23

Lean ≠ More Air I believe the source of the misunderstanding is in how the term "lean" is being interpreted. A lean mixture doesn't indicate the presence of more air. It indicates the presence of a higher proportion of air compared to fuel (air-fuel ratio, or AFR). Quick example Mixture A has 1,000 g of air, 80 g of fuel. AFR = 1000/80 = 12.5 ...


10

It sounds like you already know why a gasoline engine keeps the fuel/air ratio as close to the stoichiometric ratio as possible, but just for the sake of information for anyone else: The stoichiometric fuel/air ratio is the amount of oxygen required to burn all of the gasoline completely. A "lean" burn leaves some oxygen leftover and a "rich" burn means the ...


10

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 subscription) and usage in other contexts does parallel their usage here. I did some cursory research but gave up, the folks on the English site may be able to help ...


8

There are two issues with cold fuel: cold fuel is harder to vaporize (as HandyHowie mentions) cold fuel is likely to condense on cold engine parts, making its burning harder, less predictable So more fuel is added than necessary - using a richer AFR - in anticipation that a decent proportion of fuel will not be burned. In other words, during cold starts ...


8

I wouldn't You have a carburetor on that bike. You may need to do some adjustments, if not, you will make the air fuel ratio leaner and that will be really hard on your exhaust valves. The more oxygen you have in your air fuel ratio beyond 14.1:1 will increase your combustion temperature. This, in turn, can damage your exhaust valves due to too much heat....


8

Lean operation vs exhaust catalysts: The three-way catalytic converter fitted to gasoline vehicles can't operate under lean engine conditions because the reaction of NOx to nitrogen and oxygen is a reduction reaction, and for this to occur there needs to be a corresponding oxidation. In the three-way catalyst that is the oxidation of CO and hydrocarbons to ...


7

It's not that the catalytic converter can't handle more air per se, it's that running lean increases the temperature of combustion (I actually don't know why, but now I'm curious) and the catalytic converter needs to run inside it's chemical operating range. Something to do with the chemistry that I also don't know. As for advantages for turbo boost and ...


7

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 Sensor 1 Bank 1 (which is also a cause of P1172). If everything checks out good, the other cause of a P2195 points towards the MAF having some debris in it. From ...


7

The oil stuff is more than likely caused from what the intake pulls out of the crank case through the PCV. If you can get a hold of a couple cans of Seafoam, this should take care of the residue about as easy as you can do it without taking the engine apart. Use the rubber hose to the right of the photo to introduce it into your system. As an engine gets ...


7

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 exactly enough air to burn the fuel is known as the stoichiometric mixture and is about 15:1 for gasoline. That means 15 parts air to 1 part fuel. You can have a ...


6

Actually running rich is less dangerous than running lean. I don't know specifically about Subaru, but in general, running lean can cause detonation more easily. And yes, while 14.7:1 is the stoichiometric ratio deemed as perfect for an air fuel mixture, running rich has the big advantage of reducing the chances of pre-ignition or pinging. In a turbo car, ...


6

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 additional flow. So, the idea that your bike is running rich doesn't really resonate. It certainly can be and if it is it could be indicative of another issue ...


5

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 * Volumetric flow rate = 700 kg/m³ * 1.27 l/h = 0.2469 g/s ¹ Dividing the air mass flow rate by mass flow rate yields the AFR number: ...


5

I am highly surprised that no one mentioned it specifically, but the answer is detonation. Poisson Fish was close, but extra wear from increased cylinder temperature isn't the main problem. The main problem is the extra heat causing petrol to self-ignite before the spark and destroy the motor. Diesel doesn't suffer from this problem as it basically works on ...


4

So after LOTS of research, it turns out that my Subaru Forester XT is running at 10.5 AFR at WOT because Subaru's don't like our 95RON fuel very much and it's a safety precaution to add an additional margin for error to prevent knocking if I ever tried filling up at a dodgy fuel pump in rural Africa.


4

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 both AFR sensors failed at the same time, but unlikely. Don't replace potentially expensive AFR sensors without doing basic checks first. Check for vacuum ...


4

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 effectively burn unburned fuel and oil contained in diesel fuel which is essentially kerosene. Emissions devices NOT on a diesel dragster Exhaust Gas Re-circulation ...


3

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 be going lean (higher air to fuel ratio ... 16:1, 18:1, and much higher). The computer or carburetor in most vehicles will control the amount of fuel going in ...


3

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 ratio. It means that when the fuel and air are burned, they must be in this ratio if you want them to combine completely, with nothing left over (well, none of ...


3

You have hit the nail on the head. When the car is in closed loop, this part is important, the fuel trims reflect the current A/F ratio. When a vacuum leak develops, first the car will compensate withe the sort term fuel trims. When the STFT stay high long enough (every car is different) they will cause the LTFT to drift. Current fuel systems are so ...


3

When the engine is cold, the fuel won't evaporate properly, so what would normally be a correct mixture on a hot engine will actually be a weak mixture when cold. To overcome this, more fuel is added when the engine is cold to give a more ideal mixture for starting.


3

If you do a hard reset of the PCM, you're computer will be back to the baseline trim the computer starts with from the factory prior to any self-adjustment. This will get you to your desired trim much quicker than trims which have been in place for a while. To do a "hard reset", pull the negative side battery terminal and leave it off for 30 minutes. This ...


3

A narrowband sensor can only measure 14.7:1 AFR (stoichiometric) , where as wideband sensors allows you to measure a range of AFR ~(<10 to ~20). ECU's that rely on narrowband output maintain the AFR at stoich by using closed loop control (cruise etc) and may use various interpolation methods for increasing the open loop accuracy for AFR other than stoich. ...


3

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. It sounds like you might have a stuck choke or perhaps your idle adjustments are off. That said, when the engine is stopped, there is no airflow to pull in ...


2

Here is a maintenance manual for another JLO 2-cyl 2-stroke engine. While it isn't exactly the same, I would bet the maintenance would be the same between the models. As an aside, since the motor is air cooled, ensure the fans and shrouding are in place on motor before you try to start it. Doing some searching, your engine (and variants) were used ...


2

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. However in normal operation, diesel is sprayed into the cylinder and burns as it exits the injector and comes into contact with the heated air. Only the diesel ...


2

As the name implies, long term fuel trims usually require the vehicle to be driven for some distance in order to adapt and re-learn changes. Depending on the vehicle, it may even require a couple of hundred miles. That said, the fuel trims can be reset in many vehicles via certain scan tools, so one may not have to drive to let the LTFT's settle to their ...


2

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 combustion wouldn't be possible if the mixture was homogeneous), very close to the injection point it is extremely rich (so rich that combustion isn't possible), and ...


2

Running a lean mixture by itself isn't necessarily going to cause detonation, pinging or knocking. WW2 era old timer piston aircraft pilots used to run seriously lean mixtures on long hauls to increase range and it was safe to do so when they were at cruising altitude and power settings. You'd never consider doing it in a climb or at a high power though. ...


2

One additional point to touch on is that leaner and richer are relative to what conditions the engine already runs under. In terms of chemical reactions, car engines tend to run a little rich by default -- more fuel than is needed for all of the air -- because it reduces the frequency of detonations in the mixture. If you alter things so they run leaner ...


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