The NGK (4929) DPR8EA is our pick for the best spark plug, which has ribs that are corrugated so that flashovers can be prevented. Corrosion is also out of the way due to the zinc dipped shell. The copper core is made with a solid construction so that the spark is good.
Our step-up pick is the NGK BKR7EIX Iridium and it can prevent leakage of gas from combustion with the use of the triple gasket seal. Moreover, it has anti-seizing and anti-corrosion features while the corrugated ribs on insulator can keep the flashover at bay while maintaining extreme ignitability.
The budget pick is the NGK (7222) BPR4ES and it is ideal for small engines, such as those with ATVs or all terrain vehicles, plus those with off-road motorcycles. It has a part number of 7222 and it has a spark plug socket requirement of 13/16 inches.
- 1 A Little Background
- 2 How we Picked
- 3 Our Pick
- 4 Flaws but Not Dealbrakers
- 5 Step-up Pick
- 6 Budget Pick
- 7 Best Spark Plug made of Iridium
- 8 Best Spark Plug made of Platinum
- 9 Best Spark Plug with a V-Power Center
- 10 Best Spark Plug for Small Engines
- 11 Best Spark Plug with Copper and Nickel
- 12 Best Spark Plug for Motorsports
- 13 Best Spark Plug with Laser Iridium
- 14 The Competition
- 15 Other Frequently Asked Questions
- 16 Wrapping It Up
A Little Background
The spark plug, also known as the ignition device that makes up the ignition system of your car or engine. It is an essential part of your engine that should be replaced when necessary. Do remember that when you don't have this ignition device working properly, you will have a hard start with your engine or car.
It is inevitable that you may need to replace the ignition device sooner or later so that your engine can be maintained as much as possible.
The ignition device can vary depending on the manufacturer of the car or engine and thus, can have various sizes, in terms of the thread size. The ignition device is usually measured in mm or millimeters in terms of its measurement.
You should consider the measurement on your engine and see if it matches the ignition device that you want to buy. This can make sure that it will fit well and you would have not wasted money in the long run.
The operation temperature of the ignition device can be from 500 degrees Celsius up to 800 degrees Celsius. This is why there are some cold and hot ignition devices. This can also dictate the durability and the suitable temperature of the ignition device. You should ask the manufacturer or seller if the ignition device that you want to buy would be something that is either a hot or cold device, as different ones can have a different configuration.
Common makers of ignition devices include Bosch, NGK, ACCEL, Denso and many more. Bosch and NGK are the most commonly used ones by a variety of engines, from motorcycles to cars, RVs, motorhomes, ATVs, lawn mowers and many more.
Different engines of various machinery can take a different kind of ignition device so you should be wary about what you install. The first thing you should know is if it can accept the ignition device of a specific brand or act as a replacement for it.
When you do look for your ignition device, you should know about the part number as dictated in the user's manual of your engine or car. The part number can range from 4 to 5 numbers and can vary depending on the manufacturer's specifications.
For instance, the NGK manufacturer usually has 4 digit part numbers for the ignition devices. If you cannot find the part number of your ignition device in the user's manual or don't have a user's manual, consider contacting the manufacturer of the ignition device or engine for reference depending on which is missing.
How we Picked
If you want to choose the best spark plug, you should consider the following:
Year, make and model of your vehicle: the ignition device should have an indication on where it will fit. For instance, Amazon prompts you to input the year, make and model of your motorcycle or vehicle so that you will not have to fiddle with return and exchange programs when a certain ignition device or part does not fit onto your vehicle or engine.
This makes the job easier - even buying a ignition device will require you to tell about these information to the sellers at a car shop or engine shop.
Part number indicated in your vehicle: whatever is indicated in your user's manual on your vehicle or engine, you should look it up and follow it when you are looking for a ignition device. Oftentimes, you can also find that a different part number may work in certain circumstances or one of a different brand. This means that your engine is quite universal and it will be easier for you to look for parts for it.
Size of the ignition device: usually measured in millimeters (mm), the ignition device should have measurements in this aspect so that you will know if it fits or not. Sometimes, this is the reason why certain part numbers of ignition device also fit into your engine even if it is not really the part number indicated in your user's manual, which can be useful.
