New AFM killer
01-06-2015, 03:54 AM
#1
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New AFM killer
From German miata forum
mx-5.net - die Diskussionsforen von www.mx-5.de - Anzeige des Themas #51372 - Luftmassenmessung im 1.6er NA - Interesse?
I's a simple project to delete the old flow meter with a new MAF
mx-5.net - die Diskussionsforen von www.mx-5.de - Anzeige des Themas #51372 - Luftmassenmessung im 1.6er NA - Interesse?
I's a simple project to delete the old flow meter with a new MAF
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01-06-2015, 10:35 AM
#10
Point is; there are a LOT of Miatas out there that have not been boosted and the main failure point in a pre '94 control circuit is the mechanical AFM.
A rebuilt AFM is close to $300 and not reliable.
Even in the turbo world, there are some of us that prefer to keep it simple, albeit we don't get to tweak and tune to maximum power.
A rebuilt AFM is close to $300 and not reliable.
Even in the turbo world, there are some of us that prefer to keep it simple, albeit we don't get to tweak and tune to maximum power.
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01-06-2015, 11:31 AM
#11
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Yes is for sale, little price.
I bought one a few days ago, has not yet arrived.
Utilities?
A original engine "breathe" better, gain of 2-3 hp at high revs (as when using the afm of rx7).
More air flow ... more power
I bought one a few days ago, has not yet arrived.
Utilities?
A original engine "breathe" better, gain of 2-3 hp at high revs (as when using the afm of rx7).
More air flow ... more power
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01-08-2015, 07:28 AM
#15
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Most user of the german mx5 board don't want megasquirt because they think it's not worth it on a N/A application. They experiment a lot with modifications like this one because it's relatively easy and doesn't involve a lot of tuning. Also you need to have it inspected by the TUEV to get it street legal and while a few companies work together with the TUEV engineers to be able to certify a ms most people consider them illegal and don't want to bother with it. The funny part is, while the AFM modification may be not too flashy in a stock looking engine bay it's illegal too because you changed emission relevant parts 
Last edited by m00se; 01-08-2015 at 07:29 AM. Reason: correcting spelling garbage
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01-08-2015, 01:12 PM
#18
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Yeah, it's pretty straightforward. U1 is a microprocessor which is taking in the analog signal from the MAF on pin 23, and using either a lookup table or some formula to output an inverted analog signal on pin 15 via T2. (It's also driving a relay to trigger the fuel pump, presumably when MAF > nothing.)
Not sure what the cute little arrangement at pins 20 & 21 is about, but I assume it's there for a reason. Aside from that, nothing much else to it.
I'm a little surprised that the CPU isn't taking in an IAT signal, as I would have thought that it would be helpful in correcting from mass to volume, but then I admit that when I implemented this same concept in software back around '06 or so with the Greddu EMU, I didn't use IAT either (admittedly, I was using MAP/RPM rather than MAF as my input.)
I'm sure it'll work just fine, and you're right in that it's probably time for a circuit like this to exist, as working VAF sensors are going to start getting hard to find.
Not sure what the cute little arrangement at pins 20 & 21 is about, but I assume it's there for a reason. Aside from that, nothing much else to it.
I'm a little surprised that the CPU isn't taking in an IAT signal, as I would have thought that it would be helpful in correcting from mass to volume, but then I admit that when I implemented this same concept in software back around '06 or so with the Greddu EMU, I didn't use IAT either (admittedly, I was using MAP/RPM rather than MAF as my input.)
I'm sure it'll work just fine, and you're right in that it's probably time for a circuit like this to exist, as working VAF sensors are going to start getting hard to find.
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05-08-2015, 03:07 PM
#19
UPDATE UPDATE UPDATE
I bought one to try. Very professionally done. Works great.
Much more economical than replacing a defective AFM and restricts the airflow less on an 89~93 NA or Turbo where the AFM hasn't been eliminated.
Using an early 1.8 air box, it almost looks stock.
Much more economical than replacing a defective AFM and restricts the airflow less on an 89~93 NA or Turbo where the AFM hasn't been eliminated.
Using an early 1.8 air box, it almost looks stock.
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