MAF conversion: MAP vs BP sensor?

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May 16, 2005 | 07:32 AM

02FX4Dude

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From: Waukesha, WI

MAF conversion: MAP vs BP sensor?

Hi All,

I have a "junkyard" MAF conversion on my 87 F150, 302. The generally accepted procedure with the MAP sensor has been to disconnect the vacuum from the sensor and leave the wiring intact, thus making it the BP sensor for the Stang puter.

However I'm now getting some conflicting information. I was checking, among other things, how BP sensor readings affect AF ratio on fordfuelinjection.com. The site states the MAP sensor and BP sensor are different, even though they look alike. Sure enough, the charts (on the website) do show a different calibration.

Being brief, I crunched some numbers and find at 102kpa barometric pressure(currently in my hometown) a MAP sensor should give 238Hz, while a BP sensor will put out 161Hz. So using the MAP sensor as a BP sensor would make the Mustang computer think the pressure is at 185kpa.

Question is: should I worry about this or just get back to what I'm supposed to be doing here at work.

You out there EPNCSU2006?

Thanks
Brian

May 16, 2005 | 08:38 AM

fefarms

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102 KPA is sea level, more or less.

185 KPA is well above normal atmospheric pressure. The computer may wonder what the car is doing at the bottom of the lake -- just kidding, the computer will probably just quietly accept "185KPA" as the same value as "sea level".

I suspect folks re-use the MAP sensor in this fashion because it provides a time-varying signal and the computer doesn't set codes. The net effect is to disable the BARO function -- the computer will always think the vehicle is at sea level.

The BARO function doesn't do all that much with a MAF sensor computer anyway. I think it is primarily to adjust mixture ratio for starting. In Waukesha you are far away from places like Leadville, CO -- the kind of elevation where the BARO sensor might actually make significant changes in how the computer controls the engine.

May 16, 2005 | 10:24 AM

EPNCSU2006

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Joined: Nov 2002

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From: Concord, NC

I used the truck MAP sensor at first, but later changed it to a BAP sensor from a mustang and noticed no difference in how the engine ran.

May 16, 2005 | 10:37 AM

02FX4Dude

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From: Waukesha, WI

Quote:

Originally Posted by fefarms

...
The BARO function doesn't do all that much with a MAF sensor computer anyway. I think it is primarily to adjust mixture ratio for starting.
...

and

Quote:

Originally Posted by EPNCSU2006

I used the truck MAP sensor at first, but later changed it to a BAP sensor from a mustang and noticed no difference in how the engine ran.

OK, that's what I was wondering was how much the sensor was used for calculating AF ratio while driving. If I can't notice it in performance or MPG I'll leave it.

Thanks.
Brian

May 16, 2005 | 09:22 PM

EPNCSU2006

Lead Driver

Joined: Nov 2002

Posts: 9,557

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From: Concord, NC

To be honest, I don't really know why Ford used the BAP sensor with a mass air sensor anyway. Startup seems to be the best explanation, when the mass air meter would read low. Otherwise, the MAF should account for changes in density due to elevation or otherwise.

Nov 1, 2018 | 03:28 PM

jtab

Mountain Pass

Joined: Oct 2017

Posts: 231

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From: Bismarck ND

I realize how old this thread is, but it is exactly what I was looking for, so I'm reviving it.

My pickup, a 1993 F250 460, was running very rich, and I thought a MAF conversion would help with that. Now, after my MAF conversion, my pickup is still running very rich.

I'm suspecting the MAP sensor. So if I'm going to replace the sensor anyway (after i do some o-scope testing) am i better off replacing it with the same MAP sensor or a true BAP sensor?

Thanks,
-Joe