DIY_EFI Digest Saturday, 2 March 1996 Volume 01 : Number 062 In this issue: Re:ducted-fan-engine [admin] List services (automated monthly post) Re: Totally tubular, man RE:RE: Ducted Fan Engine Re: Just a few GM TPI Questions Re: LO VS. HI RE:RE: Ducted Fan Engine tubing and timing Optical Dist sensors Re: Detonation at idle Re: LO VS. HI Re: Totally tubular, man Hi-res crank sensor. Re: Detonation at idle Re: Totally tubular, man See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: "Hans Hintermaier" Date: Fri, 1 Mar 1996 11:58:39 MET Subject: Re:ducted-fan-engine I wrote: >If you reduce compression and fit a spark-ignition-system, you can >use normal-gas without nitro and therefore won't have any corrosion >inside the housing. Sorry, I didn't read carefully! You were talking about jet-engines, not model-piston-engines. Of course, it wouldn't make too much sense with a piston-engine. This mailing-list also is a good english-training for me... Hans hiha@xxx.de ------------------------------ From: jsg (John S Gwynne) Date: Fri, 1 Mar 1996 06:10:08 -0500 Subject: [admin] List services (automated monthly post) This message is post monthly as a reminder of the available list services. For help: Send "help" to Majordomo@xxx. To post: Send to "[list name]@xxx.edu" To subscribe: Send to Majordomo@xxx.edu subscribe [list name] [your email address *only* if different than your "From" address] To unsubscribe: Send to Majordomo@xxx.edu unsubscribe [list name] [your *registered* email address if different than your "From" address] The archives to all the mailing lists are available through Majordomo. Send "index [list name]" to Majordomo@xxx. You will find a file "archive_date_index" whose contents show the period covered by each of the archive files "archive_num_*". Digest mode is available for all of the mailing list. Send "lists" to Majordomo for a listing a mailing lists served. To switch to the digest mode, unsubscribe to the regular list and then subscribe to the digest version (i.e., diy_efi-digest). WWW sites: diy_efi http://www.cpsc.ucalgary.ca/~fridman/diy_efi efi332 http://www.cim.swin.edu.au/wwwhome/aden/efi332/332_index.html Other related sites: http://devserve.cebaf.gov/~bowling/ http://spbted.gtri.gatech.edu:80/hpe/hpe.html Please send information to be added to this posting to jsg@xxx. John ------------------------------ From: renns@xxx.com (Roger Enns) Date: Fri, 1 Mar 1996 07:48:34 GMT Subject: Re: Totally tubular, man > >Where can I find mandrel bent "U" shaped aluminum and steel tubing for >fabricating intake and exhaust plumbing? > > Dan Bocek Check out the exhaust section of your JC Whitney catalog. They have a good selection of 45s, 90s, and 180s of various diameters. I have ordered a variety of sizes, and have been pleased with the product. Seems to me that all sizes were .050" wall thickness. Roger Enns (renns@xxx.com) ------------------------------ From: ducharme@xxx.com Date: Fri, 1 Mar 96 09:11:22 EST Subject: RE:RE: Ducted Fan Engine I was referring to a Ducted Fan engine, which in my experience is a piston engine driving a fan, used in models of jet aircraft. I've been away from modeling for a couple of years, and other than one notable example, I was unaware that anyone had successfully built a model-size gas turbine. In general, model engines *are* long-lasting and basically reliable (I have some '70s vintage engines I wouldn't hesitate to fly again), but as a powerplant to drive a supercharger, there are better alternatives. How about a free-piston engine to drive the turbine directly? Or, yet, a combustion chamber (a la a real gas turbine engine) to generate hot gas? - - Just another wacked-out thought... ------------------------------ From: Jens Knickmeyer Date: Fri, 1 Mar 96 15:59:39 MET Subject: Re: Just a few GM TPI Questions wrote: > > Could fine dirt affect a hot wire MAF? I would say so. The Bosch hot wire systems clean the wire by heating it up after the engine is stopped. I do not know about other