MAF Selection - DeeEmm/DIY-Flow-Bench GitHub Wiki
Selecting a MAF sensor
The most important information you need to consider when selecting a MAF sensor is what output type does it have and what does this output mean in real terms. Most MAF sensors provide a 0-5v output signal, which integrates nicely into an MCU infrastructure as that also uses 5v, but we need to know what any given voltage actually represents in terms of flow.
Fortunately some manufacturers publish data-sheets that include technical information on the output characteristics of their sensors. Generally this is in the form of a graph that shows voltage on one axis and flow (usually in mg/sec, kg/min or kg/hour) on the other. From this you will be able to create a table that plots Voltage against CFM. This is an easy conversion to carry out, more information on how to do this can be found in the 'Customisation' section.
You may also find data published online that lists MAF voltage to flow values. There are some links on the Reference Information page that may be of help.
Some MAF sensors however do not give a volts to flow type of output. They may provide an output that is frequency related or is in strokes versus time, where strokes describes the rise and fall of the waveform. Whilst these types of MAF sensors are planned to be integrated for the V3 release, they will not work with the current V2 code. You can however use a frequency to voltage converter to translate the frequency output into 0-5v signal. This will allow you to connect the MAF as per a regular voltage based MAF. However you will need to generate a relationship table that plots Voltage against Flow.
There are also some sensors that do not have a volts > data-value relationship in their datasheets, but instead use 1024 datapoints thus providing a 10bit data-structure that can be directly used by the Arduino. This type of output also relates to the output voltage range of the sensor, so as long as you know the minimum and maximum voltage output, you can translate the data-values into voltage-values.
So it is a good idea to research your MAF sensor before procuring it, as just getting any random sensor from the local wreckers yard may not yield you with a usable sensor. Make sure you have access to the sensor data before buying it, or even better use the projects default recommendation.
It should also be noted that calculating MAF mapping from OBD2 data is not accurate. The intake systems in cars are very restrictive and highly influence the results, such that unless you use the entire intake system in your bench, the MAF will read completely differently from the published / measured data.
MAF selection should also be relative to what you plan to test. There is no point in choosing the Bosch 0280218067 MAF with a max flow of 885cfm, if the largest thing you will flow test only flows 15-20cfm. This would mean that you are only using 5% of the overall range of the MAF, which impacts accuracy as the resolution of the system is massively reduced.
So when choosing your MAF, consider the max flow rate that you may need to measure and then size the system accordingly,
The following table outlines the MAF sensors currently supported by the DIYFB project.
| MAF | Part Number | Application | Flow KG/h | Flow CFM | Diameter | Type | Tested | Validated | Link |
|---|---|---|---|---|---|---|---|---|---|
| AC Delco | 92281162 | LS2 | 1607 | 788 | 94 | Voltage | No | No | Forum |
| Bosch | 280218067 | Ausi RS4 | 1805 | 885 | 82 | Voltage | Yes | No | Forum |
| Delphi | AF10118 | 5.0 Explorer | 491 | 241 | 70 | Voltage | Yes | No | Forum |
| Bosch | 280002421 | Kia Sportage | 1000 | 490 | 82 | Voltage | Yes | No | Forum |
| Bosch | 280218008 | Volvo S80 | 850 | 417 | 78 | Voltage | Yes | No | Forum |
| Bosch | 280217531 | Alfa 156 | 640 | 314 | 71 | Voltage | Yes | No | Forum |
| Bosch | 280218019 | Fiat Bravo | 480 | 235 | 62 | Voltage | Yes | No | Forum |
| Bosch | 280217123 | OPEL Corsa | 370 | 181 | 50 | Voltage | Yes | No | Forum |
| Bosch | 280218038 | Audi S4 B5 | 658 | 322 | 73 | Voltage | No | No | Forum |
| VDO | 5WK96132Z | BMW M54B30 | 1024 | 502 | 72 | Voltage | No | No | Forum |
NOTE: Sensors previously validated under pre RC9 versions of the codebase need to be converted and revalidated for use with firmware from version RC9 onwards. We will update the table above as each sensor is validated.
Additional sensors can easily be added if flow data is available. Check out the individual sensor discussions to see what data is required.
It is also possible to increase or decrease the effective range of a published sensor by changing the diameter of the MAF housing. This works with cartridge style MAF sensor inserts. The insert can be used in larger (or smaller) diameter ductwork and the new duct diameter entered into the DIYFB configuration. The firmware will then scale the flow data, allowing the MAF sensor to measure higher flow rates than the MAF could in its standard housing.