Rocky Mountain Coversion
- Thread starter Brablec
- Start date
I'm in the middle of doing it now. Spent the whole of today in the cockpit cutting wires from the RMI edge connector and splicing them on to my custom D10 harness.
I'm replacing the Hall effect current sensor with a shunt, the oil temp sensor goes because the D10 needs a thermistor, oil pressure and fuel pressure should be OK, carb temp looks identical, the MAP sensor I'm hoping is pretty standard, fuel sender and tach pickup (from mags) are straightforward, and the CHTs and EGTs connect straight in. The D10 only gives you two contact inputs, but I've kluged the aux thermocouple input to act like a contact input. In general I've retained the RMI philosophy of taking the shields to master ground (pin 3) and the sensor return lines to a signal ground (pin 5, 16, 17) since it's good practice and the splices were all in place.
I guess when the power goes on my sins will be revealed.
Peter
I'm replacing the Hall effect current sensor with a shunt, the oil temp sensor goes because the D10 needs a thermistor, oil pressure and fuel pressure should be OK, carb temp looks identical, the MAP sensor I'm hoping is pretty standard, fuel sender and tach pickup (from mags) are straightforward, and the CHTs and EGTs connect straight in. The D10 only gives you two contact inputs, but I've kluged the aux thermocouple input to act like a contact input. In general I've retained the RMI philosophy of taking the shields to master ground (pin 3) and the sensor return lines to a signal ground (pin 5, 16, 17) since it's good practice and the splices were all in place.
I guess when the power goes on my sins will be revealed.
Peter
- Joined
- Mar 23, 2005
- Messages
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Peter,
Overall that looks reasonable, except for MAP. We use a GM automotive sensor. If yours looks like this it might will work, if it doesn't, it won't. There are three versions that look like ours, only one works.
Overall that looks reasonable, except for MAP. We use a GM automotive sensor. If yours looks like this it might will work, if it doesn't, it won't. There are three versions that look like ours, only one works.
Thanks Peter. It sounds like I will only need a couple new senders/sensors and most of the ones I already have will work. I purchased the a/c with the RMI unit in it so some of the stuff you talked about is a little bit foreign but I think I get the picture. Was Dynon helpful in explaining what components you needed to purchase for the conversion? I hope all works well when you hit the switch the first time.
Doug
Doug
Thanks DS. From memory (I'm an hour's drive from the hangar) my MAP sensor looks similar, maybe identical. RMI had a number of 2 bar sensors that were interchangeable as far as RMI were concerned. These are
Wells SU-129
GM #16009886
AC Delco #2131520
Standard AS-4
Additionally, the schematic calls out a GM# 629 6249.
Are any of these known to work or not work?
Doug, Dynon Support is very helpful if you ask a specific question, and sometimes they volunteer valuable info like the previous post. I wouldn't expect them to advise me generally on the conversion because their expertise is Dynon, not RMI. If a lot of us change from RMI to Dynon now that RMI is phasing out, then DS may get to know what works best. But I think that's a way down the track. The only time I found them less than forthcoming was when I wanted to source a thermistor to modify the RMI oil temperature sensor. I wanted a two lead sensor to avoid the potential ground problems with the Dynon single wire sensor. Someone "upstairs" decided this was a Trade Secret. Even then however, the support man slipped me a list of calibration points which helped me towards a solution. The support is very good.
And by the way, you can download the RMI manuals from http://www.rkymtn.com/
Peter
Wells SU-129
GM #16009886
AC Delco #2131520
Standard AS-4
Additionally, the schematic calls out a GM# 629 6249.
Are any of these known to work or not work?
Doug, Dynon Support is very helpful if you ask a specific question, and sometimes they volunteer valuable info like the previous post. I wouldn't expect them to advise me generally on the conversion because their expertise is Dynon, not RMI. If a lot of us change from RMI to Dynon now that RMI is phasing out, then DS may get to know what works best. But I think that's a way down the track. The only time I found them less than forthcoming was when I wanted to source a thermistor to modify the RMI oil temperature sensor. I wanted a two lead sensor to avoid the potential ground problems with the Dynon single wire sensor. Someone "upstairs" decided this was a Trade Secret. Even then however, the support man slipped me a list of calibration points which helped me towards a solution. The support is very good.
