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Lean / Rich, Ignorant Question - 11/9/2006 8:33:59 PM   
Zephirus79


 

Posts: 57
Joined: 11/9/2006
From: , GA, USA
Status: offline 		Im just getting into the hobby so let me say that first.

How do you know if an engine is too lean or rich? I hear people saying you can adjust the mixture at both low idle and full throttle. I dont have my engine yet but I would like some information to start reading or perhaps a good webiste on rc engines.

Are there any tests to see if you are running too lean or too rich? Im sure over time, you can just listen to the engine and know...


From what i understand, lean is when its not getting enough fuel which increases rpm somehow (id think it would be opposite) but it also causes high temperatures to occour

Rich is when you are pumping in too much fuel and the engine floods or stalls from having so much...
       Post #: 1

RE: Lean / Rich, Ignorant Question - 11/9/2006 8:49:22 PM   
w8ye



Posts: 17464
Joined: 12/11/2001
From: Taylortown, OH, USA
Status: offline
quote:

ORIGINAL: Zephirus79

Im just getting into the hobby so let me say that first.

How do you know if an engine is too lean or rich? I hear people saying you can adjust the mixture at both low idle and full throttle. I dont have my engine yet but I would like some information to start reading or perhaps a good webiste on rc engines.

Are there any tests to see if you are running too lean or too rich? Im sure over time, you can just listen to the engine and know...


From what i understand, lean is when its not getting enough fuel which increases rpm somehow (id think it would be opposite) but it also causes high temperatures to occour

Rich is when you are pumping in too much fuel and the engine floods or stalls from having so much...

If you lean out a rich engine by turning the needle valve clockwise, the engine will speed up in the beginning but if you keep turning the needle valve clockwise, eventually it will become too lean and sag and quit on you. You will notice it is also too hot. There is an ideal position you are seeking where as the engine runs it's fastest and then you richen it back up a few hundred rpm.

Your assumption about being too rich is correct.

Here is a section that will explain some of your questions....
http://www.easyrc.com/engines/index.html

< Message edited by w8ye -- 11/9/2006 8:51:27 PM >

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RE: Lean / Rich, Ignorant Question - 11/9/2006 10:13:28 PM   
jaka


 

Posts: 4526
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
You determine if an engine runs lean or rich by listening to it!
That simple!

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RE: Lean / Rich, Ignorant Question - 11/9/2006 10:14:32 PM   
Dr1Driver



Posts: 3589
Joined: 7/25/2002
From: Spartanburg, SC, USA
Status: offline 		The best test for a too-lean condition is the pinch test. Start the engine and run it up to full throttle. From BEHIND the engine, briefly pinch the fuel supply line to the carb. If the engine sags and dies immediately, it's too lean. If it runs a while, then picks up speed slowly, it's too rich. If it picks up speed slightly, then starts to sag, it's about right.

Dr.1

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RE: Lean / Rich, Ignorant Question - 11/10/2006 1:46:58 AM   
Rod Bender



Posts: 466
Joined: 1/22/2006
From: Swansboro, CA, USA
Status: offline
quote:

ORIGINAL: Dr1Driver

The best test for a too-lean condition is the pinch test. Dr.1


Ah,

Beat me to it. We are assuming this person has a 2 stroke, so yes, the pinch test is your ticket... Greg


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RE: Lean / Rich, Ignorant Question - 11/10/2006 5:49:27 AM   
RVM


 

Posts: 1975
Joined: 3/12/2006
From: Sacramento, CA, USA
Status: offline 		Pinch test works on 4-strokes too, but to a lesser degree.

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RE: Lean / Rich, Ignorant Question - 11/10/2006 6:40:52 AM   
Rod Bender



Posts: 466
Joined: 1/22/2006
From: Swansboro, CA, USA
Status: offline 		You can do the pinch test on a 4S, but its harder to distinguish the "sweet spot". Guys with out a tach lean it out until it stumbles, then back it off 1/3 of a turn. Guys with a tach will find the max rpm, then back off 500rpm ....... Greg

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RE: Lean / Rich, Ignorant Question - 11/10/2006 1:20:54 PM   
wcmorrison



Posts: 774
Joined: 10/2/2002
From: Weatherford, TX, USA
Status: offline
quote:

ORIGINAL: jaka

Hi!
You determine if an engine runs lean or rich by listening to it!
That simple!


That's true, but what do you listen for? You need to be a little bit more explicit.

Cheers,

Chip

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       Post #: 8

RE: Lean / Rich, Ignorant Question - 11/10/2006 2:27:10 PM   
bob27s



Posts: 4821
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline
quote:

ORIGINAL: wcmorrison


quote:

ORIGINAL: jaka

Hi!
You determine if an engine runs lean or rich by listening to it!
That simple!


That's true, but what do you listen for? You need to be a little bit more explicit.

Cheers,

Chip


Some good advise here. The pinch test will get you in the ballpark. When in doubt, error on the rich side.

Let me add my two cents... since I believe you have recognized this anyway at this point....

Learning how to set up a model aircraft engine, what to listen to, what to look for, and why........ are all things your flight instructor (and perhaps other club members) should be teaching you.

Watch others - and you will quickly identify those around you who are experienced and can guide you and help you learn.

Although there are many years of experience here on this board, there is simply no substitue (no simulator, and for the most part no video recording) that can teach you the way an engine behaves, and how to properly adjust it. It has to be a hands-on, in your face experience. And that experience will continue over your continued years of modelling. Every type of engine is just a bit different, carb designs may be differenent, but the principles are the same. Yes, folks here can tell you what to do, what to turn, and what to look for, but its hard to replace an actual hands-on event.

Setting up the aircraft, radio, and engine are must be learned, and are JUST as important as actually learning how to control the plane.

My instructors and club members taught me the basics, and I found the aspect of the engine just as fastenating as the airplane itself. Some folks at the time were simply satisfied if the engine started and continued to run. Others were more particular, and demanded reliability. Through these folks I discovered that spending 10-20 minutes setting up a new engine or new engine installation, was time well spent - I got tired of dead-sticks and flame-outs when landing. So I took it upon myself to learn how to properly set the low speed mixture and transition more carefully.



< Message edited by bob27s -- 11/10/2006 2:29:25 PM >


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RE: Lean / Rich, Ignorant Question - 11/10/2006 4:20:36 PM   
Cyclic Hardover



Posts: 7218
Joined: 5/7/2002
From: New Mexico, USA
Status: offline 		As far as the low end goes, while the engine is at an idle, safely remove the fuel line from the carb or pinch it. Either way, wait for the engine to quit. Listen to the rpms as the engine stops. If the rpms increase as the engine quits, low end too rich. If the rpms just go down and quit, too lean. I set mine for a very slight increase.

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