Well Bill,
if the Kolsman window is where you set your altimeter setting (mb or inches mercury) you will never see field elevation (pressure) unless you are at sealevel.
E.g. if you have 29.92" at sealevel (and in the window) you still have 29.92 in the window (you set it there!) when you get to 6500'. Your actual ambient pressure is around 23.42".... (which you should be reading on your manifold pressure gauge - engine stopped...
Unless, I got it wrong the last 15 years and 9500 hours - ohhh my...!!
TJ
On 6/4/07, Bill Schertz <wschertz@comcast.net> wrote:
Al, thanks for the clarification on what sensor the EM2 is reading.
When I set an 'old fashioned' altimeter to field elevation, the engine is not running, isn't the Kolsman window reading the local pressure -- ie the 'manifold' pressure?
Bill Schertz
KIS Cruiser #4045
----- Original Message -----
Sent: Sunday, June 03, 2007 11:55 AM
Subject: [FlyRotary] Re: EC-2/EM-2 manifold pressure
When I have my EM-2 on, EC-2 off, the Manifold pressure reads the barometric pressure (29.7 today).
When I then turn on the EC-2, the manifold pressure increases to 32.9. This seems peculiar, have you noticed anything like this?
Bill Schertz
KIS Cruiser #4045
When the EC2 is off, it is using the reading from the sensor in the EM2. When it is on, it is reading the sensor in the EC2. I have also found considerable disagreement on these sensors. I also found that I had to change the calibration on the MAP pressure channel on the EM2 to get the correct reading (with EC2 on, we don't care what the sensor in the EM2 is reading). I have no idea why the calibration should be different on different units that use the
sam
e sensor; but there it is. You can get a vacuum gage (actually a pressure gage, so you have to subtract from atmospheric) at a reasonable price from McMaster-Carr, or I could loan you mine.
Also, it should not necessarily read the barometric pressure; you have to adjust for altitude. Barometric is equivalent sea level (or something like that).
Al
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