Elements used: some ignition devices have various elements, such as copper, nickel and iridium. Usually, rarer elements like iridium can be pricier and are mostly intended for engines and vehicles that require a better power for starting and also for longevity and durability. Whereas, copper and nickel are much more common in terms of the rarity for the ignition device element.
As our top pick, the NGK (4929) DPR8EA can prevent flashover due to the corrugated style of the ribs. Moreover, a greater spark can be produced due to the core being made of solid copper material. What’s more, gas leakage can also be prevented due to the triple gasket sealing technique that has been used on this kind of ignition device. It is a great device for use in high speed riding.
The shell has been dipped in zinc so that corrosion will less likely happen to this device. Fouling will also be reduced due to the fact that it has been designed with a longer insulator core. It has a part number of 4929 and it is great for ATVs and off-road motorcycles.
It has a thread pitch of 12 mm by 1.25 mm. It will fit most models of Yamaha and Honda and will have good effects on the cylinder. It will also work on the Suzuki M50.
Flaws but Not Dealbrakers
While not a deal breaker, the NGK (4929) DPR8EA may not fit on certain vehicles, so you should input first your vehicle type and model.
The NGK BKR7EIX Iridium is our step-up pick, which has superior anti-fouling capabilities so that you are ensured of a smooth ride. Thanks to the extreme ignitability, it will be easy to ignite for supporting most high-performance engines of today that you may have. It also has anti-seizing properties and it can fight corrosion due to the construction. Because it is made of iridium, it has a high melting point so it can stay strong for the competition.
The iridium tip that gives it durability is of 0.6mm laser welded fine construction, which can give it durability as well. The electrical quenching effect is diminished due to this element. What’s more, gas leakage is also prevented due to the included triple gasket seal. Adding to the anti-corrosion properties would be the trivalent metal plating that is present in the device for superior protection. It has a part number of 2667 and it can also fit '99 Honda Civics.
The NGK (7222) BPR4ES is our budget pick, which has a 13/16 inch of spark plug socket that is required. It has a part number of 7222 and it is made for off-road motorcycles as well as ATVs. It can fit most brands like Kawasaki and it can also work on mower cylinders out there. If you have models like the Kawasaki FX600V and the Kawasaki FR691V twin, it will definitely fit.
It might also fit on the 6300 Yamaha generator and it is very easy to install. Also, the SS 88 motor can indeed work well with this kind of device. What’s more, it can also be a replacement for a RC12YC Champion brand. Also, if you have a Hustler Raptor Kawasaki engine then it can be a great replacement for the ignition component.
Best Spark Plug made of Iridium
The Bosch 9608 Double is made out of iridium material so that it does not compromise ignitability and performance and can give your engine up to 4X longer service so that you don’t have to maintain it all the time. The dual firing pin made of iridium as well as the inlay being made of a ground electrode makes it durable overall due to the corrosion resistant iridium with form and function that is sufficient for most gear and engines.
Additionally, the 360° continuous laser weld makes it easy to stay durable for the years to come. For a better performance, the fine wire firing pin, which is at 0.6 mm, also makes things better. It has a part number of 9608, there is no gapping needed and there is no anti-seize with this kind of device for ignition. Also, while quite similar to the OEM spark plugs, it has a warranty of 7 years.
Best Spark Plug made of Platinum
The Denso (4504) PK20TT is made out of platinum material, which makes it durable enough to stand up to extreme stress due to the great dielectric strength. What’s more, no matter what temperature it gets to, the thermal conductivity of this kind of product is super good. The ground electrode has been enhanced with a 11 mm titanium material as well for better durability and conductivity. If you have it, you can also get rid of a small stumble.
What’s more, if you install this in a car engine, it has the capability of saving you fuel with its fuel economy feature. And because you are saving up on fuel, a better acceleration can be achieved as well. Purified alumina powder insulator has been used for this kind of ignition device, with an OEN part number of DENS7 and manufacturer part number of PK20TT. It has a warranty for parts and labor.
Best Spark Plug with a V-Power Center
The NGK (3951) TR55 has a unique design of a v-power center that is an electrode at 45 degrees. It has a nickel tipped electrode for better longevity and a solid copper core so that it can be used for a very long time as compared to ordinary plugs. Electrical insulation has also been upgraded due to the transfer of the alumina ceramics when it comes down to heat.
