DIY_EFI Digest Saturday, 18 May 1996 Volume 01 : Number 143 In this issue: re: Re: a/f ratio with LPG Re: a/f ratio with LPG Re: a/f ratio with LPG Re: Bosch ECU Schematic for 1981 BMW 528i hello KE-jetronic closed loop See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: SRavet@xxx.com Date: Fri, 17 May 96 9:53:37 CDT Subject: re: Re: a/f ratio with LPG Darrell Norquay Wrote: | what happens. By the way, O2 sensors do read oxygen content, at least in | that they are proportional to the difference between the exhaust O2 | concentration and the ambient air. They are unaffected by concentrations of | other gases, and generate a voltage by pumping O2 across an electrochemical | cell. This is a post that Dale Ulan sent in about a year and a half ago about O2 sensors, in which the EPA published a paper that said O2 sensors don't actually measure oxygen until they reach 900 degrees. Dale didn't have the SAE paper number at the time. If anyone else recognizes this reference, could you please post the article number? I'd like to add this one to the EFI reference. Are you still here, Dale? - ------------ begin That's what everybody thought, too... About 3 or 4 years ago, a few people from the EPA wrote an SAE paper on the subject of oxygen sensors. My copy of the paper is at school, so I can't quote the names or give you the SAE paper number. But I can summarize it, because I was suprised, too. The EPA was going to do a study of oxygen sensor aging and break-in periods, and quantify how this affects exhaust emissions. They built a test setup with a heater (which would heat up the sensor and the gas it was exposed to), and a valving system that would allow them to purge the test system with nitrogen gas, and then give samples of other gasses. What they found surprised them... The most obvious test is to see what temperature was required for the sensor to sense oxygen. So they cranked up the O2 flow, and started heating. The O2 sensor started to respond at about 800 or 900 degrees C. No exhaust system operates that under normal road-load conditions. At this point, they decided that their study should concentrate on this lack of O2 sensor activity. What they discovered was that the O2 sensor would respond to carbon monoxide and hydrogen. At normal operating temperatures, they concluded that the O2 sensor is not capable of sensing oxygen at all. Few people seem to have read this paper, though, so most people out there think that the oxygen sensor actually senses oxygen in a vehicle. It *can* sense oxygen, but it'll have to be glowing pretty bright to do it. I would suggest going to your local technical library and finding this SAE article. It will be in one of the annual article abstract books, somewhere between 1989 and 1993, and may be present in either the big thick SAE publication hardcovers, and/or in 'Sensors and Actuators', an SAE special publication series. I haven't seen any papers arguing against their conclusions, but if there are, I'll hopefully eventually find them and read them. - -Dale - ----------- end Steve Ravet sravet@xxx.com Baby you're a genius when it comes to cooking up some chili sauce... ------------------------------ From: Seth Allen Date: Fri, 17 May 1996 08:05:25 -0700 (PDT) Subject: Re: a/f ratio with LPG On Thu, 16 May 1996, Bruno! wrote: > Date: Thu, 16 May 1996 13:31:57 +1000 (EST) > From: Bruno! > To: diy_efi@xxx.edu > Subject: a/f ratio with LPG > > Hi everyone, > > I was wondering if it is possible to use a normal (i.e petrol) O2 sensor > when running a car on LPG, as opposed to unleaded fuel. > > Thanks in advance, > > Bruno. (u933234@xxx.au) > > "A sewer rat might taste like pumpkin pie, but I wouldn't know cos I > don't eat the filthy muthaf***a" > > Well, how well do you want it to work. The real answer is no. We generally buy the correct O2 sensor. Usually a gasoline sensor causes the gaseous fueled cars to lean. Like 20 percent. A correction circuit can be thrown in, but it is probably easier in the end to get the right sender. That's my experience and opinion. - --Seth Allen WWU Vehicle Research Institute ------------------------------ From: Seth Allen Date: Fri, 17 May 1996 08:12:38 -0700 (PDT) Subject: Re: a/f ratio with LPG On Thu, 16 May 1996, Darrell Norquay wrote: > Date: Thu, 16 May 96 21:21 PDT > From: Darrell