systems... Jens ('92 VW Polo-G40) ------------------------------ From: bs73@xxx.edu (Brad Sheridan) Date: Fri, 1 Mar 1996 10:16:38 -0500 (EST) Subject: Re: LO VS. HI > > What is the dynamic difference between low impedence peak-hold injectors and > high impedence injectors. Tell me Tell me Tell me. > > Mike The low impedance injectors have a slightly shorter turn on time. Brad ------------------------------ From: pjwales@xxx.net (Peter Wales) Date: Fri, 01 Mar 1996 10:30:26 -0500 Subject: RE:RE: Ducted Fan Engine >How about a free-piston engine to drive the turbine directly? Or, yet, a >combustion chamber (a la a real gas turbine engine) to generate hot gas? > >- Just another wacked-out thought... You call that a whacked out thought? Try this. As you have plenty of gasoline on board so why not use a gasoline motor. A lawn mower engine or a weedwhacker would do nicely if geared up. It may not make enough power so you might have to turbocharge it. Which leads me to the final whacked out thought. Feed the exhaust from the weedwhacker engine into the input of the turbo thus using it as a backup boost generator. Connect the throttle of the weedwhacker to a servo controlled by boost pressure to maintain a closed loop system. Now you have full boost at idle. Thats a proper weedwhacker idea Peter Wales pjwales@xxx.net President Superchips Inc Chairman Superchips Ltd "Timing is everything" Superchips home page with all the answers http://www.superchips.com ------------------------------ From: "bclemen@xxx.EDU> Date: Fri, 01 Mar 96 10:28:02 EST Subject: tubing and timing Alum. tubing bends can be purchased from: Woolf AircraftProd. 1-313-721-5330 GM's 2.2 4cyl. is currently using a 7 notch disc (6 even spaced 1 odd) on the crank and 1 notch disc on the cam for ign. ------------------------------ From: David Schmidt Date: Fri, 1 Mar 1996 07:54:34 -0800 Subject: Optical Dist sensors Nissan Sentras, and 240SX's from at least 91' up have this same setup, in case anyone wanted to tear one up from a junkyard. I would guess the Maxima has one too. It isn't just for their high end car! Dave > As a matter of interest the Nissan 300 ZX Twin Turbo distributor has 2 > sensors in it. One reads crank angle from the 360 lines on the disc and the > other reads an encoded cylinder number from the 3 digit code. Japanese > engineering! >I was actually surprised that no one was doing this. (until now, that is) ------------------------------ From: ehernan3@xxx.com (Edward Hernandez (R)) Date: Fri, 1 Mar 1996 12:09:32 +0500 Subject: Re: Detonation at idle "Should there be a very slight detection of detonation (knock) at idle with engine hot?" No. You need ridiculous timing advace to knock at idle. You are probably(and unfortunately) hearing a mechanical problem such as piston slap or bad lifters. ------------------------------ From: Sean McManus Date: Fri, 1 Mar 1996 11:48:18 -0800 (PST) Subject: Re: LO VS. HI Mike: If you want the "stuff" on injectors, pick up SAE Recommended Practice J1832. According to this document, peak and holds open with about a one msec delay and close with about a 1/2 ms delay. Saturated injectors open with about two ms delay and close with about a one ms delay. Seems that saturated works well on most applications, peak and hold more appropriate for engines with high specific output, say more than 100 hp/liter, where they need a lot of max flow but at the same time need good control for very small pulse widths (ie idle, low load and rpm). Sean McManus University of Washington Formula SAE Yamaha FZR 600 power On Thu, 29 Feb 1996 MTaylorfi@xxx.com wrote: > What is the dynamic difference between low impedence peak-hold injectors and > high impedence injectors. Tell me Tell me Tell me. > > See ya, > > Mike > ------------------------------ From: tarun@xxx.com (Tarun Patel) Date: Fri, 1 Mar 96 12:41:52 EST Subject: Re: Totally tubular, man Is JC Whitney catalog ON-Line ?? ------------------------------ From: einarp@xxx.no (einarp) Date: Fri, 1 Mar 