Motor Vehicle Maintenance & Repair Stack Exchange
Motor Vehicle Maintenance & Repair Stack Exchange

Questions tagged [air-fuel-ratio]

A term describing the ratio of air (available oxygen) to fuel (available hydrogen and carbon) in the combustion process. It is said to be rich when more fuel is available than air and lean when there is more air than fuel.

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Why or why not increase engine efficiency by running the car "fuel-lean" (using a turbo or supercharger)?

Everyone wants their cars to use less fuel, right? I read the following passage about running the car fuel lean from this website: Run the engine fuel-lean, that is, use excess air. It is well known that fuel-lean running improves the efficiency.…
Max Goodridge
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What's the meaning of a "lean" vs "rich" air fuel mixture

I'm learning about vacuum leaks on engine intakes and I'm hearing this terminology of lean air fuel mixture. I thought I heard of a rich mixture before too. What's a normal mixture referred to as? A balanced mixture? Also just for clarity, this…
jxramos
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How is AFR calculated from ODBII readings

In another post (A most intriguing cold-start misfire mystery) I found this quote: Mass air flow = 3.66 g/s Fuel flow = 1.27 l/h, Fuel rail pressure = 380 kPa This indicates to me that AFR is around 14.88, close to stoich. How is AFR calculated…
cdunn
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Is it possible to fit mashroomhead air filter in Honda Stunner CBF 125?

I have Honda Stunner CBF 125 2009 model. I just need to know is it possible to replace the typical air filter with mashroomhead air filter to improve the bike performance? Is there any other way that I can use to improve my bike performance?
Shell
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Why is cold-start fuel mixture enrichment necessary?

I know a rich mixture is more fuel added than air in the ratio required (14.7:1), but how can it affect anything? I mean, if fuel is added but with no air it can't combust, so how can that affect the ease of starting an engine when cold? Since it…
user3407319
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Why does a petrol engine need to maintain an air-fuel ratio, while a diesel engine doesn't?

This simple question has been bugging me for a while. The amount of fuel injected into a petrol engine is calculated according to the amount of air entering through the throttle valve (as measured by the mass airflow/manifold absolute pressure…
I have no idea what I'm doing
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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?

I've read on the internet, in a couple of maintenance books and asked a few buddy mechanics and they all seem to point to the fact that a healthy diesel engine should not produce black smoke and that the common reason why this happens is because of…
user1969903
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How to fix P2195, P1172, P1174 and P2197 error code for Honda Accord LX 2004?

Make: Honda Model: Accord LX Year: 2004 Error codes: P2195, P1172, P1174 and P219 Mile: The vehicle was driving for over 6 months Symptom: there was a missing fuse for the A/F ratio sensor heaters. After the fuse was replaced, the PCM sets P2195,…
Arockia
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Oily Sludge in the Intake Manifold

When taking off the throttle body to clean my IAC, I noticed that there was a thick layer of oily sludge coating pretty much everything inside the intake manifold: I have two queastions: How did this oily sludge get there in the first place? Could…
Robert S. Barnes
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Bike currently running rich due to aftermarket exhaust, will adding an aftermarket air filter without any ecu work fix it

I have an MV Agusta Brutale 675 with a GPR Carbonox slip on installed. The air filter is stock and no work has been done on the ECU. My problem is: at this state it's running rich as one can smell un burnt gasoline in the exhasut fumes. It's also…
glenrules7
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2003 F150 5.4L V8 Long Term Fuel Trim High Bank 2

I am currently chasing a lean condition in my Ford F150. My fuel trims were reading high on one bank (bank 2) and I am curious when I find the vacuum leak or whatever is causing the high readings, how long will it take for the long term fuel trim to…
Eric
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Do these 02 Sensor readings from obd1 look correct?

I have an issue at MOT test where I get high CO readings. I've triple checked the following: Exhaust leaks New downpipe Air/Vacuum leaks Compression MULTEC electronic Carb new idling control stepper Injector test Plugs/leads/coil/distributor/rotor…
Andrew
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Percent of Air and Fuel used for Combustion

I've had this question for a long time. I know the percent will differ based upon the throttle position and will be either by stoichiometric ratio or rich mixture. The stoichiometric ratio (AFR) for petrol (gasoline) is 14.7 : 1 right? So if it…
NANDAKUMAR THANGAVELU
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Why do Subarus run so rich under boost

This isn't a general question regarding air/fuel ratios. I want to know why Subaru specifically insists on making their cars run ridiculously rich under boost. For instance, my 2007 Forester XT has an AFR of 10.5 under full boost (hard…
Captain Kenpachi
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Why would one install widebands on vehicles that are setup for narrowbands?

A recent post on one of the forums I frequent has piqued my curiosity. From my limited reading on the topic, widebands do a better job of quantifying air-fuel ratios than their narrowband counterparts, which are sufficient for simple, qualitative…
Zaid
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