AFR Clarification

[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:)

[steelcomp]

So what's your question?

[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. :D
Pretty good for a weekender.
Would have been spot on if I'd been an insurance salesman.
Any further questions ultra? :D

[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)
:D :D :D

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

[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.

[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. :D
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. :D
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.

[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

[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. :D
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. :D
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

[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:

[Beer-30]

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:
The O2 sensor is plumbed deeper into the tube, where it hits exh gas only and the water goes AROUND the bung. Of course, this must be done prior to where the water mixes with the gas - toward the end of the collector.

[IndianaTahiti]

The O2 sensor is plumbed deeper into the tube, where it hits exh gas only and the water goes AROUND the bung. Of course, this must be done prior to where the water mixes with the gas - toward the end of the collector.
Seems like that would work at idle but under throttle seems like its gonna get wet where ever ya put it?:confused:

[steelcomp]

I will state it again, an AFR of 16:1 in a marine application will cause to much heat and likely piston damage. Based on what experience? You're making a statement of fact here, and I'm wondering if it's based in any real information. Have you melted pistons in a marine app while accurately monitoring the AFR? Was this during a dyno test? How do you know this to be true?

[ULTRA26 # 1]

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:
Gaffrig makes a Pyrometer (EGT meter) that can be very helpful with jetting issues. The sensor is mounted deep in the manifold or header so that the sensor stays dry.
All of the marine wide band stuff that is out there is really pricey.
Based on what experience? You're making a statement of fact here, and I'm wondering if it's based in any real information. Have you melted pistons in a marine app while accurately monitoring the AFR? Was this during a dyno test? How do you know this to be true?
I melted 2 pistons in my marine 502 blower motor running an EGT at slightly over 1500, As a result I disused AFR's with many quality tuners, both marine and auto. I was running the motor too lean. I also viewed a dyno printouts of the fuel maps from both my Saleen and my Cobra. At WOT, 12.6:1 12.9:1 were optimum.
Under a load, such as a marine application, or at WOT 16:1, or similer lean condition, will cause excess heat, detonation and piston failure, forged or the otherwise weaker hypereutectics.
There are many variables, such as octane, head material, piston material, valve material, engine temp. etc, for there to be many absolutes regarding AFR's. The only absolute that I am sure, regarding marine engines, is to lean is very bad and 16:1 is too lean.

[Beer-30]

Seems like that would work at idle but under throttle seems like its gonna get wet where ever ya put it?:confused:
Nope. In fact, water pretty much kills O2 sensors, so they absolutely have to be in dry exhaust. Jacketed manifolds / headers have the inner tubes for actual exh and outer tubes around them for the water to pass through. The O2 bungs are placed in the dry tube area and the water passes around the bung. The water doesn't mix with the gasses until the tail end of the collector which would be AFTER the O2 sensor.
I think you are thinking of water INJECTED headers only - which, you're right - would not work as the water is injected into the exh gas near the ports. Most of the over-transom headers I have seen on jet boats and such that are running Oxy sensors are dry headers only - no water at all.
Edit: Now that I re-read your first post, I see you are indeed talking about O/T injected headers. That clarifies it.

[ULTRA26 # 1]

What's it like to start a thread on my "blunder", and find out I was RIGHT? LMFAO!!!!!!!
Getting his arse handed to him as I type, by me, among others. LOL
Yep, Tuner it is. LOL.
You sure are a top notch "investigator". LMFFAO, MORE!!!!!!
Ultra's latest lack of "investigation". LMAO (http://www.***boat.com/forums/showthread.php?p=2726473#post2726473)
Smokin
The first post quotes you accurately. Your 16:1 and explanation simply don't apply to marine engines. Marine engines run under a constant load, remember. If you recall you were questioning the efficiency of my 496 Mag HO, compared a carbed 454.
Since you aren't capable of taking my word for it please discuss this matter with an expert, and come back and post your findings. I would hate to see someone here take your word as the gospel, and have it cost them a piston or two.
What's it like to start a thread on my "blunder", and find out I was RIGHT? LMFAO!!!!!!!
Getting his arse handed to him as I type, by me, among others
Does acting like complete a**hole give you pleasure?
Whatever gets you off Smokin.