Fuel economy can be saved due to the new and unique technology of the v-power center, which leads eventually to lower emissions and better savings for both you and the environment. The possibility of combustion gas leakage is greatly reduced due to the sealing process caused by the triple gasket design. What’s more, carbon buildup and pre-ignition can be avoided due to the design. It has a part number of TR55 and it will mostly work for the 2004 Silverado.
Best Spark Plug for Small Engines
The NGK (6703) BPMR7A is a great pick for small engines due to its design. It has an OEM part number of BPMR7A and it can prevent flashovers due to the ribs that have a corrugated design. Unlike old models of this device, this one has improved anti-fouling so that it can work well for different purposes. What’s more, it can withstand terrible temperatures due to the greater heat transfer.
There is also sufficient corrosion resistance with this device so that you don’t have to replace it more often. This device is also high in dielectric strength and it is coupled with features that can help you to eliminate combustion gas leakage with it. Your yard blower can start right up with this new device, if it needs some replacement. It can also work for most chainsaws, like the Stihl chainsaw.
Best Spark Plug with Copper and Nickel
The ZGR6STE2 Copper is a device that is a combination of copper and nickel in its design and construction. What’s more, there is a copper core center electrode that makes it of heavy duty in terms of its reliability. The core is also enhanced with yttrium element for added performance. Fuel economy is given while it can also potentially improve cold starts. The ground electrode made of chromium and nickel is bearing v-profile.
This device is also a 12-point design and most people will find it as an OEM replacement counterpart for the 2007 BMW 335i as well as the JB4 2008 335i. If you are looking for its OWM part number, it is 12120037244. It is also backed by a warranty for both parts and labor. Do note, however, that you are recommended to use one with an internal magnet when changing this for your original part.
Best Spark Plug for Motorsports
The Bosch 9600 Double is made for motorsports and cars, as it is made for pre-gapped replacement without losing function and durability. It has 4 times service life than others and it has a 360° continuous laser weld hat keeps the internal parts intact for a longer period of time. Moreover, the iridium firing pin is also well-protected from corrosion threats due to this covering and also due to the design of the ground electrode inlay.
For its OEM part number, it is 9600. This device also has no anti-seize and no gapping is needed. It has been proven to boost your engine HP and gas mileage and it can also be a replacement for your old ones to improve your engine’s longevity and performance. The pre-gapping means that it is super easy to install. There is a warranty of 7 years for this product for parts and labor.
Best Spark Plug with Laser Iridium
The NGK (5068) IFR8H-11 is a uniquely designed iridium made ignition device that is powered with laser iridium. Its included ground electrode provides long life and a better ignition capability alongside the center electrode trip which has been laser welded for quality design and durability. In addition to that, there is also a welded platinum disc for added longevity. A better heat transfer can be the enhancement of this ignition device due to the high alumina ceramics.
Electrical insulation is also provided at its best because of the nickel tipped electrode and the copper core that is solidly built. Additionally, the carbon buildup and pre-ignition characteristics of this laser iridium product. There is also a triple gasket sealing that keeps leakage off the bay. It can be ideal for ATVs or all terrain vehicles as well as off-road motorcycles out there, with an OEM part number of 5068.
There were other ignition devices that did not make it to our list because they lacked in durability and part number, and were unclear whether they would fit any engine or vehicle or not. It is also important that the ignition device is well-protected against hazards that often happen in an engine for it to last longer.
Other Frequently Asked Questions
Q: What are the different parts of a ignition device?
A: The ignition device has the following parts:
This is also called the terminal, and is the part of the ignition device that is attached to the wire. It is also covered by insulation material and is also near the center electrode of the whole ignition device.
The hex head is where you can use a wrench to attach the ignition device onto the engine with the plug. It is a vital part of the ignition device that you should consider with the size that fits your engine.
The crush washer is also known as the seat of the ignition device, which lies on the cylinder head and is below the part of the gasket. It can be made with a tapered design and can vary depending on the type of cylinder head that you have.
Usually made from titanium or stainless steel, this part of the ignition device is also called the ground strap. It makes the thing that is the spark, which ignites your engine and makes use of the interaction of the fuel and air that is thanks to the action of the piston, so that the ignition device works.
Q: What are the different steps in manufacturing a ignition device?
A: In order to make a ignition device, you have to consider the following steps:
1. Making the shell
To make the shell of the ignition device, solid steel is used and is molded in a very low temperature. In other ways, bars of steel can also be used for making them. Rollers are used for knurling the shell of the ignition device.
