Emax owners (and those soon to be owners). Please look at the thread entitled “Keep a cool head / CHT temps,” just approved and posted in COPA Response!.
In reply to:
Emax owners (and those soon to be owners). Please look at the thread entitled “Keep a cool head / CHT temps,” just approved and posted in COPA Response!
(Only COPA members will be able to reach that URL).
- Mike.
Kudos to Dave Raab for that fine detective work! That explains why I’m seeing higher CHT’s on my new '22 than on the old one. Now on to the cool oil temps…
-Curt
Since I do not have an analog CHT gauge in my SR22 as I had factory installed Emax, how do I know if I have “the problem” or is it assumed that everyone has this problem?
In reply to:
Only COPA members will be able to reach that URL
An incentive to join!
Brian,
In reply to:
Since I do not have an analog CHT gauge in my SR22 as I had factory installed Emax, how do I know if I have “the problem” or is it assumed that everyone has this problem?
Our tentative working assumption, based on Dave Raab’s terrific detective work, is that all Emax installations are facing this issue. Further information will be posted on COPA Response! as it becomes available.
Brian-
Do your OAT’s match between the Davtron and E-max? Mine are 1-3deg. C. diffferent
Thanks Marty
Re: how to verify if your Emax CHTs are reading high as reported…
I followed the suggested procedure in the Response post by finding an Emax datafile which recorded engine parameters when I was tweaking my Avidyne setup options after a software upgrade. with the warm aircraft in my hangar.
I had taxied the aircraft for just a couple of minutes and shut it down perhaps 10 minutes earlier. The engine was still warm but relatively stable in temperature.
My oil temp was 97-98 deg. F and the OAT was 92-94 deg. F. All six CHTs were in the 115 - 120 deg. F range.
If I believe that under these circumstances the oil temp would be about the same as the cylinders, the 20-25 degree hotter cylinder head indications is consistent with the reported discovery of a systematic indication error.
It would probably be better to do this when the plane had simply been sitting in a hot hanger for a long time as it would be more likely that all the components were at the same temp, rather than with a cooling-down engine…but we haven’t had too many hot days yet this year.
Simply powering up the Avidyne on a hot day (engine off) over 80 F and looking at the indicated CHTs and OAT ought to do the job, too.
Nice detective work finding this, guys!
I don’t know that I’d want to pay money to get this fixed - I can always mentally subtract 25 from what I see…especially since the error is on the side of safety and actually makes the Emax hard-coded-but-too-high redline closer to being reasonable.
Tim
Mike:
Mine are different by about the same range; average of 2 degrees different with the Davtron always colder.
At $5750, it needs to be right. Are you going to reduce your climb rate to get CHT’s that you are comfortable seeing or are you going to let the guages read 25 deg higher because your’e “sure” they are 25 degrees off? This needs to be an Avidyne-paid fix.
In reply to:
Simply powering up the Avidyne on a hot day (engine off) over 80 F and looking at the indicated CHTs and OAT ought to do the job, too.
It will. I stumbled on that last week and sent it to Dave to figure out. OAT was around 81F, The CHTs were all around 102F except #3 which was the old probe - it was 0F since it doesn’t record on the Avidyne if less than 100F
Michael:
In reply to:
Are you going to reduce your climb rate to get CHT’s that you are comfortable seeing or are you going to let the guages read 25 deg higher because your’e “sure” they are 25 degrees off?
In my case I haven’t had any problem keeping CHTs in line at normal rate of climb on my 22 but then again it’s not summer yet. This would be a bigger issue for a 20 owner. My point was that since Avidyne in their “wisdom” has hard-coded the yellow line at what looks like 420 or so and I’d rather keep it well under 400, the offset actually moves the yellow & redlines to somewhere more useable. I don’t see much difficulty being “sure” how much the error is once it’s measured and known as already posted.
I see your point about this being something Avidyne ought to pay for - 25 degrees out of say 400 is over 6% error, quite a bit for such an expensive device.