[steelcomp]

Gaffrig makes a Pyrometer (EGT meter) that can be very helpful with jetting issues. The sensor is mounted deep in the manifold or header so that the sensor stays dry.
All of the marine wide band stuff that is out there is really pricey.
I melted 2 pistons in my marine 502 blower motor running an EGT at slightly over 1500, As a result I disused AFR's with many quality tuners, both marine and auto. I was running the motor too lean. I also viewed a dyno printouts of the fuel maps from both my Saleen and my Cobra. At WOT, 12.6:1 12.9:1 were optimum.
Under a load, such as a marine application, or at WOT 16:1, or similer lean condition, will cause excess heat, detonation and piston failure, forged or the otherwise weaker hypereutectics.
There are many variables, such as octane, head material, piston material, valve material, engine temp. etc, for there to be many absolutes regarding AFR's. The only absolute that I am sure, regarding marine engines, is to lean is very bad and 16:1 is too lean.I'm still not seeing where you knew anything about what your AF was in any of these examples. 12.6 and 12.9:1 may have been optimal based on what? Power output? Cyl head temp? Ex temp? The sound of the motor?
Way too vague here.

[ULTRA26 # 1]

I'm still not seeing where you knew anything about what your AF was in any of these examples. 12.6 and 12.9:1 may have been optimal based on what? Power output? Cyl head temp? Ex temp? The sound of the motor?
Way too vague here.
I posted facts. If you want to run your motor at 16:1 like your buddy says it's OK to, have at it. I'm not here to argue.

[steelcomp]

I posted facts. If you want to run your motor at 16:1 like your buddy says it's OK to, have at it. I'm not here to argue.Don't run from the question, just show where your facts support that 16:1 is a dangerous AF for marine app. You impressed us all with your Saleen and Cobra AF numbers (which have nothing to do with marine app) but I'm not hearing facts to back up anything relating to 16:1 in marine app. "He said, she said" isn't factual. I just want to know where you get your hard numbers to back your statement, that's all. It's not about me, my engine, SLSS, or anyone else. You made the statement.
As far as being my "buddy"...That's rich...the two of you sound like an old married couple, which is what this thread is really about. It's just bleed over from Pol. Rhetoric, and you're still just trying to "one up" eachother. I think someone here on the boards described it a while back as "dick sword fighting". :notam:

[ULTRA26 # 1]

Don't run from the question, just show where your facts support that 16:1 is a dangerous AF for marine app. You impressed us all with your Saleen and Cobra AF numbers (which have nothing to do with marine app) but I'm not hearing facts to back up anything relating to 16:1 in marine app. "He said, she said" isn't factual. I just want to know where you get your hard numbers to back your statement, that's all. It's not about me, my engine, SLSS, or anyone else. You made the statement.
As far as being my "buddy"...That's rich...the two of you sound like an old married couple, which is what this thread is really about. It's just bleed over from Pol. Rhetoric, and you're still just trying to "one up" eachother. I think someone here on the boards described it a while back as "dick sword fighting". :notam:
Nothing to run from. If you believe something other than what I have posted, I would suggest that you discuss this matter with tuning experts, as I have. Bob Teague, (TCM) Gary Taylor, (GTI) Ray (Raylar), Gary Teague (GT Marine) or any expert marine engine tuner will confirm that anything above 14.5:1 is too lean in a marine application.
This is not a pissing contest. I have stated what I know to be fact.

[cfm]

Wow, I can't believe I read all that (including links given) on only one bag of popcorn. LOL.
You guys are all too much. Both sides. Good entertainment.
BTW: How did AFR get pointed out as the mainstay of pollution in engines ? There is a lot more to it than that. 'Too' Lean is not always better for emmissions and/or even fuel economy. I'll leave it at that for now.
Switching topics but still on emmissions - anybody ever see what the effects of volcanoes have on our climate and atmosphere ? If not, do some research and be prepared to get intrigued.
If someone can find out a way to keep volcanoes from exploding we will be pretty well off. LOL.
Yes - I believe we all have a responsibility to be 'cleaner' than we are. Not just emmissions, but garbage and a bunch of other things.

