High CHT's on Takeoff

[BigTex]

Ever since installing my EDM-700 I've been fighting/obsessing over really high CHT's on take-off. As soon as I take off, my CHT's spike to an alarming 450 degrees for about 3-4 minutes. As soon as I can back off on power and gain climb out airspeed (~ 120mph) all of my CHT's come back down in the 350-380 range. Any thoughts or techniques on how to keep down or better manage CHT's on take-off?

[andrew]

The temperatures spike like this immediately at take-off? I normally don't linger between take-off and establishing a cruise climb unless I have a real need for it, how aggressive is your climb? I can definitely get the temperatures to rise if I hold the plane in an aggressive climb, it normally takes a few minutes though.

What sort of condition are your baffle and baffle seals in?

I believe the C has a ground adjustable cowl flap. Have you tried adjusting this?

[BigTex]

I'm generally pretty aggressive on climb out to about 1000' AGL then bring back power for cruise climb. Then I bring back the power and start my cruise climb. Just re-looking at the data, my hottest cylinder (#2) at take off was 389 and in about 1.5 minutes shot up to 445. Then you can see where I brought power back an all were below 400 within 5 minutes and down to 350 after 10 minutes.

Baffling is in decent shape but it's something I'll definitely start looking at first.

It's actually pretty cool to be able to have this kind of data readily available to you to perform this kind of detailed analysis. I've captured 5-6 flights so I've got a pretty good baseline to work with.

[carusoam]

Sounds like good instrumentation on your C. Do you have the dog house type box controlling air flow?

Look to improve all seals around the engine, cracks in the doghouse.

Are your flaps adjustable? Working properly?

My experience with a 65C was the single CHT probe and analog gauge. I would see similar behavior as well.

The procedure to move from take-off power to climb as soon as practicable seems to apply. At least with the JPI, you are collecting data that you can readily see. When you lower the nose, does 120mph lower the temps enough? How about 130?

Best regards,

-a-

[BigTex]

It does have the dog house so I'll need to go over the baffling in detail to see where I can improve and/or seal up gaps.

Once I'm configured for climb out 2400/24" @ 120mph, the temps come down to where I expect them. I'll experiment with maybe keeping my climb out to around 500fpm so that I can get up to cruise speed sooner.

[jrwilson]

I have a 1963 20C and those numbers are very high. I never see over much over 400 degrees on initial climb out and that is in the summer. Like others have mentioned, probably your doghouse and make sure your cowl flaps are opening right.

[jwilkins]

My 62 C had lower CHT temps on climb out after I installed the Lasar cowl mod to close up the cowl opening under the prop.

I thought it was odd, but the AP said it was not uncommon as the original cowl had terrible air flow characteristics.

I only had a single probe CHT so never knew what the rest of the cylinders were doing.

[gregwatts]

It has been quite awhile since I had my C model.....but I would suggest keeping your climb rate around 500'-700' fpm and climbing out at 26' and 2600 rpms, which is what is recommended in your POH. The cowl closure is a worthy mod.....IMO.

[N33GG]

?

[danb35]

Am I reading this right that #2 is at 389 on the ground, even before the takeoff roll? Does it use the same type of probe as your other cylinders? You should still have the factory CHT gauge installed, so depending on what cylinder it's on (it's on #1 in my F), you'll have a different probe there. If the CHT sensor for your JPI on #2 is a spark plug gasket type, that could account for higher reported temperatures on that cylinder.

I can't imagine why you'd want to pull power back for the climb--seems to me you'd want max power for that. You could have higher airspeed (and thus better cooling) for a given rate of climb, or better climb rate for a given airspeed. Your engine is rated for continuous operation at full power, but even if it weren't, you aren't generating full power once you're above sea level.

[Ron McBride]

It has been recommended on the MAPA list do not reduce the throttle after takeoff, there is an enrichment made at wide open throttle only, this may help until you are at cruise.

Ron

[carusoam]

Dan,

I think you hit the target dead center. The C's cooling is a limiting factor. The engine is capable of 27 squared, but it gets hot.

