High CHTs

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hoyaj
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Re: High CHTs

Post by hoyaj »

Steve wrote:
Seems as if "institutional memory" at Diamond has failed. But it was a long time ago. When we ferried our plane back from the factory in May 2002, we learned that we had to run what we considered high fuel flow settings at cruise to keep #1 cylinder head temperature under control and a pretty wide range between the hottest and coolest CHTs. W
To resurrect this thread, our 2003 model (with 2 blade upgrade)has been for about 2 years exhibiting the very hot cyl #1 issue (i.e., >400F even at 100KIAS when operating below 2K MSL at 2400RPM, WOT), even though it has the correct passenger side air inlet dimensions for the "Arizona" mod. 80-90 knot departures generate readings in the 410-432F range rapidly. We've done all of the common sense checks, and then some since 0 SMOH. (bafflling /cowl inspections, probe swaps) This is now a 10 month old, 140SMOH engine, and the engine was exhibiting these cyl 1 temps prior to MOH.

On a recent flight at 65% power and 6000 feet, 16C OAT, 9.8GPH, I recorded the following numbers

Cyl 1 EGT: 1401, CHT 404
Cyl 3 EGT 1411, CHT 356

(Cyls 2 and 4 run 370-380 most all the time)

The oil analyses are coming back with increasing chrome, so premature ring failure is likely. :tap:

Discussions with Ontario have not generated information that would seem to lead in the direction of a resolution. Have looked at all of the high cyl temp posts, and it seems to be an airflow problem as EGTs don't support an impeded fuel flow / assymetric mixture theory. Hoping someone here has some ideas.
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Rich
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Re: High CHTs

Post by Rich »

This looks like cooling airflow to #1 cylinder is being restricted. Have you checked the part number on the piece itself? If you do have the "Arizona Baffle", I wonder if it's possible to have been improperly installed.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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BlackMammoth
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Re: High CHTs

Post by BlackMammoth »

Could also be a bad CHT sensor...
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41000
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Re: High CHTs

Post by 41000 »

Can anyone describe this Arizona baffle install?
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Steve
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Re: High CHTs

Post by Steve »

41000 wrote:Can anyone describe this Arizona baffle install?
The right front carbon fiber baffle piece is switched out for one of a different design. Additionally, the hole in the right front air inlet is enlarged.

Steve
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Rich
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Re: High CHTs

Post by Rich »

The reason I question whether the baffle is there and installed properly is that your numbers correspond to what I saw throughout my first year of ownership. Constantly saw #1 rogue behavior > 400 deg at cruise. After installation, problem gone. All CHT's run 360-370 with EGT's at 1450-1480. The only time I ever see >= 400 deg is extended fairly steep climb at high DA and ambient temps. Even then, we're only talking 410-420 or so.

The aircraft logbook entry refers to having installed a particular kit and removing/installing baffling "at #1 and #3" cylinders. Kind of cryptic and I don't see the particular service bulletin and such to specifically describe the work to be done.

Lance claims it didn't make much difference in his plane, but it sure did in mine.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: High CHTs

Post by Gasser »

What year, serial number did this become standard?

My #1 and 3 stay cool. My 2/4 tend to be 20-30 degrees hotter.
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hoyaj
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Re: High CHTs

Post by hoyaj »

Rich wrote:This looks like cooling airflow to #1 cylinder is being restricted. Have you checked the part number on the piece itself? If you do have the "Arizona Baffle", I wonder if it's possible to have been improperly installed.
Well, Ontario believes that the baffle mod was standard on my cowl by the time it left the factory in 2003. I didn't find a part number, but they provided the measurements for comparison (> 100mm at the widest points.)

Frankly, our numbers correlate to excessive air pressure loss around the number 3 cylinder, keeping it nice and cold, some evidence of which we found on the baffle "bra" (1 inch of play/give behind the number 3 cylinder). Adjustment to the baffle assembly to tighten the attach points reduced the give, but did not result in evening out the temps.

The temp probe from 3 was swapped, with no change. Remember also that the used oil is now confirming that something is causing excessive ring wear. My read of Deakin and Busch says heat is likely the culprit.
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Rich
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Re: High CHTs

Post by Rich »

Gasser wrote:What year, serial number did this become standard?

My #1 and 3 stay cool. My 2/4 tend to be 20-30 degrees hotter.
As long as temps are within reasonable limits, I believe a 20-30 degree variance among CHT's is not considered abnormal.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Charles
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Re: High CHTs

Post by Charles »

As stated in my initial post, I have the same issue with #1 CHT and I've been able to manage it reasonably well through LOP operation (with negligible performance impact), so getting a permanent fix was not a high priority. But after seeing the dramatic improvement observed by a fellow DA40 2003 owner who had the Arizona baffle installed earlier this year, I placed an order for one and can't wait to get it installed. I'll be glad when I don't have to worry about CHTs so much all the time.

Using Hoyaj's settings of 9.8gph at 65% power (a Best Power setting) would certainly cause my #1 CHT to go through the roof. By operating at Best Economy or leaner, it wouldn't be a problem.
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