Cooling System

[SonexN76ET]

I have now also been struggling with cooling issues. When waiting to take off after my run up or just idling on the ramp the engine quickly starts to overheat. As a result I have not flown yet. The radiator is mounted below the engine about 18 inches ahead of the firewall. I have tried enlarging the openings for both the intake and outlets for the radiator cooling air but none of my efforts so far have improved things. My next step is the use Evans coolant and add a cooling fan to pull air through the radiator. Extremely frustrating. If that doesn’t work I may try a side mounted radiator as Murray did.

Jake

[13brv3]

I'd strongly recommend NOT going to Evans to try to solve an overheating issue. The normal 50/50 mix cools much better. It's tempting to like that high boiling point of Evans, but you will run your CHT temps up considerably. Below is from my notes using the EMS logs to document the temps.
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Since the CHTs were on the high side, and since I’ll likely be adding power to the engine, I drained the Evans, and replaced it with a 50/50 mix of DexCool and distilled water. This is the current Rotax recommendation, and I knew it would cool better. I made a brief flight today, with a climb and cruise similar to yesterday’s flight.

The highest CHT went from 248 with Evans, to 221 with Dex. A brief cruise at 5300 rpm gave 242 with Evans, and 216 with Dex.

Coolant temp went from 216 with Evans, to 208 with Dex. A brief cruise at 5300 rpm gave 212 with Evans, and 200 with Dex.
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Without airflow, nearly any aircraft will overheat, but yours does seem worse than it should be. It would be interesting to try an electric radiator fan on the ground to verify that resolves the issue. If it doesn't you have to start wondering if you don't have coolant flow for some reason.

I'd also want to know the air temp going into the radiator. I'm not clear if you're using hot air from the cowl for the radiator, or if it has a cool air inlet.

[Skippydiesel]

One of the many attempts to improve my cooling system was to add a fan - helped a little but no where near enough.

The reality is the big fan up front will deliver more air than a little 12 V job.

The problem is how to get that big fan air to go through your radiator.

[SonexN76ET]

You both make great points. I will keep at it and try several different options to overcome my overheating issues. I appreciate your advice!

Jake

[13brv3]

You both make great points. I will keep at it and try several different options to overcome my overheating issues. I appreciate your advice!

Jake

A picture of the radiator arrangement might help. Are you sure the air is completely purged?

[Skippydiesel]

Hi Jake,

The photo of your cowling front on, shows impressive workmanship BUT does not assist the conversation very much.

Please detail what each air inlet is for - oil cooler?, coolant Radiator?, carburetor cooling/air supply, cylinder head cooling?, other?

AND most importantly photos showing the all important exit air.

You wont get air into the cowling, if you don't have an adequate exit, for the air to move out.

[SonexN76ET]

I am reworking the radiator intake to allow more airflow and will post some photos in about two weeks after i return from some travels. I will also post some photos of the exit air outlet. I am wondering in the Sonex B side outlets would be beneficial for the cooling?

Jake

[Skippydiesel]

Jake,

I seek further information;

What temperature is your coolant (Radiator), heads, oil getting to?

[avee8r]

I just finished adding the B Model side vents to my AeroVee A Model, Easy job. Rough calculations show it almost doubles the outlet area.

Haven’t flown it yet so I’m not sure what the CHT difference will be.

Happy Landings
John
N50NX

[Skippydiesel]

I just finished adding the B Model side vents to my AeroVee A Model, Easy job. Rough calculations show it almost doubles the outlet area.

Haven’t flown it yet so I’m not sure what the CHT difference will be.

Happy Landings
John
N50NX

Hi John,

Great you are getting "things" where you want them, however the Rotax 9 range has very diffrent cooling management issues to an AeroVee.
As yet there seems to be little consensus on where heat exchangers should/could be located, same goes for in/out air