"reactive" - sorry to bring this up again.

[Briz]

We're starting on a new build bike to run in 2014. It'll be a 50s BSA and running in vintage class - A-VBF or A-VBG.
The rules on ignition advise against 'electronic reactive ignition systems'.
I have searched the site and read previous questions on this, but cant find a definitive answer as to what exactly is meant by 'reactive'
It'd be great to have this nailed down; who wrote this rule? can that person enlighten us? It isn't -as far as I know- a term that means anything specific in relation to ignition systems.

[donpearsall]

I have never heard of an Electronic Reactive Ignition either. I am betting it was a typo and they really meant Electronic Reluctance which is the early breaker-less ignition system that uses a rotor and a stator for timing.

I would be interested to know what a reactive ignition is too, if there really is such a thing.

Don

[Buickguy3]

  Look at the discussion about this in the V4-F engines in the roadsters. Even the tech people seem to be at odds about what they mean V-S what the rules say.
    Doug 

[panic]

JM2¢?
Reactive means "adjusts automatically to feedback such as knock sensor".

[NathanStewart]

No, it's not a typo.  Reactive is what they meant but I'm not sure there's a universally accepted understanding of what "reactive" really means (or what it doesn't mean). 

I seems that people closely associate "reactive" with "feedback" or "feedback loop" and the only kind of ignition feedback that I'm aware of is for knock (as Panic points out).  I think what many people think "reactive" means is that if there's some kind of change beyond the expected, that a "reactive" ignition can account for this unexpected change and change the ignition timing accordingly.  That's not really "reactive"... that's what standard mapping is.  Or if that's what people really think "reactive" means then how is the expected change of inputs (ie the expected change in rpm or engine load) not "reactive" but an action that's the result of sensing an unexpected change (ie you normally make 5psi of boost but all of a sudden you're making 7psi of boost and the ignition knows to pull timing) is?  I'd argue that the ignition system had to "react" to the normal expected changes in engine speed and engine load in order to have any kind of change otherwise you'd have a single ignition timing value (locked timing - no advance/retard).

Briz, it's interesting that you bring this up because just last Friday I led the first part of a multi-part discussion on this subject at the last SCTA board meeting but my primary interest is vintage (auto) engines in vintage (car) bodies.  IMO, "reactive" is not really a good word to describe what it is that they're trying to keep out of the vintage class.  I think the general idea is to not allow computerized ignitions.  Instead of me listing a bunch of different ignitions that I think the rules are trying to prohibit, why don't you let us know what it is you plan on using and we'll see if it's "reactive" or not.  I believe that there's going to be some movement towards better defining what all this stuff means over the next year.

[Cereal KLR]

Sounds like the operative word here is "electronic".

Vintage class limited to magneto/distributor or battery/points/coil ?

[manta22]

I think Panic's definition is spot-on.

Regards, Neil  Tucson, AZ

[Briz]

Thanks for the input guys.
I'd really like not to have to run points! Hate 'em.
On my street BSA, I adapted stock evo HD stuff :

Which works really well. Whether that is considered computerised or not I dont know.
Alternatively, how about something like this:
http://www.ebay.co.uk/itm/130882195862?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

[NathanStewart]

What controls the timing of the spark?  Doesn't look like a centrifugal advance but it's hard to tell. 

[Briz]

No, not centrifugal. Is that likely to be the deciding factor?
I can see its a hard judgement to make, like (on a car) how about a points distributor running thru an MSD box? With a rev limiter? and then a boost-retard? where do you draw the line?
We're thinking of going blown methanol anyway so could get away with fixed advance. But we'll need a good fat spark and I really hate points!

[NathanStewart]

Yes, it really does come down to what's controlling the timing of the spark.  I don't think you have to run points as things like a Pertronix points replacement modules are allowed (on cars at least).  All the Pertronix does is turn the coil on and off - just like a set of points - but it still relys on the centrifugal advance mechanism for any kind of timing advance.  Seems like that magic black box might be responsible for controlling your timing and I don't know if that'll fly or not (I'm thinking not).  Personally, I think the worst case scenario for you would maybe mean running fixed timing.

The other part of the discussion I was mentioning before is to look into better drawing a more definitive line making it more clear (clearer?) as to what's allowed and what isn't.  If you'd like my opinion on what I think should be allowed feel free to shoot me a message.       

[V4F STR 60]

Oh my, here we go again...  

I'm not sure how the rules are written for bikes, but in V4 and V4F it clearly states that "any ignition may be used".  The board reinforced this definition when it refused a proposed rule change for 2013.  I have been assured that the rule will be interpretted as the rule book is written, until and/or if, the wording is changed.

As one who has used the word "reactive" in the past, it is one I regurgitated following a discussion with a few tech inspectors a couple of years ago.  Whether it is the right choice of words or not, I do not know, as I am just a dumb hick from Montana.  The context I have used it in is an attempt to describe a situation where an ignition box would "react" to a sensor on the engine, like a boost sensor, and then retard ignition accordingly.

 

[panic]

Vacuum spark, OEM for what, 80 years? is "reactive".

[V4F STR 60]

Vacuum spark, OEM for what, 80 years? is "reactive".

Exactly...   

[NathanStewart]

The context I have used it in is an attempt to describe a situation where an ignition box would "react" to a sensor on the engine, like a boost sensor, and then retard ignition accordingly.

What about the situation where an ignition box "reacts" to a sensor on the engine, like a crank position sensor (or even two of them), and then adjusts ignition according?  Isn't that "reactive" too?

Vacuum spark, OEM for what, 80 years? is "reactive".

Exactly...   

If a vacuum advance distributor is "reactive" to vacuum then a centrifugal advance distributor is "reactive" to engine speed, yes?

If this is what we think "reactive" means then I guess having a "non-reactive" ignition means that it can't react to anything (change in engine speed, change in load, etc).