advanced engine instrumentation ?

[Bruce Tuncks]

Thanks Markdun. The LM355 is sold as a temperature IC I know. Do you turn on the carby heat when you think the temperature is going to zero?

[RFguy]

why does everybody love the LM335 ?

[Markdun]

Thanks Markdun. The LM355 is sold as a temperature IC I know. Do you turn on the carby heat when you think the temperature is going to zero?

Yes, particularly when warming up the oil on those cold frosty mornings after the fog has lifted.

I’ve never had icing in the carb in either with the Jab motor or the VW, both with CV Bing carb’s mounted in similar places at the rear of the motor & just below it. My VW set up had a ‘T’ there on the inlet runners with a flange bolted to the crankcase which kept it warm like the Jab inlet. Still I’ve known of people who have landed on a railway track wrecking their undercarriage, saying it was due to icing. So I’m cautious. Same for vapour in the fuel.... not so much for the Bing carb which has a reasonably large float bowl to separate out the vapour, more for the Rotec TBI carb I have on the Corby.... never experienced it and don’t want to!

RF guy, I suppose people use the LM335 because most commercial engine monitoring systems allow for it as a plug and play. And it’s cheap and readily available.

[Kyle Communications]

Yep its cheap...I made my own temp sensors for oil and water for use on the RDAC in the Girlfriend..they work a treat..far cheaper than the MGL ones. I just got some throw away original temp sensors and drilled out the guts and epoxied the LM335 inside with the appropriate cables and ran them to the RDAC...works perfect and very accurate

[RFguy]

Does anyone know what the peak gas pressure is (in Pascals) where the EGT thermocouples are stuck in the exhaust manifold ?

[Bruce Tuncks]

It would depend on the power and the impediment to outflow. I would guess , in the absence of a blockage like a potato, it would be about 1psi or 7kPa max.

[RFguy]

Hi Bruce.OK, thanks.

I am sizing the sensor I need to insert at the EGT probe location . This sensor will look at the envelope and spectrum of the exhaust gas pressure sequence.

Based on the amount of noise these things make, that implies a pressure range of about 100 Pa peak superimposed on whatever is the static pressure at that location.

Why at the EGT ? I want to look at the difference between say a single sensor at the combined output of multiple cylinders versus at each cylinder- if there is any subtle very high bandwidth information available there. The manifold will act like a peaking low pass filter.

 

A single sensor is simplicity of course.

[Markdun]

Yep its cheap...I made my own temp sensors for oil and water for use on the RDAC in the Girlfriend..they work a treat..far cheaper than the MGL ones. I just got some throw away original temp sensors and drilled out the guts and epoxied the LM335 inside with the appropriate cables and ran them to the RDAC...works perfect and very accurate

Water? Do you have an espresso machine in the cabin?.... now that would be style, although require more landing stops!

 

I make up my own CHT probes. Just bought some J or K thermocouple wire (can’t remember which),at one end expose the wires and twist together, then crimp into an appropriate, other end plugs into the RDAC. For EGT I buy $12 Chinese probes and mount them in a Jubilee clip with a 5mm stainless pull rivet (remove the pull shank and insert the 3.2mm egt probe into the rivet). Oil pressure & fuel pressure are 5v, 3 wire probes $25 each, as is the Hall effect rpm sensor & the Arduino current sensor. Only fuel flow sensors are expensive, but then I took an old Navman fuel flow out of retirement. I compared it to the Red Cube and could find no performance difference once calibrated.

Edited August 31, 2020 by Markdun

[Kyle Communications]

ok 50/50 water and glycol...my next 2 aircraft is going to have drink holders thats for sure...I have coffee cups that have caps and are thermos style.....I cant survive without caffine :)