2. Assembling the side electrode
Using nickel alloy wire, the side electrode of the ignition device is made and is also welded to the shell. A bend is given to the ignition device side electrode and is rolled for the electrolytic process with a silver coating.
3. Preparing the insulator
The insulator is usually made out of ceramic material in which is installed with the use of hydraulic pressure. This process is usually computer controlled so that it will be precise in making the ignition device.
4. Setting the center electrode
The center electrode is also made out of nickel alloy, and a steel terminal stud is where it is welded onto. The flange is also made after going through a series of pressure procedures.
5. Wrapping up the packaging
After the whole process finishes, the ignition device is packed in plastic film and then into the carton with the manufacturer’s label and instructions for using.
Q: What are the uses of a ignition device?
A: The ignition device can be used for the following instances:
1. For a combustion engine – one of the main uses of a ignition device is for a combustion engine to be working properly. It is the main source of starting the power of any combustion engine, especially that of a vehicle, such as your car, truck, van, SUV, ATV, motorcycle and many more. Anything that is defined as a combustion engine will not work properly without the mechanism that is the ignition device.
2. Gives power to a vehicle – as we have mentioned, since the combustion engine applies to vehicles such as cars, trucks, vans and the like, the vehicle is powered and the fuse is ignited with the use of the ignition device. Without the ignition device, there would be no starting your car at all. Without a properly working ignition device, there would be a hard start for your car or vehicle.
3. Gives power to a power tool – the other use of the ignition device is that it can also work on the engine of your power tool. Examples of power tools that may require a ignition device is anything that uses fuel, such as a brush cutter, chainsaw, weed trimmer, jackhammer and anything that needs to be primed, choked and pulled onto the string in order to start, much like the engine of the car that you have in your garage.
4. Provides power to any machinery – aside from your car and your power tools, the ignition device can also be used for powering up machinery that uses combustion engine. Examples of this include generators that are gas powered and anything else that is powered using gasoline or fuel. The concept of using the ignition device is applied to anything that uses a combustion engine in order to work properly.
Q: What are the differences between various ignition devices?
A: Various ignition devices can have different criteria that can set them apart, so that you will be able to tell which one is the best. To tell apart ignition devices, you need to be able to judge them by the following criteria:
1. Type of metal, in which higher melting temperatures can be achieved if you use iridium elements other than nickel and copper. Iridium is usually more durable than nickel and copper, hence it can be more pricey, but many people do note that iridium is not as conductive as nickel and copper, hence less people actually use it. However, if you want a longer lasting ignition device, you should choose iridium over nickel and copper.
2. Measurement of diameter, in which the center electrode is directly involved. This allows you to fit the ignition device accordingly. The diameter can usually come in millimeters or mm so that you should measure the ignition device of your unit first before getting a replacement, so that you can check out the other options out there that may have a different part number but will have a similar fitting to your vehicle engine when you test it.
Q: What are the different ignition device metals or elements that can be used?
A: If you aren’t familiar with the metals or elements / materials that are used in making ignition devices, here are some of them:
Element full name
Size of ignition device
Less than 50%
Less than 50%
Less than 95%
Less than 1%
Less than 50%
Less than 50%
Less than 90%
Less than 90%
Less than 50%
Q: What are the tools needed to change ignition devices in a car?
A: When you want to change the ignition device in a car, you should be prepared with the tools of the trade that you should have in hand, before you do so. Here are the tools that you will need to service a car in terms of changing the ignition devices:
Q: What are some possible sizes of a ignition device socket set?
A: The ignition device can come in a variety of sizes, usually measured in mm or millimeters, which can make a difference in terms of fitting. Some may fit on your ignition device socket while some will not, despite the manufacturer saying so. Different sizes for the socket set of a ignition device can be available, such as:
Q: Do brands of ignition devices make a difference in performance?
A: It is common notion that people may refer to the brand of the ignition device that is indicated in the user’s manual. However, the brand of a ignition device can really vary depending on what is:
1. Recommended by your manufacturer – this can usually be found in the user’s manual of your ignition device, which can vary depending on the manufacturer’s specifications.
2. Fits as a replacement OEM for your part – this can be the case if there is no such part number available for your ignition device as indicated by your manufacturer. In this case, you just have to find one that has a size that is similar to the ignition device that you have on the old machine.