[ULTRA26 # 1]

Don't run from the question, just show where your facts support that 16:1 is a dangerous AF for marine app. You impressed us all with your Saleen and Cobra AF numbers (which have nothing to do with marine app) but I'm not hearing facts to back up anything relating to 16:1 in marine app. "He said, she said" isn't factual. I just want to know where you get your hard numbers to back your statement, that's all. It's not about me, my engine, SLSS, or anyone else. You made the statement.
As far as being my "buddy"...That's rich...the two of you sound like an old married couple, which is what this thread is really about. It's just bleed over from Pol. Rhetoric, and you're still just trying to "one up" eachother. I think someone here on the boards described it a while back as "dick sword fighting". :notam:
Here is a post from Bob at Dana Marine Products which discusses Dana's dyno testing of the 496 Mag and Mag HO with Dana's new exhaust system.
The lean spot was basically the same on the dyno and the water, in between 3000-3800 rpm it gets pretty lean. I'm not an air flow/fuel flow expert, but the O2 temp readings were 14.01-14.02 in that range. It gets a little better at higher RPM's, but it's still pretty high, 13.8. Both the dyno guy (professional engine builder) and our brothers at ECM felt that was too high for continued usage. Once you factor in ambient air temperature, that # could change. It's one of those things, can you run them without changing the fuel pressure? The answer is yes, but I gotta tell you, it would make me feel pretty uncomfortable if I wasn't strongly urging my customers to make the change. It's such a simple change, It would be foolish not to do it.
Wow, I can't believe I read all that (including links given) on only one bag of popcorn. LOL.
You guys are all too much. Both sides. Good entertainment.
BTW: How did AFR get pointed out as the mainstay of pollution in engines ? There is a lot more to it than that. 'Too' Lean is not always better for emmissions and/or even fuel economy. I'll leave it at that for now.
Switching topics but still on emmissions - anybody ever see what the effects of volcanoes have on our climate and atmosphere ? If not, do some research and be prepared to get intrigued.
If someone can find out a way to keep volcanoes from exploding we will be pretty well off. LOL.
Yes - I believe we all have a responsibility to be 'cleaner' than we are. Not just emmissions, but garbage and a bunch of other things.
In answer to your question
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
I merely pointed out that running a marine engine at 16:1 would be way too lean. From this came the lesson on internal combustion engines. I agree, it's been entertaining.

[SmokinLowriderSS]

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:
I'm not running a darned thing that involves electronic technology. Just not set up for it at all.
Reading spark plugs and knowing how the engine runs.
My wet headers are thru-transomed, and are water jacketed. So are ultra's manifolds I am certain.
I do not believe you COULD run an O2 sensor with an INJECTED header of any type, for just the water contamination cooling reasons you described.
You need $3000 sets of JACKETED headers where the O2 sensor can be kept dry untill the header cooling water is added all the way back at the back of the collector.

[SmokinLowriderSS]

the two of you sound like an old married couple, which is what this thread is really about. It's just bleed over from Pol. Rhetoric, and you're still just trying to "one up" eachother. I think someone here on the boards described it a while back as "dick sword fighting". :notam:
Pretty astute observation there Steel. :D

[Blown 472]

I'm not running a darned thing that involves electronic technology. Just not set up for it at all.
Reading spark plugs and knowing how the engine runs.
My wet headers are thru-transomed, and are water jacketed. So are ultra's manifolds I am certain.
I do not believe you COULD run an O2 sensor with an INJECTED header of any type, for just the water contamination cooling reasons you described.
You need $3000 sets of JACKETED headers where the O2 sensor can be kept dry untill the header cooling water is added all the way back at the back of the collector.
You rule

[IndianaTahiti]

I'm not running a darned thing that involves electronic technology. Just not set up for it at all.
Reading spark plugs and knowing how the engine runs.
My wet headers are thru-transomed, and are water jacketed. So are ultra's manifolds I am certain.
I do not believe you COULD run an O2 sensor with an INJECTED header of any type, for just the water contamination cooling reasons you described.
You need $3000 sets of JACKETED headers where the O2 sensor can be kept dry untill the header cooling water is added all the way back at the back of the collector.
I have a old junk set of headers that I could put some bungs in and just shut off the water to them while I am using this method,seems like this would be less time consuming and cheaper than 3000 headers.Besides I dont like the look of headers that dont exit over the transom:devil:

[SmokinLowriderSS]

That would work just fine, and if you did 8 bungs, you could work with each cyl. separately if you wished.
Nobody sees my headers.
I run with a covered engine. :D Lowrider is a "sleeper". :D

[Blown 472]

That would work just fine, and if you did 8 bungs, you could work with each cyl. separately if you wished.
Nobody sees my headers.
I run with a covered engine. :D Lowrider is a "sleeper". :D
How would you tune each cylinder?

