Spark In Time On The Firing Line (1962) Pt 1

[Music] today we're going to take a look inside the modern motorc car because because the ch I spark plug company would like to present a spark in time on the firing [Music] line first if we can get the car engine out where we can all see it I mean see inside the engine a cutaway thank you we can now see a basic purpose of the ignition system that of producing the spark spark please that ignites the fuel charge in the combustion chamber once more please the ignition system must also time this spark accurately making sure that each piston is pushed down at just the right moment to get maximum power and efficiency now this appears to be a pretty simple assignment but the job keeps getting tougher as demands increase for engines with more and more power faster able to handle long stretches of turn bike driving at high speeds pulling heavier and heavier [Music] loads yet operating economically and really reliably all this means that with higher engine compression ratios it requires higher voltages to push a spark through greater extremes of pressure and today's high compression engines must operate through a tremendous range of temperatures from the melting heat of a Long Mountain pull to Subzero winter starting 12,000 Sparks must be triggered for each mile an 8 cylinder car travels this means that at high speeds each spark buug must work perfectly up to 40 times each second too fast to see in its machine gun rapidity and each one of these Sparks must be Precision timed to an unvarying tolerance of 1 10,000th of a second no wonder that to get the full efficiency designed into our modern engines ignition systems must be maintained and serviced properly with good modern equipment backed up by adequate knowledge what's more all components of the ignition system must be of top quality not only the spark plugs which operate under great extremes of voltage temperature and pressure in a kment but all the parts which work to supply the plugs with their sparking voltage for the spark plug doesn't make the electricity that's the job of the rest of the ignition system hey what are you oh you're getting the ignition parts out so you can arrange them in a simple diagram the battery is the source of electricity in practically All Automotive ignition systems to make a circuit we need a electricity to its destination and a return path to complete the circuit to simplify wiring connections are grounded to the engine or frame and this can always be a assumed even though it isn't shown of course this circuit will not work since car batteries have 6 or 12 volts available while a minimum pressure of about 5,000 volts is required to push a spark across the spark plug gap that is why the ignition coil is so important it has the job of taking the low battery voltage and transforming it into high voltage high enough to spark across the Gap to make it work a switch device is needed in the low voltage or primary circuit when it is on the low voltage flows through the primary windings in the coil building up a magnetic field when the current is Switched Off This magnetic field collapses cutting across the secondary coil windings this action builds a high voltage in the secondary whatever is needed up to 30,000 volts to jump the spark gap of course this all happens extremely fast and many times each second switching the low voltage circuit on and off is part of the job of the distributor which contains all the mechanically moving parts of the ignition system hooked into the low voltage circuit the breaker points make and break the primary current a timing switch which is synchronized to the engine's Rotation by this revolving cam to eliminate arcing across the breaker points as they open a condenser is added which serves as an electronic spring or shock absorber soaking up unneeded current this also helps the magnetic field collapse more rapidly here now is a workable ignition system for a one cylinder engine but most engines have four six or eight cylinders we'll make it four in this case to keep it simple so we need four plugs each to be fired at a different time time in proper sequence this is the function of the distributor that of Distributing the high voltage from the coil to the right plug at the correct moment the lead from the coil goes into the center of the cap connecting to a rotor which directs the high voltage to each plug in its turn since each spark plug fires every other engine revolution in a four cycle engine the rotor and cam turn at 1/2 engine speed to spread the power impulses evenly each engine is designed with a definite firing sequence the rotor fires the plugs in this 1 3 4 2 sequence for instance in most four- cylinder engines and of course each plug must reliably get the fire going 7 to 40 times each second while fighting off punishing pressure blows searing blasts of heat corrosive burning gases and other corrosive deposits which try to short out the high voltage charges and prevent them from jumping the Gap all right no Guillotines a spark plug leads a tough enough life as it is without overdoing it and it's certainly no wonder with all of the extreme conditions under which spark plugs must do their job that spark plug people must spend so much time developing special electrode Alloys which will stand up under electrical erosion chemical corrosion and heat attack seals which hold permanently and prevent leakage from extreme pressures ceramic insulator materials which can withand heat shock and high voltages while conducting heat away from the firing tips and all the other features which give modern-day spark plugs their tremendous dependability and there must be many different kinds of plugs designed especially for different types of engines different sizes different heat ranges and a variety of special requirements and those who want the best in quality know when it's time to change their SP uh it's time to change the um subject speaking of timing the ignition system not only has to get the spark to the right cylinder but it must get it there precisely at the right instant to complete burning of the fuel charge just as the Piston has passed the top of its stroke and is starting down this timing will give the maximum power push from the expanding gases if ignition is timed too soon and the Piston is going up when it meets the power push coming down disagreement over Direction results and if ignition is timed too late the push power of the expanding gases is [Music] wasted all right Coffey braks over let's get back to work though the spark must be timed to the precisely right moment that moment isn't always the same so we'll make a simple graph to show when running at low speed how much time is taken up by the spark combustion and the push of expanding gases all of which take a fixed amount of time to occur this is slow down considerably of course when correctly timed sparking comes soon enough so that combustion is completed at or near the top of the Piston stroke top dead center it's called so the maximum power push coincides with a Piston's thrust downward it's the setting of when the points open that control spark timing since this opens the primary circuit so the magnetic field in the coil will collapse and build the sparking voltage in the secondary circuit moving the points changes the timing of when they're opened by the cam moving them too far against the Cam's direction of rotation will make them open sooner advancing spark timing to where power is lost retarding the spark timing too far also wastes power so correct basic ignition timing at idling speed is set with a timing light to get the maximum power push but what if we speed up the engine without changing the spark timing since it takes just as long for spark comb bution and power push to take place the faster the engine rotates the more the spark should be Advanced some means must be provided for changing the timing to suit different speeds and conditions an automatic spark Advance there are several ways of doing this each based on changing the relationship of the points and the cam by devices sensitive to the engine's [Music] performance the automatic spark Advance only only works as needed and doesn't affect basic timing which Remains the Same once it is set it's worth noting that Breaker Point spacing will affect timing each manufacturer specifies settings for what is known as cam or dwell angle the number of degrees of Cam rotation during which the points dwell or remain closed adjusting the points to a wider Gap decreases this dwell angle this advances the timing since the points open sooner and there isn't enough time for the primary circuit to build a good magnetic field in the coil narrowing the gap between the points increases the dwell angle and timing is since the points will open later if the points are too close together they carry too much current and tend to burn that's why careful setting this precise mechanism is so important to good ignition performance here now now is the working ignition system battery to store low voltage electricity coil to transform low voltage to high voltage breaker points to time the collapse of the coil's magnetic field with a condenser to help it collapse faster Advance mechanisms to adjust spark timing to conditions rotor to dispatch the high voltage to the correct cylinder and spark plugs to fire the fuel mixture and we should add an ignition switch for turning the system on and off and perhaps some sort of resistor in the primary circuit such as are used in many 12vt systems to cut down the voltage after permitting a higher voltage for starting these should be included if for no other reason than to remind us they too should be checked as possible culprits if the ignition system isn't working properly