Thanks for sharing this, it’s indeed illuminating!
There is a cooling mod available for the Mirage which frankly should be installed at the factory, it’s transformative in the climb. The Mirage is not a great climber, but the example in the video is frankly pathetic, I guess it doesn’t have the cooling mod. At ISA+8 , with full fuel and bags, I climb at 125kias, 34usg, 700fpm on average to FL150 with my highest CHT at 360 degrees. Above FL150 up to FL200 it’s closer to 600fpm, and 500fpm above that.
ISA+5, 700fpm at FL110, CHT349
See this (uneven) picture at ISA+12, 500fpm at FL160, CHT360
Question: with your CHTs so cool, is there not an even better IAS/fpm trade off?
I just downloaded rainviewer.
It is a great complement to Meteoblue which looks great but is notoriously inaccurate on occasion!
Set Rainviewer to display only rain, not clouds. Improves accuracy, imo.
Denopa thanks for the additional info. Indeed this is a lot better than what Dick reported.
With regards to your question: there are other limiting factors in the Extra 400 and I found 120 KIAS to be a sweet spot.
I sometimes went to 1100 or 1200 fpm briefly but usually oil temps start to creep… Need to OH the oil cooler and then we will see.
I have also set myself a self inflicted limit of 130F for inlet air (post intercooler). This is frequently the first hurdle on a hot day
PS very envious of your engine monitor! happy?
@denopa, as I was marveling at your engine monitor photos I noticed that you too have CDT and IAT values.
And then something triggered my curiosity!
The data displayed by your engine monitor regarding intercooler efficiency is so much better than what I see that it made me scratch my head.
So I did some number crunching for confirmation (I analyzed the lower picture, but upper one is similar)
Data as displayed, converted to all F for convenience
Altitude 16100 ft
OAT = 23 F
CDT = 123F (this is a very low value for 35 inches of MP at these atmospheric conditions – On my aircraft CDT would be above 200 F)
IAT = 26 F (only 3 F more than atmospheric. Again very low. On my aircraft IAT would be above 120F, same ballpark as your CDT of 123).
If we calculate intercooler efficiency from the above data we get (CDT-IAT)/(CDT-OAT) = 0.97
97% intercooler efficiency in an aircraft is not plausible.
For the sake of comparison, the Extra 400’ s intercooler efficiency is between 40 and 50% and I have a vague recollection of seeing 50-60% from a Mirage somewhere.
So I would like to dare an explanation. What if somebody got stuff mixed up when installing your engine monitor? What if:
“CDT” were actually IAT? So the probe would be located AFTER the intercoolers instead of between turbo and intercooler ?!
“IAT” were measured BEFORE the turbo? (in the air box)
Edit: I did some googling and found this article which was the source I mentioned:
CDT is 256F and IAT 133 F at FL180 climbing at 35.5 inches MP.
You are exactly correct. Of all the things in my new engine instruments, that’s the one thing they messed up. Unfortunately once those holes are in, it’s too late.
The thing I like best is the ability to see graphs live, in-flight, on the iPad, of how all the measurements have varied, and be able to open the logbook where all that data is stored automatically on every flight. So if something seems out of sorts, you can see how it changed during the current flight, but also how it looked on other, similar flights, while you’re still in the air.
Why did you choose 130F as a limit for IAT?
Ah I am glad.
I would like to take my hat off to you for being so objective.
Your iPad interface is a dream come true.
This would be even more useful in such an unknown entity as the Extra. The EDM930 is really a very primitive piece of hardware and it is far behind Garmin’s user interface and build quality.
Based upon my own installation experience, here a simple idea I can recommend to you to correct the issue you have:
IAT is the most useful value to track, and you have it – just labeled “CDT”. (Mine is labeled TIT2 lol)!
Idea to get everything 100% tidy:
Disconnect but keep in place the probe that is incorrectly called IAT so that you do not need to plug the hole in the airbox (or wherever they did it).
Connect the wires that used to go from the engine monitor to this probe to the probe that was incorrectly labelled CDT.
Now you have your IAT gauge showing real IAT at a cost of 0.
Buy another probe (around 200 € plus maybe 100 € labour)) and have that installed on the hot side of the intercooler.
Connect the wires recovered from the old “CDT” probe to this.
Now you have CDT too and therefore computed DIFF.
This DIFF will give you a good indication of how well your intercoolers are working over time. Divide DIFF by the delta between CDT and OAT and you have intercooler efficiency. From Joe Casey’s blog you can see what this value is for different flight regimes on another Mirage and this way you can watch the condition of your intercoolers/airflow.
My intercooler tends to collect a film of clean engine oil.
My A&P IA says I use too little MP in cruise. I am not sure 29.5 inches is so low…
I wash my intercooler at least once a year and that is enough.
Don’t know how the intercoolers and relevant baffling age in the PA46, but with this setup fully working you would have an easy way of analysing trends.
To your question about my 130F IAT limit.
130 F is about 55 C. This limit was recommended by a retired formula one motorist who has also designed an aircraft engine.
He took into account the relatively low boost (39.5 inches or 1.3 bar) to decide that 55F was the safe limit to stay clear from detonation.
Have you set yourself a limit?
On hot days, I manage the climb on the basis of IAT.
Every time it hits 130, reduce MP by 1 inch and adjust climb rate to maintain 120 KIAS.
So on a very hot day, my first limiting factor really is IAT, before coolant or oil…
As I mentioned before, intercooler efficiency in the PA46 is a solid 10% better than in the Extra 400, which gives me hope for improvement.
If I could find a way to improve mine by this much, a massive improvement of time to climb on hot days would result.
So far no progress worth mentioning…
Have you set yourself a limit?
No, I lack any basis to do so (at least I did before your super useful post). I have not yet seen CDT (which means IAT in my messed up set up) above 130. TIT is usually my limiting factor in the initial full power climb, and then it becomes CHT (although I need to get new baffles because my CHT is quite a bit higher than it used to be, and they’re in really poor shape so I hope it will improve things).
Thanks to your gentle nudge, and given my plane was at the shop for a software upgrade, I got this fixed. My intercooler efficiency seems to be 43% so I might get it cleaned. Thanks a lot for sharing your insights!
Hello again @denopa. Sorry I missed your post until now. Thanks for reporting back and I am very happy that you were able to implement the change :-)
My actual knowledge of the PA46 is very limited and theoretical… (reading – in search of benchmarks to measure progress with the Extra).
The site I linked to shows better intercooler efficiency than 43%, so yes, you should definitely look at cleaning your IC as you said.
You may also want to look for leaks on the intake side and adverse pressure on the suction side caused by leaks,
The leaks that ruin the suction could be anywhere – if any of the high pressure air makes it to the “other” side, we lose.
I wish I could make my Extra’s IC work at 55% efficiency – this would allow top speed to hit 225 KTAS at FL250 by removing the POH power decrease above FL200.