Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site watdaisy.UUCP Path: utzoo!watmath!watdaisy!gvcormack From: gvcormack@watdaisy.UUCP (Gordon V. Cormack) Newsgroups: net.auto Subject: Re: eliminating distributors Message-ID: <6845@watdaisy.UUCP> Date: Sun, 6-Jan-85 13:23:03 EST Article-I.D.: watdaisy.6845 Posted: Sun Jan 6 13:23:03 1985 Date-Received: Mon, 7-Jan-85 02:31:52 EST References: <458@amdcad.UUCP> Distribution: net Organization: U of Waterloo, Ontario Lines: 47 A number of fallacies have been perpetrated in the discussion of electronic ignition. I wish to address some of these. First, an ordinary ignition coil has a step-up ratio of only 80:1, not 1000:1 as suggested. In fact, when the breaker points open, a potential of about 400 volts occurs across them and hence across the primary circuit of the ignition coil. Most electronic ignition systems operate with a nearly identical coil, but apply a 400 volt power supply directly to the primary of the coil, rather than depending on the inductance of the broken circuit. Supplying the 400 volt supply does, of course, require another step up transformer . This transformer is (relatively) low-voltage and low-power (It is of similar complexity to that found in the 6V battery replacement that drives your Walkman radio). Furthermore, this 400 volt supply can be shared among the ignition circuits for all the cylinders. It is infeasible to switch the 32kv output from the coil using semiconductor electronics. I can buy conventional coils for <$10 each at my local Canadian Tire store, so I don't see how the manufacturing cost could be much more than a couple of dollars. For a production system, the manufacture of four (or six) -plexes of coils would be of comparable complexity to the manufacture of the distributor. I would like to defend the conventional distributor a bit. First, it is a simple and reliable device. I have NEVER had to replace a distributor cap (except one I smashed in an accident), nor have I had to replace a rotor. Shorting is caused either by poor sealing in the original manufacture or by some nerd removing the cap (which is not necessary with a breakerless ignition). Second, the distributor provides dynamic timing adjustment as well as switching the high-voltage ignition pulses. A centrifugal mechanism advances the timing at high engine speed. A vacuum advance retards the timing under heavy acceleration or when the engine is about to stall. In order to replace these devices, one has add transducers and a considerable amount of logic to the ignition system. In conclusion, I think that totally electronic ignition systems will eventually take over from mechanical. However, the complexity of the system is increased, albeit encapsulated in some multi-hundred dollar "control module". That control module will require no adjustment during its lifetime. But when it fails, don't expect to be able to dry it off with a rag, or to file it down a bit, or do anything else other than to call a tow truck and wait while your local garage orders a new one.