Prop RPM

[CBarber]

I am using an alternative engine, a Mazda 13b turbo rotary.  I have an engine  RPM monitor that gives me my engine RPM that is made for the rotary from RWS (Real World Solutions), a one man show that provides rotary PSRU, engine monitors and controllers.  It is an electronic ingnition and the engine RPM is read from the engine controller.

The rotary runs at high RPM's, 4000 to 6000 plus. My PSRU is a 2.17 reduction drive.   The RWS unit gives me the engine speed fine.  HOWEVER, I want to use the Dynon engine monitor to provide the propeller speed instead of engine RPM.  What type of sensor do y'all at Dynon suggest for prop speed.  My IVO prop uses a small magnet embeded in the prop for its constant speed adjustments, is there an equivilant araingment that you could suggest? Or, what would you suggest for this reading.

I regret my ignorance on this topic.  I searched the manual and the forum but have not found anything that I can currently wrap my mind around, so I may have found the answer and not even realized it....yeah, I am building an airplane...... :

Thanks.

Chris Barber
Velocity N17010
Ellington Field
Houston

 

[dynonsupport]

You have a few options.

1) Do you actually need to display the prop speed as measured, or are you OK with SkyView calculating it off RPM? You can configure SkyView to show you RPM divided by 2.17. This assumes that you can get RPM from your engine controller easily.

Configuring SkyView to do this requires a touch of work that isn't in the manual, so let us know if you want to go that way and we can help.

2) You may be able to steal the signal from the prop controller. If it has a magnet, it has a sensor somewhere. You can likely pull the signal off this sensor from one of the wires and use that with SkyView. You'd probably need to talk to IVO about the sensor and see what wire pulses and at what voltage. We can deal with small voltages and we don't put a big load on the signal so it can probably be shared.

3) Add another hall effect (magnetic) sensor to pick up the magnet that is already there. This is possible for sure, but we're not experts at what parts are sold out there to do this.  Theoretically, Westach PN 720-14R should do what you need if you can get it mounted right.

http://www.aircraftspruce.com/catalog/inpages/integra6724_11.php

Let us know what way you want to try first and we can help more.

(Previous Mazda RX-8 owner, so I love me some rotary goodness!)

 

[CBarber]

I will likely use option 1. My ECU does have a tach output. The manual for the ECU seems to have a bit of conflicting information that I have to wade through the information regarding the voltage. It makes reference to a 5v output but also discusses 12v out so I need to figure out which SV wires to use, low or high. I hope if I chose poorly, I don't make things FUBAR.

On a related note, the tach output from the Engine Control Unit (ECU) only has ONE signal wire, however the SV has two (actually four, if I understand properly, two for over 10 v and two for belor 10 v). Since I only have one wire from the ECU, which wire from the SV should be connected to it? Does the other SV wire go to ground??? Yeah, to the engineer types on here this must sound very basic, but I am just a dumb cop (and recovering attorney ). As always, thanks.

Chris Barber
Houston
Fly Rotary
(or taxi around Ellington Field in a very expensive go-cart...so far?? )

 

[CBarber]

Ok, got the tach working. So, what do I need to do to have it give my PSRU at the prop speed of 2.17?

Again, thanks.

Chris

 

[dynonsupport]

Quick follow ups for anyone with equivalent questions:

If you have a voltage that might be 5V-12V, you can use the low voltage input. You won't hurt anything. Even 20-ish volts won't hurt the low voltage input.

If you have only one tach output, you can hook it to either the left or right on SkyView. It doesn't care and it will work automatically.

Do not ground the unused RPM inputs, just don't hook them to anything.

Ok, to make it work and read prop RPM:

You need to be running the latest software (3.2). We actually made this a lot easier than it would have been in the past, where you would have needed to edit a text file on your computer. Now you don't.

First, you need the system reading the right RPM. Not just any RPM, but the correct speed. This means you need the right pulses/rev set up. With most electronic ignitions, this will be 1, but it might be 2, or 0.5, or some other number. No harm in trying and adjusting until it works, or maybe your ECU manual makes this clear.

This is all adjusted in the setup menu under SETUP->EMS SETUP->ENGINE INFORMATION

If you only hooked to one input, you only need to adjust the left or right number, and if you forget which you used, adjust both.

To make this read prop RPM, it's as easy as multiplying the number that gets you the right RPM by 2.17. So if you had one, enter 2.17. If you had 2, 4.34. If you had 0.5, 1.09.

Now it will read prop RPM, not engine RPM.

 

[CBarber]

Thanks. I am heading out to the hangar in a couple of minutes and I should be able to give it a try.

Chris

 

[CBarber]

Worked like a charm guys. Thanks again.

Chris

 

[cleesgt]

I'd like to simultaneously display both engine rpm and prop rpm on a D1000. I have a rotary engine, with a PRSU that has a 2.17:1 reduction ratio. In the sensor debug page of the D1000, the Pin 32/34 will read an rpm of 3000 for "Value" and 1382 for "Val (cal)" [I don't remember if that's exactly how the column headings are spelled]. 3000:1382 is 2.17:1, so the ratio is working. What I can't figure out is how to get two separate RPMs displayed. I can get either 1382 or 3000 to display. I've tried splitting the tach output to left and right channels, both high voltage and low, but no success getting separately displayed rpm's. Any advice?

 

[mmarien]

I believe the two pin pairs 32/34 and 33/35 are the only pins that read a pulse. They are interfaced to a single RPM gauge. See the explanation starting on page 7-3 of the Installation Manual. The right column of Table 15 explains the function. A blank in that column means it has a fixed function. Voltage is the most universal function, but unfortunately it won't work for your situation. :-/

Best bet is to mount a separate Tach. Nothing says you have to be conventional.

 

[cleesgt]

Thanks mmarien. I now understand why there are L and R tach inputs (both L & R magneto channels required), and why there are two separate lines on the D1000 debug page, pin 32/34 for L channel, and 33/35 for R channel. I'm frustrated by no potential solution for two RPM readings. Two recommendations for Dynon: 1) enable two RPM displays - a separate "info" widget for RPM; or two needles on a dial, etc, and 2) explain this limitation in the installation manual, as it affects all non-direct drive installs. Why is this important - because there are limitations for both engine and prop, yet the D1000 doesn't allow displaying both (unless I'm wrong). Thanks again for your help.

 

[dynonsupport]

There is a way to monitor and display two different RPMs. It's so rarely asked for that it's not officially supported, but we can help you do it. Give tech support a call or email and we can help.