Hello,

I have an application where I am wanting to run parallel MAF sensors on a 2.7t. The engine is going in a Boxster so the need for parallel MAF’s is driven by spatial constraints and the desire to keep using ME7.1 engine management to maintain readiness monitors.

I have an Arduino nano that I am using to read 2x MAF sensors from a 1.8t (06a906461l), using lookup tables to first convert from voltage to mass air flow (g/s), then add together (sum) to get total mass air flow, then covert again to a voltage that the stock hitachi MAF sensor (06C133471A) would output, then output that voltage to be read by the me7.1 ecu.

I’ve got this all rigged up on a test bench. I am using a y-pipe to connect 2x 1.8t mass air flow sensors to 1x hitachi S4 sensor so that I can compare my simulated voltage (parallel MAF voltage being crated by the Arduino) to the hitachi sensor voltage that I am trying to emulate… I am doing this to check that my hardware and software is doing what it should be doing. Then I have a leaf blower attached to the setup to pull air through everything.

I can tell that my 2x 1.8t readings are almost exactly the same. This gives me confidence that the sensors are good and my measurement setup is ok. My issue is that the Arduino simulated voltage isn’t as close to the actual hitachi voltage that I’d like. In example, when air is moving and the hitachi sensor reads about 3.2v (which is about 107 g/s), the Arduino spits out 3.0v. The hitachi sensor is used, but came from a good running car. Also, if the sensors was degraded, I’d expected it to read low as opposed to high.

My question for the forum is… I am using the mass air flow vs voltage tables from the associated ecu bin files to make my conversions… should these be reliable enough to make my voltage-maf conversion with? I COULD adjust my conversion table to dial the Arduino into this hitachi sensor, but it seems like I should be able to just use the tables from the ECU’s. In all, the Arduino and the hitachi sensor are about 6% off of each other at 3v… is this too much? Error will likely be greater at higher mass air flow levels. What do you think?

Fair point, Arduino table and MLFHM could be anything being that I have control over both. Just trying to get started with something usable.

Do you have any idea what sort of accuracy should be excepted out of a MAF sensor? I found a Bosch document that stated 1.5% for new hot film MAF sensors… I realize the tune will have to be dialed eventually, I’m just trying to set a target for how good my Arduino+2x MAF’s need to be before I stop thinking about it and move on.

Would really help to have a calibrated flow bench.

Thanks!!

its better to run it with stock maf and yours and then compensate difference with KFKHFM/MLHFM
1 point of comparing its a waaaay far from any precision

p.s. what about "add ushfm_w, uushk_w" would be much easily than arduino.. yay or nay? 

That's plenty consistent. I'd say build your MLHFM based on your data and call it a day

I'm sure you already know this, but the flow profile of a leaf blower is going to be very different from actual flow with airbox and the fact that it is pulling not pushing etc

Introducing another point of failure is dumb.

Either run SD or if you really want two mafs then wire 2nd maf to rear O2 input and add them together in software in the ECU.

There is absolutely zero reason to run a piggyback, and I seriously doubt you are going to get the construction right where shit won't fail due to vibration or moisture.

A couple of things to take from your comment -

1. I should check response at lower flow rates (3-5.5 g/s is spec for idle), this will give me a better read on drivability and idle stability. It would be acceptable if both the hitachi and Arduino read within 3-5.5 g/s.

2. Check the effect of putting a straight section in front of the 1.8t mafs. I’m sure that the cone filter mounted on the maf housing doesn’t explain the 9% because during testing I could put my hands on the filter in an effort to divert flow and the effect on measured air flow were very little… but this could be worse at lower flow (idle). I’m aware that it is recommended to have a straight section in front of the maf, but that isn’t really a luxury I have. The OE setup has the maf mounted directly to the air box which is basically a velocity stack in a box… so OE doesn’t exactly have a 12” straight in front of the maf sensor either.

This kind of goes back to my original question of how close is close enough? With the 1.09 scale built in, the flow curves line up pretty well, so the system in the picture (2 MAF’s, cone filters on MAFs as shown, Arduino) is representing the hitachi MAF as accurately as the graph shows.

I'm curious about this, why wouldn't KFKHFM apply?

In any case, I agree with the rest of your statement.

The reason this is so popular, of course, is that hacking arduino code is much easier than hacking in ASM and has a much much much lower barrier to entry.

I'm not flat out discouraging him because it's at least less dumb then alpha-n.