Date: Mon, 28 Jul 2003 14:56:26 -0400 From: Malcolm William Mason <MWM1nopsamJHU.edu> Subject: Re: Gas economy
I apologize to all for the repetitions. I am still getting used to this and hope that I have neither offended nor inconvenienced. Seriously, thanks for all your haelp and forberance. Malcolm On Mon, 28 Jul 2003 00:49:18 -0400, Malcolm William Mason <MWM1nopsamJHU.edu> wrote: > > >I have "checked" the EDU values by using the trip odometer and gallons >fromFull to Full. The values I get are comparable. The gallons ar4e >checked reularly by the jurisdiction's (state or province) Weights and >measures departments and mileages on major highways in the U.S. and >Canada are posted in 0.1 mile or 100 metre increments by the >Departments of Highways and are very accurate. > >True, the fuel injectors wear with time but this is compensated for by >the fuel management system. >The data are empiric and "jibe" with the EDU. My best guess is that it >is quite accurate. > >Malcolm > > > >On Fri, 25 Jul 2003 15:10:01 GMT, hohnopsamlid.invalid (Goran Larsson) >wrote: > > >>In article <vi2ev7mb5kmdd0nopsam.supernews.com>, >>Andy Hookins <andrew.hookinsnopsamamnopsamodata.co.uk> wrote: >>> "Goran Larsson" <hohnopsamlid.invalid> wrote in message >>> news:HIL041.Jt1nopsamove.se... >> >>> > The EDU measures two signals for its fuel consumtion numbers. One signal >>> > is the distance driven, i.e. the same signal that is used by the >>> > speedometer, odometer, and some other functions in the EDU. The other >> >>> I defer to your knowledge over my speculation >>> (i.e. my previous post elsewhere in this thread). I just >>> assumed that the EDU is a dumb display driver, but you >>> say it has signal acquisition and computational abilities, >>> is that right? >> >>The EDU that I am familliar with is the one used on the 9000. That EDU >>had a wire directly wired to one of the injectors (for the injector open >>time) and one wire to the speedometer (for the speed signal). All >>numbers shown on the EDU was calculated inside the EDU itself. >> >>> > signal is the time the injection valves are open. As the volume that >>> > passes through the injection valves over a certain time is known it is >>> > easy for the EDU to calculate the fuel volume used. Later Saabs with >> >>> This description implies to me that there is another method >>> of determining fuel used - maybe the fuel tank sender, to >>> compensate for diffeences in fuel injector characteristics. >> >>The injector characteristics must be known. How else is the engine >>management computer supposed to determine the correct time to keep >>the injector open? >> >>The fuel pressure over the injectors is determined by the fuel >>pressure regulator. It should be constant and fixed. Knowing >>the characteristics of the injectors and the time they are open >>allows the EDU to calculate the fuel consumption. The engine >>management computer can not read the fuel pressure, so if it is >>wrong then both the amount of fuel injected, and the values shown >>on the EDU, will be wrong. >> >>> Is that what you are saying or am I just reading more into >>> this than I should? >> >>I can't answer that as I don't know what you are reading that >>shouldn't be read.
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