AbandonedBronco
Famous Member
Hi all,
Still getting used to the nuances of the Holley Sniper I have installed (love it so far).
However, one thing I have some curiosities about.
Holley documentation states the conversion between the pressure that the MAP sensor reads (kPa) and the vacuum gauge reading (hg).
100 kPa = 0 hg
75 kPa = 7.5hg
50 kPa = 15hg
25 kPa = 22.5hg
0 kPa = 30hg
Basically, this comes out to
Engine vacuum (hg) = 30 - kPa * 0.3
The issue I'm having is that there's quite a disparity between what the MAP sensor is reading, and what my vacuum gauge is reading (which is on direct manifold vacuum).
At idle, my MAP sensor reads 40kPa, which mathematically comes to 18hg. However, my vacuum gauge reads 14.5hg (which would be about 52 kPa). There's quite a difference between 14.5hg at idle and 18hg. I checked the vacuum reading with 3 different vacuum gauges, and they all read similar.
Shouldn't these be reading roughly the same? They're both intake manifold pressure (or lack thereof).
Thoughts?
Still getting used to the nuances of the Holley Sniper I have installed (love it so far).
However, one thing I have some curiosities about.
Holley documentation states the conversion between the pressure that the MAP sensor reads (kPa) and the vacuum gauge reading (hg).
100 kPa = 0 hg
75 kPa = 7.5hg
50 kPa = 15hg
25 kPa = 22.5hg
0 kPa = 30hg
Basically, this comes out to
Engine vacuum (hg) = 30 - kPa * 0.3
The issue I'm having is that there's quite a disparity between what the MAP sensor is reading, and what my vacuum gauge is reading (which is on direct manifold vacuum).
At idle, my MAP sensor reads 40kPa, which mathematically comes to 18hg. However, my vacuum gauge reads 14.5hg (which would be about 52 kPa). There's quite a difference between 14.5hg at idle and 18hg. I checked the vacuum reading with 3 different vacuum gauges, and they all read similar.
Shouldn't these be reading roughly the same? They're both intake manifold pressure (or lack thereof).
Thoughts?