Coolant/oil heat exchangers

Hey folks! Just a quick update (although no diagrams of the cooling system, sorry about that!):

Did the coolant flush over the weekend and replaced it with fresh Shell Dex-Cool Extended Life (50% distilled water). I did also find that the fins on the radiator were bent to hell. So I pulled that off and straightened them out with a screw driver (cheap combs didn't work that well, probably because I was time constrained in the MX bay and didn't take my time).

Another mechanic did stop by to see what I was up to. We walked through the cooling layout together and found that there really isn't a whole lot of air flow optimization going on. He suggested my best route forward is to optimize the airflow going through the cowling and ensuring there aren't any inefficiencies. Since I'm a digital 3D artist by trade, would be a lot of fun to design some molds and create some custom fiberglass ducting (or other appropriate material).

Once I got everything put back together, I conducted some pattern work flight testing in ~75F OAT. I found that cooling worked much better for sure, although still too hot for my liking. Generally:

Flight (TOC from 115% power climb, 6th lap)

Note: Other laps I did 100% power and flatter climbs after 500ft AGL which kept temps much lower.

Oil: 240F

CHT: 250F

Coolant: 248F

OAT: 73F

Ground after pattern work (2 minutes to parking):

Oil: 214F

CHT: 214F

Coolant: 213F

OAT: 75F

I will say that my engine reaches these temperatures much slower now! Once leveled out, temperatures are coming back down much more nicely than before and stay much lower. It's enough that I would be comfortable doing cross countries again. Convenient considering I had planned a long trip in July.

That being said, I do have work to do in the cowling regarding air flow and certainly want to tackle that in the near future.

Edit: To answer Peter's question, there's no reason that the overflow bottle was that low. Coolant system was well contained when I checked it. It now has fresh coolant and updated levels for me to work off of and track though.

Hi Steven,

I would be interested to know what your Climb Out performance is:

Air Speed

Ft/min

Engine RPM

MAP

Just for SA, you're using a Laminova C43-180 heat exchanger and a Watt-Man Thermo-Bob thermostat. I use the same in my plane without any oil cooler. That being said you have to account for roughly 15% more heat that needs to be dissipated by the coolant. I am using a radiator from a Honda CB900F and ducting that allows maximum pressure recovery in front of the radiator.

Steven Burrichter wrote:

Hey folks! Just a quick update (although no diagrams of the cooling system, sorry about that!):

Did the coolant flush over the weekend and replaced it with fresh Shell Dex-Cool Extended Life (50% distilled water). I did also find that the fins on the radiator were bent to hell. So I pulled that off and straightened them out with a screw driver (cheap combs didn't work that well, probably because I was time constrained in the MX bay and didn't take my time).

Another mechanic did stop by to see what I was up to. We walked through the cooling layout together and found that there really isn't a whole lot of air flow optimization going on. He suggested my best route forward is to optimize the airflow going through the cowling and ensuring there aren't any inefficiencies. Since I'm a digital 3D artist by trade, would be a lot of fun to design some molds and create some custom fiberglass ducting (or other appropriate material).

Once I got everything put back together, I conducted some pattern work flight testing in ~75F OAT. I found that cooling worked much better for sure, although still too hot for my liking. Generally:

Flight (TOC from 115% power climb, 6th lap)

Note: Other laps I did 100% power and flatter climbs after 500ft AGL which kept temps much lower.

Oil: 240F

CHT: 250F

Coolant: 248F

OAT: 73F

Ground after pattern work (2 minutes to parking):

Oil: 214F

CHT: 214F

Coolant: 213F

OAT: 75F

I will say that my engine reaches these temperatures much slower now! Once leveled out, temperatures are coming back down much more nicely than before and stay much lower. It's enough that I would be comfortable doing cross countries again. Convenient considering I had planned a long trip in July.

That being said, I do have work to do in the cowling regarding air flow and certainly want to tackle that in the near future.

Edit: To answer Peter's question, there's no reason that the overflow bottle was that low. Coolant system was well contained when I checked it. It now has fresh coolant and updated levels for me to work off of and track though.

As I said earlier - 

"Your coolant and oil temperatures appear to be just within Rotax max.

I would be uncomfortable with this, preferring to see cruse temperatures, both oil & coolant, in the low to mid 90C (194-203F) range"

You seem to be flying in, what I would consider, mild climatic conditions  and engine temps are well above optimum. Should you start flying in hotter conditions you may be in danger of seriously overheating your engine.

With the above temps, you may want to consider doing more frequent oil changes eg every 50 hrs.

If you are still using the oil - coolant heat exchanger for cooling, you may need to install a larger capacity Radiator (coolant - air heat exchanger) to deal with the extra heat load on the coolant system.

I tried posting a reply which doesn’t seem to have gone through so here it is again. Most of the comments seem to be from folks not running a 914 which generates more heat than those without a turbo.  My 914 needed much more airflow across the cylinders and I had to add NASA ducts in the cowling top to put airflow to,the rear cylinders as well as cutting larger holes in the cowling front for airflow to the front cylinders. Also I added a duct which provides airflow direct across the turbo. All this extra airflow input is easily balanced with the large exit space below the cowling where the retractable nose gear fits.  
From your photo it looks as though both your coolant and oil radiators are behind the exhaust muffler and turbo? if so they are right where the maximum heat is being generated.  Most Rotax installations have the coolant radiator in front of the muffler.  Oil not so much.

Suggest you study the 914 Installation Manual which gives good guidance on the airflow requirements.  Best of lick.