Register now to get rid of these ads!

Technical Four Cylinder Ignition Timing

Discussion in 'The Hokey Ass Message Board' started by PhredH, Jul 25, 2019.

  1. PhredH
    Joined: Feb 28, 2015
    Posts: 103

    PhredH

    1916 Willys inline 4 cylinder. Generator shaft driven magneto has been removed and 4 cylinder distributor is being driven by generator shaft. Magneto had internal reduction gear to turn rotor at 1/2 crankshaft speed. Distributor now turns at same speed as crank shaft.

    I understand that a distributor "normally" turns at 1/2 crankshaft speed, but with this setup:

    When properly timed for #1 cylinder, will ignition fire at all four cylinders at compression and exhaust stroke (a wasted spark, perhaps), fire at only two cylinders, or what will happen?

    Will engine ever run with this distributor setup?
    Firing order is 1-3-4-2 if needed

    Thanks in advance HAMBERS

    Peace, Phred
     
  2. It should run but will have a wasted spark.
     
  3. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    It will fire #1 correctly. The next time it fires what should be #3 all the pistons will be half way up and down. Which should ignite the incoming charge for #3. Then when # 3 is up on compression #4 will fire at BDC. You could switch the wires and fire #3. Now as 3 goes down and 1 &4 come up at the half way point it will fire again. When #1 is up it will fire correctly. So you will run on 1 and 3. 2 and 4 get left out.
     
  4. PhredH
    Joined: Feb 28, 2015
    Posts: 103

    PhredH

    Rich,
    In conclusion, the 4 cylinder engine would be running on “1 1/2” cylinders. In other words, will not “run” even close to good.
    Keep those cards and letters coming if there are any conflicting theories
    Phred


    Sent from my iPhone using The H.A.M.B. mobile app
     

  5. Ive seen 4 cyl engines run with a v8 dist that has 8 cam lobes. and 2 cyl engines run on a 4 cyl dist. of course they where still turning at 1/2 of engine rpm? Why did you remove the MAG? just add a external coil and a mag becomes a dist.
     
  6. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    The setup you describe should fire at the top of the compression stroke, and again at the top of the exhaust stroke, resulting in a wasted spark. I don't know why it would not run normally although, wear on the distributor and points will be greater than normal.
    Lots of 4 stroke motorcycles had a similar arrangement firing both ends of a coil, one coil firing 2 cylinders, with a stray spark on the exhaust stroke. Honda built millions of motors like this, so did many other companies, I believe Harley Davidson had it first.

    You could switch the 1 and 4 plug wires, or the 2 and 3 plug wires and it wouldn't make any difference.
     
  7. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    There are millions of cars with crank trigger ignition and separate coils for each cylinder, I should think they do the same thing (fire on the compression and exhaust strokes).
     
  8. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 12,604

    Johnny Gee
    Member
    from Downey, Ca

    ^^^^^ They do. Theory is to burn off unburned fuel. Emissions thing.
     
  9. My dad had an old IH 6 cyl powerplant that had a similar issue. No mag and the shaft spun at crank speed, He mounted a Ford six distributor horizontally and hooked the two together with sprockets and chain. The sprocket on the distributor was twice as big as the drive....just like a timing chain, slowing it to 1/2 speed.
    It ran his sawmill for years like that. Sorry, no pics....
     
  10. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    A four cylinder distributor fires every 180 degrees. Twice per revolution. If you run it at crank speed it will fire every 90 degrees, Four times per revolution. Since only two cylinders come up on compression per revolution the other two sparks will take place when the pistons are half way down. Wasted spark ignitions fire two plugs at once. This deal will only fire one plug and that plug wire will always be attached to the same plug. So it will fire once for real and once wasted. But the cylinders firing at 90 degrees rotation are always going to fire at 90 degrees. Two will always fire at TDC. Two will always fire at 90. By the time the crank has made one full revolution, the rotor will have made one full revolution..There is no way any cylinder will ever fire at BDC
     
    Last edited: Jul 25, 2019
  11. The 'wasted spark' ignitions that turn at crank speed use just two point lobes, not four...
     
  12. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    And they don't have rotors and caps. But this gut wants to run the stock mag at crank speed. Not happening.
     
  13. Agreed... Actually, only two cylinder applications use two lobes. All four cylinder set-ups I've seen use a single lobe and either two sets of points or two ignition pick-ups, each one firing it's own coil. One coil fires a pair of cylinders.
     
  14. PhredH
    Joined: Feb 28, 2015
    Posts: 103

    PhredH

    Updates
    The generator the drives the mag and the distributor turns at crank speed. The mag had internal gearing that reduced the input speed to 1/2 the input speed. The mag has some internal shorts/melted spots and of course does not work anymore. The distributor idea was to be a quick, inexpensive work around to having the mag rebuilt or replaced. The distributor is a 4 lobe type, looking like a Bosch VW style.

    So a two lobe distributor should work in this setup.
    Old Wolf's idea of adding an external coil sound intriguing... Some additional thoughts/diagrams would be appreciated.

    Thanks HAMBERS

    Phred
     
  15. Ned Ludd
    Joined: May 15, 2009
    Posts: 5,026

    Ned Ludd
    Member

    UJM-type 4-cylinder motorcycles usually ran wasted-spark ignition with two double-ended coils. Perhaps adapt the points assembly from one of those?
     