Norquay > To: diy_efi@xxx.edu > Subject: Re: a/f ratio with LPG > > At 01:31 PM 5/16/96 +1000, you wrote: > >Hi everyone, > > > >I was wondering if it is possible to use a normal (i.e petrol) O2 sensor > >when running a car on LPG, as opposed to unleaded fuel. > > > >Thanks in advance, > > > > Bruno. (u933234@xxx.au) > > > > I've been running O2 sensors in my Camaro on LPG for a year or so now, > but I'm still not sure they read back any useful info. The Stoich A/F ratio > for propane is around 23:1, and although Stoich is Stoich no matter what the > fuel (at least in theory), they seem to read lean most of the time. I'm > reasonably certain that my mixture is not as lean as indicated, but I have the > sensors mounted in the header collectors which is fairly far from the engine, > so it may be a problem with location rather than the sensor itself. I want > to try some heated sensors to see what difference it makes, I'll let you know > what happens. By the way, O2 sensors do read oxygen content, at least in > that they are proportional to the difference between the exhaust O2 > concentration and the ambient air. They are unaffected by concentrations of > other gases, and generate a voltage by pumping O2 across an electrochemical > cell. > > Regards > dn > Heated O2 ensors are a good idea as the cold combustion characteristics of gaseous fuels tends to let them cool off and "drop out of the loop" at idle. Or stuff them right up in the manifold. But you still may need a heater. Just my opinion. Incidently we got a Neon on CNG to meet ULEV emmisions. We were pleasantly suprised when we did the federal test. Seth Allen Vehicl Research Institute ------------------------------ From: michael glidewell Date: Fri, 17 May 1996 15:29:07 -0400 Subject: Re: Bosch ECU Schematic for 1981 BMW 528i At 09:10 AM 5/13/96 -0600, you wrote: >Hi Michael > >He has no schematics. I have not found anyone with schematics of the ECU. >Bosch will not realease the schematic, and I haven't found anyone that has >created them. > >what are you trying to do with the schematic? > >Werner Werner: Being a EE I look to EFI electronics where I might be able to improve things without major cost impact. I wonder if it would be possible to turn the L-jet into a multiport injection system by firing each injector individually and possibly improve the city fuel consumption (its 12+ mpg). Or maybe I could bring out some of the parameters and adjust for max performance/ economy. Maybe I could repalce with a microprocessor and and do more calculations per second resulting in smoother idle/ economy or performance. I guess I can't leave things well enough alone also. - ---------------------------------------------- Michael Glidewell Boston, Massachusetts glide@xxx.net KE1CP BMW 528i BMWCCA http://www.shore.net/~glide/ ------------------------------ From: "Josh Karnes" Date: Fri, 17 May 1996 16:58:12 +0000 Subject: hello hey. just joined this list, and i really don't know what to expect. anyway, i am a member of the internet z-car club, a real 240z fan, and i also subscribe to the bmw digest. my primaty intrest in efi is with bosch l-jetronic systems and their modification, particularly the one in my bmw and those found in z-cars. i am an engineer at a high-tech firm here in austin. so, that's me. _____________________________________________________________________________ Josh Karnes joshk@xxx.com Renaissance Man http://www.tanisys.com/~joshk/home.htm Tanisys Technology http://www.tanisys.com Austin, Texas '78 BMW 530i | '72 Datsun 240Z | IZCC #308 _____________________________________________________________________________ *** opinions expressed herein are MINE, ALL MINE!! *** ------------------------------ From: James Weiler Date: Fri, 17 May 1996 16:02:35 -0700 (PDT) Subject: KE-jetronic closed loop Hello everyone. A recent discusion has prompted me to ask how an oxygen sensor feeds back on a mechanical injection system? Does it contol a fuel pump relay that alters the pressure? It makes sense how feedback works on an electronic system by altering the pulse width of the injectors. But there is no pulse width in a CIS system. Thanks to anyone who can educate me james@xxx.ca(james wieler) ------------------------------ End of DIY_EFI Digest V1 #143 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".