Easily calibrate a MAF sensor signal after changes to the intake system. Scale a MAF signal with MAF CAL.
Increase or decrease MAF sensor signal by +/-50% to optimise engine fuelling (Not compatible with frequency based MAF sensors. Outputs 0-5 volt signal).
NOTE: This is a universal product. It may or may not be compatible with your engine setup. Read the product description to assess it’s suitability for your setup.
MAF CAL Usage Examples
Compensate for larger MAF housing, different MAF sensor, altered MAF location, performance intake kit.
In general, with MAF CAL you can compensate for changes in the intake which have caused the MAF sensor to no longer measure airflow correctly and which have led to high long/short term fuel trims (wideband lambda equipped engines) and/or changes to air fuel ratio (narrowband equipped engines).
Key Features
-11×1 2D calibration map
-Adjust MAF signal according to MAF signal only
-Fail safe bypass. If MAF CAL unit loses power, MAF CAL is bypassed & MAF sensor is connected directly to engine ECU.
MAF CAL – Inputs & Outputs
12v Power (ACC)
Ground
MAF In (0-5v) – Intercept
MAF Out (0-5v) – To engine ECU
Load In (0-5v) – Tap (Optional. Connect to ground if unused)
12 Volt Out – Optional. External sensor power if required eg MAP
Power Ground – Optional. External sensor
5 Volt Out – Optional. External sensor power if required eg MAP
What’s Included
MAF CAL unit
MAF CAL Android app (downloaded from website)
MAF CAL unit connector and crimp connectors (user makes their own loom)
MAF CAL instruction manual (downloaded from the website)
Build sheet (contains details of components used & BT password)
Key Benefits
Dedicated to MAF scaling/calibration. No unnecessary features, easy to understand.
Connects to car with as few as 4 wires
Programmed through your existing Android phone/tablet. No small LCD displays, no scrolling through sub menus, no laptop required.
Unit mounted in engine bay. No wires coming into cabin. Programmed wirelessly.
Why Use MAF CAL?
Depends on the type of lambda sensor used by engine ECU.
Wideband Lambda Equipped Cars
To reduce the short term fuel trim (STFT)/long term fuel trim (LTFT) corrections the ECU is making to achieve its target AFRs. (Where originally the trim corrections were acceptable but subsequently they became excessive due to changes in the engine intake and/or MAF placement and/or MAF piping and/or the MAF sensor itself).
Narrowband Lambda Equipped Cars
To achieve the target AFRs after a change to the intake system resulted in targets not being met.
In short, the purpose of MAF CAL is to compensate for any change which altered airflow through the MAF sensor since the current engine map was done.
What MAF CAL Cannot Do/Is Not Designed To Do
MAF CAL is not designed to compensate for a bad engine map and/or, to tune an engine.
It is intended to calibrate the MAF signal going to the ECU, so the ECU receives a more accurate picture of the amount of air actually entering the engine.
The assumption is the engine had an accurate/good engine map as a base point. But a modification was made to the MAF sensor (types of changes detailed above) where the air flow measured by the sensor no longer accurately represents the actual amount of air going into the engine. MAF CAL is intended to re-adjust this “corrupted” signal so the signal received by the engine ECU represents actual air flow.
How Does MAF CAL Adjust the MAF Signal?
MAF CAL uses an 11×1 2D map to adjust the MAF signal.
MAF signal correction is based on MAF signal input. For example at 2.5 volts input, the output signal should be increased by 5%, 3.2 volts input, the output should be increased by 7%.
MAF CAL does not adjust the MAF signal according to RPM, engine load etc.
MAF signal is adjusted according to the MAF signal only.
How is MAF CAL Programmed?
Using MAF CAL Android app which connects to main unit via Bluetooth. MAF CAL unit is designed to be mounted in the engine bay (away from heat and moisture) and is a fit and forget item.
MAF CAL vs Apexi SAFC/AFC Neo vs MoviChip MAF Manager – Differences
There are/were dedicated products available whose purpose was to tune the vehicle’s MAF sensor signal in order to tune the engine ie where current tune in the engine is not correct for the modifications (cams, injectors etc) done to the engine.
These products used load/TPS and RPM to alter MAF signal to get the desired air fuel ratio (and were intended for use on engines using a narrowband lambda sensor).
MAF CAL on the other hand is designed for engines which have a good engine map but where the intake has been changed in some way (as detailed above) leading to MAF sensor signal no longer giving the engine ECU and accurate picture of the amount of air entering the engine. MAF scaling restores accuracy to the MAF signal.