Full power and full hot drives cyl temps into uncomfortable ranges.

Protecting the cylinders by improved cooling, and minimizing high power setting within reason...

The J cowling and other similar mods are greatly appreciated by their owners.

The C is a very capable bird, but takes more oversight/patience to manage well.

BigT,

What's your cyl temp red line? If you follow this particular guideline it's acceptable behavior, but not recommended.

Is everyone targeting the same 420F and below CHTs?

Best regards,

-a-

[Hector]

I have the single CHT gauge in my 67C on the #3 cylinder. I typically go 26/2600 per the POH at around 1000 feet and 120MPH and my CHT never goes over 400. In fact at this climb setting, with cowl flaps full open, the CHT remains around 380-390. Of course I have no idea what my other cylinders are doing, and honestly i'm not sure how accurate my current gauge is either. EDM700 installation scheduled early in 2013.

[scottfromiowa]

Read Bob Kromer's article on climbing a C model (MAPA LOG). His council makes sense to me...

[jimosborn]

Ever since installing my EDM-700 I've been fighting/obsessing over really high CHT's on take-off. As soon as I take off, my CHT's spike to an alarming 450 degrees for about 3-4 minutes. As soon as I can back off on power and gain climb out airspeed (~ 120mph) all of my CHT's come back down in the 350-380 range. Any thoughts or techniques on how to keep down or better manage CHT's on take-off?

First, congrats on installing the EDM-700 monitor. An all-cylinder engine analiizer is inarguably THE best investment an owner can make to monitor and prolong engine life by dealing proactively when things don't look right.... like now. A monitor with the fuel flow option is particularly helpful for troubleshooting from the captured traces upon download, hope you have the FF option.

As to your CHT issue (anything over 400df is WAY too much); since baffling issues and my agreed recommendation to use full power during TO & climb have already been discussed, lets look for some clues within the engine setup, starting with fuel flow (gph). Specifically, during TO & climb at fulll power, what are your EGTs and FF?

By rule of thumb, FF should be rich enough so EGTs settle in the neighborhood of <1300df for adequate internal cooling. Second, and very importantly, do you know for sure that magneto timing is set to spec? Advanced timing causes higher internal cylinder presssure (hence higher CHT). Ironically, an inverse symptom of that condition is lower EGTs. Definately worth checking those things out!

[Lood]

At what altitude are you operating from and what's your mixture setting during take off and climb?

[carusoam]

Welcome JimO,

Well written first post.

Best regards,

-a-

[scottfromiowa]

I saw 1100FPM climb last week pitched for 120MPH. Full throttle full rich. Cylinders all nice and cool. Give that formula a try and see what temps are. The fuel is a great "cooler" of the engine in climb. I am VERY cautious about leaning in climb, but I do lean to a target EGT of 1250-1300 (above 2500 feet). I do NOT adjust prop until cruise and MP stays fire-walled unless I am remaining below 3500 feet. 380 is my never exceed temp on cylinders. My #2 reads 50 degrees high and will reach 380 leaning in climb on a hot day. I enrichen a bit if this occurs. On really hot days I just burn some gas until I get to cruise altitude.

[Hank]

Scott, that's part of the difference between E- and C-models! I don't have an analylzer, just factory single point, but a friend's F almost matches your climb rate/temp, which is much better than a C can achieve. We just don't have the power for that. I'm happy to see 1000+ FPM at takeoff, but that's at 100 MPH not 120. My limiting factor is usually Oil Temp getting to the top of the green line. Hot summer days can take a long time to reach altitude, climbing at <500 fpm for several thousand feet. So far, I've not had any CHT issues.

Full Throttle, Full Prop, Mixture Full Rich until at least 5000 msl, then I sometimes remember to lean for my Target EGT. Outside of hot summer days, I can go from turning the key to level cruise, trimmed, power set and leaned, at 7500-9000 msl in ~15 minutes, which is good enough.

