Spark Plugs

Spark Plug Basics: Click Here


NGK plug designations decoded:

Ex: BR7ES, BPR8EIX

Copper = ends in S
Iridium = ends in IX
P = Protruding (affects heat range, raises it a little)

7 is the stock heat range for the evo, anything higher is colder and anything lower is hotter; general rule of thumb on any spark plug is lower numbers are hotter then higher numbers

So transulating the examples:
BR7ES = non protruding, stock heat range (for the evo), copper
BPR8EIX = protruding, one step colder (a lil warmer then a BR8EIX though), iridium

Source: KLancer1997 (EvoM)

Reduce gap by .004" for every 50hp over stock.
Average rule of thumb is one step colder for every 100hp over stock.

iTune wrote:

You want to run the largest gap possible to properly expose the spark to the mixture. If you run too big, the spark with actually be blown out, causing misfires, if you run too small, the firing end temp increases, thus does the cylinder temps/pressures. Rule of thumb is to start larger and work your way down until you no longer have misfires. Trust me on this. All engines are different, the gap requirements will change from engine to engine, setup to setup.

Heat range will effect a lot as well, the colder the heat range, the more fouling becomes a problem, make sure your set-up warrants a colder heat range plug.

The non-protruding tip (BR7ES) plugs pull 50-200*F more from the combustion chamber than the protruding tips (BPR7ES). This equates to about half a step colder.

Eg. BPR7ES = stock heat range, BR7ES = 1/2 step colder, BPR8ES = 1 step colder.

READING THOSE SPARK PLUGS!


To read a plug, you must first prepare it properly for reading, so it will give you the real story. That means you can't just go over to an engine and yank the plug. You have to know how the machine was operated in the period just before you look at the plug, and the machine must be run in some steady condition for a while before taking the reading.

You can't just make a fast pass down a dirt road, then pull into the pits and let the engine idle for a while before shutting it off. This kind of a reading from a spark plug will be totally worthless. A plug can tell you only about a recent, sustained, single operating condition.

First off, the engine should be in reasonably good tune and mechanical condition, and the plug should also be in reasonable condition and the plug proper for the engine.

Then you can begin by making a flat-out, full- throttle run up a slight incline for about a mile. If you try that with a worn engine, or in bad tuning condition, it may not last the flat-out mile.


But if it does, at the end of your run, pull in the clutch and kill the ignition. Coast to a stop and don't run the engine anymore until you yank the plug. That is called cutting clean. What the plug will now tell you is how things were inside the engine at full throttle.

The best way to read the plug after removing it from the engine is to use an illuminated magnifier. With that, you can see small details and get more information. The average person just looks at the plug with his natural eyeballs and learns some things, but not as many things as with a magnifying glass.

The main indicator is the general appearance of the insulators. If it looks like it has been too hot ? it has. If it's showing some deposits, chances are it's too cold.

Now you're ready for a second plug reading, and this one should be taken at mid-throttle. The full-throttle test tells you about the condition in the combustion chamber while it was on the main jet, because that's what controls mixture strength at full throttle.

The half-throttle reading tells you about the needle and needle jet (or mid-range jets) performance, because they control that part of the engine performance. Most average tuners won't even perform this part of plug reading and tuning, and will be happy with full throttle runs and readings.





source: offroad.com

PLUG VARIATIONS

You'll find all kinds of plugs, plug materials, designs and variations. And you'll also find wild claims and promises to match. Most plugs have what is called the conventional gap style, and it doesn't have any letter identification. It is the common plug used in cars and motorcycles. There are zillions of these around, giving good service.

In the I-gap, the side electrode is cut back partially so it only coversabout half of the center electrode. This design is less subject to foulingdue to something getting between the electrodes. This is often considered to be a special design for two-stroke engines.

A Y-gap, or extended-nose plug, has a wider heat range than a conventional plug, which means it operates well over a greater range of temperatures. The insulator nose and gap will stick out pretty far into the combustion chamber when this plug is installed. Because of the extended nose, the tip of the plug is farther out into the combustion area and receives more heat at low engine speeds. This tends to prevent fouling at low operating temperatures.

