From ozone.breath at gmail.com Sat Oct 21 23:15:21 2006 From: ozone.breath at gmail.com (Erik Berg) Date: Sat, 21 Oct 2006 21:15:21 -0700 Subject: [Efi332] newbie (also Autronic EFI and Bosch ignition modules) Message-ID: Howdy all, I'm an EE with several car projects; right now I'm trying to sort out a problem with my '65 Lotus Elan, which uses an Autronic ECU and a distributorless wasted spark ignition system. The previous owner built both the EFI system and the ignition system. The ignition system uses Bosch ignition drivers and Mitsubishi coils. I have been having problems with the car eating coils. I wonder if they are getting too hot. The coils are mounted right to the head (they probably get pretty hot just from this) but also I wonder if the ignition modules are working correctly. I haven't gotten the ignition modules out yet to check the part numbers, but I was told by the PO that they are the type that controls the dwell. Apparently, the Autronic only sets the advance; the ignition drivers somehow (anyone know how they do this?) figure out ahead of time when to start charging the coil, to charge to full current before the ECU triggers the spark. Regards, Erik Berg -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.diy-efi.org/pipermail/efi332/attachments/20061021/fb518496/attachment.html From BowTieVette at aol.com Sun Oct 22 14:13:26 2006 From: BowTieVette at aol.com (BowTieVette at aol.com) Date: Sun, 22 Oct 2006 15:13:26 EDT Subject: [Efi332] newbie (also Autronic EFI and Bosch ignition modules) Message-ID: Hi Erik, I think the _only_ way to kill off coils is by overheating and/or overdriving them. I don't know exactly how automatic dwell systems work, but I'd guess that they probably rely on limiting current at a certain value or on sensing di/dt. They must have some short term learning or memory feature to apply to the next spark event. Regardless of the mechanism, if it isn't working or is tailored for a higher impedance coil with longer charge cycles, that's not going to help coil life. You can check by scoping the coil current draw. Typical dwell durations are around 2-4 ms. I imagine the cylinder head heat isn't helping much either. Do you mean they are mounted to the head or the valve covers? Hopefully if its the head, its on the intake side and not the exhaust side! Are there any insulators? Are the coils finned? HTH In a message dated 10/22/2006 12:16:19 A.M. Eastern Standard Time, ozone.breath at gmail.com writes: Howdy all, I'm an EE with several car projects; right now I'm trying to sort out a problem with my '65 Lotus Elan, which uses an Autronic ECU and a distributorless wasted spark ignition system. The previous owner built both the EFI system and the ignition system. The ignition system uses Bosch ignition drivers and Mitsubishi coils. I have been having problems with the car eating coils. I wonder if they are getting too hot. The coils are mounted right to the head (they probably get pretty hot just from this) but also I wonder if the ignition modules are working correctly. I haven't gotten the ignition modules out yet to check the part numbers, but I was told by the PO that they are the type that controls the dwell. Apparently, the Autronic only sets the advance; the ignition drivers somehow (anyone know how they do this?) figure out ahead of time when to start charging the coil, to charge to full current before the ECU triggers the spark. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.diy-efi.org/pipermail/efi332/attachments/20061022/3d34811b/attachment.html From andreic at chichak.ca Sun Oct 22 18:44:29 2006 From: andreic at chichak.ca (Andrei Chichak) Date: Sun, 22 Oct 2006 17:44:29 -0600 Subject: [Efi332] newbie (also Autronic EFI and Bosch ignition modules) Message-ID: <7.0.1.0.0.20061022172549.0204a328@chichak.ca> > The ignition system uses Bosch ignition drivers and Mitsubishi coils. I have been > having problems with the car eating coils. I wonder if they are getting too hot. The > coils are mounted right to the head (they probably get pretty hot just from this) but > also I wonder if the ignition modules are working correctly. The Bosch ignition modules will charge the coil then shut down after a short period of time. The dwell time is satisfied so it stops the current flow. After a little while longer it completely shuts down (as seen by my experiments). BUT the ignition module is basically just a great huge transistor switch that switches the coil to ground. I'll bet that you are blowing coils because the coils need a ballast resistor and you don't have one. There are a couple of coil styles, low resistance and high resistance. Low resistance are about 0.5 Ohm on the primary and the high resistance ones are about 3 Ohms. The low resistance ones are expected to either be run with a system that can handle them or with (typically) an external resistor. This coil is fed raw power during start then switched over to a 3 Ohm current limiting resistor during run. Running without a resistor will have the coil drawing about 24 amps all of the time and it will make a big spark - for a while. Your di/dt will be huge compared to the normal 4 amps for the same period with the resistor, but you have to dissipate 36 times the heat if I have my math right. With a high resistance coil you just draw 4 amps during start and running. Andrei > Regards, > Erik Berg ------------------------------ Andrei Chichak 4024-120 Street Edmonton, Alberta Canada T6J 1X8 (780)434-6266 Lat: 53? 28' 40" N Lon: 113? 32' 27" W From andreic at chichak.ca Mon Oct 23 11:16:34 2006 From: andreic at chichak.ca (Andrei Chichak) Date: Mon, 23 Oct 2006 10:16:34 -0600 Subject: [Efi332] newbie (also Autronic EFI and Bosch ignition modules) Message-ID: <7.0.1.0.0.20061023101624.02049038@chichak.ca> > The ignition system uses Bosch ignition drivers and Mitsubishi coils. I have been > having problems with the car eating coils. I wonder if they are getting too hot. The > coils are mounted right to the head (they probably get pretty hot just from this) but > also I wonder if the ignition modules are working correctly. The Bosch ignition modules will charge the coil then shut down after a short period of time. The dwell time is satisfied so it stops the current flow. After a little while longer it completely shuts down (as seen by my experiments). BUT the ignition module is basically just a great huge transistor switch that switches the coil to ground. I'll bet that you are blowing coils because the coils need a ballast resistor and you don't have one. There are a couple of coil styles, low resistance and high resistance. Low resistance are about 0.5 Ohm on the primary and the high resistance ones are about 3 Ohms. The low resistance ones are expected to either be run with a system that can handle them or with (typically) an external resistor. This coil is fed raw power during start then switched over to a 3 Ohm current limiting resistor during run. Running without a resistor will have the coil drawing about 24 amps all of the time and it will make a big spark - for a while. Your di/dt will be huge compared to the normal 4 amps for the same period with the resistor, but you have to dissipate 36 times the heat if I have my math right. With a high resistance coil you just draw 4 amps during start and running. Andrei > Regards, > Erik Berg