C

Camillo

Well Known Member
Hi.
I read some posts but they didn't help me.

When I lean the engine, engine starts running rough before the lean of pick. So I have to enrich it in order to let it run smoother. Approx. I have 770 Celtius degrees EGT on cylinders 2 and 3 and 15° less in cylinders 1 and 4. This happened since ever. Now airplane has 127 hours and spark plugs were moved but not changed (the same that came with the engine). I have a new Lycoming O-320. Airplane is flying since April 2011. Engine is started up regularly, once per week. I only run AVGAS and magneto timing was performed 30 hours ago. I guess I have Champions REM38E and a set of 40E ready to install.

I guess this could come from bad spark plugs, but in a few posts I read a few different reasons and I am a bit confused.

Thanks.
Camillo
 
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Camillo,
It's very difficult to impossible to get a non-fuel injected engine to run LOP. Since you say you're running an O-320 my guess is it's probably your induction system which means you're most likely stuck running ROP.
 
i have a O-360 experimental engine from lyc thunderbolt with flowed heads. when i lean it there is no roughness. unfortunately i dont have enough engine monitoring to try lean of peak but it will lean to the point of the engine quitting with no engine roughness. thats it.
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to improve atomization

A couple of tricks you can try is to pull the throttle back just slightly to have the throttle plate induce some turbulence and improve atomization. Another trick is a touch of carb heat. One or both of these might allow you to run leaner before the onset of roughness. If you are below ~9.5 GPH (~75% power), all CHT are below 380-400, and it is smooth, you are not hurting it.
 
As the others have said, carbureted engines don?t like to run lean of peak.

However, I can do it but only because I have dual electronic ignition (P-mags). Also, you are supposed to only run LoP up high and at or below 65% power.

Typically, with mags, you have to run rich of peak.
 
So, I have to resign. Important thing I learnt is that this is normal for a carbureter engine!
Thanks.
Camillo
 
N941WR said:
As the others have said, carbureted engines don?t like to run lean of peak.

However, I can do it but only because I have dual electronic ignition (P-mags). Also, you are supposed to only run LoP up high and at or below 65% power.

Typically, with mags, you have to run rich of peak.
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They say that but we run 85% power LOP, and TN Bonnaza guys run 95% power LOP. Its all about CHT
 
jetdriven said:
They say that but we run 85% power LOP, and TN Bonnaza guys run 95% power LOP. Its all about CHT
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But both the Bo and your Mooney 201 are injected and the Bo has a Conti engine, which may make a difference.

You are correct, it is all about CHT's but it is also about how rough the engine runs and fuel distribution with a carb is an issue. Thus, if you run lower % power, there is very little chance of damaging the engine.

With my O-360 powered RV-9, I can run it at 155 KTAS LoP while burning around 6.6 GPH. That is way down the power curve. But, I will only do this at 8000’ or above.
 
There's nothing wrong with running LOP down low as long as you stay below 75%. Flying high just makes the management for normally aspirated engines easier because the mixture setting danger zone (aka the red box) gets smaller with altitude because HP natually drops until the danger zone disappears altogether.
 
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Fuel injection makes it much easier. My regular pilot friends freak out when I run 29" MP, 2200 RPM, and pull the mixture to 7 GPH (~150 LOP)

or 11 GPH. (83%)
 
Camillo,

Your O320 will certainly run LOP, I do it with a few here that belong to friends.

I have written a whole article for the SAAA magazine here recently on doing it, and while it has not been printed if you send me your email address I could send you a copy.

First things you need to know are;
1. All induction leaks fixed. You will surely have some. Intake gaskets and the rubber hose couplings.
2. Spark plugs. Gap 0.016 to 0.018" and check the resistance of Champions. They should be under 3K ohms and any at 5K or more, throw them out. Tempest seem to be stable. you can buy them instead. Don't change the heat range. Re-Gap and resistance test every 50 hours for optimum performance.
3. Timing, make sure this is set at 25 degrees, on both mags. Unless your engine is meant to be different.

There are a few techniques with throttle plate position and carby heat that will take too many characters to post here.

As for running LOP at high powers..... Sure, just make sure you are Rich enough on the ROP side or LEAN enough on the LOP side. If your carby engine will do it down low, why not? The cylinders don't know the difference. You just need to know what you are doing. Trouble is most only know enough to get themselves confused and into trouble.

You are correct, it is all about CHT's but it is also about how rough the engine runs and fuel distribution with a carb is an issue.
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Folks I want to dispell this little Myth. So bare with me a moment. It is not all about CHT at all. CHT is an important tell tale, however you can be running high ICP's and still be at a CHT you think is acceptable. For example my engine runs most of the time from 295/310 in winter and 310/330 on a hot day in summer. So if I were to use the 380F limit in the cruise :eek: that would be bad. At reduced airflow in the climb, that is different. It is important to understand what is going on here.

So following the advice of using a "Target CHT" as i think Mike Bush wrote about once, is not good advice at all. It all depends. When John Deakin writes about 380F being the rough limit on normal ops, that is based on a conforming engine in say a Bonanza, or most others, however, in Alaska in Winter he would also tell you that your old limit of 380 is now much lower. So its not a hard rule. Its a fuzzy rule. And you need to know what this all means.

One of my favourite photos, its a little blurry but study close. 29.6"MP yes that is real, high QNH day, 2430 RPM and about 80F LOP. TAS166 and all CHT's around 300-310F on a mild Autumn day.

photo2-3.jpg


All the questions, and all the myths I read here and elsewhere on the internet are all covered in a well known course. You can even do it online from Italy Camillo for a few hundred dollars.

Off to burn some Low Level High Power, LOP Avgas, have a good day Y'all.:)
 
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