8 plugs, 4 cylinders ?

[Tomsmazdaranger]

I've heard a lot of answers to this so far and it sounds to me like there's a lot of guessing. Better horsepower and better fuel economy or animations better emissions. Okay but how? Is your firing slightly off or do they fire on different strokes as I've heard? I must say I find that one a little bit hard to believe.

 

[bobbywalter]

its secret squirrel stuff. you have to be a squirrel to understand.

 

[bobbywalter]

 

[StephenF]

What I have heard it is for better emissions mostly. I have a 2012 F-250 with the 6.2L. It also have 2 plugs per cylinder. Love the engine, but hate the extra cost of the plugs and wires, but at least it isn't an extra coil. I don't believe yours fires on both strokes, but I'm not an expert either.

 

[Ranger850]

My 87 Nissan D21 has 2 plugs per cylinder, The exhaust side takes a hotter plug. In my case, it's strictly emmisions. I've heard that some guys dont even run the wires for the exhuast side and just run it like that with no loss of power issues at all. I also have a Distributor and rotor set up, not coil paks.

 

[superj]

I had that engine in my 98 mazda pick up, i think. Usually the second set of plugs are after burner plugs for more complete ignition of the fuel/air charge allowing for (supposedly) more power.

My truck didn't feel any more powerful than the 4 plug Rangers we had as company trucks

 

[Tomsmazdaranger]

Thanks guys. I'm thinking that the second plug probably fires a little later than the first like an after burner. One thing that I am sure of is that this two spark plug design is s prone to cracked heads. I had a 1990 ranger that I thought had a blown head gasket. I first just replaced the gasket and this did not stop water from coming out the l exhaust and the engine overheating do I took the head to a machine shop for resurfacing and was told it was cracked.. the crack was in the number one cylinder between spark plug ports about a half an inch apart. So I bought a used head from the junkyard and took it to the machine shop for them to resurface and they told me showed me that this head was cracked and exact same spot. So iI bought a rebuilt head from a machine shop I put this in my truck and it worked fine for about 2 minutes and then started blowing water out the exhaust again. I assumed then that the block was cracked so I bought a rebuilt long block from AutoZone for like $1,700. I later tried to sell my rebuilt head to the machine shop and they showed me that it too was cracked in the exact same place as the other two Iin the number one cylinder between the spark plug ports. Anyway three failed heads all failed in the same place crack on the number one cylinder between the spark plug ports.hlThis head had been repaired or pinned which faile

right away. Seems like a design flaw to me.

 

[RonD]

OK, the real reason

Simply better power, period, in vehicles that is

If you are a pilot or know one that flys a piston engine aircraft then they can tell you why
Planes have dual spark plug engines, but for two reasons
First is reliability, better to have 2 separate spark systems, just in case, lol
But also better power
On take off BOTH spark systems are activated for best power, once cruising one spark system is shut off for safety, just in case, and on a longer flight they will switch over to other spark system, and go back and forth
And on landing BOTH spark systems are activated, for safety, losing the engine close to the ground is not for the faint of heart, gliding is highly over rated

So it has long been known that dual spark plugs make better power
Vehicles don't need the safety factor just the more power thing

Problem has always been how to do it with a single distributor
Look at this distributor cap: https://www.partsklassik.com/images/Product/large/2265.jpg
4cyl engine
You also need Dual coils
The rotor is setup so both spark plugs for say #1 get spark at the same time but each spark plug from its own coil

Porsche 911 cap here, 6cyl: https://www.123ignition.de/ignition/CustomUpload/374O357O340O338O356O369O350O321O365O335O/verteilerkappe-porsche-911-rs-st-rsr-doppelzuendung.jpg
And here: https://www.aasesales.com/cdn/shop/products/48_972b48a7-7327-41b1-89d5-e87418ad1953_2048x.jpg?v=1571438709

AMAZING stuff, lol, its for extra power, not emissions, MPG or anything else just POWER

Anyway, point being is that Dual spark plugs is better power, I mentioned that right?
So BOTH spark plugs fire at the same time or there would be NO POINT in having dual spark plugs in one cylinder
So disregard the "alternating" thing, obviously they hadn't thought it thru, i.e. what is the point of have dual spark plug and alternating them................so they last longer, lol

With the advent of distributorless spark systems the door was wide open for dual spark plugs, and Ford stepped thru it with the Lima engines

Head space is also an issue, and getting to a 2nd spark plug, V6s and V8s can be hard to machine for a 2nd plug thats easy to get too
Dodge did it on their Hemi's for a few years

But...............4 valves per cylinder, dual overhead cams, 2 intake valves, 2 exhaust valves per cylinder, NO they don't alternate, LMAO, sorry had to take the shot

So the 4 valves made even better power and a better use of head space so dual spark plugs fell out of favour..............except in airplanes


What Ford does use is Waste Spark, very first spark system even invented for gasoline engines
Its crank shaft timed, like magneto spark in your lawn mower, it sparks at every TDC
Much simpler system than cam timed like a distributor
So a spark plug fires once per RPM instead of once every 2 RPM, so a spark is "Wasted" on the exhaust stroke of a 4-stroke engine
But there is no pressure in the cylinder on the exhaust stroke so virtually no wear on the spark plug when it fires
In a Waste Spark system you should only use regular plugs, no coating, OR Double coating plugs, single coating will wear out same as no coating in 1/2 the cylinders

 

[bobbywalter]

i posted that video with scotty from the starship enterprise narrating for non squirrels........if you watch it. there should be no question as to wtf the deal is.