OT: an ignition problem.



Think some of the Maestro/Montego range used the same. Given how many problems dizzy caps and rotor arms give it seemed strange not to go the whole hog to twin coils and wasted spark.
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Probably saved 17p to keep the dizzy.
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Huge wrote:

A fair bit more than that in the early days - power transistors or triacs were fragile and expensive to do the sorts of 400V needful in either a CD or 'break the coil primary circuit' apps.
With the advent of mains SMPSs and power MOSFETS that's no longer the case.
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Dave Plowman (News) wrote:

I have never had a problem with either.
I had a tracking coil once. That is in fact the sum of all my non contact breaker/capacitor ignition problems on *anything* (except a case of recessed spark plugs where the recesses got full of water)..
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wrote:

Dealer supplied distributer caps and arms (Lucas) would run about 4 years or 400000 miles without showing significant corrosion. Replacements from a motor factors (CI) would have a lifespan less than half and deterioration in performance would be significant after 2 years. Trying to run them for much longer could lead to a breakdown, although you will have a thousand miles of rough running before it finally cops it. The single coil with distributer was continued with by Rover up to 2000 while other companies struggled with reliability issues of the split coil systems. During the mid 80's when the Naestro/Montego line was introduced, BL (or whatever) where looking to achieve very efficient running cars and the single coil with distributer has the edge. The 1.3 maestro was capable of 55mpg with outstanding acceleration for its size. 3rd gear acceleration from 20mph to 80mph in under 8 seconds, through 1st and 2nd I was able to out-accelerate an XR2 I doubt that would be possible with wasted spark ignition.
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On 26/01/2012 7:34 a.m., thirty-six wrote:

This is all very interesting to me - I didn't realize that distributors had been done away with. I suppose if I look inside the bonnet of our newest car (Toyota Corolla ca. 2006) I'll see that it doesn't have one.
I don't understand why wasted spark ignition should give less power.
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I don't believe it, never mind don't understand it.
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On 26/01/2012 11:22 a.m., Huge wrote:

I was being polite (for a change).
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It doesn't. It's a very common modification - I'm running EDIS on my old Rover, so no more distributor.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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In article

Why? Basically each (identical) coil has two outputs which are identical. They can go to either plug of that pair. So either they're all 'reverse polarity' or none are. There is no difference in the spark polarity or whatever intrinsic to wasted spark - indeed plenty motorbike engines used a conventional points system to achieve this As did the 2CV.

Where on earth did you get that from?

Modern engines use fancy plugs for a long life. Near 100,000 miles isn't uncommon. But the original basic design will work just fine with wasted spark, although EDIS is designed to use plugs with resistors built in.

Of course the ignition is mapped by the ECU. You can produce any spark timing you want using this - unlike a mechanical system which is constrained by springs and bob weights. Which often don't work well when new let alone after some miles and a bit of wear.
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wrote:

Are you sure on that, because as I see it under the description you give, the coil with the lower loading, which would be the cylinder not under compression would spark and soak off all the flux energy, while the compressed gas gave a resistance to sparking.

A three cylinder engine, yes that would truly be wasted.

Reversing the polarity of the low tension on an ignition coil and examining the sparking electrodes, the tip becomes pitted, evident after a few hundred miles.

That same mileage can be got from standard plugs with greater energy dispersion and a more efficient and faster combustion giving improved fuel economy and more torque.

Wow!
Erratic behaviour spuriously associated with mechanical advance is ill- founded. The faults leading to poor engine response may be disguised by electronic mapping. Electronic mapping may well be used to follow an imposed torque response to smooth out a poor engine (or other reasons), rather than let the well-built engine develop full torque and efficiency at the desired level. This disguises developing engine faults.
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Perhaps you forgot the sea salt and kelp powder.
MBQ
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thirty-six wrote:

sure, but why does a wasted spark reverse the polarity on the coils? you mist have no understanding of electricity to say that.

Mere hand waving. There is no evidence to support anything you say whatsoever.
Its sounds akin to gold plated 10Gigahertx braided litz wire speaker cables to me..

in other words not everybody wants the same thing out of an engine. Smoothness, economy and power as well as long service life are all to an extent antithetical.
Golly. even F1 engines have 'fuel save' versus 'overtaking' modes built it,.
So what on earth are you saying that everyone doesn't know already?
Nothing.

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wrote:

That was the design of the systems I studied at BTEC level 4. As far as understand it is inherent in the wasted spark system, of course there may have mbeen changes in the last 8 years which overcome the problem, but it seems it's all been hushed up.

Restricting the engines performance due to smoothing of the torque output by fudging the ignition, reduces the engine's efficiency, meaning lower gears are held longer. This in no way is a fuel save mode.

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In article

Could you go back to your case notes, or point at the textbooks it used?
I can't think of any reason why wasted spark should ever (have) require a reversed coil connection.

The Ford EDIS system I've referred to is much older than 8 years. Dates back to the last century. But wasted spark has been used long before that. And it's not much used today on car engines. It's beauty was it only required a crank signal. Full sequential requires a camshaft one too. As electronics have come down in price, most now use one coil per cylinder and a combined trigger from crank and cam.
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Dave Plowman (News) wrote:

For once I agree with you. Its arrant nonsense
The sparks are always of the same polarity. That's according to how they are wired up. The alternate spark only is a matter of time, not polarity.

I think its wuite ofetn used because... It's beauty was it only

..it avoids the cam trigger.. In teh end its a matter of cost and packaging. If you can do way with a cam sensor you save space and money. AND there is almost NO downside to firing the plug in the middle of the exhaust stroke on a 4 cylinder. I suspect it gets more complicated at 6 cylinders+ tho.

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Ford used EDIS on 4,6 and 8 cylinder engines. Maybe even more, for all I know. It might be a problem on an engine with an odd number of cylinders, though. ;-)
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On Thu, 26 Jan 2012 17:28:37 +0000, Dave Plowman (News) wrote:

... although it triggered a memory and prompted me to check the wikipedia entry for the Alfa twin-spark engines, which claims:
"As both plugs are connected to the same coil the spark one of them operates with reversed polarity and requires decreased breakdown voltage"
(http://en.wikipedia.org/wiki/Alfa_Romeo_Twin_Spark_engine)
... of course, it's Wikipedia, which doesn't make it right ;)
cheers
Jules
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Interesting. With EDIS, they are connected to the same 'coil' in as much it has just the one feed to it. But the two plug outputs aren't simply in parallel - there is a reading of 12K ohms between them, so I'd guess the coil has twin secondaries. Since it is likely an auto transformer, I suppose it could look like the outputs are in anti-phase. But the spark isn't a simple DC arc anyway, and I've never heard of one of the plugs from a pair wearing faster than the other, and it hasn't happened here even when using the original plugs designed for conventional ignition.
I'll see if I can find a schematic of the EDIS coil.
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wrote:

Isn't it?

That's because the dissipated energy is smaller so the effect isn't noticable by looking at the plugs, hence they "last forever". The smaller energy dissipation is noticable in how fast the flame front develops, the hotter and fatter the spark the faster the flame moves and the greater the available torque. I suppose one could use a lower energy output when torque demands are lower and at lower speed this may be beneficial in assisting a quiet running engine for creeping about town under the cover of darkness.

Just pulse it with a button cell and check for direction of needle deflection.
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