Static MP Reading

baldcaldwell

baldcaldwell

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We have not started the engine yet, so maybe this will change after we are running. Just curious why my manifold pressure is not indicating the outside ambient pressure with the engine off. See the pic.


IMG_2757.jpeg
 
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M

maartenversteeg

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Hello Rob,
The Kavlico sensors are the ones to be used for Fuel and Oil pressure, not for the MP sensor. There is a completely different sensor to be used for the manifold pressure as this is a much lower pressure range
 
swatson999

swatson999

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baldcaldwell

baldcaldwell

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I
rkorff said:
This is the one I use Bob. Works well for me. Part number 100434-000. Notice it reads in inches of mercury, not psi.

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MAP, 1/8" hose, 0-60 In Hg
Category:
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SKU 100434-000

$65.00

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Qty​
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MAP, 1/8 hose, 0-60 In Hg





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Click to expand...
I have one of those... It came with the RV-10 FWF kit I purchased from Vans (I'm building a Bearhawk). I had too many issues with the install. No place to mount it (for me). Needed a restrictor that I could never seem to source. Ordered multiple restrictors and hoses and finally gave up on it and then came across the Garmin Kavlico version referenced above... So between the Dynon version and the Kavlico version, I think I'm well over $250 invested in trying to establish a MP sensor for this thing.... :mad:
 
swatson999

swatson999

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baldcaldwell said:
Checked wiring and lines. Can't find any issues there. I'm using the kavlico P4055-150G Pressure Transducer. Anyone know if this create erroneous MP readings?

Click to expand...

Well, it *might* work, who knows...but the part number listed is for up to 150 PSI. Sea level atmospheric pressure (standard) is just about 15 PSI. So you're probably already starting out with the wrong part.

But be that as it may, and assuming you plumb it correctly to the cylinder, you'd probably need to figure out the right parameters for it to work with the Dynon EMS, either on pin 26 (the original MAP data pin), or one of the EGP pins. And then, of course, you'd need to get it from PSI to InHg on the display.
 
baldcaldwell

baldcaldwell

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swatson999 said:
Well, it *might* work, who knows...but the part number listed is for up to 150 PSI. Sea level atmospheric pressure (standard) is just about 15 PSI. So you're probably already starting out with the wrong part.

But be that as it may, and assuming you plumb it correctly to the cylinder, you'd probably need to figure out the right parameters for it to work with the Dynon EMS, either on pin 26 (the original MAP data pin), or one of the EGP pins. And then, of course, you'd need to get it from PSI to InHg on the display.
Click to expand...

That makes total sense... Still wondering why Garmin recommends this transducer for their G3X if it is a 150PSI sensor.

I will keep looking for something. I am too far along in my build to try to mount something on the interior (cold) side of the firewall. Would be a MAJOR set back if I absolutely had to go that route.

Thanks to everyone for your thoughts on this issue...
 
kurtfly

kurtfly

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MAP needs to be absolute pressure. Gage pressure is for oil and fuel pressure. The physical construction of Absolute pressure sensor has a vacuum on the other side of the diaphragm. Gage pressure the diaphragm is vented to outside static pressure. If you want to use the Kalvico P4055 series the part needs to be P4055-30A-E4A. 30 psia is what you need. This will allow up to ~60 ‘MP. The P4055-150G will never work in a manifold pressure application. Must have the “A” in the part number.

I bet Garmin sent you the wrong part.

Dynon Sensor calibration file requires the MAP Engineering Units to be in PSI. The SV internal programming will convert to inHg when it is displayed.

The Kalvico typical output is 0.5 VDC to 4.5VDC. This calibration is y=7.5X-3.75. this makes the SV calibration:

sensor={
id=P4055-30A
;VERIFIED POLY, FILTER?
function=PRESSURE
pins=C37_P26
; THIS NAME IS FOR A SPECIAL CASE FUNCTION WHICH WILL NOT APPEND "PRESSURE" TO THE END OF THE SENSOR NAME
name=MAP
;The below are in PSI, not inHG, like all pressure senders
min_val=1.25
max_val=29.5
resolution=1
round=.1
is_piecewise=0
low_coeff={
c_x4=0
c_x3=0
c_x2=0
c_x1=7.5
c_x0=-3.75
}
low_resistance=NONE
low2high_cross=0
high_coeff={
c_x4=0
c_x3=0
c_x2=0
c_x1=0
c_x0=0
}
high_resistance=NONE
high2low_cross=0
window=.2
shift=3
age=16
}
 
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kurtfly

kurtfly

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Another note: for manifold pressure restrictor. I had used a brass screw in fitting on my Lycoming # 3 cyl.. Before installation, using a propane torch I filled the fitting with plumbers solder. Then drilled a #60 hole through the solder. This allowed the pressure change to be seen and provided the protection from a overly lean cylinder if MAP hose failed.
 
baldcaldwell

baldcaldwell

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Status update...

I have given up on the Klavico sensor will be using the Dynon MP sensor on the engine side of the FW as shown in some of the posts here, and confirmed even further after some digging. At this point, I am trying to gather up the correct fittings to connect cylinder #5 to the sensor that I am mounting to the passenger side of the FW. I have ordered a 1/8" NPT to 1/4" barb hose fitting and some Aeroquip 306-4 hose to attach to the MP sensor probe. I will create a .040 restrictor (maybe a #5 button head as suggested above) to go in the hose barb on the cylinder. Hopefully this should work. If anyone has any thoughts on this, please let me know...
 
Raymo

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I have my MAP sensor mounted nicely on the top engine mount tube with two Adel clamps. I didn't want more holes in my FW.

Call Tom at TSFlightlines.com. He'll get you everything you need. Might even have a restrictor fitting for the cylinder (as is used for the oil pressure fitting).
 
baldcaldwell

baldcaldwell

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Been using Tom for all of my fuel lines. Great guy! Was planning to call him for this setup once I finalized my setup. Thanks!
 
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