| [GMCnet] Jim B sounds interesting posts [message #325923] |
Fri, 10 November 2017 12:36 |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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Hi Kieth,
I want to quibble a bit with your forth sentence. I think you meant to say, [So if you add ethanol the indicated AFR is incorrect, but a Lambda of 1 is still stoichiometric.] The AFR at Lambda = 1 will differ depending on the fuel used since, as you say, Lambda = 1 is a measure of the amount of oxygen remaining in the exhaust relative to the oxygen in the incoming air. Mix in 10% alcohol and stoichiometric is no longer 14.7 but instead is something more like 14.1. Put in 85% alcohol and stoichiometric is more like a little under 10:1.
All this techie talk aside, we know we cannot be running our coaches lean under load without experiencing high internal temperatures. How high is too high is likely a function of too many variables to usefully parse here. I think the operative point is the behavior of what currently passes for gasoline radically alters what all of us grew up thinking would be the relationships between things like compression ratio, timing, power output, EGT, optimum AFR, etc. Hence, much of our prior experience goes out the window.
I do agree with you that a wide band O2 sensor is critical to determining how your carb or fuel injection is behaving in your coach at any given point in time and a given engine load. What to do if it is too lean for too long is fodder for another discussion.
I started this topic because I think Jim Bounds post’s are showing us a lot about why some of our owners are experiencing both difficulties with carbs and EFI, as well as engine life. I remain concerned about our owners, especially new owners, questing for better fuel consumption at the potential expense of engine longevity. It takes a looooong time to recoup the cost of a new engine through 1-2 MPG increases in fuel consumption.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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> I'm still trying to figure out exactly what E10 looks like on a O2 Sensor,
> I have a wide band sensor I use with my carb.
>
> From what I understand, an O2 sensor doesn't actually measure air fuel
> ratio directly but computes it from oxygen in the exhaust.
>
> This measurement is called Lamda. A Lambda of 1 gives you a stoichiometric
> AFR no matter what the fuel mix
>
> So if you add ethanol the indicated AFR is incorrect, but an AFR of 14.7 (
> a Lambda of 1 ) is still stoichiometric.
>
>
> I think that anyone tuning anything these days has no excuse to not be
> running a WB O2, theyre cheap and accurate.
>
>
> The other question is where on the AFR curve should we be running.
>
> I'm betting about stoichiometric or slightly richer. But no one seems to
> be publishing that info
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Jerry & Sharon Work
78 Royale
Kerby, OR
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