Mailing List flyrotary@lancaironline.net Message #10566
From: Russell Duffy <13brv3@bellsouth.net>
Subject: EM-2 MAP readings
Date: Wed, 18 Aug 2004 14:48:30 -0500
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>
Message
Greetings,
 
I've taken up enough of Tracy's time on the phone today, so I figured I'd post this to the list, and he (or anyone else) can comment. 
 
As I mentioned, my MAP reading is only 27 on the ground, at full throttle.  I thought I had this isolated to the intake being too restrictive, but Tracy suspects it's more a matter of the way the ports are positioned on the TWM throttle body.  He also mentioned that someone else (Al, maybe) had the same issue, with lower than expected MAP readings when using the ports on their TWM.  Is anyone using the TWM TB ports, and seeing near 30 MAP?  I sure wish I had documented this little tidbit of info from the previous version.
 
I tried to check the EM-2 MAP reading today, but as usual, came away with more questions than answers.  Tracy said that the EM-2 would read MAP using it's internal sensor, when the EC-2 was off, along with displaying NOP on the RPM display.  When the EC-2 is on, he said it should read the MAP from the EC-2 sensor.  There's only one cal, so you can only calibrate one, or the other, but you really only use one of the sensors, so this isn't a problem.  
 
So, I turned on the EM-2, and read 30.0.  According to my altimeter, that's probably not quite right, but very close.  Next, I turned on the EC-2.  Now, the MAP shows 20.4.  At this point, I got excited, figuring the MAP just needed to be calibrated.  I looked at the cals and decided to correct for the "sensor offset".  This will only be meaningful if you're familiar with the later EM-2 programming.  Once I corrected the sensor offset, the EC-2 on reading was now 30.0, and the EC-2 off reading was 39.6. 
 
To test the range of the cal, I hooked up a vacuum pump to the EC-2 MAP hose, and pulled about 10 inches of vacuum.  Unfortunately, the EM-2 still reads 30.0.  Nothing I could do with the vacuum line would change the MAP reading, so I have to conclude that the EM-2 won't read this correctly, even with the EC-2 on, unless the engine is running.  I did try both controller hoses BTW.  
 
When I realized that wasn't working, I set the sensor offset back to where it was originally, and figured I'll just have to put a vacuum gauge in the MAP line the next time I run the engine.  Unfortunately, that probably won't be before Sat. 
 
Cheers,
Rusty (one step from ordering another SlingShot kit)
 
 
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