Why does the engine run evenly and smooth on lean mixture on carburator engine?

XCHCUI

MEMBER
1990 OPEL CORSA

Hello.
This question related to engine with carburator.
I would like to understand why the engine run evenly and smooth when the air/fuel mixture is lean?
I understand why the engine run evenly and smooth while the mixture is rich and why the engine run rough with too rich mixture, but I don't understand why when go from rich mixture(while the engine run evenly)to the 1:14.7 fuel/air ratio, the engine start to run rough(~ 1 lambda), but if we pass the 1:14.7 ratio into the beginning of the lean mixture area, the engine start to run evenly and smooth again?
What is happening?

Thanks in advance.

3 Replies

CJ MEDEVAC

MECHANIC
11,004 POSTS

THIS HERE HAS HELPED ME MORE THAN ANYTHING IN GETTING MY CARB RIGHT. HE EXPLAINS JETTING/ POWER VALVE SELECTION/ ETC

YOU MAY HAVE TO COPY AND PASTE IT TO A NEW TAB

http://www.bob2000.com/carb.htm

HERE'S MORE SHOWING MY SET-UP/ YOU WILL SEE PICS OF MY O2 SENSOR WHICH RUNS MY AIR/ FUEL GAUGE

https://www.2carpros.com/questions/1980-jeep-cj7-new-fuel-tank-sending-unit-dash-gauge-wiring-checked-out-good-gas

THE MEDIC

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Saturday, May 23rd, 2015 AT 5:52 PM

XCHCUI

MEMBER
91 POSTS

Thanks, CJ MEDEVAC, for the links, but nothing there explains or deal with the theory:why does the engine run evenly with rich(lambda<1, but not too rich), why the engine is not run evenly when I decrease the a mount of the fuel to get a mixture of 1 lambda, while when I decrease more the amount of fuel, to get a lean mixture(lambda>1, but not too lean)the engine, suddenly, run evenly again.
What is the theory behind that?
I read tens article about the subject, as you attached, but didn't find a good explanations, besides the fact that this is what happens.

Thanks in advance.

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Sunday, May 24th, 2015 AT 3:05 AM

CJ MEDEVAC

MECHANIC
11,004 POSTS

I RECKON YOU'RE GETTING SORTA TOO SCIENTIFIC FOR ME!

THIS OTHER LINK IS PROBABLY AS FAR AS I CAN TAKE YOU, MOST OF IT IS OVER MY HEAD, YOU'VE PROBABLY GANDERED OVER IT ALREADY!

http://en.wikipedia.org/wiki/Air%E2%80%93fuel_ratio

OUT OF CURIOSITY, 'ZACKLY WHAT ARE YOU DOING, AND WHAT END RESULT ARE YOU AFTER?

THE MEDIC

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Sunday, May 24th, 2015 AT 7:15 PM