Cylinder Head Temps

[Gasser]

To me, the most important question haven't been asked yet. Where in relation to peek EGT were you running? Everybody jumps on air baffling and temp sensors first when the most common reason for a hot cylinder is running the engine at a fuel flow that gives you cylinder pressures that are too high and too near top dead center. This in turn generates e hot temps. The high cylinder pressures are hard on your engine and the high temps shorten the engine life.
Yes, running at a low altitude with high power settings in that 50 deg rich of peek area will certainly give you that apple but at what cost.

At a low alt you should probably be running 120 to 140 degrees rich of peek if in that 75% plus power settings to be at a safe area.

I'm betting those temps are real and fuel setting and power setting related, not airflow or a bad temp probe.

[Gasser]

As for one being hotter than the other three, that cylinder is probably running slightly leaner than the other three and so when rich of peek, the leanest cylinder will run the hottest as its closer to top center with the highest peek cylinder pressures co pared to the others. In other words, its too lean on the rich side of the curve.
I'm betting that if you pulled it past peek to a lean of peek setting the engine would run rough...maybe.

I looked at my fuel flows two days ago at 3500' full throttle and 2450 RPMs. 140 degrees ROP gave me a fuel flow of just under 13 gph and hottest CHT was 370 degrees. Pulled to a LOP setting and temps quickly cooled to 350 degrees. Speed on 13 gph was 144 KTAS. Speed on 8.8 gph was 138 KTAS. Not too bad for 3500'. The numbers are much better above 6500'. These were all safe settings out of Deacons red box. I always recommend a good engine management course.

FWIW

Jeff

[pabrouss]

As for one being hotter than the other three, that cylinder is probably running slightly leaner than the other three and so when rich of peek, the leanest cylinder will run the hottest as its closer to top center with the highest peek cylinder pressures co pared to the others. In other words, its too lean on the rich side of the curve.
I'm betting that if you pulled it past peek to a lean of peek setting the engine would run rough...maybe.

I looked at my fuel flows two days ago at 3500' full throttle and 2450 RPMs. 140 degrees ROP gave me a fuel flow of just under 13 gph and hottest CHT was 370 degrees. Pulled to a LOP setting and temps quickly cooled to 350 degrees. Speed on 13 gph was 144 KTAS. Speed on 8.8 gph was 138 KTAS. Not too bad for 3500'. The numbers are much better above 6500'. These were all safe settings out of Deacons red box. I always recommend a good engine management course.

FWIW

Jeff

Thanks for the info. I'm not a mixture master, but I'll get someone to help me check this out. And yes, everything is fine at higher altitudes.

[hookem80]

I'm a relatively new pilot and DA40 owner and this is my first post to this forum.

I've noticed recently that my #1 cyliner head temp is difficult to keep below 390 at low altitudes. I have to richen the mixture to 11 or 12 gph to bring the temp below 380. The other 3 cylinder head temps are all 375 or below at 10 gph. I usually fly at 10 gph to get max true airspeed of 145. I've had a mechanic look at it and the timing was adjusted from 25 tap dead center to 23. This has done nothing to alleviate the issue.

Any ideas? ALL are welcome.

I am of a different opinion here, and I would like to know what density altitude, manifold pressure, RPM and outside air temp you are referring to when you say "I usually fly at 10 gph to get max true airspeed of 145". if you get too aggressive on pulling the mixture back down low at high MAP and RPM, you can overheat and mistreat your engine and run the risk of the dreaded detonation problem.

I have about 850 hours on my 2004 DA 40 and I can tell you that if I am running it hard (wide open throttle - WOT and 2400 or 2500 rpm) below 6000' density altitude, I would definitely need 12+ GPH for cooling and detonation prevention below 6000 DA.

Have you read any of John Deakin's articles on AvWeb? They are called Pelican's Perch and John is a definitive expert on how to run our normally aspirated piston engines. http://www.avweb.com/news/pelican/182583-1.html is a link to one of his articles, there is a lot of sage advice here, and if you heed his advice you will protect your expensive engine and cylinders!

