Leaning Techniques or Devices

How to keep the Cessna 170 flying and airworthy.

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Ron Williams
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Joined: Fri Apr 26, 2002 6:34 pm

Leaning Techniques or Devices

Post by Ron Williams »

Well the newly-overhauled engine is running really well, but my old tried and true leaning techniques are causing it to run too lean (6 G.P.H. at 70% power).
I discussed installing a CHT or EGT as the solution, but my A.I. is suggesting an Alcor System.
Would you guys that that have installed CHE, EGT or the Alcors on the O-300 give me the benefit of your experience.
Where do you install the EGT?
What CHT should I see:
Which Alcor model is the best for my 170A and what should I expect to pay :?:
Ron Williams
In a Quandry in Wichita
zero.one.victor
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Post by zero.one.victor »

Can you elaborate on your "tried & true leaning techniques" and "running too lean"? Also,I think most engine rebuilders caution about leaning too agressively until the top end is broke in.

Eric
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N1478D
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Post by N1478D »

Ron, don't have anything but the tach to lean from, but was wondering if you are still going to make Oshkosh?
Joe
51 C170A
Grand Prairie, TX
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GAHorn
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Post by GAHorn »

Alcor is merely a manufacturer of an EGT system. A good mfr, by the way, who makes temperature-compensated systems. Their literature is available thru Aircraft Spruce. 877/477-7823 They make both single probe, and 6 probe systems. If you install a single-probe EGT system, it should be installed on cylinder #2. (Left, rear)
CHT systems should be considered secondary temperature indicators and are only vaguely helpful with regard to leaning. By the time CHT tells you things are too hot from leaning, it's almost too late for the valves. (CHT is nice, but is only required in aircraft that have adjustable cowl flaps.) With C145/O300 engines CHT's normally run around 200-240 C, (400-460 F)with a redline of 275 C. (525 F).
Ron Williams
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Joined: Fri Apr 26, 2002 6:34 pm

Leaning Techniques

Post by Ron Williams »

zero.one.victor wrote:Can you elaborate on your "tried & true leaning techniques" and "running too lean"? Also,I think most engine rebuilders caution about leaning too agressively until the top end is broke in.

Eric
I would lean until I started to get an RPM drop, then richen a couple or three notches on the mixture control. Before the overhaul this method would give me about book numbers (around 8 GPH).
I installed a rebuilt carburetor from Precision, which required only adjustement for idle. During the first 5 hours I ran the engine full rich, but started the leaning process in the next 4 hours--it was running about 6 GPH (too lean for the power setting of 70-75%).
Soooo, I'm looking for a way to lean more accurately.
ron williams
Wichita
Ron Williams
Posts: 16
Joined: Fri Apr 26, 2002 6:34 pm

Post by Ron Williams »

gahorn wrote:Alcor is merely a manufacturer of an EGT system. A good mfr, by the way, who makes temperature-compensated systems. Their literature is available thru Aircraft Spruce. 877/477-7823 They make both single probe, and 6 probe systems. If you install a single-probe EGT system, it should be installed on cylinder #2. (Left, rear)
CHT systems should be considered secondary temperature indicators and are only vaguely helpful with regard to leaning. By the time CHT tells you things are too hot from leaning, it's almost too late for the valves. (CHT is nice, but is only required in aircraft that have adjustable cowl flaps.) With C145/O300 engines CHT's normally run around 200-240 C, (400-460 F)with a redline of 275 C. (525 F).
Are the probes installed in the exhaust header or in the cylinder head?
ron
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GAHorn
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Post by GAHorn »

Ron Williams wrote:
gahorn wrote:Alcor is merely a manufacturer of an EGT system. A good mfr, by the way, who makes temperature-compensated systems. Their literature is available thru Aircraft Spruce. 877/477-7823 They make both single probe, and 6 probe systems. If you install a single-probe EGT system, it should be installed on cylinder #2. (Left, rear)
CHT systems should be considered secondary temperature indicators and are only vaguely helpful with regard to leaning. By the time CHT tells you things are too hot from leaning, it's almost too late for the valves. (CHT is nice, but is only required in aircraft that have adjustable cowl flaps.) With C145/O300 engines CHT's normally run around 200-240 C, (400-460 F)with a redline of 275 C. (525 F).
Are the probes installed in the exhaust header or in the cylinder head?
ron
EGT probes are installed in accordance with the mfr's instructions, usually 3 inches downstream of the exhaust riser flange. ("header" infers a "gathering system" of some sort. An exhaust "riser" actually rises from the muffler to the cylinder exhaust flange.)
CHT thermocouples on the C145/O300 engine consist of the sparkplug gasket type (on the lower plug).
Ron Williams
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Joined: Fri Apr 26, 2002 6:34 pm

I've ordered the Alcor Basic (single probe EGT).

Post by Ron Williams »

gahorn wrote:
Ron Williams wrote:
gahorn wrote:Alcor is merely a manufacturer of an EGT system. A good mfr, by the way, who makes temperature-compensated systems. Their literature is available thru Aircraft Spruce. 877/477-7823 They make both single probe, and 6 probe systems. If you install a single-probe EGT system, it should be installed on cylinder #2. (Left, rear)
CHT systems should be considered secondary temperature indicators and are only vaguely helpful with regard to leaning. By the time CHT tells you things are too hot from leaning, it's almost too late for the valves. (CHT is nice, but is only required in aircraft that have adjustable cowl flaps.) With C145/O300 engines CHT's normally run around 200-240 C, (400-460 F)with a redline of 275 C. (525 F).
Are the probes installed in the exhaust header or in the cylinder head?
ron
EGT probes are installed in accordance with the mfr's instructions, usually 3 inches downstream of the exhaust riser flange. ("header" infers a "gathering system" of some sort. An exhaust "riser" actually rises from the muffler to the cylinder exhaust flange.)
CHT thermocouples on the C145/O300 engine consist of the sparkplug gasket type (on the lower plug).
You are exactly correct.
How do I know on which cylinder riser the probe should be installed on my 1950 'A' Model?
When it is installed do I lean to peak and then enrichen 50 or 75 degrees?
Sorry for all the questions, George, but you have been through this, or at least monitored these strings.
ron williams
Wichita
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GAHorn
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Post by GAHorn »

Install it on Cylinder #2, as recommended by TCM.
Lean in accordance with their recommendations also, found in the Cessna 170 Owner's manual, and TCM Operator's Manual, form X30015, pg. 4. "At any cruising altitude adjust mixture control for best rich power by moving toward "LEAN"postiion to obtain maximum RPM, with fixed throttle, then return toward "FULL RICH" until RPM drops just perceptibly. Readjust for each change in power or altitude. (An EGT gauge will assist in confirming the proper setting.)
Ron Williams
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Joined: Fri Apr 26, 2002 6:34 pm

EGT Probe Installation

Post by Ron Williams »

George, I just hung up from talking with Cessna--the proper cylinder for installation of the EGT probe is #3 (right middle), at least thru the A models. I did not specifically ask about the B's. They checked the certification data for the cylinder that leaned first and was the hottest. The cert. test data showed no. 3. It sounded like the No. 2 came with the changes (maybe the pressure cowl), because I think the installation on the 1956 172, e.g., was no. 2.
I know there was a Service Kit, AK-172-16 that was a CHT installation kit that put the CHT on no. 3.
Did any of the 'B' models have a CHT or EGT as standard or optional equipment.
ron
(sweating in Wichita)
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