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Thread: AFR Clarification

  1. #1
    ULTRA26 # 1
    The following was found in another thread.
    Seems to me air fuel ratios such as these in a marine application would be disastrous.
    Originally Posted by SmokinLowriderSS
    What's the fuel consumption comparison between a:
    lean-running carbureted 454 CID V-8 running arround 16:1, and a
    lean-running injected 496 CID V-8 running arround 16:1
    Originally Posted by SmokinLowriderSS
    You don't know much about gasoline engines, do ya?
    Pay attention here.
    Stochiometric (perfect) gasoline air ratio for burning in an internal combustion engine is aproximately 13.7 parts air, to 1 part gasoline, by volume. 13.7:1
    A "rich" mixture may be down arround 12 parts air to 1 part gasoline. If I recall correctly, it gets unstable down in the 11's. 12:1
    A "lean" mixture, is generally up in the 16 parts air to 1 part gasoline.
    Up in the 17:1 range, it again, becomes unstable
    A lean mixture has the most air, and allows the gasoline to burn most completely in reality, not under "stociometric book perfection"
    Appreciate the input

  2. #2
    steelcomp
    So what's your question?

  3. #3
    SmokinLowriderSS
    Not bad for dusting off a 20 year old memory, while NOT searching endlessly on the web.
    I flipped a coin on "Volume" or "Mass", and was wrong.
    I also flipped a coin on which DIRECTION the figures went, And got THAT part right. LMAO.
    Here's how K&N's 10-LED mixture gauge reads: (Lt= Light)
    ................Economy ...................Best All Arround .......................Power
    ..............Lt 1.....Lt 2.....Lt 3......Lt 4.....Lt 5.....Lt 6......Lt 7.....Lt 8..... Lt 9.....Lt 10
    Gasoline ..17.1 ... 16.0 ... 15.1 ... 14.7 ... 14.7... 14.7 ... 14.7 .. 14.0 ... 13.2 ... 12.1
    Alcohol .. 7.6 ..... 7.1 ..... 6.7 ..... 6.5 ..... 6.5 ..... 6.5 .... 6.5 .... 6.1 .... 5.8 .... 5.3
    Propane ..17.9 ... 16.8 ... 15.9 .. 15.6 ... 15.6 ... 15.6 ... 15.6 .. 15.0 ... 14.0 ... 13.0
    Oh, my memory of Stociometric mixture being 13.7:1 was also in error, by 1 full point. Should have been 14.7:1.
    Pretty good for a weekender.
    Would have been spot on if I'd been an insurance salesman.
    Any further questions ultra?

  4. #4
    SmokinLowriderSS
    About 12 - 13 to 1 is where a gasoline engine will produce the MOST power,
    lot's of hydrocarbons, along with a bunch of CO. Around 11 to 1 it will
    start to rich misfire.
    16 to 1 is perfectly ok for most engines and gives the best fuel economy.
    Heavy loads might cause excessive temperatures and engine damage can result at this lean a condtion though. HOx's will be much higher in this mixture
    range. Very rough idle would be achived if the mixture is not richened up
    for no load condtions. Imports can run in this range due to emssion laws,
    and is why they can achive better fuel economy.
    Around 17: 1 is where a lean miss starts to occur.
    14.7 : 1 is a stociometric and is good for emssions, and moderate power
    Just for you ultra. (http://ackthud.com/shawnfogg/mixture.htm)

  5. #5
    ULTRA26 # 1
    About 12 - 13 to 1 is where a gasoline engine will produce the MOST power,
    lot's of hydrocarbons, along with a bunch of CO. Around 11 to 1 it will
    start to rich misfire.
    16 to 1 is perfectly ok for most engines and gives the best fuel economy.
    Heavy loads might cause excessive temperatures and engine damage can result at this lean a condtion though. HOx's will be much higher in this mixture
    range. Very rough idle would be achived if the mixture is not richened up
    for no load condtions. Imports can run in this range due to emssion laws,
    and is why they can achive better fuel economy.
    Around 17: 1 is where a lean miss starts to occur.
    14.7 : 1 is a stociometric and is good for emssions, and moderate power
    Just for you ultra. (http://ackthud.com/shawnfogg/mixture.htm)

    Smokin,
    Your original post referred to marine engines. Are you standing by your 16:1 AFR in marine a application?

  6. #6
    cfm
    AFR's aren't a great indicator for fuel usage. It's just a measurement of air vs fuel being used.
    BSFC's are much better. This measurement is fuel used per horsepower. Using less fuel for the same horsepower produced/used/required will give better economy. Many think a high BSFC is from running rich and a low BSFC is from running lean - this is not usually true unless the tune up is way off. Many things effect BSFC - combustion chamber, compression, engine tolerances, valve timing, exhaust and intake configuration, etc,etc,etc.

