Engine Temperature

·         Kerry Paronella

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Hi Doug

I have just completed a 50hr service on our 230, being 150 hrs since the rebuild. I am a little paranoid about the temperature of the engine since the stripdown showed symptoms of being extremely hot.

Flying yesterday I notice that the head & exhaust temperatures were higher than normal. The exhaust temps were the most changed where the 5 & 6 pots were about 10+ deg higher at 730's during normal cruise (at 2900). The only item I can see in the engine bay is that I have slightly too much oil in the engine; a guess would be 150ml or 6mm on the dipstick. All else seems to be in order and in fact, the engine is very clean, dry and sounds fine. Baffles and air ducts are all in good condition. The change has only occurred on the first flight since the service.

As the air temperature is quite cool at the moment I am concerned enough to enquire as to what your thoughts are? Is too much oil likely to increase the engine temperatures or should I be looking elsewhere?

Cheers

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·         Doug Smith

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Hi Kerry,
Running the oil level "high" - which for a jab is generally anything above about the "halfway between the marks" level - can raise the temps a bit. But usually not a lot. It will tend to burn or eject a lot of oil when that full too.

Those egts are higher than ideal... What fuel are you using? I'm assuming you took it off run-in oil at the service? What are your oil temps like?

An obscure factoid for you: cooler temperatures actually have the effect of making the Bing run a bit leaner, raising temperatures. Because of that effect it might be worth going up a size or two on the needle jet and seeing what happens. Or, as a spot check, pull the carby heat on (obviously staying within the limits of the manual) and see if that effects your temps much.

Regards,
Doug.

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·         Kerry Paronella

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Thanks Doug - I did not give the carby leaning a thought. I am using Avgas and have for the 150 hrs since the rebuild. Oil is 100+ as per the recommendation. I have a 2+ hr flight tomorrow so will experiment with carby heat and rev range and advise.

I checked the oil today getting prepared for tomorrow's flight and noticed that the level has not changed on the dipstick so doubt that any has yet been blown out to the receiver.

I will report the findings in a day or two.

Cheers

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·         Kerry Paronella

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Hello Doug

I completed a 2.3 hr flight each way over two days. Your call on the carby heat was correct and slight application bought the engine temps down, mainly on exhaust as head temp did not alter much at all. Also as you predicted the old level did drop to a normal level. Less than a teaspoon in the recovery bottle so I am assuming that it was burned out. No carb heat was needed to be applied toward the end of the flight but at stages I did keep the RPM up at tad to keep the temps down, as can be seen in the attached happy snap.

The (what I consider) high exhaust temp is now back to one cylinder as has been the reading since fitting the dynon at engine rebuild at the factory. Results varied at altitude as expected but generally the engine is back to what it has been.

I looked at snaps taken of the dynon 12 mths ago and all readings are the same within a very close number. Oil temp and pressure exactly the same.

Thanks for your thoughts on the matter and I will be taking the plane back to the factory for the 200 hr service so the one cylinder can be investigated further to be bought in line with the other five, where possible.

Cheers

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·         Doug Smith

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Sounds good Kerry 🙂
Just keep in mind that the carb heat trick is intended as a diagnostic tool - you don't really want to be running around with it on all the time... and if you do use it then ideally you want it to be either fully on or off - not half on as that can cause some issues.
If you're headed to Bundy then chances are that as it warms up outside then you'll need it less and less.
Regards,
Doug