"Cruise climb" is used when I have to climb from one cruising altitude to another, not for when I'm leaving an airport and climbing to altitude. In the winter, I follow (100 mph - Altitude in thousands) for airspeed in the climb; in the summer, I increase airspeed/reduce climb rate to keep Oil/CHT in the green.

Our 180-hp, carburetor-equipped Cs cannot match a 200-hp, fuel injected E/F in the climb. . . . .

[jlunseth]

The piece of information we are missing is where the OP has his mixture set. I am guessing it is "leaned for climb" at TO.

[scottfromiowa]

Thanks Hank, I appreciate and enjoyed reading your post

[BigTex]

The piece of information we are missing is where the OP has his mixture set. I am guessing it is "leaned for climb" at TO.

My home field is at 660' MSL and my climb outs is with mixture full rich. I do bring the power back to 25"/2500 rpm right after I tuck up the gear. I do climb pretty aggressively (1000fpm) for the first few minutes then bring the power back to 24 squared and 120 mph until I'm at my desired altitude. I do also monitor EGT and lead for 1250 degrees.

What I'm hearing, is to check my baffling. I'm also going to adjust my takeoff procedures by reducing my climb outs to 500fpm until I reach 120 mph. I try several power settings to see what works best.

[gregwatts]

It seems to me.......aside from the CHT issue........the climb profile that you describe is very inefficient. You may want to try.....after gear and flaps up, accelerate to 110 kts and climb at 26 squared and 110 kts to altitude. I believe you will see better results in the temps as well as your time enroute.

My opinion only!

[jimosborn]

My home field is at 660' MSL and my climb outs is with mixture full rich. I do bring the power back to 25"/2500 rpm right after I tuck up the gear. I do climb pretty aggressively (1000fpm) for the first few minutes then bring the power back to 24 squared and 120 mph until I'm at my desired altitude. I do also monitor EGT and lead for 1250 degrees.What I'm hearing, is to check my baffling. I'm also going to adjust my takeoff procedures by reducing my climb outs to 500fpm until I reach 120 mph. I try several power settings to see what works best.

Gary, in your various power settings experiments, shooting for 1250 EGT is certainly the correct thing to do but doing so with less than full throttle during climb defeats the purpose of using excess fuel flow for cooling, this mostly due to backing-off whatever mechanical power enrichment feature is designed into your fuel delivery system. Besides, what's the logic of manually reducing manifold pressure to some arbitrary "square" number as you climb, then need to feed-in 1" MP every 1,000 just to maintain the target MP'? Too, beyond using your current technique to control CHT (which is only a band aid for an underlying problem), why sacrifice climb performance with such low power setting?

Habits, training and ad hoc "recommendations" aside, I doubt that you will find any POH limitation or restriction on the use of full throttle at any RPM normally used for climb. In other words, if 2400 RPM is your preferred climb setting... fine (though I'd opt for not less than 2500), but anything less than full throttle and mixture settings targeting 1250 EGT portends more harm than good in terms of CHT and engine longevity.

Oh, you've yet to identify FF at full throttle & full rich mixture .. hopefully you do have a FF gage of some sort? Too, so as to not leave any stone unturned in your quest to solve the high CHT issue, please don't ignore my suggestion to verify magneto timing to be on spec. You'd be amazed how much difference just a degree or two off spec will make.

Cheers!

[danb35]

Habits, training and ad hoc "recommendations" aside, I doubt that you will find any POH limitation or restriction on the use of full throttle at any RPM normally used for climb.

There's no limitation, but at least in my F POH, there's Mooney's ill-advised recommendation to reduce power for the climb. In any event, though, assuming there isn't any difference in the probes, seeing over 380 on the ground (presumably after a cold start, and without really extended ground idling) indicates that something is very wrong. Admittedly, I generally fly out of a small uncontrolled field, but my hottest cylinder doesn't generally reach 200 before takeoff. I wouldn't think that baffling would cause that, nor inadequate fuel flow; I guess mag timing might.