Regards
Trey

N22QQ
Diamond DA 40.447
KGDJ

[Gasser]

I'm a relatively new pilot and DA40 owner and this is my first post to this forum.

I've noticed recently that my #1 cyliner head temp is difficult to keep below 390 at low altitudes. I have to richen the mixture to 11 or 12 gph to bring the temp below 380. The other 3 cylinder head temps are all 375 or below at 10 gph. I usually fly at 10 gph to get max true airspeed of 145. I've had a mechanic look at it and the timing was adjusted from 25 tap dead center to 23. This has done nothing to alleviate the issue.

Any ideas? ALL are welcome.

I am of a different opinion here, and I would like to know what density altitude, manifold pressure, RPM and outside air temp you are referring to when you say "I usually fly at 10 gph to get max true airspeed of 145". if you get too aggressive on pulling the mixture back down low at high MAP and RPM, you can overheat and mistreat your engine and run the risk of the dreaded detonation problem.

I have about 850 hours on my 2004 DA 40 and I can tell you that if I am running it hard (wide open throttle - WOT and 2400 or 2500 rpm) below 6000' density altitude, I would definitely need 12+ GPH for cooling and detonation prevention below 6000 DA.

Have you read any of John Deakin's articles on AvWeb? They are called Pelican's Perch and John is a definitive expert on how to run our normally aspirated piston engines. http://www.avweb.com/news/pelican/182583-1.html is a link to one of his articles, there is a lot of sage advice here, and if you heed his advice you will protect your expensive engine and cylinders!

Regards
Trey

N22QQ
Diamond DA 40.447
KGDJ

Yes yes yes...exactly.

GAMI has an excellent engine management course. I highly recomend! I am a deakonite

[pabrouss]

I'm a relatively new pilot and DA40 owner and this is my first post to this forum.

I've noticed recently that my #1 cyliner head temp is difficult to keep below 390 at low altitudes. I have to richen the mixture to 11 or 12 gph to bring the temp below 380. The other 3 cylinder head temps are all 375 or below at 10 gph. I usually fly at 10 gph to get max true airspeed of 145. I've had a mechanic look at it and the timing was adjusted from 25 tap dead center to 23. This has done nothing to alleviate the issue.

Any ideas? ALL are welcome.

I am of a different opinion here, and I would like to know what density altitude, manifold pressure, RPM and outside air temp you are referring to when you say "I usually fly at 10 gph to get max true airspeed of 145". if you get too aggressive on pulling the mixture back down low at high MAP and RPM, you can overheat and mistreat your engine and run the risk of the dreaded detonation problem.

I have about 850 hours on my 2004 DA 40 and I can tell you that if I am running it hard (wide open throttle - WOT and 2400 or 2500 rpm) below 6000' density altitude, I would definitely need 12+ GPH for cooling and detonation prevention below 6000 DA.

Have you read any of John Deakin's articles on AvWeb? They are called Pelican's Perch and John is a definitive expert on how to run our normally aspirated piston engines. http://www.avweb.com/news/pelican/182583-1.html is a link to one of his articles, there is a lot of sage advice here, and if you heed his advice you will protect your expensive engine and cylinders!

Regards
Trey

N22QQ
Diamond DA 40.447
KGDJ

Yes yes yes...exactly.

GAMI has an excellent engine management course. I highly recomend! I am a deakonite

OK. Much to think about. I'm in the middle of my instrument rating instruction, and I'll work with my instructor on this for starters. Thanks!

[smoss]

Interesting topic, but not a single person has brought up outside air temp. I live in Las Vegas, and commonly fly to other roasty places like Scottsdale, AZ and Palm Springs. In the summer here, regardless of what I do, my CHT's in cruise at 8,000 - 10,000 MSL range are typically 375-390 (at 100-140 rich of peak). I don't think it has anything to do with poor baffling, or running to lean, just a function of it being hot as heck outside! Sure, I can pour in extra fuel, but no doubt would foul my plugs in an attempt to get any meaningful reduction. Climbing like a dog through 6,000 MSL with OAT's still > 90 F, or 70F in cruise today at 8,500 MSL, and the cooling gradient just isn't there. With that said, the 3 other DA40's that have been based in Vegas and ran hard, to say the least, on flight school lines, have all gone strong for several thousand hours... and I know that when I flew them in my training, keeping CHT's cool was probably the last thing on my mind (I do recall hitting the yellow several times--easy to do if maintaining Vy for more than a few minutes on takeoff in 110 F). Not that I'm saying CHT doesn't play a part in engine longevity, just that it might be a smaller factor than many think.

