General > General Technical Chat
Ignition systems
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Benta:

--- Quote from: SeanB on October 01, 2021, 02:52:31 pm ---Going to guess that is for multipulse ignition, for ultra lean operation, so you will have enough spark to ignite the fuel mix, even if the plug area is transiently non combustible, you have enough high energy sparks that the lean mix will strike before TDC and complete combustion to a large degree.

--- End quote ---

Interesting. Never heard of this before.
I know of multiple pulse direct injection (FSI, TSI, TFSI, whatever they like to call it), where only the immediate area around the spark plug has stoichiometric mix and the rest is lean.

Please give an example of a production engine that uses multipulse ignition.

LaserSteve:
Yes,

 We Ohioans love our Kettering, EE..  Except for his love of Tetraethyl Lead Additives..

Many of the buildings from his companies  still survive in Dayton...

Steve
bdunham7:

--- Quote from: Benta on October 01, 2021, 04:58:21 pm ---Please give an example of a production engine that uses multipulse ignition.

--- End quote ---

I've seen both Ford and BMW products that use multistrike.  Ford in particular has been using it for a decade-plus now.
james_s:

--- Quote from: langwadt on October 01, 2021, 04:40:36 pm ---sound like a story that gets better every time it is told, adding lots of spark energy isn't going to magically add sginificant power and running lean definitely isn't

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Lean burn is done for fuel economy, not power. It has been a common technique for decades, lean out the mixture as much as possible during light load when it is less likely to ping and the total heat energy is not enough to burn valves.
james_s:

--- Quote from: paulca on October 01, 2021, 09:09:53 am ---Was watching a video about Harley Davidsons.  They really are a pile of junk.  The engineering is many places is, well, really, really poor.  It's not even like they evolved and adapted with the times/tech, they don't/didn't.  And.... are now dieing.

They used a single crank pin for 2 pistons, not because that was a good choice, but because they couldn't be bothered to have two crank pins, balance the engine and have a sane firing interval.  They use a 45* firing interval as a result.  So BANG, BANG................ BANG BANG.  Then because they were cheap skates they decided that per-cylinger ignition was too much effort so they just fire both plugs.  This results in the BANG, BANG, POP.....  The POP is caused by the engine being so poorly made there is enough combustable exhaust gas in the exhaust strike to ignite!

With an unbalanced crank, the bike shakes violently when idleing.  So they mounted the engine on rubber.... with a cheap and nasty steel frame that flexed.  Resulting in many deaths caused by death wobble oscilations.  They added a counter balance (to fix the unbalanced pistons) such that the vibration of the unbalanced mass was forward/back, not up/down, hence the shaking.  The only saving grace is that when moving, some of that insane vibration is muted by the road motion.

I think the video making summed it up by saying, Harley's, you either get them or you don't.  I don't.

--- End quote ---


Yes, it's clear that you don't. They are not really my cup of tea either, but I do appreciate that they are one product that has had the sense to not mess with a successful formula. A modern Harley is very similar to one that was made 20, 40 or even more years ago and that is a great part of the appeal to people who buy them. I do love the sound personally, and I like the fact that it's essentially a slice of a radial engine. A friend of mine is a motorcycle enthusiast, he has several Japanese sport bikes, an electric bike and a Harley, he rides the latter the least, but he has said that riding it has a very manly feel and he loves it for a cruise on a nice day. It's an iconic vintage classic that you can still buy new.

If Harley changed their design to be more modern, they would lose what makes them unique and they would completely alienate their entire customer base while then trying to compete in a market that is saturated by other brands, it would be the dumbest move they could possibly make. They'd lose their existing customers and you still wouldn't buy one.
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