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Old 10-15-2007, 01:07 PM   #1
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Default Calling people with wiring/voltage knowlege

OK... i want to build/find something that can take a 0-5v signal and step it up to a 7-12v signal. i.e. sensor is sending out a 3v signal and needs to be stepped up to 10v signal. For the life of me i cannot find any information on building/buying such a device.

What i want to do is take out the 7-12v MAS on my car and put in a 0-5v MAS from a 96-97 Miata. Then run this signal to a SAFC. From the SAFC i need to step up the signal voltage +7 to the 99 ECU can read it.

I know it would require a 12v power supply to add the voltage to the output signal... but after that... i have no clue as to what i'd need.

I dont get why Mazda decided to go with a 7-12v range for the 99-00 cars.

Or.... is there a MAP sensor out there that runs on 7-12v? Might i be able to use that?


Or for MSPNP to be available for the 99-00 Miata
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Old 10-15-2007, 01:26 PM   #2
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just run a MS piggy and dont run any MAF.
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Old 10-15-2007, 01:28 PM   #3
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Not to worry, Magna will chime and and explain how to accomplish this...

What's a SAFC? I'm suspecting there's a better way to do this. Why are you switching the sensors around?
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Old 10-15-2007, 01:45 PM   #4
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Quote:
Originally Posted by patsmx5 View Post
What's a SAFC? I'm suspecting there's a better way to do this.
A SAFC is an old-timey electronic gadget that lets you run larger injectors by attempting to attenuate the airflow signal to the ECU, tricking it into reducing the injector output pulse duration. Kinda like an EMB, except more expensive and without the benefit of ignition control. Do a Google search for Apexi.

Back to the OP- I wasn't aware that NB's used a 7-12V system. Seems a bit odd to me... Although, would this perhaps help to explain the trouble folks have been having with EMU on NB? Can you positively confirm this 7-12v output?
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Old 10-15-2007, 02:08 PM   #5
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if switching over to a MAP sensor was as easy as hooking up an SAFC no-one would have a MAF.

Just stepping up the voltage doesnt mean you're going to be able to use it. If that were true you'd be able to use any 0-5v MAF on any 0-5v MAF car.

For one, different MAFs put out different voltages for different CFM's not to mention I would assume that some use a linear voltage output and some may not. Hell, some might output voltage backwards....mebbe.

P.S. Never heard of a 12v MAF or MAP sensor either. Not saying they dont exist but 5v has had perfect resolution for 20 years, why would they change it now?
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Old 10-15-2007, 02:28 PM   #6
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Well, i used the SAFC-II (4 buttons, not the ****) on my M1 and i loved it. Im not worried about ignition control at all.... not for 10psi with a big fmic. So using the SAFC to control larger injectors is nice and simple to tune.

Yes, i have read that the 99-00 (maybe 01+?) use the 7-12v output signal. I can double confirm this when i read that people were having problems using the SAFC on the 99-00 cars... but i insisted on trying for myself. When i hooked everything up and set the SAFC to read, it was showing 100% signal when turning the car on. The reason is that the minimal voltage for the operation of the MAS is 7v whereas the SAFC uses 0-5v input (output from the MAS) to manipulate. Well when the MAS shot out 7v to show no air, the SAFC saw a max reading and just dumps fuel at startup.

Also seen on m.net that someone was using a volt meter when trying to install a SAFC and was seeing 7.2v when sitting with the key in the ignition in the on position.

And on the old HKS Super AFR, there was a special setting just for the 99+ Miata.. which also points to a completely different voltage range then the normal (0-5v)

Last edited by Doppelgänger; 10-15-2007 at 02:38 PM.
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Old 10-15-2007, 02:39 PM   #7
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Originally Posted by Braineack View Post
just run a MS piggy and dont run any MAF.
yeah..... does that go to using a MAP sensor?
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Old 10-15-2007, 02:47 PM   #8
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There are 0-5, 5-0, 6-10, and 7-12. Those are the types I know of...
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Old 10-15-2007, 03:05 PM   #9
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Hmmmmmmmmmmmmmmmmmmm.

I really want to get my hands on an NB to analyze at this point. But if this is true, then it goes a long way towards explaining the NB-EMU dilemma. I just re-checked the EMU software, and the scales for MAP(v) have a maximum upper limit of 5V.

Seriously. Anybody with an NB who is near Carlsbad, CA, I want to inspect your car.
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Old 10-15-2007, 03:18 PM   #10
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Come on Joe, ROADTRIP
(you know you wanna)
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Old 10-19-2007, 12:40 PM   #11
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Gonna jump back in here because we have some more data. Musanovic posted a recent datalog of his '01 running an EMU. Here is 36 seconds representing a takeoff from idle, and some normal acceleration and shifting:


Airflow is red, RPM is yellow. The scale on the left is AFM(v).

At idle, the AFM output is around 2 volts. During this part of the file, it rises proportionate to RPM, reaching about 3.7v peak. The maximum recorded value on this log is 4v, occurring around 4,000 RPM at an unknown MAP.

So... Do we think that Mazda used a 0-5 volt system from '89 through '97, switched to 7-12 volt for '99 (and possibly '00) and them immediately went right back to 0-5 volt for '01 and beyond? Anybody have a log from a '99-'00 they can share?
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