96 17:17:35 CET Subject: Hi-res crank sensor. It seems I was not expressing myself very exact when I presented this: * x _ _ _ _ _ _ _/ \_/ \_/ \_/ \_/ \_/ \_ I should also have mentioned that I assumed the sensor signals would be run through a zero crossing detector first. Like for example the LM1815. A short pulse would come out of it starting at the zero crossing of each sensor. That will again coincide with the point where it is "on the top of" the tooth, like "*" in the above drawing. The pulses out of "X" will come inbetween the pulses from "*". Set the pulse time short enough that the pulses from the two sensors will not be active at the same time even at the highest RPM. It should look something like this: __/\ _____/\ ______/\ _______/\ ____ Sensor "*" output \/ \/ \/ \/ ______/\ _______/\ ______/\ ______/\ __ Sensor "x" output \/ \/ \/ \/ ___II________II________II________II_____ Zero Cross "*" ________II________II________II________II_ Zero Cross "x" ___II___II___II___II___II___II___II___ OR of the above My point with this is that each of the two sensors are detected at a point of their waveform that is not dependent on the shape of the tooth, or the distance sensor/tooth. It's only depending on one sensor being above the middle of the tooth at the same time the other is midway between two teeth. If we had a nice sinewave shaped signal out of the sensor, it would have been much simpler. We could just detect positive and negative peaks of one sensor. But look at the sensor signal and you will see it looks more like my ASCII drawing than a sinewave at low RPM. It will approach a sinewave as speed increases and the "_" part (of the sensor signal) shrinks. I think some of the the previous postings assume a sinewave signal. For the DIY'er with lots of time on hand: Log the time interval between zero crossings related to each cylinder during cranking, and you can tell if one cylinder is low on compression relative to the others. It should be possible assuming you have 300 pulses per revolution as you would get from the above picking pulses off of a 150 tooth flywheel ring. - -- einarp@xxx.no ( Maserati Biturbo Spyder ) ------------------------------ From: "George M. Dailey" Date: Fri, 1 Mar 1996 17:18:57 -0600 Subject: Re: Detonation at idle At 12:09 PM 3/1/96 +0500, you wrote: >"Should there be a very slight detection of detonation (knock) at idle > with engine hot?" > >No. You need ridiculous timing advace to knock at idle. You are >probably(and unfortunately) hearing a mechanical problem such as >piston slap or bad lifters. > ====================================================== On my last 350 TBI engine, I noticed that if the engine was hot (190 deg. F) and the inlet air was hot, if you advanced the timeing you would hear what sounded like detonation. You did not have to go far! When the timeing was retarded the sounds would go away. Let me also add that you don't hear the sound just off idle and it's around the same sound level of the injectors clicks. The hood must be up to even hear the sounds. When under full throttle, I'm sure that it's slightly detonating. I'm not sure if the ECM is detecting 100% of the detanation. I once herd that the GM ESC will rattle just a little, some times, at full load. I've herd a TBI rattle with the nock sensor disconnected at full load. My TPI is no way near this. BTW 79,000 miles on the clock, car was driven every day, auh 'aggressively' but well pampered as far as maintenance is concerned. It kissed another car. Thanks for your input Dudes. GMD ------------------------------ From: John Napoli Date: Fri, 1 Mar 1996 20:14:29 -0500 (EST) Subject: Re: Totally tubular, man It is not, but they have an 800 #. BTW, for mandrel-bent tubing, try your local muffler shop! Regards, John On Fri, 1 Mar 1996, Tarun Patel wrote: > Is JC Whitney catalog ON-Line ?? > > ------------------------------ End of DIY_EFI Digest V1 #62 **************************** 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".