Ignition coil question

Steve Walker fired this volley in news:Lrydnd- jfMPkiQzOnZ2dnUVZ snipped-for-privacy@giganews.com:

Of course it should be! We're not talking about both cylinders going TDC at the same time, we're talking about timing relative to TDC on each.

Ignition "Timing" has never referred to which cylinder fires when, but when it fires relative to TDC.

Lloyd

Except it has a "controlox" instead of points and condensers - but the pickups can still be adjusted to set the timing. My STRONG suspicion is he can put in 2 identical coils (which he SHOULDdo,) and he will still have a timing issue

Sounds like a Ford Ranger or a Nissan??

Electronic ignition - and computerized timing advance on the only 2 2 plug per cyl automotive/light truck engines I'm aware of.

Combined with a digital delay. The spark timing and the pulse on the position sensor are 2 totally different points in time, with the actual ignition event timing being calculated by the microcomputer based on the input from intake air temperature, throttle position and/or Manifold Absolute Pressure and/or Mass Airflow sensor, plus coolant temperature sensor, and in some cases a transmission shift sensor (knowing what gear the engine is in) based on the crankshaft and/or camshaft sensor (which is not just a single signal at TDC.) In a lot of cases it's a 42 tooth "gear" with 2 teath missing, which allows the computer to calculate exactly where the crank is at all times after as few as 2 complete turns of the crank (1 complete firing cycle) They are COMPLETELY different than the old "integrated ignition" and "High Energy Ignition" and "duraspark" systems of old. A lot closer to Chrysler's old "lean burn" system in concept

snipped-for-privacy@snyder.on.ca fired this volley in news: snipped-for-privacy@4ax.com:

A lot of them tried it in prototype, and should have stuck with it.

Anyone who's flown knows the difference in power that occurs when you switch to just one plug. ALL ATC'd aircraft (with piston engines) have dual ignition circuits. In aircraft, they're totally independent -- absolutely NO common components between the two systems, and often they are magneto systems to simplify the system, and ensure ignition in the absense of DC power in the aircraft.

Lloyd

snipped-for-privacy@snyder.on.ca fired this volley in news: snipped-for-privacy@4ax.com:

Snicker! We're talking about a kid's two-cylinder MOTOSICLE! Not a friggin CAR!

LLoyd

Likely one is from a point ignition system with no ballast resistor (nominal 3.5 ohm) or with Ballast resistor (Nominal 1.5 ohm) and the other is from an electronic ignition unit (nominal .5 or 1 ohm depending on the system), or one is for with ballast and one without. On a point system he'd be frying points on the low resistance coil, while electronic ignition systems "generally" are more "agnostic" when it comes to coil resistance/current.

2 plug per cyl systems are a requirement on large bore engines to ensure all of the charge gets lit. On a small bore engine they are not required, and the ONLY reason for using them was emission compliance.

And as far as magnetos and reliability - there is a good reason they use two!!! Many "experimental" planes are using electronic ignition on at least one set, and there are STCs (Supplemental Type Certivicates) to allow installation of electronic ignitions (like lightspeed) on virtually ANY certified plane. With the electronic ignition systems you get more power and better fuel burn (lower fuel consumption) as well as generally easier starting, as well as better plug life, less fouling, - all advantages when an old "tractor engine" is all that's keeping your ass in the air.

Clare Snyder, Technical Director RAA (Recreational Aircraft Association) Canada

And some of todays "motorsicles" are more sophisticated in their engine management than many cars (They have to be to put out the power they do and still meet emission requirements)

I understand this is LIKELY some old beater of a bike with a relatively unsophisticated "points replacement" kettering electronic ignition - in which case the difference in coil resistance may cause problems but is quite unlikely to be the cause of a (measureable) timing error.

On a parallel twin they will fire exactly at the same time or exactly

180 or 360 degrees apart. The timing spec before or after TDC will be the same on both cyls UNLESS there is a cooling issue that woulds have one cyl a few degrees off to prevent heat related detonation issues and the like (like #3 cyl on the old beetle engine, which with the Bosch 009 distributor, had a 2 or 3 degree retard.

On a V twin, one cyl MAY be retarded for the same reason. The OP still has not indicated what make, model and vintage this "scoot" is - and without that information we are all just guessing.

If one fires too quickly after the other, there may not be sufficient time to build up the field for the second one.

I know that my wife's Mazda RX-2 (Wankel engone) had two distributors, two coils, and two spark plugs per rotor -- one near the leading edge and one near the trailing edge. At a guess, this was to ensure more complete combustion.

It made it fun trying to figure out how many cylinders for income tax purposes (when you got different mileage allowances depending on the number of cylinders. So to analyze it:

Actual number of cylinders: 0

Number of rotors: 2

Number of spark plugs: 4

Number of firing strokes per rev: 6 (three per rotor -- about equivalent to a V12).

So -- how many cylinders could I claim? :-)

Enjoy, DoN.

Depends on the *exact* wording of the law, but I bet that you can claim zero and cite the definition. For a parallel, look up the history of the mansard roof architecture of houses.

Joe Gwinn

I'm sure that I *could* have claimed zero without problems, but it would have been more to my benefit (at that time) to claim 8 or 12. There was a higher deduction for mileage with the larger number of cylinders. :-)

Claiming 4 would have been safe enough (and I think that is what I did), since I could say that I counted spark plugs. :-) But that would have been no better than claiming zero -- the borderline was between four and eight. :-)

Enjoy, DoN.

WE auto mechanics (and parts mfgrs) were all still calling them condensers in the late '80s, when I got out.

I wonder how critical that is in that application. I think I missed the OP.

Yes, ideally.

OK, Mr. Deep Pockets Shotgunner.

Would not be to your advantage to claim 0. The correct claim would be

1. In effect it is a 6 cyl 2 stroke engine. Horsepower and fuel economy to match.

As regards the need for matched coils

Before I ran out and bought matched coils, I would swap coils and see how that affects the timing. The coils may have nothing to do with the timing. Indeed I doubt if that the coils affect the timing.

Dan

So did old time Harley, :-) And BSA vertical twins too, if I recollect.

Gee, with the above qualifications there could also be all sort of "Coyote Quotes" attributed to "the Owner of Coyote Engineering".

Think of it. Fame!

Not quite up there with Lazarus Long, though.

David