DIY_EFI Digest Friday, December 3 1999 Volume 04 : Number 673 In this issue: JTEC/Chrysler ECMs HEI advance/retard 749 for 747 See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Fri, 03 Dec 1999 09:21:06 -0500 From: Jason Haines Subject: JTEC/Chrysler ECMs Do any web sites or FTPs sites exist that have information about the JTEC, JTEC+ and other Chrysler PCMs used in the current vehicles (Prowler, Viper, Durango, etc...)? Regards, Jason ------------------------------ Date: Fri, 03 Dec 1999 08:46:00 -0600 From: steve ravet Subject: HEI advance/retard > Date: Thu, 2 Dec 1999 18:32:58 -0600 > From: "Ken Kelly" > Subject: ECU's and HEI > > Out of curiosity, I've been trying to think of ways to manage an engine by > building my own ECU. Obviously, this is an arduous task, but one I'm not > afraid to embark on. > > I started off by figuring out the inputs and outputs and determined that I > could do it with a few of the new high-speed BASIC Stamps from Parallax, but > lately I'm beginning to wonder if it can't be done (easier) with an analog > system - i.e. transistors/diodes/resistors/capacitors and have pots for > tuning? I believe this is the way Holley does most of their systems aside > from their 4D and 4Di systems. > > My main big question, however, is HOW do the HEI electronic systems work? > How does the computer adjust retard and advance? Is it a signal varied by > voltage, frequency, or what? I'm at a total loss for this concept. The other > parts of the engine I have figured out (injectors, MAP, TPS, O2, etc.) but I > can't quite see how the timing works on the electronic versions of the HEI. > (I see it has a seperate 4 wire interface?) I once saw a diagram that showed how the timing relationship worked. Basically the pickup in the distributor tells the ECM where the rotor is, the ECM sends a signal back that says fire the coil now. the time difference between the two is the advance. There are plenty of details like are the edges positive or negative that I don't know. Bruce or Shannen probably do. I was hoping the diagram was on the ftp site, but I don't see it there as .jpg, .bmp, or .pdf. It someone remembers what I was talking about and can supply a pointer to it that'd be great. It looked like a scope display of the timing signals, and was annotated with labels and arrows. oh yeah, if you want to roll your own and like motorola assembly then look at the efi332 list (efi332.eng.ohio-state.edu/efi332) - --steve - -- Steve Ravet steve.ravet@xxx.com Advanced Risc Machines, Inc. www.arm.com ------------------------------ Date: Fri, 3 Dec 1999 09:54:14 -0700 From: cwagner@xxx.net Subject: 749 for 747 I have an extra 747 and would like to trade it for a 749 computer. The computer still works. If interested, contact me of list. Chet ------------------------------ End of DIY_EFI Digest V4 #673 ***************************** 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".