Skyview tach fluctuating (Rotax 914)

[TOMARK]

Hello I need help with our Dynon Skyview the SV-EMS tach indicating correctly until I got 3000rpms than it starts fluctuating +- 600 rpms and will not stablize. Engine is rotax 914. We connect PC to the TCU and the rpms look good. what can be the problem? Also the rpms drops to much when we trun of left magneto and right ftom 4000 to 1600 rmps. See attachement

 

[Dynon]

What are you hooking that tachometer signal up to?

 

[TOMARK]

We are reading RPMS from the TCU unit from the pin number 13 and the ground is on the 26.

 

[Dynon]

So just to be clear, you should have the following connections:

Connect Pin 13 of the TCU to SV-EMS-220 Pin 34 (Low Voltage RPM Left Input).
Connect Pin 26 of the TCU to any of Pins 3, 5, 13, 16, 17, or 30 (Ground).
Do not install a resistor in the wires between the TCU and the SV-EMS-220.

Does that sound like your installation?

Are your fluctuations showing higher or lower than correct RPM?

 

[TOMARK]

Yes that is correct. But my college yesterday put a 100k ohm resistor and one diode between the TCU and the SV-EMS and it seems that work even that the installation manual says that we shouldnt do so. Now the RPMS from the TCU is the same as SV-D1000 indicating. But I´m not sure about this solution. Without the resistor the fluctuating was + and - 500 sometime.

 

[Dynon]

Well, it's more that it shouldn't be necessary. The resistors just serve to change the level of the voltage pulses. So if that helped, it's absolutely acceptable. It certainly won't harm anything. I'd just make sure that you still have a consistent and accurate reading when at lower RPMs (where the voltages being output from the TCU are lower, and then are further reduced by the resistor)

 

[TOMARK]

Thank you for your advice, but why is than in installation manual trictly write not to instal restistors there?

 

[TOMARK]

Also I want to ask something. We need to measure the Mainfold pressure and I cant find anywhere what kind of sensor will comunicate with daynon skyview, can you recomend me some MPS sensor for the Dynon skyview? We need to have an indication when the turbo starts to run and also we need information of the MPS. Thank you

 

[Dynon]

We sell the compatible manifold pressure sensor ourselves, and is the one we recommend you purchase if you're going to measure manifold pressure. Also, here is a list of other parts/suppliers that provide ones that should be electrically the same:

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1132440037

 

[Dynon]

Thank you for your advice, but why is than in installation manual trictly write not to instal restistors there?

We write our manual based on the specifications that are available and what we expect to work, but occasionally there are exceptions or minor adjustments that are needed.

 

[tomplatner]

This past weekend we started a Rotax 914 with electrical hookup as indicated in v13 of Installation manual and copied here:
Connect Pin 13 of the TCU to SV-EMS-220 Pin 34 (Low Voltage RPM Left Input).
Connect Pin 26 of the TCU to any of Pins 3, 5, 13, 16, 17, or 30 (Ground).
Do not install a resistor in the wires between the TCU and the SV-EMS-220.

In our case, the Engine RPM was not fluctuating, but what extremely high (reading 10,000 rpm ) when engine was just above idle conditions.

We are confident the wires are all connected properly , and the ground (pin 26) is good. 

Does anyone have any thoughts or ideas?   I have a email request into Tech Support.

 

[tomplatner]

All, I have been communicating directly with Steve with Dynon Tech support staff (Rev. Case 214111) and can now confirm the following information: 1) On the Rotax 914, Pin 13 from the TCU produces a signal with a Peak-to-Peak reading of ~115 vDC at an operating RPM of around 3000 RPM. 2) The current Dynon documentation instructs users to connect the PIN 13 from the TCU to SV-EMS 220 Pin 34 (Blue wire) which is for "low voltage RPM signals <12 volts". THIS IS INCORRECT due to the fact that the signal is 115 v Peak-to-Peak. 3) The correct input pin on the SV-EMS 220 should be PIN 32 (White/Green) which is designed for RPM input signals greater than 10 Volts.

Recently we tested connecting to TCU Pin 13 to EMS 220 Pin 32 and the RPM signal was correct! (We compared the RPM reading from USB cable connected to TCU with the Dynon indicated and they track)

Bottom line, working with Steve at Dynon to get the documentation corrected so that it correctly instructs user to connect to Pin 32.

Attached is picture from O-scope showing the Peak-to-Peak signal from the TCU

 

[dynonsupport]

Noted - thanks for letting us know. This has been passed along for a future update to the SkyView System Installation Guide.

All,  I have been communicating directly with Steve with Dynon Tech support staff (Rev. Case 214111) and can now confirm the following information:   1) On the Rotax 914, Pin 13 from the TCU produces a signal with a Peak-to-Peak reading of ~115 vDC at an operating RPM of around 3000 RPM.    2)  The current Dynon documentation instructs users to connect the PIN 13 from the TCU to SV-EMS 220 Pin 34 (Blue wire) which is for "low voltage RPM signals <12 volts".   THIS IS INCORRECT due to the fact that the signal is 115 v Peak-to-Peak.   3) The correct input pin on the SV-EMS 220 should be PIN 32 (White/Green) which is designed for RPM input signals greater than 10 Volts.   

Recently we tested connecting to TCU Pin 13 to EMS 220 Pin 32 and the RPM signal was correct!  (We compared the RPM reading from USB cable connected to TCU with the Dynon indicated and they track)

Bottom line,  working with Steve at Dynon to get the documentation corrected so that it correctly instructs user to connect to Pin 32.

Attached is picture from O-scope showing the Peak-to-Peak signal from the TCU