And by the way, you can download the RMI manuals from http://www.rkymtn.com/
Peter
- Joined
- Mar 23, 2005
- Messages
- 13,226
Those look like the right part #s, so I bet it will work. Neat!
For those who like crawling over acres of broken glass, here's how to convert the Rocky Mountains oil temperature probe to suit the D10, so that you get away from the grounding problems that plague the single wire Dynon sensor.
Pull the RMI sensor (AD594 from memory) out of the probe body. Insert a Betatherm 10K3A1B thermistor in series with a 47 ohm 1% resistor, ensuring good thermal contact between the thermistor and the probe body. I used the white heatsink thermal compound used for mounting transistors. Take the two leads back to the D10 using pin 7 and one of the grounds at the D10. Polarity is not important. Don't let either lead short to the probe body.
I calibrated mine at 10 deg C intervals from 25 deg to 120 deg. Maximum error indicated on the D10 was 1 deg C. You can use different values of series resistance to trim the reading to exactly 120 at 120 deg. The range below 120 will fall into place. You might like to keep the resistor outside the probe to facilitate this.
Finally, configure oil temp for sensor type 3 (GRT)
If you are in the USA you may as well buy the GRT sensor. But if you're on the other side of the world like me, where the freight costs four times the price of the item, rolling your own may make sense.
Peter
Pull the RMI sensor (AD594 from memory) out of the probe body. Insert a Betatherm 10K3A1B thermistor in series with a 47 ohm 1% resistor, ensuring good thermal contact between the thermistor and the probe body. I used the white heatsink thermal compound used for mounting transistors. Take the two leads back to the D10 using pin 7 and one of the grounds at the D10. Polarity is not important. Don't let either lead short to the probe body.
I calibrated mine at 10 deg C intervals from 25 deg to 120 deg. Maximum error indicated on the D10 was 1 deg C. You can use different values of series resistance to trim the reading to exactly 120 at 120 deg. The range below 120 will fall into place. You might like to keep the resistor outside the probe to facilitate this.
Finally, configure oil temp for sensor type 3 (GRT)
If you are in the USA you may as well buy the GRT sensor. But if you're on the other side of the world like me, where the freight costs four times the price of the item, rolling your own may make sense.
Peter
PhantomPholly
New Member
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- Jul 27, 2007
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- 582
Or, you can simply fix your ground problem.
Posted by: PhantomPholly Posted on: Yesterday at 8:26am
Or, you can simply fix your ground problem.
Yes, again and again.
The two lead sensor that references the signal to the instrument ground is a far more reliable engineering practice.
[smiley=cool.gif]
Peter
Or, you can simply fix your ground problem.
Yes, again and again.
The two lead sensor that references the signal to the instrument ground is a far more reliable engineering practice.
[smiley=cool.gif]
Peter
PhantomPholly
New Member
- Joined
- Jul 27, 2007
- Messages
- 582
You can do that, too, without buying new sensor. Mind you, if I ever need to replace them I will get the two wire model (well maybe, not sure I want to have to run another wire).
Create a ground strap for the sensor
Ground the Sensor
Seems a waste to throw out a perfectly good sensor...
Create a ground strap for the sensor
Ground the Sensor
Seems a waste to throw out a perfectly good sensor...
If you're converting from RMI the ground wire is already installed.
You can't isolate the Dynon sensor from ground. Because of the high currents, low voltages and low resistances involved in the engine/airframe return path, a parallel ground wire for the sensor does not help. It just shunts some of the current and the error voltage remains.[smiley=evil.gif]
Peter
You can't isolate the Dynon sensor from ground. Because of the high currents, low voltages and low resistances involved in the engine/airframe return path, a parallel ground wire for the sensor does not help. It just shunts some of the current and the error voltage remains.[smiley=evil.gif]
Peter