Temps and data analisys

[Dorsal]

For those who like to look at data I could use some opinions. Below are links to some EMS data on SavvyAnalysis from my flight back from NY Sunday. You can select any data to look at keeping in mind that only CHT 1+2 are valid, the others you can "hide" by clicking on them. My question is based on these data do I have a problem or just need to take it easier on hot days?
I have just starting messing with SavvyAnalysis, seems kinds cool.

Final Hop OAT ~85 humid
https://my.savvyanalysis.com/public/e3ecc3e7-38d8-45b1-8fd1-97ebd754212e

Flight from NY OAT ~75 humid
https://my.savvyanalysis.com/public/df55a25f-5ae7-4742-984a-02d7fff970fd

[mr bill]

That is really impressive data recording.

[CDE2FLY]

Hey Finn...that is some slick software! I've been watching my CHTs closely as well and they're in the same ballpark in terms of peak temps. The interesting thing on mine is the difference in the two CHT readings. I monitor the front Pilot side cylinder and the rear passenger side cylinder. The rear passenger side reading is always hotter and at times indicates up to 60 degrees hotter. I attribute this to the turbocharger sitting directly the CHT probe. I've been contemplating a turbo blanket to test the theory but not sure I want to heat soak the turbo. The front cylinder temp never gets above 220 degrees. From the graphs, it looks like the data was recorded during climb, cruise, and decent. The only time I have a CHT concern is climbing on a hot day (your data looks similar). As we discussed at the fly-in, I'm using Evans coolant which it more heat tolerant but not as effective at hear transfer as anti-freeze. On a hot day (today was 95+ and I flew from White Plains NY to Massena, NY) I can't run full boost for the full 5 minutes allowed without spiking the CHT above 280 degrees but can still manage nearly 1000 fpm just off full boost so not a big deal to modulate boost. Cooler days allow continuous boost but approaching 275 degrees after 5 minutes of climb. This past winter I spent some time making the radiator plenum nearly air tight by fabricating shrouds using baffling material firmly sealed to all sides of the radiator and still have to watch CHTs while climbing on a hot day (95 degrees plus). As a point of comparison, I've flown with the cowl off on a hot day and temps were far lower so the cowl is contributing to the heat issue for sure. It would be interesting to hear from others to see if anyone can maintain CHTs below 275 degrees on extended climbs when the OTA is 95 or above.

[Dorsal]

Thanks for the input Chris, My worry is that given I do not have a turbo and not using evens my ship should be running cooler. In the final hop data set both CHTs are in the upper 200s with the rear one running a little hotter. Based on the post from DesertFox1 I may try to take a little pitch out to see if that helps. If you put RPM in the upper graph it shows my static WOT at 5200 and holds pretty constant on climb out. I will also close the gap under the radiator to see if that helps. DF1 if your reading this what are you getting for static RPM? Any other ideas?

[Dave S]

Dorsal,

I don't recall your original post explaining the type of coolant you use.

Rotax draws the line between hot and overheat on Evans/NPG/Waterless coolant (undiluted propylene glycol) for CHT at 275 degrees F. For a 50-50 mix ethylene glycol (prestone, etc) they draw the line at 245 degrees F. Although CHT is not a direct reflection of coolant temp, the difference between 245 F and 275 F reflects the relative difference in boiling point between the two coolants.

Those values were provided with my engine, I don't know if they are identical for manuals printed at a different point in time. Might be good to review the manual/CD provided with your engine to see what it says.

If calibration has not been performed on a particular CHT sensor/gauge, there is no empirical information to indicate whether or not the indication is biased one way or the other. There is manufacturing and operational variation likely in any gauge system so your actual temp could be plus or minus whatever that variation is.

Different props or prop pitch can can have an effect on cooling.....Mine is set for 5200 rpm on climb out at Best Rate & full throttle...that works out to being somewhat of a "cruise prop" setting and limits the amount of power output a bit on climb out. An Engine pitched to run 5400 or a bit more is basically capable of putting out more power per unit of time and therefore more waste heat for the coolant to deal with per unit of time.

Sincerely,

Dave

[Dorsal]

Thanks Dave, What do you typically see for CHTs and Oil temp on climb out on a hot day. I have calibrated my CHT sensor and am familiar with the limits but can exceed them fairly easily if I climb extended at full power with an OAT in excess of 85 (and a heavy plane). I am beginning to think this is not that unusual and I just need to ease up a bit under those conditions.
All input welcome.
(50/50 coolant and a fixed pitch prop)

[Dave S]

Dorsal,

On a hot day (talking 85-90 F at the surface) the CHT will normally rise to 250-260 F on initial climb out (Full throttle/5200/best rate). By the time it gets close to 260 F I am usually at 1500-2000 AGL. Cruise flight setting @ nearly full throttle/5400 rpm It will stabilize at similar temps. I don't often fly at a weight of 1550# - most of the time it is about 250# light of that

Oil temp seems to stabilize around 240 F (W/Oil cooler at the front of the cowl - no thermostat.)

I have developed the habit of starting to back off the throttle as the CHT passes 250 on its way to 260 at cruise at lower altitudes to 5200, 5100, 5000 rpm which results in the temp sliding back to 245 plus or minus.

With higher altitudes the cooler air and reduced engine power due to the reduced air density seems to have somewhat of a self limiting effect on engine temps.

One issue I am not real sure about on the series 7 with the air filter in front of the radiator is how much the location of the air filter affects efficiency of the air flow through the radiator. The filter has a pretty ragged surface to present to the airflow through the NACA scoop. On our plane - the KN filter is in front of the radiator about 20-25% of the width. Probably a good topic for discussion but I have never gone beyond thinking about it.

We also have the induction airbox and I don't know if that has any effect on engine temps.

You might be right on - depending on the prop/OAT/power setting and airspeed - just backing off the throttle a bit might be all that is needed to bring the engine temps back to where you would like them.

There can be a lot of variables between planes of the same series although it seems yours is fairly similar to ours.

Sincerely,

Dave S

[Dorsal]

Thanks Dave this is very helpful and reassuring as it is very similar to what I get. The flights that caused me concern were hot and I was at full fuel, two adults and camping gear (full bagage). Under those conditions I will watch the temps, ease up on the throttle and fly with confidence.

BTW are you runnings Evens or 50/50?

I do not have the air filter in the NACA scoop but direct on the Rotax airbox.

[Dave S]

Dorsal,

We are running Evans Waterless coolant.

Dave S