At open throttle where you might expect this plug to heat up more than a conventional design, the extended nose gets a good blast of cool, fresh mixture during each intake and therefore it gets less hot than a conventional plug. This _ extends the operating range to higher engine temperatures. This is normally considered to be a four-stroke plug.

An extended-nose plug cannot be casually substituted for a conventional plug type, because the extended nose may get hit by the piston, or a valve. If it is specified as original equipment, you know there's enough clearance for the long nose.

A G-gap plug is also called a fine-wire plug, because the electrodes are made of smaller wire. A spark will jump at lower voltage across a gap formed of sharp edges or smaller electrodes. Both the I-gap and G-gap benefit from this. The J-gap ?shows" the center electrode the sharp edge of the side electrode and that gives a lower firing voltage requirement.

The Gold Palladium fine-wire design has the same advantage, because the electrodes are smaller. When the electrodes are made smaller, precious metals such as gold and platinum are better able to withstand heat and erosion. G-gap plugs cost more, but when properly used, they are worth it.

A surface-gap plug uses a completely different construction, with no side electrode at all. An insulator fills the space between center electrode and shell. The spark jumps from center electrode directly to the shell, taking any path it chooses. These plugs are for motor-cycles with super-high-voltage electronic ignition and should only be used where they were originally. specified by the manufacturer.


source: offroad.com

Manufacturer: Plug Number Example

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NGK: PFR6A-11

P - Type
F - Shell Size
R - Resistor
6 - Heat Range
A - Firing End Construction
11 - Gap

Heat Ranges:
5 - Hotter
6 - Normal
7 - Colder

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Denso: PK24PR-P11

PK - Type
20 - Heat Range
P - Insulator
R - Resistor
P - Electrode
11 - Gap

Heat Ranges:
22 - Hotter
24 - Normal
27 - Colder

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Bosch: FR7DCX

F - Type
R - Resistor
7 - Heat Range
D - Insulator
C - Electrode
X - Gap

Heat Ranges:
8 - Hotter
6/7 - Normal
5 - Colder

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Autolite: AP2545

AP - Type
25 - Plug Family
4 - Resistor
5 - Heat Range

Heat Ranges:
6 - Hotter
5 - Normal
4 - Colder



Source: TouringBubble

Alrighty ... a little research ...

The NGK LFR6A-11 or LFR6C-11 might work ... the difference is the firing end (A and C). I'm going to look in to the differences. The thread, reach, hex, resistor and heat range all match up.

The Denso K20HR-U11 will technically work, but it's not the correct heat range ... it's a 20 and stock equivalent is 22. We should really be using a 24 in a Denso plug.

part 2

Got a little info ... basically, don't trust the Advance spark plug numbers for the IX.

Replacement for a '06 Evo calls for an NGK PGR7A ... look that up on www.sparkplugs.com and you get an "OBSOLETE" return ... that plug was replaced with the BPR7EIX. That is the replacement plug for the VIII and the projected insulator design will not work in a IX.

So, the NGK options are ...
Iridium (stock replacement) - ILFR7H
Copper - LFR6A-11 and LFR6C-11 (one step hotter)

Or, the Denso K20HR-U11 which is still too hot for the car. We would need a K22HR, or better yet a K24HR for the correct heat range for mods.

Joey ... you should just run the NGK R7437-8 and change it out every 10k ... it's even the right heat range. =)

For reference ...
Recommended replacement plugs
Plugs that fit (Nevermind ... you'll have to check for yourself. 14mm thread, 26.5mm reach, 16mm (5/8 ) hex, and with resistor)
NGK Plug Number Explanation



part 3

Just noticed ... VIII plugs run at a 19mm reach and the IX plugs are at 26.5mm reach ... that's the big difference.

So, with the NGK "LF" plug, the "L" is an offset value ...

F = 14mm thread, 19mm reach, 16mm hex
L = 26.5mm reach

So, Joey, I gave you incorrect advice with the Autolite plug ... apparently companies other than NGK and Denso assume that the 19mm reach is fine.


source: TouringBubble