Perhaps oddly, my two OAT gauges are always in agreement within 1C. I also would like to feel confident that when it says 2 C it isn’t really -2 C!
Cheers,
Tim
That’s a pretty expensive thermometer to be off 4 deg. F. Not a big deal when the OAT is 18C but it is when the OAT is -1C.
I have had a few flights now where the Davtron was at 0 degress or minus 1-2 and the Emax gauge read +1-2. Then clouds appear. Is it or is it not below freezing at this point? It is an annoyance but found by trial and error that the Davtron gave a more true reading. It would be nice if all of this expensive hardware was depicting the truth. The Emax is a wonderful device but we have seen more problem related to Emax errors or loose probes rather than TRUE engine problems.
In reply to:
we have seen more problem related to Emax errors or loose probes rather than TRUE engine problems.
I don’t want to defend the design flaws in the Emax - they should be corrected - but I think realistically when you add over a dozen individually wired probes to a hot, shaking, high power engine, you are adding a whole bunch of new possible points of failure. More stuff, more stuff to maintain. Even so, I’ll take the additional information even if a probe or wire fails occasionally.
It could be worse - they could have the life of a typical vacuum pump!
Tim
In reply to:
I have had a few flights now where the Davtron was at 0 degress or minus 1-2 and the Emax gauge read +1-2. Then clouds appear. Is it or is it not below freezing at this point? It is an annoyance but found by trial and error that the Davtron gave a more true reading.
PFD airplanes don’t have the Davtron, so all we have to go on for OAT is the MFD. Interestingly, the PFD itself has an OAT probe (sticking down from an access panel beneath the outboard right wing) but there is no display of the temperature it is recording.
I like the additional information as well. But it would be nice if they could make the failures a little more foolproof. After all, an auto engine shakes a lot too and has a lot more computer sensors and just as many wires as our Cirrus. I never seem to have have faulty readings in my car gauges.
I barely know what I am talking about because of the extensive testing which I COULD NOT have completed without my friends help. I am not an electrical engineer. Some of my explanations and terminology probably make an electrical engineer cringe!
RE: Brian Turrisi- It is a fleet wide problem, so unless your plane somehow does not have the ground loop, it is affected. Try the simple test on a day over 80 degrees.
RE:OAT’s- I did not do any testing with the OAT temps and have no idea if the ground loop creates an error in the OAT. Here is something to know about the system. The new Watlow probes are 100 Ohm resistive probes. So a 5 Ohm error in the ground loop is a 5% error. If they were 1000 Ohm probes it would be a .5% error and would probably have never been detected. The OAT is a thermocouple probe and I really don’t know how the readings would be affected. I would think one of the parameters for %HP is OAT, but I don’t think a few degrees would change that by a measurable amount. I will find out why the OAT is so far off in my plane.
Re: Tim Gieseler- I believe has a factory installed eMax so all 6 CHT’s are shifted the same. I don’t think 10 minutes would be quite long enough to stabilize. I would be curious to know what is the hottest the CHT’s got with this short run-up.
Re: Michael- I agree. I don’t want to pay to fix this error. It should be right. Besides what do you say to your passengers? “Oh don’t worry those bars are supposed to be red.” False high temperatures are showing up now, what will it look like in the middle of summer?
In reply to:
I would think one of the parameters for %HP is OAT
Although it is entertaining, I personally think the %Pwr display on the EMax is useless. The algorithm was developed using data from the POH plus input to Avidyne from Continental. It appears the Continental input made the calculation dependent on fuel flow, since you can see the %Pwr figure change as you lean. Unfortunately Avidyne has declined to publish their calculation method (unlike Arnav who produced a white paper). As a result, we really don’t know what the %Pwr figure means since it doesn’t correspond to the POH or any other known source. So we can’t use it for meaningful engine management. I’d be happier if it used just data from the POH so we’d know what it means. It wouldn’t truly be % of power but it would be meaningful. Right now it isn’t truly % of power (although it may be closer) and we don’t know what it is.
-Curt