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New MAF Project

robdimond

PCGB Member
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Bit of a project... made an MAF/AFM converter. The MAF is a common VW/Audi one and the little red PCB maps the signal to mimic the original AFM. The engine runs, but not driven yet, want to get an air filter on there first!
Plugs straight into the AFM socket and then just needs a 12V feed to run the MAF. Is there a good place to get 12V from here? I've got a wire all the way over to the blue post in the scuttle.
Why? Just because! Not sure if the 'less restrictive' and 'more responsive' are actually true... but certainly the old AFM is a mechanical device that wears, hard to repair and expensive to replace.

 
It's very similar to my SciVision MAF set up. Which once retailed at about £800 [:-]! Whilst not a true MAF set up it works well with better air flow and boost seems to build quicker with less lag. I tapped the 12v supply from a little box on the bulkhead near the fuse box and my little control box is located behind the passenger head light near the AC receiver/dryer. I think my Bosch unit is a HMF5 if I recall correctly which is readily available and has several applications including an Alfa GTV if I recall correctly. I have a couple of spare elements for a rainy day. Hot film rather than hot wire and a worthwhile upgrade vs AFM.

Stuart
 
Really interesting project! The SciVision was subjectively one of the best upgrades I've ever made, the improvement in throttle response was not subtle and transformed the way the car drove, so it should be well worthwhile.
 
Peter, good to know you got a (subjective) improvement. The other thread is somewhat raining on my parade [:D]

My main motivations are to see if I can do it and to try to create a cheaper solution for a failed AFM. The original AFM is a nicely made precision bit of kit but it's expensive and it wears out.

If I wanted horsepower then possibly a top-end rebuild on my 192k engine would make more sense than fiddling with the electronics.

I think the PCB could be manufactured really very cheaply. The MAF itself is about £100 with cheap clones going for £30 on ebay.

It replicates exactly the output of the original AFM. I built a flow bench with a Henry hoover to do the calibration! It would be possible to create a map for the early AFM as well.


 
robdimond said:
Peter, good to know you got a (subjective) improvement. The other thread is somewhat raining on my parade ....


Worry not, just because certain quarters get certain results doesn't make it written in stone. There are a great many ways to skin a cat, so you carry on.

You may, or may not, hit gold but the experience will mean that you too can write 500+ words, or more, in answer to every post on any thread remotely related to the subject. ;-)

The joy with you doing it is you will understand it intimately and can adapt and change as necessary. You may end up some blind alleys but will still learn stuff as a result. You carry on Sir. Kudos as I believe they say in internet land.


 
Hi Rob. Don't buy a clone MAF, I tried one once and my AFR readings were all over the shop. Stick to genuine.

Stuart
 
Rob, I wouldn’t worry about other threads or other opinions. Some people get off from going against the flow (of natural selection). You can’t compare findings with one component on a specific engine with a different component on a completely different engine. It’s like saying that because all black labradors have red collars that must mean that all hamsters are called Walter - no matter how much somebody with a hamster called Walter is proud of it and claims it’s exactly the same [8|]

Carry on the project and I’m sure it will reap rewards.
 
Don't worry I will keep going! If I can make it work then I'll figure out how to make the board available cheaply to other DIY'ers who want to have a go.
Currently using a genuine Bosch MAF from the VW/Audi parts bin. Possibly a wideband AFR gauge would be a good investment to get some visibility? All I can say is I revved it a bit and it runs nicely. It's doing something because it won't run without an AFM at all.

Passed an MOT today as well so am happy. Tester commented it was a very well looked after car and was a pleasure to look over. He'd just failed a Subaru a few years younger that was 'falling apart'.
 
The late cars with a Catalytic converter have an O2 sensor already. I’m lead to believe you can tell the ECU to ignore it with a combination of the region coding plug and altitude plug and then you’ve already got a hole for a new wideband sensor.

I had a wideband lambda bung welded into my new exhaust when I had it made. Lindsey Racing’s site has a guide on the best place to position it if you take this approach.

I used it to monitor AFR under full boost and then tweaked my adjustable fuel pressure regulator to hit the numbers I wanted. It meant I was right at full boost but usually too rich the rest of the time. The great thing about a closed loop system like VEMS is it knows what’s coming in via an inlet air temperature sensor and MAP but also knows what’s going out via the lambda so it constantly working to hit the programmed figures throughout the Rev/Boost table - modern technology huh!

