Hotter Ignition + Wider Plug Gap

[rgathright]

Originally Posted by DRW

I don't like multiple electrode plugs because they shroud the tip, keeping the fresh charge from reaching the plug gap. My personal favorites are iridium plugs because the electrodes are tapered and pointy. They're expensive though. ..

I agree.

From my work on flow benches, you want to expose the spark to the fuel mixture as much as possible to increase the chance of ignition.

Anyone know why they still do not put dual plugs per cylinder in car engines?

[theholycow]

Ford did it in the 2.3L 4 cylinder that was in Rangers (and probably other models). AFAIK it worked pretty well.

[FrugalFloyd]

Long distance mileage dropped about 2 mpg on one of my cars. I'd driven it about 5 years, so I pulled the plugs. Gaps were about .055. New plugs (standard ignition) brought the mileage back up.

On a 4 cylinder, there's one spark/engine revolution, right? The other three cylinders go for the ride (exhaust, intake, compression) until it's their turn to fire?

The reason I ask is because I was driving in Mexico, and as I entered a canyon, I saw a flagman on the opposite hill, waving an orange flag. As I rounded the corner, I came upon an upside-down propane tanker, with day-glo orange "PELIGRO" spray-painted on it. Next to it, another propane tanker was offloading the propane from the upside-down tanker. And there I was, sending 3000 sparks/minute into an invisible cloud of propane.

[bobc455]

Originally Posted by SentraSE-R

On a 4 cylinder, there's one spark/engine revolution, right? The other three cylinders go for the ride (exhaust, intake, compression) until it's their turn to fire?

Since each cylinder fires every other revolution, there are two sparks each revolution. The other two cylinders "go for a ride" for that revolution, then fire the next revolution.

-BC

[kit352]

on the note of spark plugs i found the best ones for mpgs are the cheapest copper ones i can find then i side gap them. talk about exposing the spark to the fuel. works well on race cars but your changing plugs very quickly at in them. on an mpg car i usually get around 30k out of them. on a hotted up race car a few thousand if im lucky. they dont work well with forced induction though. itll blow out the spark.

http://performanceunlimited.com/docu...degapping.html

[FrugalFloyd]

Originally Posted by bobc455

Since each cylinder fires every other revolution, there are two sparks each revolution. The other two cylinders "go for a ride" for that revolution, then fire the next revolution.

-BC

So I was sending 6000 sparks/minute into that cloud of propane? I'm lucky to be here to tell you about it.

[VetteOwner]

no u were sending 6000 sparks into your cylinders, your car misfires if it doesnt get spark (aka cracked plug wires)

if anything u shoulda had more power by the propane getting sucked into your intake haha.

[bobc455]

Well don't forget about the old trick to see if you need spark plug wires. Open your hood while the engine is running, and in complete darkness. If you see blue plasma or arcing (which is easiest to see in the dark and is most visible around the boots on each end of the wires), you need new wires.

(If you have a misfire in the rain, people spritz water onto the wires to check for arcing or misfire, but sometimes the problem also happens when the engine is dry)

So if your spark plug wires were junky, yes you might have been risking an explosion.

But if you idle at 750 RPM, you only have 1500 sparks per minute.

-Bob C.

[FrugalFloyd]

IIRC, I was soft-pedaling it past that truck. I was still very concerned about an accidental ignition, as I was a volunteer fireman, and our grain elevator in town burned down from a dust explosion and fire. We had to use specially built flashlights in grain elevators, and weren't allowed to use camera flashes there.

You guys are right, though. Combustion takes place in the cylinders, which is a fairly safe location. if your exhaust system is sealed very tightly, with no hot flash spots, and no backfires.

[GasSavers_JoeBob]

Originally Posted by rgathright

Anyone know why they still do not put dual plugs per cylinder in car engines?

Back in the '20s and early '30s, Rolls Royce and Nash both used engines with two plugs per cylinder. Nash did it to make a smoother running engine, RR may have done it since they used that on their airplane engines, and from what I have seen from Rolls Royces of that era, they were pretty obsessive-compulsive about the design of their cars.

Also, I saw some mention of a current Chrysler engine using two plugs per cylinder. Makes sense...Chrysler is the current owner of all the Nash trademarks and intellectual property.

Personally, I don't see much point for two plugs/cylinder in a non-aircraft engine. I like only having three plugs to change!