“Hot” and “cold” spark plugs, heat rating

The driver does not have to understand everything that concerns his car. But some knowledge can save him from unnecessary expenses and save time. For example, if you know the heat rating of spark plugs, you can extend their service life. And save on buying new ones.

This is a value for each candle that shows in what heat range it can operate. It is necessary to know it. Since if the operating rules are not followed (working at a temperature that is too low or high relative to the heat rating), the candles will deteriorate. If this happens in the garage, then only replacement will be required. But on the road, such a breakdown will be even more expensive.

What are the differences between spark plugs?

In addition to the obvious parameters, there are also those that are invisible at first glance. But they can cause difficult starting, interruptions, or even quickly lead to failure of the internal combustion engine. What differences should you pay attention to?

Thread diameter and pitch - with inappropriate characteristics you will not be able to screw it into the cylinder head.
The height of the threaded part - if a short 12 mm spark plug does not cause harm with a short mileage (until the free turns of the threads in the cylinder head become overgrown with soot), then a long one (19 mm) can “kill” the engine when it meets the piston.
Heating number is one of the main parameters. Characterizes the thermal operating mode. Excessively “cold” spark plugs will not be cleaned and will become covered with soot, due to which the engine will become unstable. Hot ones will provoke detonation, up to glow ignition. Visually, you can distinguish by the thickness and length of the ceramic cone of the central electrode.
The seal is a crushable ring or a conical fit (depending on the design of the internal combustion engine).
Hexagon size - turnkey products are available from 13 to 25.4 mm. By installing larger ones, there is a chance that a “candlestick” with a larger diameter will not fit in the well.
The connection of the high-voltage wire is a thread for a nut (obsolete type) or a tip of the SAE standard. If you have an old motorcycle, don't worry. For most products, the adapter is unscrewed.
The number and material of electrodes - there are both classic ones with one side, and various modifications - with bifurcated, two, three, and even four dischargers.

“Multi-spark” candles received their popular name from the visual effect when, at a high frequency of sparking, we notice many flashes between all electrodes. In fact, there is only one discharge, and it occurs along the shortest path. But due to the fact that the distance is almost the same, it alternately jumps between different contacts, creating the appearance of simultaneous sparks in all directions.

What is heat number

The heat number is a numerical value that expresses the period of time after which the spark plug is able to achieve glow ignition, which determines the level of compliance between the spark plug and the engine of a particular model. A large value of the heat number indicates the ability of the candle to heat up less, and a small value of the heat number indicates the opposite. Accordingly, the first type of heat rating designates a “cold” candle, the second - a “hot” one.

“Hot” or “cold” candles - which are better?

The right choice is those that comply with the vehicle manufacturer's recommendations. Conscious deviation in one direction or another is acceptable when the user clearly knows for what purpose this is being done.

For example, the car idles mostly in traffic jams or does not have time to warm up during short trips - the standard version will quickly become covered with soot, because will not self-clean. Therefore, we need “hotter” ones.

If the engine is operated under maximum load (auto racing, drifting, towing a heavy trailer), then in order to avoid local overheating and detonation, it is permissible to install a “cooler” kit.

The optimal temperature in the arrester area is 400-850 degrees Celsius. The more heavily loaded the internal combustion engine, the colder the spark plugs are needed. Recommendations for the same power unit in different versions (industrial, marine, automotive, racing) may differ.

When to use

It must be borne in mind that the operating conditions of the car engine are different - they depend on traffic on the roads, average speed, increased load, and seasons.
If you often get stuck in traffic jams, then install hotter spark plugs, and if you drive at high speeds, install colder ones. For long distances and high speeds, “cold” spark plugs are suitable, and for short distances, at low average speeds, “hot” spark plugs are suitable. The choice is influenced by the size of the engine; the larger its volume, the “colder” the spark plug. The same spark plug can be “cold” for one engine and “hot” for another. How much it will heat up during operation, and how it will give off heat, depends on the insulator material and the length of the thermal cone.

Spark plug markings

There is no single standard - the designation does not match between different manufacturers. In general, the number characterizes the time before glow (spontaneous) ignition occurs. The higher the value, the colder it is. The letter R (or Russian "Р") denotes built-in resistance to reduce radio interference.

The inscription on the insulator or housing encrypts the following data:

thread diameter and length, key size and seal type;
heat rating and heat cone protrusion;
material of the central electrode and the presence of a resistor;
dimensions, scope and design features;
interelectrode gap, type and number of electrodes.