It’a probably a step too far to try and get a positive feedback loop from the Lambda into the original DME due to the level of fidelity the EEPROM has (or rather hasn’t) but given the fact that there’s space for 4 distinct maps (albeit all 2d and limited rows) on there you never know!
 
Yeah a wideband is a great idea and gives you peace of mind fuelling is correct which is important. It's a must for a modded turbo but given your current project I'd make plans for one.

Stuart
 
robdimond said:
Peter, good to know you got a (subjective) improvement. The other thread is somewhat raining on my parade [:D]
My main motivations are to see if I can do it and to try to create a cheaper solution for a failed AFM. The original AFM is a nicely made precision bit of kit but it's expensive and it wears out.
If I wanted horsepower then possibly a top-end rebuild on my 192k engine would make more sense than fiddling with the electronics.
I think the PCB could be manufactured really very cheaply. The MAF itself is about £100 with cheap clones going for £30 on ebay.
It replicates exactly the output of the original AFM. I built a flow bench with a Henry hoover to do the calibration! It would be possible to create a map for the early AFM as well.


Not at all, I'm all for people having a go at something as long as they know it may or may not work.

The other thread was a 10K + Engine scenerio where do I or don't I dabble with an aftermarket set of electronics or stick with the engine's builder and mapper / tuner's choice of retaining all, the stock Bosch ignition fueling and the AFM systems. So I did, what I didn't expect was for it to outperform the former by a substantial margin! This was a Bonus and something I'm keen to illustrate and assist others not to be drawn too much into just because some products are marketed and hyped as the latest electronic componentry doesn't always mean it's a sure given especially in a road application (Which was mine initially - the Racing application came 3 years later)

Did you try to get it repaired ? These guys checked and recalibrated 2 units for my engine, I'm not sure if they still do this ?
https://www.atpelectronics.co.uk/c/porsche-944-air-flow-meter-throttle-body

Do you think the track / wipe arm PCB could be made cheaply also?
(See picture below)

Or you could always just buy the MAF kit from Lindsey Racing (USA) @ $500 + shipp / tax etc...
https://www.lindseyracing...R/Parts/944NATUNE.html
R
 
Thanks Roger. My AFM isn't actually broken... (it must be close to wearing out after 192k miles!) I just like a bit of a project!

$500 MAF kit... so far it's cost me less than half of that (not accounting for my time).

I think it would be hard to get the track re-manufactured. Presumably there is a source that the rebuilders use. It's resistive material screen printed on a ceramic substrate, then laser trimmed (the black lines you can see). I would expect thousands to get the necessary tooling built up to do the calibration.

My electronics just need a bog standard 2-layer PCB, which can be manufactured in China in prototype quantities for a few pounds each.


 
robdimond said:
Thanks Roger. My AFM isn't actually broken... (it must be close to wearing out after 192k miles!) I just like a bit of a project!
$500 MAF kit... so far it's cost me less than half of that (not accounting for my time).
I think it would be hard to get the track re-manufactured. Presumably there is a source that the rebuilders use. It's resistive material screen printed on a ceramic substrate, then laser trimmed (the black lines you can see). I would expect thousands to get the necessary tooling built up to do the calibration.
My electronics just need a bog standard 2-layer PCB, which can be manufactured in China in prototype quantities for a few pounds each.



I've no Prob's with tinkering, you'll learn a lot and may achieve well or come to some conclusions as a few before (It wasn't worth doing) but you'll of least of had the experience and journey... I've done similar for years, although with age I've less time to faff and now prefer to go for solutions which may appear costly but long term they are much less bother & stress.

R
 
Eldavo said:
The late cars with a Catalytic converter have an O2 sensor already. I’m lead to believe you can tell the ECU to ignore it with a combination of the region coding plug and altitude plug and then you’ve already got a hole for a new wideband sensor.
My 91 turbo didn't have a Cat, but it does have a O2 sensor in the downpipe. I think that location can only use a narrow band O2 sensor due to the heat. Some of the chip providers did disable the sensor with the plugs as you say.
 
I piggybacked a narrow band gauge into the factory sensor and had good results, If the tune is a long way out it is little help but as a monitor of what is going on its good - its easy to spot if something changes. I did go for a wideband as well in the end with a bung welded in further downstream.
Tony

 
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Plumbed in and went for a drive. It drove... absolutely fine! Couldn't say it was faster, or slower. Perhaps smelt like it was running a little rich, hard to say.
 

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