High-Tech Nitrous

I am currently involved in a thread about choosing the correct heat range plug. The thread has developed to the point where I want to talk about tuning and what the plug tells us in more depth. So I was going to post about the "Fuel Ring". Anyway, I had a small section on the site about plug reading, and had been collecting data for a few years, however I have never had the time to add this new data and present what I know. So I figure I can do that here in the blog section and later gather all my notes into a plug reading article. Here is part one, the "Fuel Ring". Remember this will be the rough draft, and may not contain everything the write-up will, or rather this blog may not be as in depth as it will be later.

Spark Plug "Fuel Ring"

The porcelain on the spark plug will have three sections that can be read, however, concerning racing and nitrous we will only be concerned with the third or deepest porcelain area which is our A/F ratio ring. Closet to the tip of the plug is the idle zone, and can be colored differently for various set-ups, however, we need not concern ourselves with this area. Though of note, if yours is grayish colored that means you drove back to the pits, not what we want, and more on that later. The middle section I like to call the cruise area, and again the racer/sprayer will not be concerned with  what it looks like, and you will understand why soon. The area we want to look at is the third and deepest area inside the plug-porcelain.

To understand the Fuel Ring, we must first see it. There are two ways to do this. First, a lighted magnifier of good quality can allow looking deep down inside the plug. The second method is best, and will leave no doubt in ones mind. It requires cutting the outside threaded jacket completely off the plug. This can be done with a Die Grinder or simply by using a hack saw. The picture below shows what a plug looks like minus the outer thread jacket.

Once viewable, we will see that the 1st and 2nd sections are cleaned off from the 1/4 run that was just made, and shutting down thereafter (remember lead paragraph and the grayish coloring?), then pulling the plugs immediately and installing replacements or towing back to the pits and pulling. The ring starts at the top and works it's way down, cleaning the 1st and 2nd sections as it reaches the point where the porcelain meets the jacket area.  It will get colored only at WOT and the Fuel Ring should be closest to where the porcelain meets the metal outer jacket area. Color is dependent on fuel type and brand. The picture looks to be VP as this fuel normally colors light gray. What ever the color, it should be shadow like. Making a couple to a few passes may be needed to set the Fuel Ring. There is another ring that sometimes comes into play.

We don't want to get the Fuel Ring mixed up with an oil ring. Some motors, and in particular the LSx platform, can ingest oil and have an Oil Ring. This ring will look like a lightly oiled ring and will be right next to the metal jacket. this ring has nothing to do with reading or setting the A/F ratio. A loose nitrous motor with a lot of blow-by may be a culprit too.

Today we have a companion tuning tool for this Fuel Ring reading, and this is the Wide Band. They go hand in hand, IMO, tuning the correct A/F ratio for your car. I know your wondering why I haven't stated what your ratio should be. Well the reading and locating of the fuel ring is what we are looking for. Generally when the nitrous company says use this ratio or a tuner that ratio, its generally a safe A/F ratio that will keep most whom will not be reading their plugs safe. However, that will not always locate your fuel ring, so it's up to the end user to use all the tools they can to dial in what your car needs and likes. What we are finding with the LSx platform is they work at a higher Volumetric Efficiency with a leaner than normal A/F ratio, compared to motors of past.

Where the rule from the street/strip vendors may be 11.2 to 11.5:1 A/F ratio, the LSx actually runs better with mid 12.X:1 A/F ratio, and some are even going leaner (at least those in the know). Think of it this way, why on earth would you run an overly rich nitrous hit when your N/A maximum power is made with a 13.2:1 A/F ratio. The reason the LSx can run leaner sprayed A/F ratios has to do with how good the cylinder heads are, or how good the breath. A stock LSx motor can easily reach the .450 Brake Specific Fuel Consumption (BSFC), and only fully built race motors a few years ago could attain a BSFC like this. Now we totally blueprint and balance our LSx and the VE goes even higher. The point here is this, what the vendors and nitrous companies recommend is not necessarily what our LSx will need or like; and the main reason we want to be able to read our plugs, so we can dial in the highest power and do it safely. Looking at the plugs along with recording our WB will allow getting our tune spot on. Once we can do this we can also move up in the size of the shot and do it with ultimate safety.

One other thing to look at while we have the jacket removed is the porcelain itself. It should have a chalky look as normal. If it has a shine that means things have got hot and melted the glass in the porcelain. Another glazing appears more glossy like and will have spots and may be caused by excess idling and/or incorrect A/F ratio. Both scenarios mean plug replacement is mandatory. Otherwise, shorting out during a run is possible and a resulting misfire. Ever wonder what one of the cause of ring lands lifting is, and why popping/backfiring out of the exhaust happens, yes, glazed porcelains in the answer.

In closing, this is the rough draft, and I will certainly be fine tuning and adding much more info on reading the plug and selecting the correct heat range in part 2 and what timing to run in part 3. Please if something doesn't make sense, let me know, or if something seems off let me know as this is written off the top of my head. We will compare to my notes and data later. Here is the picture of what we are looking for.

Robert