[pabrouss]

Interesting topic, but not a single person has brought up outside air temp. I live in Las Vegas, and commonly fly to other roasty places like Scottsdale, AZ and Palm Springs. In the summer here, regardless of what I do, my CHT's in cruise at 8,000 - 10,000 MSL range are typically 375-390 (at 100-140 rich of peak). I don't think it has anything to do with poor baffling, or running to lean, just a function of it being hot as heck outside! Sure, I can pour in extra fuel, but no doubt would foul my plugs in an attempt to get any meaningful reduction. Climbing like a dog through 6,000 MSL with OAT's still > 90 F, or 70F in cruise today at 8,500 MSL, and the cooling gradient just isn't there. With that said, the 3 other DA40's that have been based in Vegas and ran hard, to say the least, on flight school lines, have all gone strong for several thousand hours... and I know that when I flew them in my training, keeping CHT's cool was probably the last thing on my mind (I do recall hitting the yellow several times--easy to do if maintaining Vy for more than a few minutes on takeoff in 110 F). Not that I'm saying CHT doesn't play a part in engine longevity, just that it might be a smaller factor than many think.

Thanks Steve for the note. All of this discussion has led me in the direction of obtaining a much better understanding of engine management during all kinds of flight and factors, one of which is OAT. I'll go that route before going back to the shop for a solution.

[Gasser]

Interesting topic, but not a single person has brought up outside air temp. I live in Las Vegas, and commonly fly to other roasty places like Scottsdale, AZ and Palm Springs. In the summer here, regardless of what I do, my CHT's in cruise at 8,000 - 10,000 MSL range are typically 375-390 (at 100-140 rich of peak). I don't think it has anything to do with poor baffling, or running to lean, just a function of it being hot as heck outside! Sure, I can pour in extra fuel, but no doubt would foul my plugs in an attempt to get any meaningful reduction. Climbing like a dog through 6,000 MSL with OAT's still > 90 F, or 70F in cruise today at 8,500 MSL, and the cooling gradient just isn't there. With that said, the 3 other DA40's that have been based in Vegas and ran hard, to say the least, on flight school lines, have all gone strong for several thousand hours... and I know that when I flew them in my training, keeping CHT's cool was probably the last thing on my mind (I do recall hitting the yellow several times--easy to do if maintaining Vy for more than a few minutes on takeoff in 110 F). Not that I'm saying CHT doesn't play a part in engine longevity, just that it might be a smaller factor than many think.

Bet you a million bucks that if you ran your engine 40 degrees LOP you'd see less than 360 even in the heat. Problem is, you may not be able to do this. Some just don't seem to be able. Mine runs really smooth down to 40 degrees LOP. Remember the fuel is not what's directly cooling your cylinders. It's the reduction in peek cylinder pressures that result from the added fuel, and not a direct effect. You can accomplish a much better and lower peek cylinder pressure on the LOP side. When I pull LOP I will see my temps drop almost instantly. 40 deg. Lop gives cylinder pressures similar to running 250 degrees ROP. Give it a try.

Of course we are talking about cruse. Climbing ROP in the heat is a different story. Airspeed is your friend. That said, there is a lop climbing technique. I've yet to mess with this. I usually just climb at a higher airspeed to keep up with this.

[smoss]

Gasser, I am not one of the lucky ones able to run LOP. My plane runs smooth ROP and right up to peak, but just a speck past peak and gets rough. And even climbing at 100 -110 IAS my CHT's are usually 400-415 range, any faster and I'd be at my destination by the time I hit cruising alititude