Map sensor for vacuum gauge
Thread Starter
|
Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
Map sensor for vacuum gauge
Would a MAP sensor work as a vacuum gauge? If I read things right, a 2 bar unit would have the same range as a regular gauge.
I'd like to hook one to a scope and see the how the vacuum changes for each cylinder. I'm guessing that a MAP sensor would respond quickly enough for this, but I don't really know.
Honeywell makes something for this, but last I checked, they wanted around $400 for it. I'm hoping to get something for a lot less because this is mainly to satisfy my curiosity about a few things.
Thanks,
ford2go
I'd like to hook one to a scope and see the how the vacuum changes for each cylinder. I'm guessing that a MAP sensor would respond quickly enough for this, but I don't really know.
Honeywell makes something for this, but last I checked, they wanted around $400 for it. I'm hoping to get something for a lot less because this is mainly to satisfy my curiosity about a few things.
Thanks,
ford2go
Elder User
Joined: Sep 2004
Posts: 941
Likes: 4
A Ford MAP sensor won't do what you want. They produce a variable frequency output proportional to manifold pressure. You will struggle to make heads or tails of that looking at the waveform on a 'scope.
A GM style MAP sensor might produce useful results -- they produce a variable voltage output. You'll need a source of regulated 5 volts to feed it. I don't see why you'd need a "two bar sensor" unless you want to use it on a turbocharged vehicle. These sensors are readily available and cheap at your local U-Pull-It junkyard. Bring wire cutters and snip the harness so you'll have a connector to go with the sensor.
The ECM does not need the MAP sensor to react especially quickly. Plus the intake manifold itself tends to average out vacuum pulses. So how much cylinder-to-cylinder changes will you be able to see? I don't know. But it may be worth a try....
A GM style MAP sensor might produce useful results -- they produce a variable voltage output. You'll need a source of regulated 5 volts to feed it. I don't see why you'd need a "two bar sensor" unless you want to use it on a turbocharged vehicle. These sensors are readily available and cheap at your local U-Pull-It junkyard. Bring wire cutters and snip the harness so you'll have a connector to go with the sensor.
The ECM does not need the MAP sensor to react especially quickly. Plus the intake manifold itself tends to average out vacuum pulses. So how much cylinder-to-cylinder changes will you be able to see? I don't know. But it may be worth a try....
Thread Starter
|
Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
Thanks for the input. I was thinking 2 bar because I get confused about the various scales. As I recall, ordinary vacuum gauges are marked something like 0 - 30. However, as I think about it, I realize that this is referenced to inches Hg.
I'm just trying to make sure that the scale is broad enough. If a normal 1 bar sensor covers the same range, all is well. I'll get one from a junkyard, and we'll see if it's fast enough.
The Ford setup isn't out of the question, if the GM proves too slow. I'm guessing that it's a capacitive sensor, and there are ways to deal with that. However, it would be a large pain.
As for a regular vac gauge -- it won't tell me what I'm looking for. ( I do have one) . Using a scope, I can sync to the ignition or injectors to identify what's happening as it relates to each cylinder.
As I said previously, this is all to satisfy my morbid curiosity. I'm retired from 30+ years of working with electronics and computers. It's fascinating stuff, but so are engines, and now I have some time to figure some stuff out -- or at least try.
ford2go
I'm just trying to make sure that the scale is broad enough. If a normal 1 bar sensor covers the same range, all is well. I'll get one from a junkyard, and we'll see if it's fast enough.
The Ford setup isn't out of the question, if the GM proves too slow. I'm guessing that it's a capacitive sensor, and there are ways to deal with that. However, it would be a large pain.
As for a regular vac gauge -- it won't tell me what I'm looking for. ( I do have one) . Using a scope, I can sync to the ignition or injectors to identify what's happening as it relates to each cylinder.
As I said previously, this is all to satisfy my morbid curiosity. I'm retired from 30+ years of working with electronics and computers. It's fascinating stuff, but so are engines, and now I have some time to figure some stuff out -- or at least try.
ford2go
