Keeping CHT temps in range on climb-out

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dwurfel
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Keeping CHT temps in range on climb-out

Postby dwurfel » Mon Nov 20, 2017 2:07 pm

Hi all. Would like to get some tips on keeping CHT's lower during my climb-outs. Currently approaching 400 degrees to slightly above on some climb-outs. Have reduced power and enriched at times with some success. On reaching altitude everything is in 340-360 at 65%. Curious is I am doing a cross country my second take-off and climb-out the CHT never get above 380. Also, outside temps do not really affect the temps. Any advice would be appreciated. :)
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Re: Keeping CHT temps in range on climb-out

Postby CFIDave » Mon Nov 20, 2017 2:25 pm

David: Your DA40 engine temperatures appear to be normal -- they're certainly consistent with the many DA40s I've flown. Temps (in the climb only) will occasionally rise just slightly above 400 degrees on very hot days, but otherwise can be maintained around 380 or less during cruise.

The only thing I can add to keep CHTs under control during climb is to reduce your climb rate (i.e., lower the nose to increase airspeed and hence cooling airflow through the engine). I typically target 90 knots IAS for DA40 cruise climbs (which is very easy to do if you've got a newer DA40 with GFC700 autopilot with FLC feature), but you can climb more slowly at a higher speed if needed to lower CHTs.
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Re: Keeping CHT temps in range on climb-out

Postby smoss » Mon Nov 20, 2017 2:30 pm

+1 for above
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Re: Keeping CHT temps in range on climb-out

Postby Steve » Mon Nov 20, 2017 2:37 pm

Thats what I do - 95 KIAS in climb (terrain permitting). Never see CHT >390, even in TX in the summer.

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Re: Keeping CHT temps in range on climb-out

Postby Chris B » Mon Nov 20, 2017 5:09 pm

dwurfel wrote:Would like to get some tips on keeping CHT's lower during my climb-outs.

Hi David -

As suggested, increasing IAS is generally the best in-cockpit defense. But baffling has a *huge* impact on CHT. Leaks are common and very easy to fix.

See these threads:
  • Page 20 from Brock's supercharger thread: link. This was extremely helpful to me.
  • Long thread on CHT: link
  • Baffle success story: link
Also, if your CHTs are not similar in cruise, balancing the injectors ("GAMIs") can help.

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Re: Keeping CHT temps in range on climb-out

Postby rwtucker » Mon Nov 20, 2017 6:29 pm

Ditto other comments David. On hot days, low altitudes, heavy loads, etc. my CHTs sometimes creep over 400 before I notice and bring them back down by lowering the nose and sometimes the power. I can recall a few situations where I had to settle for 100-200 FPM climb to stay under 400. Completely normal so far as I know. Our DA40s have pretty small noses.
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Re: Keeping CHT temps in range on climb-out

Postby BlueYonder » Sun Dec 03, 2017 9:00 pm

I've had this problem, too. It's worse when I'm heavily loaded (say, with a 250-lb husband in the right seat). Run rich, keep the nose down, and accept a v e r y s l o w climb rate, and you're fine. I'm also doing a little better since I got the magnetos re-tuned (it worsened markedly after a rebuild last spring), and went to a multi-weight oil. Also had the baffles checked, thanks to this thread.

So there's a lot you can do. Nice to see that I'm not the only one who's gotten into the habit of watching CHTs like a hawk during climb-out.
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Re: Keeping CHT temps in range on climb-out

Postby dwurfel » Mon Dec 04, 2017 1:35 pm

Thanks everyone for your input. Your suggestions have helped alot and have helped me keep everything in check during climb. One interesting fact for me is the rise in CHT in climb out only occurs during the first flight of the day. On subsequent take-offs the same day with the engine still warm I do not see the same rise. CHT's maybe rise to 365-375.
Curious.
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Re: Keeping CHT temps in range on climb-out

Postby Colin » Mon Dec 04, 2017 2:49 pm

I defer to any engine expert here, but I would think that has to do with the viscosity of the oil and it's slower movement through the engine. I assume you are waiting for it to hit 100F before you depart.
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Re: Keeping CHT temps in range on climb-out

Postby dwurfel » Tue Dec 05, 2017 1:09 pm

My personal rule is not to start engine if the oil is cooler than 40 degrees ( normally keep it on a engine and oil pan heater
in winter 24 hours prior to flight ), lean engine right after start, start the engine run up at 95 degrees, and take-off engine oil is in the 110 to 120 range. Love to hear comments. By the way I use Aeroshell Multi-Viscosity. Nice DA-40 Colin.

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