Talk:Distributor

Question regarding diagram

From what I understand, the distributor will send secondary voltage to the spark plugs in "firing order." The numbers on the output caps read, clockwise, 1, 3, 4, 2. There are no numbers on the spark plugs, but assuming their position indicates their number, then read left to right we have spark plug #1, sparkplug #2, #3, and #4. Assuming that the rotor arm only moves in a clockwise direction, as indicated by the arrow, spark plugs numbers 1 & 3 will be "fired" before spark plug #4, and spark plug #2 will be "fired" last. Is this correct? Is this always the "order" the spark plugs are fired?

If I'm correct, is there a way to indicate this in the text, or to indicate what the spark plug numbers are (or how the numbering is done)? Ileanadu (talk) 15:15, 8 April 2017 (UTC)

There ought to be an article on firing order. For inline four cylinder four stroke engines there are only a couple of orders that make sense - largely depending on the shape of the crankshaft. For engines with more cylinders, there are many more options. Andy Dingley (talk) 16:01, 8 April 2017 (UTC)

Part of the confusion is because the distributor does not determine the firing order. The distributor selects outputs in turn but in theory the spark plug leads can be connected to any spark plug. However, as Andy said, only a few orders make sense (1342 being common on 4 cylinders). For ease of maintenance, the manufacturer often has their chosen firing order embossed on the distributor cap but it can be changed. When my car was upgraded to a later model engine, the distributor had to be moved from the rear of the camshaft to the front of the camshaft. This reversed its direction of spin, so we also swapped over 2 of the leads and now it works even though the numbers no longer match. I also remember some Australian Ford V8's circa 1975 that had a different camshaft that required a change of firing order - which was accomplished by simply swapping leads over.  Stepho  talk  11:56, 13 August 2018 (UTC)

Distributor repair

I had today for the first time to replace the distributor rotor (thumb) of my Opel Astra 1994. I did it by myself and it was far easier then expected (about 5 minutes work :) I never did it before and also did not have any education how to do it. Sunday 13.AUG.2018
BTW the old thumb caused that first (leftmost) cylinder was not firing, so it was more difficult to start the engine, the power was lower and it was more difficult to take over all the newer cars ;) Now is everything again OK ...
PS you can - of course - delete this contribution - but it is showing that the things could be easier if there is no ARM or Pentium with at least 64GB RAM, IP protected OS and IoT cloud :)))

Citroen ID19

The article says that some 4 stroke, 4 cylinder engines can have no distributor by using 2 coils and the Citroen ID19 is given as a an example. There is no explanation of how this works and I can't figure it out by myself - surely there must a switching mechanism for the 2 coils. Even searching the web for how the ID19 engine works didn't help - in fact I found a part for the ID19 distributor cap.  Stepho  talk  01:44, 15 December 2019 (UTC)

Don't know where I've seen it described ( maybe here!) but if you put a spark plug at both ends of the coil, you can fire four plugs with only two coils. There's a "wasted" spark in the cylinder that's in its exhaust cycle, and I imagine the voltage requirements are high, but it does simplify the arrangement quite a lot. --Wtshymanski (talk) 06:30, 21 December 2019 (UTC)

• It's a wasted spark system. Although the article is poor. I don't know about Citroens using it on the water-cooled engines, but they did for the 2CV. It's called a "wasted" spark because it fires twice per cycle, and one of these is during the exhaust stroke, so is superfluous. There's no switching.

Some Ford V4 engines did it too - maybe the Saab version? Andy Dingley (talk) 11:44, 21 December 2019 (UTC)

Thank you for your responses. Having 1 coil firing 2 spark plugs (ie wasted spark) is no trouble to me and a lot of modern EFI systems use variations on wasted spark. The problem was how to select which of the 2 coils was being fired. I think I have found the answer. The better versions of the ID19 engine had a standard distributor with a 4 lobe cam controlling a single set of points (typical of most cars of the era). But I found a nice diagram at http://www.modelcarsmag.com/forums/topic/96921-all-new-citroen-ds19-kit/page/8/ (about halfway down) that shows the internals of what replaced the distributor on the cheaper versions. Same shaft but no rotor. And it has 2 cams - each with only 2 lobes and driving a single set of points each (look for part DS 211-4 in the centre of the diagram). So, one set of points would drive the first coil for 2 of the cylinders and the other set of points would drive the other coil for the other 2 cylinders - with each coil driving 2 spark plugs using wasted spark. Presumably this could be used to drive 6, 8 or higher cylinder engines by using multiple lots of 2 lobe cams+points.  Stepho  talk  21:00, 21 December 2019 (UTC)

Wasted spark has pretty much disappeared now, because although it loses the distributor it still had external cabling, which was nearly as much trouble. So modern engines are almost all now using plug-top coil systems, with a single plug per coil (my car has four cylinders and eight coils). The main difference is the electrical simplicity of the HT side and how that makes a more efficient load to be driven by the coil (and so the input power to the coil drops, which makes them far more reliable). The plug gap can be increased giving a better spark, and (mostly) a gap which is no longer a sensitive adjustment. As silicon power transistors are also cheap, the ECU's PCM driver has eight separate output stages, one for each coil. There's no points or any sort of diistributor, as the timing signal is taken from the crankshaft, so even ignition timing is extremely simple and doesn't drift once set (I haven't adjusted the timing in 200,000 miles) because there's no mechanical wear path, such as a timing chain, in the timing path. I also get 75,000 miles life from the plugs, without intermediate adjustment and (thanks to unleaded fuel) no need for cleaning the plugs. Andy Dingley (talk) 22:20, 21 December 2019 (UTC)

Sorry, I worded that badly. A lot of my cars are from the 1970's and early 1980's, so for me modern means anything with EFI. A lot of the early EFI cars used wasted spark because the ECU wasn't advanced enough to handle each cylinder separately and coil-on-plug technology wasn't quite there yet. I should have also mentioned that circa 2012-2017 I used to write software for ECU's for a company converting diesel engines to natural gas.  Stepho  talk  22:59, 21 December 2019 (UTC)

nit pick on wording,

Coils are generally passive devices not intended to receive power from coupling so the "power" flow along the entire tract time averages to the same thing except for various losses, "which need routine replacement due to wear, are also eliminated when the individual coils are mounted directly on top of each plug, since the power is transported a very short distance from the coil to the plug."

What is apparently meant is the high voltage, "... the high voltage exists only over ..." . It is interesting though to contemplate as I had not thought about coil-on-plug much but it is extremely reliable from what I've seen. On old CRT's, you always got dust around the high voltage electrodes as the field gradient collected dirt. I'm not sure I ever noticed that on plug wires but the high field time is brief. I thought all vehicles now were coil-on-plug as those HV wires may as well go lol. The multiple coils eliminate a fatal failure mode and probably allow for better heat dissipation and now curious if the total winding mass is lower. Since they have resistor plus I'd imagine a few 100 ohms in the output winding wont matter. — Preceding unsigned comment added by 24.99.151.159 (talk) 13:03, 1 January 2021 (UTC)