DIY_EFI Digest Saturday, 3 August 1996 Volume 01 : Number 219 In this issue: [admin] correction: List services Re: Fuel pump sucking air (was: Re: Proper Mixture) Re: Circuits for magnetic pickups AFMs Re: Circuits for magnetic pickups re: Proper Mixture. See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: John S Gwynne Date: Fri, 02 Aug 96 10:49:57 -0400 Subject: [admin] correction: List services - -------- The EFI332 web page is now at: http://www.iris.swin.edu.au/~aden/efi332/ John S Gwynne Gwynne.1@xxx.edu _______________________________________________________________________________ T h e O h i o - S t a t e U n i v e r s i t y ElectroScience Laboratory, 1320 Kinnear Road, Columbus, Ohio 43212, USA Telephone: (614) 292-7981 * Fax: (614) 292-7297 - ------------------------------------------------------------------------------- ------------------------------ From: Donald Whisnant Date: Fri, 02 Aug 1996 11:52:48 -0400 Subject: Re: Fuel pump sucking air (was: Re: Proper Mixture) Thanks guys for your suggestions and inputs on the pump problem, I'll eventually decide what I'll do about it -- though right now I've got some more important things to knock out first -- like reverse engineering the PCM! :) ... I was curious if others had experienced this problem when converting from non-FI to FI and if so what they did about it ... Now I've got several decent approaches to take to remedy it and new ideas of things to try.... In the meantime -- I'll just fill up when it first hits the "yellow zone" ... Donald Whisnant dewhisna@xxx.com ------------------------------ From: Donald Whisnant Date: Fri, 02 Aug 1996 11:59:29 -0400 Subject: Re: Circuits for magnetic pickups For those of you who want to do the buffering with op-amps instead of dedicated chips, I'd recommend setting up a differential amp -- where you look at the "differential" of the pickup rather than grounding one lead and single-ending it... I don't have any schematics on hand at the moment, but there are a number of very nice differential amps off-the-shelf... This provides the best noise immunity... Also, be sure to twist the wires from the sensor together so that inductive coupling with other sources is minimized... And caps (as integrators) make good filters... Good luck... Donald Whisnant dewhisna@xxx.com ------------------------------ From: Brian Neill Tiedemann Date: Sat, 3 Aug 1996 02:35:58 +1000 (EST) Subject: AFMs Hi all, Some quick questions on AFM types: I know fairly well the old flappers, and Bosch type Hot Wires with analog out, and I have seen some calibrated bypass type hot wire ones by Hitachi with (I think) a frequency output..... now, I have read a little about Karmann Vortex types and am immediately interested. What pros and cons are associated with this method of air flow measurement? Is it a MASS FLOW measurement? Does a problem occur at low (read idle) flow rates (of resolution)? Are there many commercial ones around? (Reasons to use, not to use?) I have noted them in use in an Australian built Mitsubishi Magna 2.6 and they have me thinking.... the meter assembly has an atmospheric pressure sensor as well, and air temp, so a couple of these might make a nice intake for a 5 litre engine, with little need for other sensors in the intake tract (excluding TPS). All this stems from me being a little nervous about using Bosch hotwires in a high vibration offroad application. All contributions/opinions gratefully accepted...... Thanks, Brian. NOW: bnt@xxx.au ------------------------------ From: Sandy Date: Fri, 02 Aug 1996 21:16:04 -0700 Subject: Re: Circuits for magnetic pickups Tim and others... I was thinking much of the same idea, but was afraid that it was way too simple. I guess that I have to go out and get a sensor, and a wheel on a car and see how bad the noise really is. I'm guessing that it is really bad in some cases, but if I can rid my design of the lm1815, that would be very good. The circuit that you used on the Direct Ignition looked good, but again looked like it would be susceptible to noise. Do I need to ground the - on the sensor at all? If I do, don't I lose any of the balanced input benefits that I'm trying to get? If I grounded the (-) at the opamp, I would guess that I would lose ALL of the benefits of the balanced inputs. Also I messed around with some input voltage limiting, and found that zeners won't work, as they are too slow. I think however, that the TVS's will work like a champ, with only a few ns to clamp. |----------------*---------()()()-------*---*------>>> OpAmp + | | | / [pickup] [TVS] Inductors | \ Gain | | | / |----------------*---------()()()---*---|---*------>>> OpAmp - | | --- --- --- --- Small Caps | | --|-- GND This is what I was thinking, with some hysteresis on the opamp side, should do the trick, but again this is just a guess. What do you think, and what problems will be caused by not have a GND in the pickup side? More food for thought ;) Sandy ------------------------------ From: Erie Patsellis Date: Sat, 03 Aug 1996 00:50:02 -0400 Subject: re: Proper Mixture. Donald, Bosch uses an accumulator to eliminate this very problem, while I don't have may manuals in front of me you should be able to find one out of a rabbit/scirroco or for that matter any VW/Audi product, as well as volvo, MB.... The accumulator acts as a damper and resevior, using a pressurized diapraghm. I would guess you need only find one with the approx. pressure rating you need. erie patsellis ------------------------------ End of DIY_EFI Digest V1 #219 ***************************** 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".