Hotter Ignition + Wider Plug Gap
 

The previous owner of this truck put in multipronged platinums. I plan on replacing them with standard coppers to get rid of a slight miss at idle. While Im at it Im wondering if replacing the OE coil with a hotter coil (which would allow me to gap the plugs wider) would result in better fuel economy?

a friend of mine did this experiment on his truck. he got the best gains buy using taylor wires with a hotter coil and making a huge gap increase on his truck. i think he went from like .034 to .055. ended up with a 1-2 mpg increase overall.

1-2mpg on a truck is probably a pretty large gain for such a small change in equipment. I wonder what compromises caused the engineers not to design it that way in the first place?

my s10 has a .060 gap from the factory...

are you sure its because of the components or the fact that thier new?

id imagine it would do something especially the taylor wires (great wires).

altho i wouldnt mind seeing what happens if someone wants to do this.

i could replace my coil packs (still stock) and wires (been changed twice)

On my Buick, I run cold plugs with a tight gap (0.028") for nitrous. In non-nitrous situations, I used to put in a set of plugs with 0.040" gap and 2-3 heat ranges higher, but I found no appreciable difference in any aspect of engine performance in the hotter plugs. (Yes, I have a very strong coil)

-Bob C.

EDIT: That's not to say that it won't help in other situations, I have a pretty unique engine...

when he did the experiment he tried a number of different configurations. it all started with the jacobs mileage master system (which produced no gains) and it lead to his latest setup. it basically gave him some ideas. i know he went through a few sets of wires before he settled on the taylors. the mileage master gave him the idea to run a huge gap. it didnt work on the kit but he saw gains when combined with the msd coil and different wires. the jacobs coil did nothing so he switched to the msd. i believe he tried an accel coil at some point and said it didnt do enough.
im sure his original setup was worn but it was only after he tried multiple combos when he came up with his winning combo. it took him a number of weeks and plenty of item returns to get it down.

Thanks for the input folks. The coil pack is on the way so Ill soon know for sure.

If it helps I had a miss at idle too on my car and shutting the gaps down from 1.5mm to 1.1mm smoothed it out completely.
Locally built version of Chevrolet 3.8 V6 with electronic ignition.

Another thought is the gaps enlarge as the vehicle travels anyway.

Pete.

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 think the manufacturers recomend a slightly smaller than optimum plug gap because the plugs will still fire and work when other components are wearing down. If you keep the ignition and electrical systems in top shape, you should be able to run bigger gaps.

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?

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

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.

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

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.

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

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

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.

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.

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.

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!

funny u should mention that

since im restoreing a model A i love anything article wise dealing with em. a guy found a ford stamped 2 plug per cylinder head for it

also when i removed the head off my engine there was one plug that had two grounding prongs towards the electrode... goes to show you that has been done repeated times over;)

I had a '75 Chevy sportvan with a 4bbl 350, and in my quest for better mileage, I got Taylor wires, and an MSD coil. I opened the gap (at night) in increments until I could see the spark arcing to the heads, then I closed them again until the arcing stopped. I also indexed them. I got 21-23 mpg in that thing with all of it's huge windows.
My friend just got rid of an old Firetruck that had a V-12 with 2 plugs/ cyl. 24 plugs!

My Father-in-law had a Datsun or a Nissan pu truck, must be about 15 or so years ago, that had two plugs per cylinder.

Dave

The Civic Hybrid uses 2 plugs per cylinder as does a few Mercedes and all new HEMI engines.

Not all engines had both of them in the cylinder though. Some of them just had a plug in the exhaust that was there to fire in the middle of the exhaust stroke for emissions.

I was messing around over the summer, testing my battery. I disconnected all my wires to see what the bat's voltage dropped to over a long crank. my coil pack was throwing 3 in. arcs that were visible in the day (shade). At the same time i checked my wires resistance, and found that one was bad. there is a break in the conductor somewhere, but it's arcing inside the wire somewhere and works fine (It's on my list of things i should buy, still).

