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What's the meaning of a "lean" vs "rich" air fuel mixture

I do not know the etymology of these words or the history of their use in the context of air-fuel ratios, although their dictionary definitions (lean [adj.], rich, too bad I don't have an OED ...
Jason C's user avatar
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7 votes

What's the meaning of a "lean" vs "rich" air fuel mixture

A lean air/fuel mixture is when there is more air than required to burn the fuel. A rich mixture is when there is too little air for the given quantity of fuel. The ideal mixture, where there is ...
Steve Oakes's user avatar
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7 votes

How to fix P2195, P1172, P1174 and P2197 error code for Honda Accord LX 2004?

When you get a bunch of codes on a car, the best way to work through is to fix only the first code - in this case the P2195. The easiest check is to look for a disconnected cable - Rear A/F Sensor ...
PeteCon's user avatar
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6 votes
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Bike currently running rich due to aftermarket exhaust, will adding an aftermarket air filter without any ecu work fix it

If anything, your bike should be running lean Thoughts You put an aftermarket non-restrictive exhaust on your MV, that increases the flow of gasses which requires more fuel to compensate for the ...
DucatiKiller's user avatar
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5 votes
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How is AFR calculated from ODBII readings

Assuming that liquid fuel is incompressible, the missing piece of the puzzle here is fuel density, which is around 700 kg/m³. So the fuel mass flow rate is as follows: Mass flow rate = Density * ...
Zaid's user avatar
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4 votes
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Given that one of the reasons diesel engine produce black smoke is overfueling, why do diesel dragster produce so much soot?

The Primary Reason for Excessive Soot in Diesel Dragsters is Incomplete Combustion Something to keep in mind regarding diesel dragsters is that they do not use any emissions equipment to more ...
DucatiKiller's user avatar
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4 votes

How to fix P2195, P1172, P1174 and P2197 error code for Honda Accord LX 2004?

To be honest you need to be able to view live data using a scan tool. If you don't have access to these it may be cheaper to take it to a shop that specializes in Hondas. It's not inconceivable that ...
Ben's user avatar
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3 votes

Does opening the throttle mean a leaner fuel to air mixture for starting?

No (or maybe more accurately – not for long), that is why you have a choke. Opening the throttle does allow more air in, but should also be causing more fuel to come in as well to preserve the mixture....
dlu's user avatar
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3 votes

Percent of Air and Fuel used for Combustion

Upto to which point this air can be reduced. (I mean in the AFR ratio like 10: 1 , 8: 1) ? Realize, if you were to open the butterflies and nothing else were to occur (no additional fuel), you'd ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
3 votes

Percent of Air and Fuel used for Combustion

Let me see if I can clear some of this up for you. The stoichiometric ratio (AFR) for the petrol is 14.7 : 1 right? This is correct, and it's important to understand the concept of stoichiometric ...
JPhi1618's user avatar
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2 votes

Why does a petrol engine need to maintain an air-fuel ratio, while a diesel engine doesn't?

The other answers failed to note that the air-fuel ratio is dependent on the position you measure it at. So, even though the air-fuel ratio averaged over the whole cylinder is lean (so lean that ...
juhist's user avatar
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2 votes

How accurate is the air-fuel-ratio set by the ECU?

This is not a "definitive answer" by any means, but I think it gets to heart of the question. "Does it have to be exactly 14.0 ... would anyone notice 13.9/14.1?" Most likely, you wouldn't notice ...
kyle_engineer's user avatar
2 votes

Why does a petrol engine need to maintain an air-fuel ratio, while a diesel engine doesn't?

If you mixed diesel with air before it entered the cilinder and then compressed it in a normal ( Diesel engine ) compression stroke it would certainly detonate before you reached top dead centre. ...
Pilot Snoopy's user avatar
2 votes

P0171 & P0174 - Lexus LS430

The fact that the oxygen sensors are reading low at idle, but the reading increases when the revs are increased, would indicate a small air leak that becomes less significant as the throttle is opened....
HandyHowie's user avatar
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1 vote
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Link between malfunctioning throttle plate and particulate filter

I don't think there's a plausible link between a malfunctioning throttle plate and the clogged DPF because no matter what the throttle plate is doing, the MAF is still continuously measuring the air ...
MTA's user avatar
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1 vote
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P0171 & P0174 - Lexus LS430

SOLVED!! the power steering air control valve connects to two vacuum hoses, both these hoses where completely de-attached and trust me. you can NEVER notice them as the valve is well hidden deep down ...
Se7sNator's user avatar
1 vote

Do these 02 Sensor readings from obd1 look correct?

That’s a pre-cat O2 sensor exhaust leak sucking in air during valve overlap.
Ryan Pickell's user avatar
1 vote

Do these 02 Sensor readings from obd1 look correct?

It's very hard to tell if the sensor figures are correct. O2 sensors become 'lazy' over time, with slower responses to changes in oxygen levels, this could explain the lagginess of the readings. O2 ...
GdD's user avatar
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1 vote

Relationship between torque, power, specific fuel consumption, and AFR

The graph tells you how it is, i'll tell you why it is so. The reason why a leaner AFR (than stoich) is more efficient, is that it burns hotter.(but slower) It is so in every combustion. Compare it ...
Bart's user avatar
  • 2,954
1 vote
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What formula is used when deriving AFR/lambda value from emissions?

Lambda is calculated using the Brettshneider equation. Brettshneider. It takes into account the mass balance of the constituents of the gasses in the exhaust from a combustion process. Oxygen ...
Fred Wilson's user avatar
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1 vote

a/f mixture for 4 cycle brushcutter

Your Carburetor Needle and Seat Require Cleaning or Replacement Your float needle is not sealing against the seat properly allowing the gravity fed fuel to continue to flow threw your main jet as the ...
DucatiKiller's user avatar
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1 vote

What's the meaning of a "lean" vs "rich" air fuel mixture

Ideal air fuel mixture (ratio) is 14.7:1. That is 14.7 parts of air ignites with 1 part of fuel. This will archive the best fuel economy and lowest emissions. This figure is also known as Lambda 1. ...
Adam Cimler's user avatar
1 vote

Why does a petrol engine need to maintain an air-fuel ratio, while a diesel engine doesn't?

No the diesel is regulated differently but not without proportions. modern cars work similarly in that an air to fuel ratio is calculated based on the cylinder combustion needs. Due to the hotter and ...
quickC 4 U's user avatar
1 vote

Why does a petrol engine need to maintain an air-fuel ratio, while a diesel engine doesn't?

Because in a spark ignition engine restricting airflow is the only way to control the engine RPM. It would be difficult to control the RPM of the engine by varying the fuel alone without restricting ...
Eric's user avatar
  • 11

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