Within the framework of this article, it is not possible to give an exhaustive description of the labeling of various manufacturing companies; for this, an entire book would have to be written. But Topdetal consultants have the necessary information and will help you choose spark plugs for your car, offering several brands to choose from in different price categories.

Correct selection

Standard spark plug geometry: 14-19-16. 14 mm is the diameter of the threaded part, 19 mm is its length, and 16 is the size of the upper nut for which the spark plug wrench is selected. There are also less common versions of spark plugs with other geometric dimensions - it all depends on the seat in the engine head provided by the engineers. It is important that the spark plugs exactly match the calculated geometry. Installing the first spark plug you come across may result in damage to the engine piston and a major overhaul.

But it is impossible to select spark plugs only by thread size, because many more characteristics need to be taken into account: spark gap, heat rating, electrode material and their number... Therefore, spark plugs are selected according to special catalogs of manufacturers: Denso, NGK, Bosch. Or by the OEM number of the original spark plugs: to do this, you need to find the spark plug (spark plug) on the car component diagrams.

Whose recommendations should you follow: the car manufacturer or the spark plugs? Ideally, they should coincide, but sometimes there are discrepancies. Perhaps, priority should be given to candle brands - they know the features of their products better and regularly release new models that might not have yet existed when the production of your car began.

But the automaker's key requirements cannot be ignored. For example, if the instructions for the car indicate only iridium or platinum spark plugs, you cannot install ordinary nickel spark plugs, even if they are suitable in terms of geometric parameters. After all, the coils and the entire ignition system are not designed for the higher voltage required by spark plugs with a thick electrode, and such savings will sooner or later backfire. The same goes for the number of electrodes. If the engineers provided multi-electrode spark plugs, then there was a reason for this - these are the spark plugs that you need to buy. Choose your spark plugs wisely, and you won’t have to put a spark plug in for the health of your engine.

Which candle manufacturer should I choose?

Preferences depend on budget, knowledge and requirements.

If you don’t want to delve into the intricacies of design and applicability, take the “original”. It was made by one of the “grandees” of the industry, and will definitely fit your car. This is the simplest, but most expensive option.
You trust only “top” manufacturers - Bosch, NGK, Champion, Denso are at your service. These companies supply original spare parts to the assembly lines of car factories.
Want to save money? A properly adjusted “civilian” engine will work no worse with Brisk, domestic ZAZS, inexpensive Finwhale or Lecar.

Imported devices

Imported SZ designations are applied by analogy with Russian ones , but using other alphanumeric characters, which can lead car owners into some confusion. Although, in order to simplify the choice, the packaging contains information about which vehicles they can be used on. In addition, the marking of imported devices can be deciphered using special replaceability tables. But let’s look at the samples most in demand among car owners in more detail. Let's take an example of the labeling of devices from leading brands.

Assortment of imported candles

NGK spark plugs

company (Japan) is called the leader in the production of SZ . Its products are recognized as being of the highest quality and reliability. NGK spark plugs are marked as follows:

domestic devices A 11 are an analogue of products B 4 H;
And 17 DVRs are replaced by BPR 6 ES.

The marking of NGK products is quite simple to decipher. In particular, B4H:

the letter symbol B specifies the diameter and pitch of the thread, in this case it is M14x1.25, other possible designations are A/C/D/J;
digital symbol 4 indicates the heat value - this indicator varies in the range 2-11;
the letter symbol H indicates the thread size (12.7mm).

Marking of NGK spark plugs The
designation BPR 6 ES indicates that this product is equipped with a standard thread, a projection insulator (P), a resistor (R), a heating coefficient of 6, a thread size of 17.5 mm (E), the symbol S indicates the individual properties of the product.

The presence of a number at the end (usually separated by a hyphen) indicates that the electrodes have a gap of this size.

Spark generators Bosch

Bosch products need no introduction . Let's say the article number WR 7DC has the following meaning:

symbol W – thread with standard parameters (14);
symbol R – the presence of a resistor that prevents interference;
digital symbol 7—heat value;
letter D—thread size (19mm);
the letter C is a copper alloy electrode, other possible designations are O (regular alloy), S (silver element), P (platinum).

Products marked WR 7DC are an analogue of domestic spark plugs A 17 DVR, which work with engines of VAZ cars.

Bosch spark plug markings

Czech Brisk devices

Since the 35th year of the last century, the company has been producing SZ, which are in constant demand among our motorists.