MAF Scaling – Why Reduce Amount of STFT/LTFT correction?
Why do we care about long/short term fuel trims?
Adjustment Window
There is a limit on how much the engine ECU can adjust fuel trims to achieve the target AFRs, for example it may be plus or minus 25%.
If the engine needs more adjustment than 25% then two things can happen. Either the engine will throw a check engine light and/or the fueling of the engine will not be correct.
By optimising the MAF sensor signal we give the engine ECU the biggest possible adjustment window to get the AFRs where they need to be. It can also reduce the time it takes the engine to get to the AFR target because it needs to compensate less for the inaccurate MAF sensor signal (due to a new intake, different MAF etc).
Ignition Timing
Assuming we are working from a good, correct map but the fuel trims are out because of some change in the intake, ignition timing will no longer be optimised (Ignition timing is dependent on the amount of air flowing into an engine at X RPM).
If the engine ECU is having to throw a lot of correction at the fuel trims because the MAF signal is not longer accurate, the ECU will use ignition timing for the amount of air it thinks is entering the engine.
For ignition timing to be optimal the engine ECU needs a MAF signal that truly represents the amount of air entering the engine.
MAF Scaling – IMPORTANT Proviso
When dealing with an out of spec/inaccurate/modified MAF sensor, there is one very important factor to consider.
The air passing through the MAF sensor must be laminar and not turbulent.
Turbulent air is difficult, if not impossible to compensate for.
In turbulent air, at X load and X RPM, the flow measured by the MAF sensor will rarely/never be exactly the same. Flow must be laminar ie consistent, for the MAF sensor to read mass air flow correctly.
If airflow through the MAF is inconsistent (datalog MAF signal to see) because the MAF sensor placement is bad, this problem needs to be eliminated before we start adjusting the MAF signal.
Causes of a Turbulent MAF Signal
- MAF sensor mounted on bend
- MAF sensor mounted close after bend, & within 20cm-30cm.
- Removal of air vanes before sensor. Some stock air boxes have vanes to guide the air pre-MAF sensor. They are there for a reason.
- Removal of mesh before sensor. Some MAF sensors have a honeycomb or mesh before the sensor. They are there for a reason.
- Extreme heat. MAF sensors moved and mounted in area exposed to extreme heat.
- Moisture. Relocation to area where water spray/vapour can be pulled into sensor.
- Change of filter medium. Going from the stock paper type air filter to cotton/foam/metal mesh etc can affect accuracy of MAF signal when sensor mounted close to filter.
- Pipe diameter. Too large a diameter could lead to reversion through pipe at low flow rates.
- MAF housing material. If MAF housing changed to metal from plastic, sensor could be exposed to much higher temps.
Should You Use MAF CAL?
In a perfect world where the intake is not being changed regularly and you can change your engine map easily and/or cheaply, then ideally, the engine map will be changed directly without adding an external box like MAF CAL.
If you don’t want to take your car for a remap (to compensate for the MAF change or perhaps you are experimenting with different intake setups etc), then MAF CAL could be a good solution for you. It allows you to quickly and easily change the MAF sensor calibration, from your Android device.
BOV (Blow Off Valve) Assist
MAF CAL has an extra feature called BOV assist. It is designed for turbo charged cars using MAF and a BOV that vents to atmosphere.
-NOTE: We do not recommend using this function, you can read the reasons why here–
With the function turned on, when MAP reaches a certain level of vacuum, a fixed MAF voltage is sent to the engine ECU. The purpose being to prevent over fuelling between gearchanges.
Some Provisos
We recommend recirculating excess boost to the turbo inlet, post MAF. The eliminates the issue of overfuelling.
If venting to atmosphere, the BOV should be closed at idle. Which can cause issues.
In short, BOV Assist should be considered a band-aid and/or an experimental. It may or may not work for you. It is highly recommended to recirculate the air on MAF equipped engines. Recirculation has many benefits and none, if any downsides. The only possible “benefit” of venting to atmosphere is for sound purposes. If that is something that you would want. But it is possible to get a lot of that sound even when recirculating. Check the BOV Assist article for more information.
Again, we do not recommend using this feature. Generally recirculating boost down stream of the MAF is the way to go, it has many benefits and no downsides that we know off. Read more information here.
MAF Scaling, MAF Tuning – Further Reading
MAF calibration using fuel trims
MAF Scaling
All articles related to MAF sensors