[JAY4SPEED]

I have a old junk set of headers that I could put some bungs in and just shut off the water to them while I am using this method,seems like this would be less time consuming and cheaper than 3000 headers.Besides I dont like the look of headers that dont exit over the transom:devil:
You would have to weld the weep holes shut. At higher rpms with weep holes open (essentially an exhaust leak) the exhaust stream will suck in air (venturi effect) and add additional O2 to the exhaust stream. This will skew the O2 reading, causing a false lean reading.
In an EFI application, the ECM would respond to the lean O2 by adding unnecessary additional fuel.
Jay

[SmokinLowriderSS]

You would have to weld the weep holes shut. At higher rpms with weep holes open (essentially an exhaust leak) the exhaust stream will suck in air (venturi effect) and add additional O2 to the exhaust stream. This will skew the O2 reading, causing a false lean reading.
In an EFI application, the ECM would respond to the lean O2 by adding unnecessary additional fuel.
Jay
Yep, they would likely do that. I hadn't thought of it. Good call JAY.

[Unchained]

You would have to weld the weep holes shut. At higher rpms with weep holes open (essentially an exhaust leak) the exhaust stream will suck in air (venturi effect) and add additional O2 to the exhaust stream. This will skew the O2 reading, causing a false lean reading.
In an EFI application, the ECM would respond to the lean O2 by adding unnecessary additional fuel.
Jay
Any air leaks would make the O2 sensor reading be incorrect.
The ECM would only add fuel if it was tied into the O2 sensor and set up in closed loop operation.
Closed loop would be the ideal but I've never been able to run that way because my Haltech E6Kwon't read a wide band O2 sensor.
I'm not really sure how many boat EFI systems run closed loop.
Ideally the fuel maps are set up so that in closed loop the ECM will only take away fuel and not add fuel. Closed loop only functions to about 70# throttle then you're running straight off the fuel maps anyways.

[ULTRA26 # 1]

Any air leaks would make the O2 sensor reading be incorrect.
The ECM would only add fuel if it was tied into the O2 sensor and set up in closed loop operation.
Closed loop would be the ideal but I've never been able to run that way because my Haltech E6Kwon't read a wide band O2 sensor.
I'm not really sure how many boat EFI systems run closed loop.
Ideally the fuel maps are set up so that in closed loop the ECM will only take away fuel and not add fuel. Closed loop only functions to about 70# throttle then you're running straight off the fuel maps anyways.
In a marine application at what RPM would you consider an AFR of 16:1 safe?
Thanks

[Unchained]

In a marine application at what RPM would you consider an AFR of 16:1 safe? Thanks
Maybe at idle or for very light loading but I always read that 14.7:1 AFR was stoichiometric and 12.5:1 was for max power.
Also I read that any mixture richer than 12:1 sutracted hp but some applications run a richer mixture to try to get some intercooling effect from the excess fuel.

[cfm]

In a marine application at what RPM would you consider an AFR of 16:1 safe?
Thanks
Okay, you're still digging for people to answer.
My answer is when loaded (getting on plane or faster)'Not in any gas marine engine I've had my hands on.' Decelration, idle, or shut off LOL is only time I'd be okay with it.
BTW: I'm referencing I/O applications. No jet or v-drive experience here.

[ULTRA26 # 1]

Maybe at idle or for very light loading but I always read that 14.7:1 AFR was stoichiometric and 12.5:1 was for max power.
Also I read that any mixture richer than 12:1 sutracted hp but some applications run a richer mixture to try to get some intercooling effect from the excess fuel.
Most guys that I have spoken with have stated that because Marine engines are always under a load (0 vacuum) 13:1 is a safe mixture throghout the powerband. I know that Merc Marine maps it's engines at 12.7:1 to 13:1 range.
Thanks

[Unchained]

I don't think you can assume that all marine engines are under a similar load.
0 vacuum is a pretty healthy load.
My TPR Stealth Jet boat at a 3000 rpm cruise speed had 10" of vacuum and stoich would be the proper AFR.
My V drive seems to be loaded more in relation to the cruise speed RPM and I believe the vacuum is around 5".

[Blown 472]

Yep, they would likely do that. I hadn't thought of it. Good call JAY.
But I am sure you have thought on how to tune the fuel curve for each cylinder so lets hear it.