Q: How do you know when your ignition device is failing?
A: A ignition device failing can be horrible, especially if you are in a long trip. Here are some signs that your ignition device needs to be changed:
Decrease in fuel economy
When your ignition device is significantly reducing the fuel economy or efficiency, then this can mean that the ignition device is going bad in terms of its functions.
Acceleration is decreased
The problem with a bad ignition device is that the air and fuel mixture is not ignited enough. And in this case, the ignition device will not make your acceleration that good.
Misfiring of engine
There is a sound that can result into an engine misfire, which is also known as the sputtering sound that you can hear when you are starting your car or engine. In this case, the ignition device that went bad can be the culprit.
When it is very hard to start your vehicle or engine then this can be the case of a bad ignition device. This is when you might want to consider replacing the ignition device whenever needed and possible.
Q: What does the check engine light mean?
A: There can be many ways to determine the check engine light problem:
1. The check engine light can refer to a series of codes as dictated by most manufacturers. You should check with your manufacturer as to which check engine light code is which, depending on the problem. There can be many guides online for you to discover as long as you know the model of your car or engine and what seems to be the problem physically and visually.
2. Take note that the check engine light is not the same as the service required light. This can be a different kind of trouble. If you are not sure which is which then you can contact a manufacturer or you can contact a local auto shop or repair shop in case you are not that knowledgeable with such troubleshooting processes.
3. To give you a brief introduction to check engine light codes, here are some of the most common:
a. Your ignition device wires could be messed up
b. The mass air flow sensor is not working properly
c. The gas cap is somewhat loose
d. The catalytic converter is not functioning properly
e. There can be problems on the O2 sensor
Q: How do you read ignition devices in terms of physical signs?
A: The physical signs that you need to watch for when looking at ignition devices include the following:
There is nothing wrong with this kind of ignition device, so you might not need to worry about anything.
Normal but with a red coating
The fuel that you might be using is no longer in quality. This could also mean that your car or engine is getting old and deserves a better fuel for you to use.
Fouled with fuel
This can be indicated with the side electrode and the tip has some sort of shiny coating. The air and fuel mix might not be that good and the carburetor needs to be adjusted as well for it to work properly.
Damage due to detonation
This is where you will most likely need tuning up your engine for it to work properly. Additionally, if you also switch to a higher octane or higher quality gasoline for your car or engine, then that might also resolve the problem quickly.
The ignition device is worn out
This only means that you just need to replace the ignition device altogether in order to get it working once again for your car or vehicle.
Fouled with carbon
If the fouling source is carbon then that means that the side electrode and tip is black in color. This may also necessarily mean that your injectors could be leaking and there could also be too much fuel for your system.
If a pre-ignition happens then it is most likely that your engine is too hot and there is not enough fuel. This is usually audible.
Fouled with oil ash
You absolutely need to get your engine to the nearest mechanic, as this can be a dangerous situation due to the fact that your piston rings can get worn out due to the engine oil leaking out.
It can also mean that your pre-ignition has happened and that the ignition device may be too hot to be handled by your car or vehicle engine. It will usually be needed to be replaced as much as possible, and with a lower temperature ignition device at that.
Q: When should you change your ignition device?
A: There can be signs and symptoms that your ignition device may display in terms of having to change it later on, such as the following:
1. Your engine might be misfiring and can reduce in fuel economy.
2. Your gasoline keeps on running lower faster.
3. You don’t get to accelerate as fast as you did before.
4. The idle time of your vehicle seems to be rough.
5. You may experience some hard starting with it.
Q: What should I do when I need to replace the ignition device?
A: You should consider getting a mechanic if you are not sure what kind of ignition device your vehicle is using. Or, alternatively, consult the user’s manual of your vehicle, to make sure that you are ordering the right part number. Also, you should get a mechanic’s help in installing the ignition device.
Q: Is it normal to have corrosion in the ignition device?
A: Most people think of bad things with corrosion, but here’s the breakdown of things:
1. A lot of corrosion happens when the ignition devices are too old.
2. You might not be removing them when you are changing oils, which can damage them.
3. You should also consider washing your engine properly and avoid pooling of water.
4. A little corrosion is fine and does not affect your system functionally, only cosmetically.
5. If moisture gets in your vehicle engine all the time, then corrosion is most likely to happen.
Q: What are the different types of fouling problems and how can they be known?
