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Author Topic: What are the advantages of ECU-controlled spark advance control systems?  (Read 2956 times)

Offline sandy42011

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what are the advantages of ECU controlled spark advance control systems over conventional spark advance control systems?
« Last Edit: 14/06/2012 09:29:40 by chris »


 

Offline CliffordK

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Re: spark advance system
« Reply #1 on: 13/06/2012 22:09:29 »
Your classic engines use a statically set spark, usually set with a timing light at a certain speed.  Then advance the spark forward slightly based on either vacuum from the intake manifold, or centrifugal force based on the spinning inside the distributor, or perhaps a combination of the two.  It is a pretty crude, but generally effective.

My Fiat actually has points which are a bit of a pain.  One must always have a bit of sandpaper or a fingernail file around in case the points get burnt.  And, even the slightest change in the point gap will also change the timing.

The early electronic ignition systems dispensed with the points and achieved much higher reliability.  And, once the points were eliminated, one could set the timing based on a fixed rotation of the crank shaft, and also dispensing with the need for timing lights and twisting the distributor to adjust it.  It could all be pre-set, or pre-programmed.

This also allowed more advanced control of the spark.  So, rather than a rigid spark advance based on crude mechanical systems such as vacuum or centrifugal force, the spark could be tied directly into other engine parameters. 

Another point of failure was the distributor cap and rotor.  My old AMC used to burn up a distributor cap every 10K miles or so, perhaps because I was having troubles with the spark advance and had sprayed WD40 into the distributor.  Over time corrosion would build up in the distributor contacts.  If the spark is controlled electronically at the coil, then the circuitry to control which cylinder gets the spark can't be too complicated and more parts are simplified or eliminated. 

Fuel injection and Oxygen Sensor feedback loops also allowed more precise fuel control, and with the end result being a much cleaner burning engine with better fuel efficiency and lower smog.

However, there are a few trade-offs.  For example, Nitrogen Oxides tend to progress opposite to carbon monoxide and unburnt hydrocarbons, so some people complain about the engines being "detuned".

While reliability has certainly increased, and a "tune-up" is almost a thing of the past, the new systems are far more complicated.  So, in the past, one might think simply that an engine will run if it has fuel, compression, air, and spark.  On the new systems one has 100 sensors that can go out and throw off the engine.  Fortunately most of the sensors now have a self diagnostic that can tell them what is wrong.

Personally, I think manufacturers should work with "shade-tree mechanics".  With all the electronic gizmos, the engine should be able self diagnose, and tell one exactly what part is defective.  Perhaps offer a bypass/limp mode option.  Perhaps even tie into a replacement part number.  The ODBII readers are relatively cheap and a step towards this, but it could easily be built into the onboard computer & display systems.  Even if a person did not want to do the repairs themselves, this would help keep the mechanics honest.

One of the not so apparent changes is that due to both the increased complexity, and increased reliability of vehicles, service stations are all but a thing of the past, replaced by mini-marts.  Perhaps the very wide variety of tire sizes has also contributed to the downfall of service stations.

I remember one trip where I was loosing a wheel bearing, and I couldn't even buy grease at a gas station.  The best I could do was some Vaseline. 
 

Offline syhprum

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One of the features that model T Ford had was a separate  ignition coil for each spark plug this feature has found its way onto modern engines eliminating troublesome high voltage distributors a great improvement .
 

Offline Geezer

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One of the features that model T Ford had was a separate  ignition coil for each spark plug this feature has found its way onto modern engines eliminating troublesome high voltage distributors a great improvement .

They sometimes cheat and use one coil for two cylinders. Of course, that doesn't work too well if you happen to have a five cylinder engine!
 

Offline CliffordK

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One of the features that model T Ford had was a separate  ignition coil for each spark plug this feature has found its way onto modern engines eliminating troublesome high voltage distributors a great improvement .
They sometimes cheat and use one coil for two cylinders. Of course, that doesn't work too well if you happen to have a five cylinder engine!
Actually, the 123 Electronic Ignition kit for the Fiat 500 does that.

It has 2 cylinders with a 4-stroke engine.  Both pistons go up and down at the same time.

So it sparks both cylinders at the same time, hitting a spark on both cylinders on every stroke.  So, one will be sparking just before TDC of the compression stroke, and the other will be sparking during the exhaust stroke.
 

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