[ULTRA26 # 1]

I don't think you can assume that all marine engines are under a similar load.
0 vacuum is a pretty healthy load.
My TPR Stealth Jet boat at a 3000 rpm cruise speed had 10" of vacuum and stoich would be the proper AFR.
My V drive seems to be loaded more in relation to the cruise speed RPM and I believe the vacuum is around 5".
10" of vacuum at 3000 rpm in a jet is amazing. 10" is almost like coasting. Didn't think that was possible.
Okay, you're still digging for people to answer.
My answer is when loaded (getting on plane or faster)'Not in any gas marine engine I've had my hands on.' Decelration, idle, or shut off LOL is only time I'd be okay with it.
BTW: I'm referencing I/O applications. No jet or v-drive experience here.
Per the response at the top, it sounds like Jets are under less of a load that I/O which is news to me.
Thanks for your input.

[Unchained]

10" of vacuum at 3000 rpm in a jet is amazing. 10" is almost like coasting. Didn't think that was possible.
Per the response at the top, it sounds like Jets are under less of a load that I/O which is news to me.
Thanks for your input.
For my setup there was a big engine in a small hull.
The opposite scenario would be a lot different load.
Checking manifold vacuum is real easy. Everyone should know what the cruising speed load is on the motor so they can tune to it. My engine spends most of its time at around 3000 rpm which gets me about 42 mph.
I'll copy a cruise speed datalog and put it up here later.

[ULTRA26 # 1]

For my setup there was a big engine in a small hull.
The opposite scenario would be a lot different load.
Checking manifold vacuum is real easy. Everyone should know what the cruising speed load is on the motor so they can tune to it. My engine spends most of its time at around 3000 rpm which gets me about 42 mph.
I'll copy a cruise speed datalog and put it up here later.
I don't hve a vacuum guage attached but my cruise is at about 3500 and about 52 mph. I've seen data sheets on a the same engine in a similar boat and Merc's AFR numbers at 3500 rpms were at 12.9:1. 496HO Stock Merc in a 26' cat.
Thanks look forward to seeing your logs

[SmokinLowriderSS]

10" of vacuum at 3000 rpm in a jet is amazing. 10" is almost like coasting. Didn't think that was possible..
It takes very little throttle opening to get my 454 to 3,000 RPM and I am running a moderately large impeller (A-cut). That impeller only absorbs arround 87 HP to spin at 3-grand.
3,500. aprox. 136HP
4,000. aprox. 202HP
5,000. aprox. 395HP
5,500. aprox. 525HP
Jets demand power on a non-linear curve that increases faster the faster you spin them.
At idle, my impeller demands 2.0HP to spin it.
Per the response at the top, it sounds like Jets are under less of a load that I/O.
At low RPM's, they are.

[ULTRA26 # 1]

It takes very little throttle opening to get my 454 to 3,000 RPM and I am running a moderately large impeller (A-cut). That impeller only absorbs arround 87 HP to spin at 3-grand.
3,500. aprox. 136HP
4,000. aprox. 202HP
5,000. aprox. 395HP
5,500. aprox. 525HP
Jets demand power on a non-linear curve that increases faster the faster you spin them.
At idle, my impeller demands 2.0HP to spin it.
At low RPM's, they are.
At 50 MPH, what RPM are you turning? As I recall, Wes's 21, with a 572 in it, ran on the top at about 76 MPH. Hopefully Wes will chime in here. Every jet boat I've ever seen sounds like it working hard at 50, except for maybe a 19' TPR Shadow or something similar.

[steelcomp]

10" of vacuum at 3000 rpm in a jet is amazing. 10" is almost like coasting. Didn't think that was possible.
3000rpm in most jets is very light loading on the drive, requiring far less power than a prop. 10" ov vac @ 3000 is reasonable. Jets have a completely different loading than any other drive type. It's easy to "assume" that jets see tha same kind of loading, but untill you really have first hand experience with them, (which you obviously don't) it's hard to understand. It's one of the reasons jets require such a different power curve, which most guys don't realize. It's also one of the reasons it's difficult build a "fast" jet boat.
Per the response at the top, it sounds like Jets are under less of a load that I/O which is news to me.
Every drive system has it's power absorption rate. You can't expect a jet drive to have the same rate as a prop of any kind, I/O, V-dr. or direct. Apples and oranges.
Most guys that I have spoken with have stated that because Marine engines are always under a load (0 vacuum)... Very few intke/carb(or TB) systems will show zero vacuum, and then only at WOT. Under load dosen't necessarily mean zero vacuum, in fact, seldom is. You're getting, and repeating a lot of misinformation, it seems.