A: Fouling is a common problem with ignition devices, and here’s how to read them:
Type of fouling
Appearance and symptoms
There is a black build-up on the ignition device, which can also feel very sooty in appearance. It can cause misfiring for your engine.
Dry fouling is usually caused by a carburetor that is clogged and the air cleaner needing to be cleaned more properly.
The oily appearance is what makes this different from dry fouling. It can cause a poor start for your engine.
Wet fouling is probably due to the oil control ring not being able to control itself properly.
There are yellow brown deposits that are on the insulator of the ignition device, which can also give the engine some misfiring tendencies.
There is probably too much lead in the gasoline that you chose to use for your engine.
Q: What are the common causes of hard start?
A: A hard start is characterized by your engine seeming to have stalling or pausing problems with its difficulty on starting. Here are some common causes of a hard start:
Fuel is too low
If you have a low level of fuel and you have forgotten to get it filled up right away, this can cause some condensation and in which can result in a really bad starting process. To avoid this, you should always stock up on fuel before you park up your car for the day.
The oil is too thick
The thick oil can be the result of the oil filter not doing its job properly, in which you may need to get it cleaned as soon as possible. The thick oil can also be the result of a low temperature outdoors.
Battery is slow
If you happened to purchase a battery that is not too high quality, despite the low price, it can take its toll on your ignition device and can become a hard starting vehicle. This can also mean that your battery is not working properly.
Hard starting can also be the problem of the ignition switch not working properly, in which you may need to get it to an auto shop or mechanic to ask about it.
Solenoid is not working properly
The solenoid part of your car can be replaced when it is defective, but you should have it diagnosed by a trusted mechanic in order to conclude that you need it to get a replacement for.
Ignition switch is failing
The ignition switch could have been used for so many times that it has been worn out. You should just get it replaced or ask a local mechanic on what to do about it.
Q: What are the most common car care mistakes?
A: Many people have cars but very few actually maintain them. Here are some car care or maintenance mistakes that you may be making:
Not changing lights
The headlights and park lights are both important aspects in a car. Without properly lighting them, you are confusing the other motorists when you are going to make a turn or pause for a while.
Not doing a proper jump start
If you have to do a jump start, do it properly, otherwise it can be risky for both you and your car. If you need to jump start your car due to battery failure, you should consider doing it on the sidewalk or somewhere that’s not in traffic.
Attempting to fix problems you don’t know about
Let’s face it – some people want to solve their own mechanical problems on their car without prior knowledge, which can be dangerous. If you don’t know what you’re doing, get a mechanic right away.
Not checking your car tires
Car tires can get thin over time, and in this case, you may need to get them replaced sooner because if you don’t, you’ll end up getting flat easier in an emergency situation.
Brake repairs not done properly
When the lubrication job on your brake repair is not good enough, it can cause serious problems, so you should let an expert in brake repair d it for you. Brakes can save lives.
Incorrect torque for lug nuts
The torque is important for the lug nuts, otherwise your car tires will either get rough or get loose, which can cause some accidents along the way.
Q: What can you do if the car is hard starting?
A: Hard starting can be frustrating and annoying at times. Here’s what you can do:
1. Check if there is a check engine light.
2. If there isn’t, set the emergency brake on.
3. Inspect the fuel pump if it needs to be changed.
4. Check for any vacuum leaks.
5. Get it to a mechanic if you’re unsure.
Q: What’s a wire boot protector for ignition devices?
A: This kind of protector is fit for the ignition device wire, and it can benefit your ignition device by means of protecting it from corrosion as well as from misfires and the like. You need to have a durable ignition device wire boot protector to achieve this kind of feat.
Q: Which is better: an iridium, platinum or copper ignition device?
A: All these types of ignition devices can have differences, pros and cons, such as the following:
Copper – they have the best performance in conductivity but the problem is their durability.
Platinum – this one has good durability but is not really that conductive.
Iridium – has okay conductivity, has great durability but is expensive.
Wrapping It Up
As a whole, we conclude that the NGK (4929) DPR8EA is our pick for the best spark plug, due to the solid construction of the copper core, the shell that is dipped in zinc for less corrosion and the prevention of flashovers due to the corrugated ribs.l