Barometric pressure sensor (EFI help please)

[kholding]

I know it sounds like a silly question but does the BP sensor need to be mounted in the engine bay or is it fine under the dash?

 

[Viperwolf1]

Fine under the dash.

 

[Steve83]

What system are you installing that uses a BP? Most use a MAP, which needs to be connected to the intake manifold, but it can be mounted anywhere.

 

[kholding]

RJM harness.

 

[Viperwolf1]

What system are you installing that uses a BP? Most use a MAP, which needs to be connected to the intake manifold, but it can be mounted anywhere.

Speed density systems use a MAP. Mass air uses a BP sensor.

 

[DirtDonk]

Which is actually the same sensor internally, but with a "nipple guard" (insert joke here) to keep you from attaching the vacuum line.

Paul

 

[Steve83]

So is this some early car MAF system that uses a BP? The reason for a pressure sensor is to calculate density, which shouldn't be needed in a true MAF system. Factory MAF doesn't use a BP (at least on trucks).



And the early BPs were voltage-varying; most MAPs are frequency-varying, so they're not always interchangeable (regardless of nipples ).

 

[EFI Guy]

93 was the last year for BP sensors. BP is calculated internally on everything newer. I have no idea what the formula for the calculation is, but I often use the Baro hz PID when diagnosing bad or dirty MAFs.

 

[Steve83]

93 was the last year for BP sensors.

On what vehicles? Certainly not Ford trucks because they NEVER had a BP. And if you meant MAP, it's still not true of Ford trucks because my '95 4.9L has a MAP.

 

[Viperwolf1]

On what vehicles? Certainly not Ford trucks because they NEVER had a BP. And if you meant MAP, it's still not true of Ford trucks because my '95 4.9L has a MAP.

Mustangs and other cars that typically become common donors for EFI swaps.

 

[67EB_in_619]

Regardless of year and application...
Both MAP and BP can be numbered under the dash.. but one would need a vac line running back to the engine area

Sent from my SCH-I535 using Tapatalk 2

 

[kholding]

Thanks everyone. Mine is the BP so it does not need the vacuum line. I am just trying to minimize what I can from the engine compartment.

 

[mattt]

On what vehicles? Certainly not Ford trucks because they NEVER had a BP. And if you meant MAP, it's still not true of Ford trucks because my '95 4.9L has a MAP.

Talk about splitting hairs here.....you refer to it as a MAP sensor. Others refer to it as a BP, Barometric Pressure sensor. It's the same thing already! Trucks do have it by the way.....every truck I've looked at has it.

 

[EFI Guy]

Since we're splitting hairs, I guess I'll clarify.

93 was the last year for BP sensors for mass air vehicles.

Since the trucks were all speed density through 93, they didn't have a MAF, hence no BP sensor. Yes, they had a MAP because they used speed density .




.

 

[DirtDonk]

Talk about splitting hairs here.....you refer to it as a MAP sensor. Others refer to it as a BP, Barometric Pressure sensor. It's the same thing already! Trucks do have it by the way.....every truck I've looked at has it.

Well, I'll join in then too. There are TWO different parts available at the parts stores. Different part numbers, different layout of the parts.
The one shown is typically uses as a MAP sensor with a vacuum line attached.
The BAP sensor is the same body, but with a large plastic "guard" thingy permanently attached to the hose fitting to keep you from attaching a vacuum line to it.

As said, they can be used interchangeably, so someone with the pictured MAP sensor merely has to leave the vacuum lines off to, with the right computer, make it into a BAP sensor. A little harder to go the other way, but still possible.

Below is a BAP sensor. Application 86-91 (93? 95?) Mustang. I used "'90" as the search year, but I was pretty sure that it's the same for all those years.



Paul

 

[mattt]

Right there with ya Paul. I was just too lazy to find a picture that showed one with the nipple guard. ha ha....we both said nipple guard.

My understanding was that it was the same sensor for either application(SD or MAF), only difference was how it's installed.....SD with hose to the nipple and MAF with no hose hook up.

 

[Rox Crusher]

We sure have a lot of knowledge on this forum.

Now I know all I ever wanted to know about this sensor (and more).

 

[Steve83]

Well, that's clearer, now that those damned hairs are out of the way. It doesn't make sense to me for Ford to build a system that relies on air density & then call it MAF, but apparently, that's what they did. From the '92 Mustang PCED:

The Barometric Absolute Pressure (BP) Sensor (Figure 2) measures barometric pressure using a frequency. This gives the EEC-IV processor information on engine load or air density.

It is used as a barometric sensor for altitude compensation, updating the processor during Key On, Engine Off and every wide-open throttle.

The EEC-IV processor uses BP for:
-Spark advance
-EGR flow
-Air/fuel ratio

And mattttt: as I said before, they're NOT all the same. Early BPs weren't interchangeable with MAPs. It wasn't until ~'88 that the MAP replaced the old-style BP, and apparently, that only lasted until '93 (~6 model years), and only on cars.

 

[OX1]

Well, that's clearer, now that those damned hairs are out of the way. It doesn't make sense to me for Ford to build a system that relies on air density & then call it MAF, but apparently, that's what they did. From the '92 Mustang PCED:And mattttt: as I said before, they're NOT all the same. Early BPs weren't interchangeable with MAPs. It wasn't until ~'88 that the MAP replaced the old-style BP, and apparently, that only lasted until '93 (~6 model years), and only on cars.

Have you measured any EEC-IV MAP/BP sensor that did not ring out to this table.

http://www.oldfuelinjection.com/?p=27

I can't remember one, and that includes speed density v-6 and v-8 both cars and trucks, and mass air V-8 cars, I've tested over the years.

 

[Steve83]

Yes. EVERY one that I've tested was voltage-varying. I've never bothered hooking up a frequency-varying MAP to a tachometer or scope or anything else to test it because they're so common in JYs & cheap at parts stores that I just swap a known-good one every time. I probably have 6 common MAPs in my junkpile, and a few more in my tool box - I collect them at JYs when I'm buying big parts, so they don't charge me for the little stuff like that.

What's the oldest Ford EFI you've worked on? I think mine was an early-80s (maybe 82) LTD or Mark with TBI.