[Unchained]

V DRIVE DATALOG
http://www.***boat.com/image_center/data/500/datalogaug07.jpg

[502 JET]

http://www.***boat.com/image_center/data/500/datalogaug07.jpg
Does the data logger monitor the air/fuel ratio?
Why does the data acquisition show the battery at only 12.2 volts?

[Unchained]

Does the data logger monitor the air/fuel ratio?
Why does the data acquisition show the battery at only 12.2 volts?
I have another datalogger that monitors A/F but it does not tell me IAT, inj ms, or what fuel map range it's running on. It is the aux box that goes with the Innovative Motorsports LM-1 A/F unit.
My alternator is a reverse direct drive unit and it needs to be taken to just over 3000 rpms to start charging. It most likely is that I did not run it up high enough at the time I recorded that datalog to start charging.
This Haltech datalog file is from my Daytona V-drive, not the jet boat.
At 3000 engine rpm the prop is turning 3950 rpm.
The jet boat file showed higher manifold vacuum and less throttle opening reflecting less load.
The vdrive runs about 42 mph with 3000 rpm.
The smaller, lighter jet boat runs about 36 mph with 3000 rpm.
My idle manifold vacuum (out of gear) is 14" - 16"
It will actually idle in 3rd gear at a steady 1000 rpm. The EFI really shines at precision tuning. That speed it is too fast for a no wake zone so I use 2nd or 1st.

[Unchained]

JET DRIVE DATALOG
http://www.***boat.com/image_center/data/500/Jetdrivedatalog.jpg
Here's a comparison of a jet drive datalog.
I think it's interesting to see that it takes less throttle opening and the injector timing is quite a bit less to get 3000 rpm but the vdrive has more speed with the same rpm. The fuel economy is better with the vdrive even though it's a heavier boat. The prop probably has quite a bit of slip at that speed and rpm. It's an 11" x 15 three blade.
Here's a copy of the other datalogger I have from the jetboat days, http://www.***boat.com/image_center/data/520/220datalogoct05.jpg
As you can see I'm just taking a picture of the computer screen in the most low tech method possible. :D

[ULTRA26 # 1]

3000rpm in most jets is very light loading on the drive, requiring far less power than a prop. 10" ov vac @ 3000 is reasonable. Jets have a completely different loading than any other drive type. It's easy to "assume" that jets see tha same kind of loading, but untill you really have first hand experience with them, (which you obviously don't) it's hard to understand. It's one of the reasons jets require such a different power curve, which most guys don't realize. It's also one of the reasons it's difficult build a "fast" jet boat.
Every drive system has it's power absorption rate. You can't expect a jet drive to have the same rate as a prop of any kind, I/O, V-dr. or direct. Apples and oranges.
Very few intke/carb(or TB) systems will show zero vacuum, and then only at WOT. Under load dosen't necessarily mean zero vacuum, in fact, seldom is. You're getting, and repeating a lot of misinformation, it seems.
The only misinformation that have stated was 0 vacuum. The information I have stated with regard to AFR has been factual for Merc EFI Marine engines. Again, the suggestion of running a marine engine with a AFR of 16:1, except at idle or shut down, wasn't a good one. Jets are obviously different that stern or V drives. I have confirmed with more than one reliable source, that propellers are generally more fuel efficient than jets. And your right about me not having 1st hand experiance with jets. Even my Cole, had a prop.
Thanks for your input
JET DRIVE DATALOG
http://www.***boat.com/image_center/data/500/Jetdrivedatalog.jpg
Here's a comparison of a jet drive datalog.
I think it's interesting to see that it takes less throttle opening and the injector timing is quite a bit less to get 3000 rpm but the vdrive has more speed with the same rpm. The fuel economy is better with the vdrive even though it's a heavier boat. The prop probably has quite a bit of slip at that speed and rpm. It's an 11" x 15 three blade.
Here's a copy of the other datalogger I have from the jetboat days, http://www.***boat.com/image_center/data/520/220datalogoct05.jpg
As you can see I'm just taking a picture of the computer screen in the most low tech method possible. :D
Thanks for posting the data sheets.