vacuum measurement
Thread Starter
Racer
Joined: Oct 2005
Posts: 405
Likes: 0
From: 1984 crossfire, Alhaurin de la Torre Malaga, Spain
vacuum measurement
1984 Crossfire.
Help me out guys, I like to measure my vacuum because I expect a small problem there. Rough idle. I am now doing the smaller jobs to get the car right.
I understand it should be about 18 - 20 Inch Hg. How is that defined? 18 - 20 inch absolute pressure or 18 - 20 inch below ambient? I always work in absolute pressure, but because I read that 15 is low, I assume we talk about pressure below ambient.
And where do I have to measure, A T at the MAP sensor?
Help me out guys, I like to measure my vacuum because I expect a small problem there. Rough idle. I am now doing the smaller jobs to get the car right.
I understand it should be about 18 - 20 Inch Hg. How is that defined? 18 - 20 inch absolute pressure or 18 - 20 inch below ambient? I always work in absolute pressure, but because I read that 15 is low, I assume we talk about pressure below ambient.
And where do I have to measure, A T at the MAP sensor?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
By definition, it is ambient. The lower pressure (partial vacuum)above the column of mercury (Hg.) allows the ambient pressure to support a column of mercury 18" to 20" tall. If there were no pressure (absolute zero pressure) the vacuum side would be the HIGH pressure in your system. A standard, regular, automotive vacuum gauge should suit your purposes. You can measure the intake manifold vacuum almost anywhere on your Crossfire's intake. Disconnecting the MAP hose, SHOULD cause a code to be set. Where the PCV hose connects, at the front of the manifold ought to be an easy, effective, connecting point.
A vacuum leak can cause a rough idle. The TBs on your Crossfire need to be balanced for airflow for the smoothest idle. Do you have your FSM?
RACE ON!!!
A vacuum leak can cause a rough idle. The TBs on your Crossfire need to be balanced for airflow for the smoothest idle. Do you have your FSM?
RACE ON!!!
Thread Starter
Racer
Joined: Oct 2005
Posts: 405
Likes: 0
From: 1984 crossfire, Alhaurin de la Torre Malaga, Spain
Thanks a lot for the info, now I can start measuring. I design vacuum dryers with RF energy, so I am used at absolute pressure (zero is zero, ambient is 1 bar, 76 cM Hg). So I have to rethink what is what.
Thread Starter
Racer
Joined: Oct 2005
Posts: 405
Likes: 0
From: 1984 crossfire, Alhaurin de la Torre Malaga, Spain
Do not have the FSM. Like to have it, but the company does not accept the oldest and real American credit card in the world AE. And that is what I have.
