Date: Tue, 07 Mar 2000 23:43:06 -0500 From: John <papalia@udel.edu> To: cjclark@home.com Cc: David Kelly <dkelly@hiwaay.net>, cjclark@home.com, Terry Lambert <tlambert@primenet.com>, Alex Zepeda <jazepeda@pacbell.net>, Olaf Hoyer <ohoyer@fbwi.fh-wilhelmshaven.de>, chat@FreeBSD.ORG Subject: Re: Great American Gas Out Message-ID: <4.1.20000307233127.009552e0@mail.udel.edu> In-Reply-To: <20000307233400.J73820@cc942873-a.ewndsr1.nj.home.com> References: <4.1.20000307223510.009512b0@mail.udel.edu> <Message <cjc@cc942873-a.ewndsr1.nj.home.com> <20000307213615.A73820@cc942873-a.ewndsr1.nj.home.com> <200003080330.VAA09023@nospam.hiwaay.net> <4.1.20000307223510.009512b0@mail.udel.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
<snip> >> But in the end, Oxygen as it is part of a GREATER molecule does not affect >> the O2 sensor of your car. If this is the case, CO and CO2 (standard >> products of combustion) would ALSO effect the sensor. > >Well, CO is similar to oxygen in some ways, that's why it's toxic and >very flammable.... wish I knew the principle behind this sensor. I have additional books on fuel injection which are not in my possession at the moment. When I can make a phone call tomorrow (and convince my mom to go through my book shelves =) ) I can get a "text book" description. These units work somewhat (but not exactly like) Oxygen depletion monitors that are sold for personally safety use or for permanent installations (labs, etc). MSA (Mine Saftey Appliances) is one of the front runners in making those (I work for a rep firm that sold them). The principle of operation *there* is that there is a catalytic bead which is compound specific. The bead is heated. As it reacts with the specific compound (in this case, O2), its mV signal changes. Same idea in the car. What follows is REALLY long, but perhaps you may be able to pull some useful stuff out of it. I'm excerpting this from my "factory official" repair manual, from the section that discusses the "Design and Function". Mind you, it's specific for the given car (in terms of the ratios and voltages), but the system (Motronic) is very similar to K-Jetronic, and both are extremely popular in most autos around the world that have EFI (Electronic Fuel Injection) Also, this is written for mechanics, not engineers or chemists, so it's not exactly what would make us happy =) --John Title: Heated Oxygen Sensor (HO2S) "The HO2S is located in the catalysator, and provides the ECM (electronic control module) with information on the air/fuel mixture. The sensor, which is electrically heated, produces a voltage which varies according to the exhaust gas oxygen content. To measure exhaust oxygen content, the HO2S requries a supply of ambient air as a reference. Since this is supplied via the cable, the lead must not be clamped or damanged in any way, nor must oil be used on the sensor contacts since this could also affect the reference air supply. Function: The HO2S only works above a certain temperature: 285 DegC. The normal working temperature lies in a range of 350 DegC to 850 DegC. The HO2S is electrically heated. When the engine starts, a current flows through a PTC resistance. Since the HO2S is cold, the resistance is low and current passed through the circuit is therfore high. As the temperature of the PTC resistance rises, the current falls proportionally. When the engine is running rich, the exhaust gas oxygen content is low, and the HO2S gives a signal of approx 0.9V. Under leaner running, excess oxygen occursa in the exhaust and the output signal from the HO2S drops to nearly zero. The change from high to low signal level occurs at the ideal (stoichiometric) air/fuel ratio of 14.7:1. The ECM uses teh HO2S signal to continually control the amoutn of fuel injected so as to maintain the ideal mixing conditions." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4.1.20000307233127.009552e0>