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Old 07-09-2010, 12:48 AM   #1
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Default Bypassing the ugly AFM and replace with map senser with stock ecu?

Hi there,

I'm looking to clean up my engine bay in my 90 mx-5. This AFM is ugly and bulky. I was wondering if I can remove it and bypass it some how.

I was reading this performance handbook made by motorwork workshop. It said that on a 1.6l car, running without a AFM, I would need to bypass the fuel pump safety device in start up. It also show how to bypass it. It said to use a jumper wire on the connector pin E1 to pin Fc.

Now, won't that method makes the car run like crap? I was wondering what about a Honda map sensor that runs off from vaccum line instead? Or any other map sensor that might work with a stock ECU? I know the best way doing it is to buy a Megasquirt but I don't have the funds for that as of right now.

Any input?
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Old 07-09-2010, 01:50 AM   #2
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You cannot simply splice a MAP sensor into the AFM line. Don't argue with me on this- I spent a shitload of time coming up with a workable solution to the problem several years ago.

If you really want to ditch the mechanical airflow meter, you have two options. One is to install an aftermarket ECU (Megasquirt, etc) which runs natively in speed-density mode. The other is to install a piggyback device (such as a Greddy EMU) which can synthesize an AFM signal from MAP vs. RPM. Here is more info than you wanted on that topic:

Would you mind sharing a scan of the Motorbooks article?
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Old 07-09-2010, 10:29 AM   #3
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I removed the AFM in my 1990 with the help of the AEM f/IC piggyback unit. It was pretty simple, just had to do some datalogging and then synthesize the AFM values on a chart. But like Joe said, you can't do it on just a stock ECU alone.
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Old 07-09-2010, 11:47 AM   #4
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As Joe said, you can't simply splice a map sensor into the AFM line because there is no direct analog between engine load (as indicated by the map sensor) and engine load indicated by the AFM.

A few options that are intended to do exactly what you want though:

Maftranslator pro:

This was originally a product for the DSM community that translated the signal from a 90's 3" GM MAF to produce a signal that mirrored the very restrictive karman vortex maf's that those vehicles used.

You could also use a MAPECU:

Both of these products are essentially the same thing with additional features. They effectively use lookup tables to emulate having an AFM with a MAP sensor.

To be honest though, at the end of the day, they are both still just piggybacks and you would be much better off just using a full ECU. Messing with the stock ECU by lying to it (which is what any piggyback does) can have very nasty consequences because you are making it believe that it is in a different load cell than it really is, which messes with your timing as well.

Good luck.
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Old 07-09-2010, 12:41 PM   #5
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