The article number on the candles of this manufacturer, for example, DOR 15 YC, has the following decoding :

the letter D denotes a “standard” size thread (1.25mm), oriented for wrench 14, with a body size of 19mm;
the letter symbol O indicates a special design of the product, made in accordance with ISO regulations;
the letter R indicates the presence of a resistor, and the symbol X indicates the ability of the electrode resistance to form carbon deposits;
the number 15 is a heat indicator that can vary in the range 8-19 (in this case, the index 13 is not indicated by the manufacturer);
the letter Y indicates a protruding arrester;
symbol C indicates a head electrode made of copper;
1 (mm) - gap at the electrodes.

Brisk candles

Beru devices

The manufacturer Beru (Germany) produces candles and other components of premium quality. Products are marked, for example, as 14 R-7 DU, which stands for:

14 – thread size (14×1.25mm);
R – there is a resistor;
7 – heat coefficient (interval 7-13);
D – thread size (19mm) with gasket-seal under the cone;
U – head electrode made of copper+nickel alloy.

Using another designation as an example - 14 F-7 DTUO - we will explain that the marking changes slightly: the values of SZ are standard, and the nut is smaller than the installation space (F), can only be used in “low-power” motors with a seal (T), the head element of the product strengthened (O).

Beru candles

Denso devices

This company labels its products as SK 16 PR-A 11, which stands for as follows:

S – head electrode with a diameter of 0.7 mm made of iridium, the electrode on the side is equipped with a platinum plate;
K - hexagon diameter;
16 - heat coefficient;
P – head electrode protruding 1.5 mm;
R – there is a resistor;
A is a parameter specifically for this modification of the SZ;
11 - gap size.

Please note that letter designations on Denso devices may vary depending on the product series.

Denso spark plugs

Champion devices

Products from this brand are labeled similarly to other candles . For example, the designation RN 9 BYC 4 is:

R - presence of a resistor (if the symbol E is indicated, the product is equipped with a screen, O-wire resistor);
N – standard thread size (10mm);
9 — heat value (interval 1-25);
BYC – head electrode made of copper with two side elements (products of the “standard” design are marked with the symbol A);
4 - gap at the electrodes.

Champion candles

Is it worth overpaying for iridium and platinum?

If a specific core material (platinum, iridium, copper) is recommended for your car, you will have to accept it (or shorten the replacement period). Whether it is necessary to engage in tuning, changing ordinary ones to “fashionable ones” - everyone decides for himself. A serviceable engine works great even on stock ones.

Trying to revive a problematic engine that is “eating” oil and overflowing fuel is applicable as a temporary measure. It is possible that one of the several side electrodes will have less deposits, but the thin central one will still produce a flash. And the faulty internal combustion engine will start.

Work period

The brand and modification of the spark plug affect the period of operation of the candles. For example, devices made of nickel will last approximately 30,000 km. Platinum products are used for a much longer period - approximately 80 thousand km.

Iridium products , depending on the design features of the electrodes, “live” both 70,000 and 120,000 km. The resistance of SZ is not affected by the metal used in their production.

Platinum/iridium electrodes are resistant to carbon deposits, so ignition of the working mixture occurs better.

How to change spark plugs and what to do when a spark plug thread is torn off

Maintenance comes down to a visual inspection (checking with a spark probe and gap with a feeler gauge) or preventive replacement according to the instructions for the car (in Soviet times there were also collapsible spark plugs) with a mileage of 20-60 thousand km.

Leaded gasoline, malfunctions of the cylinder-piston group and difficult conditions (congestion, increased loads) can reduce the life of the kit. At the same time, there are known cases of operation for more than 100,000 kilometers.

Some practical recommendations.

Replace only on a cold engine - tightened ones “from the heart” on a warm one will subsequently be difficult to unscrew.
You should not exceed the recommended tightening force - the threads are thin, and the block head is usually aluminum. For precise dosing of torque, a torque wrench is useful.
To make it easier to change next time, run a pencil along the threaded part - the graphite will not allow it to “stick” during operation.

If you overdo it and damage the thread, use a thread restoration kit with a “spring” or a screwdriver. If you have experience, you can do without removing the cylinder head - the repair will take less than an hour.

Number of electrodes for a spark plug

Today you can find single- and multi-electrode hot and cold spark plugs on sale.
Each of these varieties has certain advantages. Today, single-electrode spark plugs are used mainly with older engines, due to their short service life and instability in operation. Modern powerful high-performance engines use multi-electrode spark plugs, which can have up to four side electrodes. They are characterized by durability and stability in operation. We note a significant reduction in exhaust toxicity and reduction in fuel consumption when using such multi-electron spark plugs. Their only drawback is their high price, which leads to a significant increase in the cost of car maintenance and repair, especially when it is necessary to replace them with a set on a six or eight-cylinder engine.