I was thinking, if it could through a arc that long, why even have a gap. if the plug didn't have the ground thing the ark would jump much further (it would be sweet if it jumped to the piston) This might be really bad for my coil pack, which i can't afford to replace right now, so i haven't played with this yet.

I really can't see why fancy wires would do anything. It's just a wire, as long as it has a good insulator and a conductor. And at 10kV or so, a damp piece of twine would be a fine conductor.

The plug gap has to be smaller because it's harder for the spark to jump the gap in the cylinder when there is air/fuel mist present. It's harder for a spark to jump the gap when the air/fuel charge is more dense, which is why turbocharged cars tend to specify smaller plug gaps, such as .028" on my car or .024" on the Mitsubishi EVO. A general rule is to decrease the gap if you're engine is misfiring.

Plug wires need to conduct electricity and they also need to make sure the electrical charge goes down the wire and not into the surrounding metal parts. So it's a great conductor surrounded by a great insulator, which makes it slightly more expensive than damp twine.

As I was thinking about this topic last night when I should have been sleeping. I thought about how much harder it is on the disrtibutor cap & rotor, when you have a hotter coil, and increased gap. This is kind of troublesome for me, since they don't make my cap anymore. I don't know if I can back fill the Aluminum points.
About the wires, it was explained to me that the wires are designed to move the energy, by having the electrons in them already, or somesuch. I didn't understand it, fully, but it made sense at the time.

Really good insolation is key, but if you've ever taken a wire apart (or ripped one i half, as i have), the conductor is wimpy. Most have less wire than a standard 22gage wire.

I would think that compressed air (with out fuel) would be a better conductor, as there are more atoms therefore more electrons in the given gap. A vacuum is the greatest insulator, as there is nothing for electricity to flow through.

The gap width would change the temp of the arc. Greater resistance equals fewer amps, with the same voltage this means less power. Power(watts)=V*i(amps) and i(amps)=V/R
so a short gap would be hotter, if all else remained the same.

That's crazy that the EVO uses a .024" gap. My car has a very similar engine (with out the bells and wissles, oh or power) and it has a recommended .044 gap

Ok a few points you guys are missing . . . first the xB has coils on top of each plug with no wires between it and the plug so it is burried in the head pretty well and only fires when the ECU tells it to on the power-compression stroke. You should have had some free power if there was propane in the air - it would add to the fuel and result in some fuel trimming if it was there long enough.

As far as larger spark gap it works like this. The bigger the gap the higher the voltage needed to jump the gap. If you make the gap twice as big you can spark with twice the energy making it ignite the A/F mixture better in the case of lean mixtures. This assumes that the voltage doubles and the current stays the same which may or may not happen since the energy of the spark is determined by the coil and the magnetic field that is collapsing to make the spark. The coil only holds so much energy but put in a high output coil and you have it. Caps and rotors have to pass the energy to the correct plug and usually that is more a problem with higher output coils and larger plug gaps since the current and voltage increases but usually they can handle it easily until the damp day comes along or the inside of your cap gets some carbon buildup in it. Spark gap is where the performance happens more than any where else - bigger gap helps to ignite the fuel under load or at idle as long as the coil can provide the voltage to jump the gap. Iridium plugs with the thinner center electrode help make the spark jump at lower voltage because of the e-field is higher on a smaller tipped electrode (a sharp point is ideal) and it is made out of platium or iridium to withstand the higher more intense spark temperatures so they will last longer. MSD Multiple Spark Discharge helps because it will spark multiple times to better ignite the fuel and can be more intense (more current) and remember the A/F mixture is swirling around in the cylinder head.
Higher pressure makes it harder for the plug to spark and high vacuum makes it easier up to a point then as there is less and less molecules of gas to ionize it gets harder to spark - neon lights have a partial vacuum so they light up so if they leak a little air back in they will fail to light up.
Dual plugs were an option and an easy modification on BMW Boxer engines and were done to cause a double flame front to ignite the fuel faster. This allowed less timing advance in high compression engines to reduce spark knock but gave a faster burn to get more power. There really is no need in todays car engines.
Spark plug wires, for those out you who still have them, have to insulate the high voltage and carry the high currents that the coil puts out. The high current is only short in duration but is still present. The wire also tends to generate some e-fields making radio and TV noise so strands of fiberglass (I think) coated with carbon dust were used to reduce the radiation that it generates. Fiberglass was used probably to prevent the wires from stretching.