  7. #7
    SmokinLowriderSS
    To make certain EVERYONE who strolls by understands.
    Over in a political discourse, dear ultra has held up as part of his "attempting to reduce his fuel consumption and help the environment to avoin Man-Made Global Warming", he ditched his previous boat with the blown 502 for his current boat wih an Ultra Efficient Fuel Injected 496. His terms, not mine. He also only drives his Lightning 3 days a month, towing the boat.
    One of his statements:
    The boat has stock Merc 496 power and is fairly good on gas. The 496 is rated as an Ultra Low Emission engine. A far cry from my blown 502 from a few years ago.
    Anyone who wants to discuss the merits, or lack therof, of M. M. G.W., plenty of opportunity over in Pol. Rhet., I won't open it here.
    At a point in his boat's "environmentally more friendliness than everyone elses" claims, I asked the following, verbatim, in it's entirety:
    Yea NFE, it's ALMOST as good on gas as the 140HP 3-banger Volvo used to comonly use.
    What's the fuel consumption comparison between a:
    lean-running carbureted 454 CID V-8 running arround 16:1, and a
    lean-running injected 496 CID V-8 running arround 16:1.
    Hmmmmmmmmmmmmmmmmmmm..........................
    Ok, not quite in it's entirety, I left off the few smileys the orriginal post had.
    The 16:1 Air Fuel Ratio (which he missed being an AFR the first time since I didn't put AFR after it), was an arbitrary number within the range of possibility, which he has attatched himself to. The entire purpose was a comparison of fuel usage to DISPLACEMENT, not fuel delivery style.
    The entire point was, comparison of fuel usage, between a 454 CID engine and a 496 CID engine, running the same air fuel ratios. Ultra continues to ignore this part, and wants to piss over a number I posted. If ultra wants to split hairs, I also never said "marine" engine either.
    A half-dozen posts later, I clarified myself:
    Oh, and ultra, the mixture numbere were NOT the point. I'll rephrase, and use small. comon, words.
    "Which is worse, a carbed 454 running something you consider safe (14:1), or a fuel injected 496 running the SAME 14:1?"
    ultra has now brought his bloviations from there to here, to see if he can find anyone to help him. He's running out of trash to talk on his own in Pol. Rhet.
    Enjoy folks. Since ultra won't explain himself, I had to set his stage for him and turn on the lights.
    Now, while ultra helps the environment at the river with his 25' EFI 496, I'm taking my 19' carbed 454 to the lake and gonna POLUTE LIKE CRAZY.
    See ya'all Sun PM or (more likely) Monday.
    The orriginal thread that prompted this one (http://www.***boat.com/forums/showthread.php?t=159368)
    All things are best taken IN context.

  8. #8
    SnoC653
    well RPM for RPM the 496 will still use more fuel than the 454 at the same ratio as it intakes more volume. That doesn't tell you which will get mpg in the boat and especially not two different boats. :idea: seems this is more a post about if you say A i'll say B and if you say B i'll say A

  9. #9
    ULTRA26 # 1
    To make certain EVERYONE who strolls by understands.
    Over in a political discourse, dear ultra has held up as part of his "attempting to reduce his fuel consumption and help the environment to avoin Man-Made Global Warming", he ditched his previous boat with the blown 502 for his current boat wih an Ultra Efficient Fuel Injected 496. His terms, not mine. He also only drives his Lightning 3 days a month, towing the boat.
    One of his statements:
    Anyone who wants to discuss the merits, or lack therof, of M. M. G.W., plenty of opportunity over in Pol. Rhet., I won't open it here.
    At a point in his boat's "environmentally more friendliness than everyone elses" claims, I asked the following, verbatim, in it's entirety:
    Ok, not quite in it's entirety, I left off the few smileys the orriginal post had.
    The 16:1 Air Fuel Ratio (which he missed being an AFR the first time since I didn't put AFR after it), was an arbitrary number within the range of possibility, which he has attatched himself to. The entire purpose was a comparison of fuel usage to DISPLACEMENT, not fuel delivery style.
    The entire point was, comparison of fuel usage, between a 454 CID engine and a 496 CID engine, running the same air fuel ratios. Ultra continues to ignore this part, and wants to piss over a number I posted. If ultra wants to split hairs, I also never said "marine" engine either.
    A half-dozen posts later, I clarified myself:
    ultra has now brought his bloviations from there to here, to see if he can find anyone to help him. He's running out of trash to talk on his own in Pol. Rhet.
    Enjoy folks. Since ultra won't explain himself, I had to set his stage for him and turn on the lights.
    Now, while ultra helps the environment at the river with his 25' EFI 496, I'm taking my 19' carbed 454 to the lake and gonna POLUTE LIKE CRAZY.
    See ya'all Sun PM or (more likely) Monday.
    The orriginal thread that prompted this one (http://www.***boat.com/forums/showthread.php?t=159368)
    All things are best taken IN context.
    Smokin,
    Spin this however you would like. I called BS on running a marine motor with an AFR at 16:1. When I explained the reasons for the difference in efficiency between a computer controlled EFI 496 motor and a carbed 454. You responded that I must have the only closed loop EFI system afloat. You also responded that I didn't know anything about gasoline engines.
    I will state it again, an AFR of 16:1 in a marine application will cause to much heat and likely piston damage. If your going to tell a story, then tell the whole story. BTW your comments are contained in post # 1
    well RPM for RPM the 496 will still use more fuel than the 454 at the same ratio as it intakes more volume. That doesn't tell you which will get mpg in the boat and especially not two different boats. :idea: seems this is more a post about if you say A i'll say B and if you say B i'll say A
    Not at all. I simply explained to Smokin that an AFR of 16:1 in a marine application will cause a dangerously high EGT and likely piston failure. It's no more than that. If I am misinformed someone please lend an assist.
    Thanks

  10. #10
    IndianaTahiti
    Just a question for one of ya,how accurate are the a/f monitors in a water injected o/t headers? Seems like the water would cool the o2 senser and give some false readings? Are you guys running the expensive wide band set ups?(auto meter) or will the led edelb. work just as good? Curious cause I am tempted to buy one to help me get the right jetting.:idea:

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