Help, I'm too cool!

[Richard]

Well. Here it is. I can't get my plane warm enough.

12500', 28", 2500rpm, 191knots.

Front engine:
TIT Peak was 1430', Normal cruise was 1350'
CHT peak was 308', Normal cruise was 268'
Oil peak was 170' Normal cruise was 150-160'

It get worse on the rear. It's cooler than my front. Am I going to harm anything with these temps? Should I do all my climbs with cowl flaps closed?

[docbob]

Is TIT lean of peak or rich of peak? Slightly lean of peak is good for the engine and results in lower CHT.
A rough rule of thumb is that an oil temperature around ambient deg F plus 100 deg F is good. Seems that at 12.5 you might even be a little higher than this. It is pretty hard to imagine how running at these temps could harm the engines. I (normally aspirated) have been looking at CHT's around 350 for 18 years.
Shock cooling during a careless let-down causes lots of damage. The lower the starting temp, the lower the shock-cooling effect. Adequate oil temperature (and, thus, flow) before full power application for takeoff is important. So a good warm-up is smart.
Bottom line: seems that you are well within the green arcs.

[Richard]

My buddy and I went up to 10,500 for three hours today. Doing all the GAMI lean stuff. He can't believe the head temps. During cruise I don't have one cylinder, front or rear over 300 degrees. 299 was the highest. I've been able to get the oil temps a little higher with some changes.

I've been able to reach 390 degrees on one cylinder but that was a 28" 2600rpm climb to 13000'.

If anything, I'm thinking it might give me alittle better cylinder life. One engine has cromed cylinders and the other has steel. The crome are running cooler than the steel. I wonder if that's just coincidence though.

[SkyKing]

Hey Richard,

Maybe if you remove all of that unauthorized, non-type certificated add-on stuff from your plane... it WILL run right! Why ask for help when the folks reading this don't have a clue as to how you've 'modified' your engines?

Gee... maybe your Airworthiness certificate says "EXPERIMENTAL." Could it be?

SkyKing

[Richard]

You're right. Just thought I'd get some input on "normal" operations. Sounds like since I'm not a "pure breed" anymore, my questions don't mean anything anyways. Guess I won't ask then.

[skymaster]

hey richard : keeep testing. everyone is jealous. wish we had the time to tinker.. did you see my waste gate inline filter. it works great . i have caa approvals and drawings. apparently few people understand how the unfiltered oil affects the controller. anyway i want to share with 337 group. if interested i will fax. 73p

[Richard]

Maybe, but Skyking has a point. As far as the filter thing goes, I fixed that problem. I am working with a company in CA for a STC on a remote filter system. I've got 35 hours on my oil and it is as clean (clear) as I put it in. I'll get sample data @ 50 hours and post it. If there is interest, they will go ahead and STC it.

Your design is extremely simple though. That makes for a perfect install. Everyone can understand simple.

[bede1@msn.com]

Richard,

I see nothing wrong with your temps. I posted the same question a year ago about my bird (very low temps) and got about the same answers as you. Nobody believed me either or thought my guages were wrong. I have had them sent back to JPI for calibration and even replaced the EGT & head probes but the temps still stay low. I made a comment oncethat Iwas having to use 1/2 cowl flaps just to keep the temps up during the winteron take off and did I get the harassment about that so I learned that if I find my bird doesn't fit the normI keep guiet about it.

[rick bell]

i usally close the cowl flaps after 400' unless in the summer (desert sw) and i'm not able to t/o right away. i usally never overheat and curise 24" x 24 rpm, close thw cowl flap a t/o and see.
do what you want to your plane, it's yours and your responsiblity, not anyone elses

[Richard]

Thanks for the word of encouragement.

Good idea on the cowl flaps. I'm usually too afraid of touching the cowl flaps until I get straight and level, but I'll give it a try.

On a recent 3 hour flight I adverged about 300' on head temps and 170-180 on the oil. Those seem about normal. The one thing I'm curious about is that since I am running a CDI ignition. It is supposed to lower your EGT's from 100-200 degrees. Currently I peak at TIT 1440. EGT's run from 1325 to 1390. Is this the norm for a Turbo 337? It's been so long since I flew it before that I can't remember.

[kevin]

Those TIT and EGT figures, as well as CHT figures, were the same on my '73 P337. My oil temps were about 30 degrees higher during this time of year. Are you sure your vernitherm is working correctly? In the middle of winter I used to have oil temps as cool as yours, and my mechanic put duct tape (I mean a kit from Cessna, sorry) on my oil cooler to solve it. I never understood that, because I thought the vernitherm would be closed anyway. But I am not a mechanic...

Kevin

[Dale Campbell]

I have a 337H normally asperated. I to had problems regulating engine temp on both engines. I added the model 1200 Egt/Cht to monitor temp. In winter the front engine was always 160 degree on oil temp, while heads where around 290 temp range. The rear would run in the normal range in winter, but on the hot side in summer. My A/P added a removable plate for above the oil cooler on front engine, for winter use. That brought the front engine oil temp up to 190 degree in winter and solved the water problem that was forming in the oil. I never have to use cowl flaps on front engine, winter or summer. Now the rear engine I have to leave cowl flaps open a lot in summer, even open a little if staying at or under 4000 feet for long period of time, if outside temp is around 80 degree or above. In winter the rear engine stays in the normal range and very seldome have to use cowl flaps even at climb. Because I am normally asperated, I can not get above 13,500, I do not have the high altitude problem.

[GJ Humphrey]

Excuse my ignorance, Richard, but what is a CDI ignition and what does it do for performance?

[Richard]

CDI stands for capacitive discharge ignition. It's the same type of ignition system running around in most automobiles today.