the power output of engine is somewhat NUMB to a minor variation in A/F ratio and the MAF tends to under estimate air flow so the engine just get leaner as the MAF gets dirty.

Obviously this is more critical with a reprogrammed [leaned out] ECU but still the MAF would have to be 10% off to make a 11:1 get to 12:1 so unlikely

[qsiguy]

....I have never seen a MAF voltage above 4.40 volts [except near 32F ambient] most top out at 4.32...

Highest I've logged on my MAF is 4.94 volts but that was at ~8 PSIG of boost, ~100 mph, 6725 RPM, 92% injector duty cycle, full throttle. I may have hit higher than that at some point but not while I was datalogging.

Thanks for posting this information, I have been wondering about the details of this MAF for a while now so this saves me a lot of time researching time. Awesome!

[qsiguy]

I've been looking over this spreadsheet and the graphics above and it looks like they added a 0 at the end of the mg/sec values on the chart above vs. what they indicate on the spreadsheet.

For example the chart above says at 2 volts you have 36260 mg/sec and the number on the spreadsheet is 3626. I know the chart shows what the VQ numbers are which are in the ECU BIN, just not sure where they determined to just add a 0 at the end.

[Q45tech]

3626 mg is 3.6 grams or enough air to make 3.6/1.2 = 3.0 HP36260 mg ~~ = 30 HP ....................about what you need to cruise 80 mph in a Q.

XLS Chart needs an extra ZERO added.

Create your own MAF vs speed in gear. Everything SEEMS to correlate pretty well when you examine the idle voltage and change loads with AC.

Things are never perfect when you try to show an exponential equation.