  16. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    A two lobe distributor will fire to plugs every revolution. The trouble with that is that they will be the same two plugs. You have four plugs to fire. And we still have the 90 degree problum to deal with. Run the distributor off the cam or use a reduction drive like RMR&C
     
  17. Ok Ive done it on tractors and cat pony engine mags you throw the internal coil away. Only use the points and condenser in the mag. run a hot wire to the + side of a coil run a wire from the points to the - side of the coil. then the coil will produce spark. run a spark lead from the coil to the center carbon of the cap. it might require some fabbing if your mag cap don't have a provisionfor a coil wire.
     
  18. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    Or if you like the Bosch distributor. These are two Pinto (almost the same as VW but without the slow #4 lobe) adapted to early 4 cylinder engines, You could maybe adapt your Bosch distributor to the existing lower and save the gear reduction. Requires some skill, talent and equipment. But it worked for me. img122.JPG
     
  19. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    Don't forget to get a distributor that turns the same way as the mag did. Otherwise you get centrifagle retard. I did that in 62. Put a Reo dist. in a GMC. Dropped right in. Started fine. Really killed the top end.
     
    Hnstray and RMR&C like this.
  20. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    A normal 4 cylinder distributor runs at half engine speed and fires each cylinder every 640 degrees, in other words, every second revolution. But always at the same time in relation to the piston.

    If you drive it twice as fast, at engine speed, it will fire twice as often, once every 360 degrees, but always at the same time in relation to the piston. If it is timed to fire when the piston is at TDC it will fire every time the piston is at TDC.

    This means it will fire at the end of the compression stroke and at the end of the exhaust stroke. So every second spark will be wasted.

    Many cars and motorcycles have ignition that fires every revolution, and no harm done. There is no reason this distributor won't work.

    The only drawback is, the distributor will run twice as fast as normal which will presumably wear it out twice as fast. It will also cause point bounce to occur at half the RPM but since this is a low speed 1916 engine I doubt it will make any difference. The engine won't rev high enough to over speed the distributor. It will make a difference to the centrifugal advance if any, unless you put in stronger advance springs.
     
  21. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    Did Willys offer a distributor for this engine? Maybe you could find the factory setup and avoid all this agony.
     
  22. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 6,251

    Ebbsspeed
    ALLIANCE MEMBER

    V-Twin Harleys and most multi-cylinder Hondas have the points pulsed by the camshaft. On the early single cylinder Honda pushrod engines they were pulsed at crank speed, and used a wasted spark ignition.

    A two-lobe distributor will not work. If you happen to have a dual POINT distributor you could use one set of points to fire 1 and 4 from a dual-tower coil, and the other set of points to fire 3 and 2 via a second dual tower coil. This assumes that the two sets of points would open 180 degrees from each other. Most dual point distributors are nowhere close to having this much separation in opening, so you would have to do some modifications to the breaker plate. You would also need to grind off all but one lobe on the points cam.

    In spite of all the internal shorts/melted spots, if the points still operate properly in the mag, doing what @Old wolf recommended is by far the best and easiest option. I have a John Deere Model B two cylinder tractor that I modified the mag on so that an external coil could be used. It's worked like a charm for 25 years and still going strong.
     
  23. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    360 + 360 = 720. And as I said. If the rotor is turning at the same speed as the crank, the points will open every 90 crank degrees. One revolution. 4 events = 90 degrees. But if the crank only turns 90 degrees the piston will be half way down or up depending. It's really simple if you can get your head around it.
     
  24. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    Rusty- Say #1 is at tdc on compression. It fires. Great. How far will the rotor and point cam turn before it fires again? 90 degrees. How far does the crank need to rotate before another piston is at TDC? 180 degrees. Not so great. That would be #3. So you can get 1 and 3 to run. 2 and 4 will always fire at 90 BTC or ATC. unless you know someone really good at switching plug wires on a running engine.
     
    Hnstray likes this.
  25. Ok here are pictures of two mags made into a dist. the first is on a cat D4 2 cyl pony engine. Its kinda hard to see what was done. the others are a 6 cyl Hercules on a welder. You see how I drilled a plug wire sized hole in the cap until I made contact with the brass that went from the original mag coil to the center carbon in the cap. and simply ran the coil wire from the delco 12 volt coil to there. there used to be a cover on that 6 cyl mag over the points. it was gone when I got the welder. I used a external condenser and ran the negative wire from the coil directly to the points. Way back in the 50'sMy dad had the mag on a one cyl engine on a david bradely walking tractor converted to use a 6 volt coil. had a battery box fixed to hold the battery. Said the extra weight of the battery gave it more traction. If your mag spins has a rotor and opens and closes a set of points it can be made to work. its not rocker science don't overthink it. mag coil 001.JPG mag coil 002.JPG mag coil 003.JPG mag coil 004.JPG mag coil 006.JPG mag coil 005.JPG
     
    Last edited: Jul 26, 2019
    RichFox likes this.
  26. PhredH
    Joined: Feb 28, 2015
    Posts: 103

    PhredH

    Thanks to all for this discussion. I first posted because I could not get my head around the distributor/crankshaft relationship.
    Rich summed things up well in post #23.
    Thank you again, the HAMB is a great place for knowledge.
    Peace, Phred
     
  27. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    Glad to help. Now the question is, Did Rusty get it?
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.