Non resistor spark plugs - Fuel Economy, Hypermiling, EcoModding News and Forum

EcoCivic · 09-02-2019, 04:23 PM

I have wondered about non resistor spark plugs for several years. Whether they could be used, what problems they could cause (if any), how big of a benefit there would be, etc. So I did a crude experiment where I modded a spark plug to a non resistor to see if the spark was stronger. Basically what I did is I twisted the top terminal off, drilled the resistor out, put a 1/2 inch long piece of 12 gauge wire in the ceramic to replace the resistor, and put the top back on. I then removed 2 coils from the engine, put a modded plug in 1 and a stock plug in the other, started the engine, and observed the spark.

What I noticed was that the spark produced by the modded plug was significantly stronger than the spark produced by the stock plug. I swapped the coils around to see if maybe one coil was stronger than the other, but the result was the same: The plug without the resistor produces a stronger spark. This makes since because by definition, a resistor reduces the voltage and current available to produce a spark. Here is a video of the test I did.

https://www.youtube.com/watch?v=cqBizaZ8gCg

Just for the heck of it, I put the modded plug in and drove it around for a month. No problems. The engine still ran great, and there was no interference with the radio or any of the car's electronics.

I then took it a step further and decided to get a set of non resistor spark plugs. I would have modded the other 3, but modding 1 plug took over an hour and I didn't have time or patience to do another 3.

However, finding non resistor spark plugs for my car proved to be quite difficult. I looked at NGK racing plugs, but I couldn't find one in the heat range I needed, so I looked at Nology spark plugs. I found that their D4YS spark plug was what I needed because it was the correct heat range and it was physically the same as the OEM spark plugs. Same size, same crush washer, same threads, etc, the only difference is that they have a silver tip and no resistor.

So I ordered a set of Nology D4YS Silver non resistor spark plugs, which cost me about $40 shipped. Once they arrived, I gapped them to OEM spec, installed them, and went for a drive. The car runs great! No problems whatsoever. The radio still works fine, all the electronics seem happy, and the engine runs smoothly. So I guess if there is any interference from these spark plugs nothing cares, which makes me wonder why they even use them. Maybe just because they are cheaper or some kind of FCC regulations or something?[\

2016 Versa · 09-02-2019, 04:35 PM

Lots of time years ago non resistor plugs would cause lots of interference in the radios in cars. Maybe with the advancements in electronics technology and in spark plug technology that's no longer true. I also remember when many cars came from the factory with only AM radios which were also more prone to interference.

EcoCivic · 09-02-2019, 04:43 PM

Quote:

Originally Posted by 2016 Versa

Lots of time years ago non resistor plugs would cause lots of interference in the radios in cars. Maybe with the advancements in electronics technology and in spark plug technology that's no longer true. I also remember when many cars came from the factory with only AM radios which were also more prone to interference.

Maybe that was also because the cars back then had spark plug wires that could act as antennas to radiate interference? My car has the coils right on the spark plugs, so no wires. I don't see how much interference could escape since the spark is contained in the sealed combustion chamber anyways.

Stubby79 · 09-02-2019, 04:55 PM

They're there for a reason...if you don't develop any problems, congrats...if you're not seeing an actual benefit (in the form of increased MPG), then I suggest sticking to what the manufacturer originally put in there.

Potential reasons not to...
RFI.
More current = over heated coil.
More current = melted spark plug electrode.
Potentially messing with spark timing, leading to better or worse gas mileage and/or higher emissions.

Despite all that, I'll be interested in seeing your results. My attempts, in my youth, at using high end plugs and "racing" plug wires resulted in worse gas mileage.

Stubby79 · 09-02-2019, 04:56 PM

Quote:

Originally Posted by EcoCivic

I din't see how much interference could escape since the spark is contained in the sealed combustion chamber anyways.

Oh dear...I'm leaving now.

EcoCivic · 09-02-2019, 05:19 PM

Quote:

Originally Posted by Stubby79

They're there for a reason...if you don't develop any problems, congrats...if you're not seeing an actual benefit (in the form of increased MPG), then I suggest sticking to what the manufacturer originally put in there.

Potential reasons not to...
RFI.
More current = over heated coil.
More current = melted spark plug electrode.
Potentially messing with spark timing, leading to better or worse gas mileage and/or higher emissions.

Despite all that, I'll be interested in seeing your results. My attempts, in my youth, at using high end plugs and "racing" plug wires resulted in worse gas mileage.

Great points, thanks. I don't expect to have a problem with the spark plugs because they are designed to not have a resistor and have a silver tip, but I wondered about possibly causing a problem with the coils by using these spark plugs. But the other side of that argument is that this may be easier on the coils because they won't have to work as hard or produce as much voltage to jump the gap with less resistance.

Do you think it's possible that the interference from these spark plugs could damage something over time, even though nothing seems to care at the moment? Or is it more likely that the electronics will simply not work correctly?

Gasoline Fumes · 09-02-2019, 09:52 PM

I had non-resistor plugs and I made non-resistor wires for my carbureted 1984 Civic Wagon. Other than making lines on a TV from about 100 feet away, I didn't notice any difference. I also did not track my MPG with that car. Does a stronger spark make any difference if you're not having any misfires?

EcoCivic · 09-02-2019, 10:00 PM

Quote:

Originally Posted by Gasoline Fumes

I had non-resistor plugs and I made non-resistor wires for my carbureted 1984 Civic Wagon. Other than making lines on a TV from about 100 feet away, I didn't notice any difference. I also did not track my MPG with that car. Does a stronger spark make any difference if you're not having any misfires?

Interesting, thank you. And yes, a stronger spark can improve performance and efficiency, even if you don't have a misfire. The reason is because a larger, stronger spark will ignite more air and fuel at once, which means faster flame propagation. This is more important at higher RPMs where there isn't as much time for the air/fuel mix to combust, but yes it can make a difference.