UPDATE -

New coil pack finally arrived. Installed a regapped the now one week old copper plugs to .060in (from .044in). Although the idle is smoother, no FE or power improvements jumped out at me. Ill monitor the averages the next few days to know for sure, however.

https://www.shopatron.com/products/pr...24.0.0.0.0.0.0
found msg coils for a saturns

https://www.taylorvertex.com/

but no taylor wires for a saturn :( what's comparable to taylor?

im awesome like this

just got this advice on saturnfans(this advice is for saturn, maybe other cars..)

Stay with stock coils or you will be very sorry and out about 100.00. As for wires Magnecor makes a 7mm direct fit wire set that functions just fine and should last for a good while. https://www.magnecor.com/magnecor1/main.htm Get the part number for the set you want and then do a search for a discount. The 7mm set is a 60 or so list and it can be found for 40 or so if you look.

btw the guys there are extremely intelligent when it comes to fixing cars

UPDATE -

Two things I have noticed.

1) FE is improved in low RPM with moderate throttle. For example at 35mph in 5th gear up a hill... This suggests incomplete fuel burning with the stock ignition under low RPM load.

No other times has a FE increase been noted.

2) The engine gets hotter quicker sitting still. Generally with the ambient temps low like they have been, the truck would sit at 205F or so at the stop lights around here. However, since the hotter coil, the temps have been reaching the 220-225F area. This could be counter productive in the summer months if it means having to turn on the E-fan to bring the temps back down.


Eagle - If you don't upgrade the rest of your ignition system, the house brand wires at any auto parts house are a much better option. You'll never see FE savings return from buying expensive wires.

Re: Hotter Ignition + Wider Plug Gap
 

Can anyone provide suggestions on how to upgrade to a "hotter" coil ? I have a 94 Geo Metro XFI 3cyl. we are trying to figure out why I am seeing a nearly 8-10mpg drop on E10 compared to E0 one of the thoughts going around is the car is not "sparking" hot enough to properly light the E10 blended fuel so fuel economy suffers much more than normal.

So how would I go about finding or getting a "hotter" coil that will plug into my metro?

any help would be greatly appreciated !

Re: Hotter Ignition + Wider Plug Gap
 

You should try advancing the timing by a couple degrees before buying anything. Also check the condition of the plugs, wires, coil and the wires that feed the coil. Older cars from wet climates tend to build up corrosion on electrical terminals and plugs.

Re: Hotter Ignition + Wider Plug Gap
 

we have checked EVERYTHING we can think of. Brand new complete tune up. I changed out everything including the O2 sensor.

Seafoamed everything. ripped out the EGR and cleaned the crap out of it including the ports in the block and put it back together.

One of the things we came up with was a Hybrid SUV that also got 30% reduction of FE on E10 the dealer fixed it by correcting the computer programming to a proper "hotter spark" to properly light the ethanol blend.

So we are thinking ok lets try that with my cars and "see what happens"

the car runs GREAT. smooth clean no issues or complaints. E10 46mpg E0 55mpg (my FE got better as the weather got hotter but the 8-9mpg separation continued)

Compression is good 185 all 3 (not bad for 150,000 miles)

The timing is advanced as far as I can without damaging the car (5') so I can't advance it anymore without modifications.