Engine diagnostics based on spark plug condition

In addition to its direct function (sparking), it is an accurate diagnostic tool. By the nature of the deposit one can judge the quality of the air-fuel mixture and the state of the CPG:

sandy shade, uniform - normal appearance;
soot velvety - a rich mixture. Absent (white color) - depleted;
tracks on the cone - “breakdown”, indication for replacement;
black oily flakes - oil entering the combustion chamber;
erosion, melting, chipped ceramic parts are signs of detonation.

Timely monitoring of spark plugs will ensure reliable engine starting, stable power characteristics and fuel economy. Spend a few minutes on the ignition during maintenance - and the engine will delight you with trouble-free operation.

Ilya Ilmarin

Domestic devices

Russian spark generators for all types of transport comply with the international regulations ISO-MS-1919 , which allows their replacement with imported analogues in terms of key characteristics. In addition, labeling of products manufactured by Russian enterprises is provided for by regulation OST-37.003.081 . The markings of domestic devices should be deciphered using alphanumeric characters.

We read the designation of Russian SZ

So, the thread parameters on the body are indicated by the first letter symbol “A”, which hides the parameters M14x1.25 - the value that distinguishes “standard” type spark plugs. Marking of devices with the M symbol assumes thread parameters M18x1.5 (key for installation/disassembly 27).

The letter symbol is followed by a number indicating the heat indicator - the higher this value, the lower the temperature required to form a spark. The heat index of domestic candles is in the range of 8-26. The most common candlesticks are 11/14/17. SZ marking according to the heat value divides products into “cold”, installed on high-power motors or “hot”.

Marking of Russian candles

Let's look at an example of what values are included in the Russian-made SZ marking . Let's take a product marked with code A 17 DV - this is a candle with a classic thread, heat index 17, thread length (D) 9 mm (if this value is less, then the symbol is not affixed to the marking), symbol B usually denotes an insulator with a protruding thermal tip.

If the product marking contains the letter symbol P (A17 DVR), this means that the head electrode is equipped with a resistor that suppresses interference. The letter symbol M indicates the use of copper materials with high heat resistance, which contributes to the creation of the shell on the head element.

In the designation AU 17 DVRM, the letter symbol U indicates an increased hexagon size (16mm instead of 14). With an even larger hexagon size (19mm), the letter symbol M - AM 17 B is marked.

Examples of possible designations of domestic products with interpretation

A 11 is a basic product with an M14x1.25 thread, a 20.8mm hexagon, a heat index of 11, a thread length of 12.7mm, a non-protruding heat cone, without a resistor, a head electrode made of heat-resistant material.

A 11 R is an analogue of the previous sample, which has a built-in resistor.

Spark plug parameters

A 17 DV is a basic type product with an M14x1.25 thread, a 20.8mm hexagon, a heat value of 17, a thread size of 19mm, there is a thermal protruding cone, without a resistor, a head electrode made of a heat-resistant alloy.

A 17 DV-10 is a product similar to the previous sample (A 17 DV), which has an increased spark gap (0.7mm - in the basic design this value is 0.5mm).

AU 17 DVRM is a basic type element, thread M14x1.25, hexagon 16mm, heat value 17, thread size 19mm, a heat cone protrudes from the body, with a resistor and a head electrode in a heat-resistant shell made of copper alloy.

Causes of glow ignition and detonation

Glow ignition occurs when the insulator and electrode overheat, as a result of which the electrodes melt. Most often, the cause of overheating is incorrectly selected spark plugs, or rather, selected “hotter” ones than required. If the “correct” spark plugs are selected, then the reason must be sought in the power system; perhaps the reason lies there. For example, the mixture may be too lean due to an incorrect carburetor setting or malfunction of one of the sensors (on an internal combustion engine with gasoline injection), most often the mass air flow sensor. It would be a good idea to make sure that no foreign air is sucked into the intake manifold, and also check the valves and, if necessary, make adjustments, since an incorrectly set ignition timing can cause constant overheating of the spark plugs.

Detonation occurs due to a violation of the gap between the electrodes, when using gasoline with a low octane number, as well as in the case of early ignition. All of this can lead to cracking and chipping of the heat cone. For a piston group, detonation is much more dangerous and often causes pistons to burn out. Detonation manifests itself in the form of strong engine vibration, as well as regular “shots” from the exhaust pipe.