| Re: [GMCnet] Jim Bounds interesting recent posts [message #325916 is a reply to message #325915] |
Fri, 10 November 2017 10:54   |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma:
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Senior Member |
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Keith,
We acquired a Lambda meter back in 1994 to help program the Hal Tech ECM
that I was running. Back then it was a $ 2,200 instrument.
We used that to help us with EFI as well as carb units.
Until then, I had no idea of how the ratio was based.
Since graduation from engineering, I just don't have the mind to get into
details like I should.
Glad to see that you understand. Thanks.
On Fri, Nov 10, 2017 at 8:21 AM, Keith V wrote:
> 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
>
>
>
> ________________________________
> From: Gmclist on behalf of Gerald Work glwork@mac.com>
> Sent: Friday, November 10, 2017 9:58:58 AM
> To: GMC Motor Home Post
> Subject: [GMCnet] Jim Bounds interesting recent posts
>
> I have followed with interest his comments about why carbs no longer work
> (todays gas won’t vaporize correctly for use in a carb) and now why our
> engines are blowing up mote frequently (they run too hot under some
> condition).
>
> Take a look at the presentation I did on Fitech (
> http://www.bdub.net/FiTech_is_the_Real_Deal.pdf). Near the end are two
> important slides that I think help explain what he is saying. The slide
> with the two charts is very telling. Those charts are based on an engine
> running pure gasoline with a stoichiometric air/fuel ratio of 14.7:1. One
> chart shows peak power at an air fuel ratio of around 12.5:1 (quite rich)
> while peak economy is around 16:1 (way too lean for our engines to survive
> for very long). Those charts are based on UNADULTERATED gasoline. The
> curves for gasoline laced with alcohol would look much differently.
>
> The slide on the next page shows stoichiometric A/F ratios for various
> chemical compounds. For octane it is 15:1, for ethanol it is 9:1. We not
> only have been adding ethanol, we have also added a number of other
> distillates and removed others. So, just as he has been saying, everything
> we learned about engines when we were all much younger is out the window
> given whatever it is we now pump into our fuel tanks. Just for giggles,
> see what happens to those curves if the only change was adding 10%
> alcohol. The stoichiometric would shift from 14.7 to 14.1. Now guess what
> happens if you go to lean, either because you reprogram your fuel injection
> to do that, or because your carb gets dirty inside and does it on its own
> without you even knowing it, or because you monkey around with the jets,
> air correctors, power valve springs, etc. in the hope of better mileage.
> On flat land you might get away with that if you drive at 50 to 60 mph
> where the air drag is low, but climb any kind of hill or load the engine up
> with head wind or by speeding up and you will quickly be running way too
> lean for the conditions and way to hot for any kind of engine longevity.
> Just what he has been saying.
>
> I am not a petroleum engineer so don’t know for sure how those curves
> change shape for whatever is in our fuel today, but my guess is however
> those curves change the result is we should now be striving to burn MORE
> FUEL day in and day out if we want to keep these old engines healthy. I’m
> going to guess there is a direct correlation between fuel consumption and
> engine life. Likely 8mpg is around the BEST one should shoot for these
> days.
>
> How many times have we heard people say that their coaches ran much better
> and got much better fuel economy driving in Canada on premium fuel with no
> alcohol. The only way that could happen is if that coach was set up way
> too lean for driving on gasoline laced with alcohol. My thoughts anyway.
>
> 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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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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