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Date:         Mon, 10 Sep 2007 19:51:03 -0700
Reply-To:     Michael Elliott <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Michael Elliott <camping.elliott@GMAIL.COM>
Subject:      Re: My poor MPG, O2 sensor seems okay
Comments: To: pdooley <psdooley@verizon.net>
In-Reply-To:  <0JO600K2KNC3JR0I@vms046.mailsrvcs.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I'm not certain what the value is in doing that. Mellow Yellow handily passes California emissions testing so I know it's not running rich or it would fail hydrocarbons. And the output of the O2 sensor, sitting as it does right around the nominal value without going very high (rich) or very low (lean) suggests that the ECU is getting useful measurements and is managing to keep the mixture right around stoichiometric combustion. It seems to me that if the engine was running so rich that it would be causing the considerably poorer mileage than what others report (and I don't lead-foot it), then I would expect to see a darn rich mixture all the time and not expect to have to examine the minutiae of the O2 sensor's output to see some hidden richness.

At this point I'm pretty convinced that my fuel is not blowing out the tailpipe unburned -- it ain't black, the plugs aren't black, the exhaust never smell rich. I'm moving on to check compression.

-- Mike "Rocket J Squirrel" Elliott 71 Type 2: the Wonderbus 84 Westfalia: Mellow Yellow ("The Electrical Banana") 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano KG6RCR

On 9/10/2007 7:38 PM pdooley wrote:

> Mike, do you have another vehicle with good O2 sensor? > Just scope that one and compare. > > -----Original Message----- > From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of > Michael Elliott > Sent: Monday, September 10, 2007 9:22 PM > To: vanagon@GERRY.VANAGON.COM > Subject: Re: My poor MPG, O2 sensor seems okay > > Hi Mark > > I know about meter sampling rates. I grew up with analog meters and really > miss how good they were for showing changes in voltage or current whereas > digital meters are piss-poor at that but much better at displaying values. > > I could easily hook up the scope, but unless I know what a normal rate of > bounce and range of bounce are, the results won't offer much enlightenment. > > -- > Mike "Rocket J Squirrel" Elliott > 71 Type 2: the Wonderbus > 84 Westfalia: Mellow Yellow ("The Electrical Banana") > 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano > KG6RCR > > > > On 9/10/2007 6:02 PM Mark Drillock wrote: > >> Mike, the voltmeter approach depends on the sampling rate of the meter. >> Using a scope instead gives a more real time reading and also a good >> indication of the cycling rate at which the O2 reading goes from rich to >> lean and back again. Ken's monitor is good for this as well and much >> cheaper besides. Some of us have scopes already so we get to have more >> fun than most, if we care to. >> >> Mark >> >> Michael Elliott wrote: >> >>> Hi Kenneth, I got one of your O2 sensor monitors a couple weeks ago and >>> did a quickie clip-lead hookup to the sensor this afternoon in addition > to >>> looking at the voltage with my DVM. The monitor works as advertised, a >>> good deal for a measly 20 bucks, and the little bouncing dot is fun to >>> watch. On Mellow Yellow it mainly ranges one or two bars above and below >>> the center bar, maybe spending a little more time on the center bar, > which >>> I presume to mean that on the average the mixture is neither too rich nor >>> too lean. >>> >>> I can confirm that Mellow Yellow exhibits the same behavior as your web >>> page describes, viz: >>> >>> 1> When the engine is first started the Dot * "floats" in the middle of >>> it's range. (DVM says about .35mV at first) >>> 2> As the engine/O2 sensor starts to warm the Dot creeps towards rich. >>> (Yup -- slowly climbs to about .45mV). >>> 3> When the ECU switches to closed loop operation the Dot swings back and >>> forth rapidly. (Yup, centered around .55mV. Mark Drillock suggested >>> hooking my scope to the sensor to see how exciting it truly is. I'm not >>> sure I'm ready for that much excitement!) >>> >>> I have not tested full throttle to see if my sensor reacts like your next >>> step: "4> At full throttle the Dot stays pegged in the rich zone," which > I >>> will do tomorrow. >>> >>> With regard to your Step 5 "An old O2 sensor caused the Dot to jitter and >>> move lazily as opposed to a new sensor which gave crisp and rapid Dot >>> movement from one end to the other." I can say that the dot here bounces >>> around in quite a lively fashion with no laziness observed. >>> >>> Mark suggested that I take the van out onto the highway and see what the >>> monitor reports. This is a good idea since highway driving is about 95% > of >>> my driving this should give me an indication of whether my poor gas >>> mileage is because it's all going out the tail pipe. >>> >>> The "Here is a good link O2 LINK" link on your page is broken, BTW. >>> >>> -- >>> Mike "Rocket J Squirrel" Elliott >>> 71 Type 2: the Wonderbus >>> 84 Westfalia: Mellow Yellow ("The Electrical Banana") >>> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano >>> KG6RCR >>> >>> >>> >>> On 9/10/2007 5:12 PM Kenneth Lewis wrote: >>> >>>> Mike, >>>> If you read the tech sheets there is more to a "good " O2 sensor than >>>> voltage swing. They talk about "slow" sensors also. I have some info >>>> (plus >>>> my O2 sensor monitor) on my website : http://neksiwel.20m.com/ >>>> Ken Lewis >>>> / >>>> >>>> >>>> ----- Original Message ----- >>>> From: "Mike "Rocket J Squirrel" Elliott" <camping.elliott@GMAIL.COM> >>>> To: <vanagon@GERRY.VANAGON.COM> >>>> Sent: Monday, September 10, 2007 6:47 PM >>>> Subject: [VANAGON] My poor MPG, O2 sensor seems okay >>>> >>>> >>>>> As I've posted previously, my 84 1.9L auto only gets about 15.5 MPG >>>>> while others have reported somewhat higher mileage. Even after > filtering >>>>> out those who seem to be quite optimistic, and paying especial > attention >>>>> to those who deny not keeping careful records, Mellow Yellow still >>>>> trails the pack. It gives us great sadness. >>>>> >>>>> It has been proposed that my poor numbers might be due to a funky O2 >>>>> sensor, or crummy compression. I'll get to the compression tomorrow or >>>>> the next day, but right now I have hooked up my handy-dandy voltmeter > to >>>>> the sensor and with the engine warmed up, it is outputting between .36 >>>>> volt and .66 volt, ranging around about .55 volt. This seems kinda >>>>> normal, from what I read. >>>>> >>>>> -- >>>>> >>>>> Mike "Rocket J Squirrel" Elliott >>>>> 71 Type 2: the Wonderbus >>>>> 84 Westfalia: Mellow Yellow ("The Electrical Banana") >>>>> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano >>>>> KG6RCR >>>>> > >


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