Spark plugs are one of the most misunderstood components of an engine. Numerous questions have surfaced over the years, leaving many people confused.

This guide was designed to assist the technician, hobbyist, or race mechanic in understanding, using, and troubleshooting spark plugs. The information contained in this guide applies to all types of internal combustion engines: two stroke engines, rotary engines, high performance/racing engines and street vehicles.

Spark plugs are the "window" into your engine (your only eyewitness to the combustion chamber), and can be used as a valuable diagnostic tool. Like a patient's thermometer, the spark plug displays symptoms and conditions of the engine's performance. The experienced tuner can analyze these symptoms to track down the root cause of many problems, or to determine air/fuel ratios.

SPARK PLUG BASICS: The spark plug has two primary functions:

* To ignite the air/fuel mixture * To remove heat from the combustion chamber

Spark plugs transmit electrical energy that turns fuel into working energy. A sufficient amount of voltage must be supplied by the ignition system to cause it to spark across the spark plug's gap. This is called "Electrical Performance."

The temperature of the spark plug's firing end must be kept low enough to prevent pre-ignition, but high enough to prevent fouling. This is called "Thermal Performance", and is determined by the heat range selected.

It is important to remember that spark plugs do not create heat, they can only remove heat. The spark plug works as a heat exchanger by pulling unwanted thermal energy away from the combustion chamber, and transferring the heat to the engine's cooling system. The heat range is defined as a plug's ability to dissipate heat.

The rate of heat transfer is determined by:

* The insulator nose length * Gas volume around the insulator nose * The materials/construction of the center electrode and porcelain insulator

A spark plug's heat range has no relationship to the actual voltage transferred though the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors; the length of the ceramic center insulator nose and its' ability to absorb and transfer combustion heat, the material composition of the insulator and center electrode material.

Heat rating and heat flow path of NGK Spark Plugs Heat Rating and Heat Flow Path

The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850°C. If the tip temperature is lower than 500°C, the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850°C the spark plug will overheat which may cause the ceramic around the center electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10°C to 20°C.

Tip Temperature and Firing End Appearance Tip Temperature and Firing End Appearance

The firing end appearance also depends on the spark plug tip temperature. There are three basic diagnostic criteria for spark plugs: good, fouled and overheated. The borderline between the fouling and optimum operating regions (500&def;C) is called the spark plug self-cleaning temperature. The temperature at this point is where the accumulated carbon and combustion deposits are burned off.

Bearing in mind that the insulator nose length is a determining factor in the heat range of a spark plug, the longer the insulator nose, the less heat is absorbed, and the further the heat must travel into the cylinder head water journals. This means the plug has a higher internal temperature, and is said to be a hot plug. A hot spark plug maintains a higher internal operating temperature to burn off oil and carbon deposits, and has no relationship to spark quality or intensity.

Conversely, a cold spark plug has a shorter insulator nose and absorbs more combustion chamber heat. This heat travels a shorter distance, and allows the plug to operate at a lower internal temperature. A colder heat range is necessary when the engine is modified for performance, subjected to heavy loads, or is run at high rpms for a significant period of time. The colder type removes heat more quickly, and will reduce the chance of pre-ignition/detonation and melting or damage to the firing end. (Engine temperature can affect the spark plug's operating temperature, but not the spark plugs heat range).

Below is a list of some of the possible external influences on a spark plug's operating temperatures. The following symptoms or conditions may have an effect on the actual temperature of the spark plug. The spark plug cannot create these conditions, but it must be able to cope with the levels of heat...if not, the performance will suffer and engine damage can occur.

Air/Fuel Mixtures seriously affect engine performance and spark plug operating temperatures.

* Rich air/fuel mixtures cause tip temperature to drop, causing fouling and poor driveability * Lean air/fuel mixtures cause plug tip and cylinder temperature to increase, resulting in pre-ignition, detonation, and possibly serious spark plug and engine damage * It is important to read spark plugs many times during the tuning process to achieve the optimum air/ fuel mixture

Higher Compression Ratios/Forced Induction will elevate spark plug tip and in-cylinder temperatures

* Compression can be increased by performing any one of the following modifications: a) reducing combustion chamber volume (i.e.: domed pistons, smaller chamber heads, milling heads, etc.) b) adding forced induction (Nitrous, Turbocharging or Supercharging) c) camshaft change * As compression increases, a colder heat range plug, higher fuel octane, and careful attention to igni-tion timing and air/fuel ratios are necessary. Failure to select a colder spark plug can lead to spark plug/engine damage

Advancing Ignition Timing

* Advancing ignition timing by 10° causes tip temperature to increase by approx. 70°-100° C

Engine Speed and Load

* Increases in firing-end temperature are proportional to engine speed and load. When traveling at a consistent high rate of speed, or carrying/pushing very heavy loads, a colder heat range spark plug should be installed

Ambient Air Temperature

* As air temperature falls, air density/air volume becomes greater, resulting in leaner air/fuel mixtures. * This creates higher cylinder pressures/temperatures and causes an increase in the spark plug's tip temperature. So, fuel delivery should be increased. * As temperature increases, air density decreases, as does intake volume, and fuel delivery should be decreased

Humidity

* As humidity increases, air intake volume decreases * Result is lower combustion pressures and temperatures, causing a decrease in the spark plug's tem-perature and a reduction in available power. * Air/fuel mixture should be leaner, depending upon ambient temperature.

Barometric Pressure/Altitude

* Also affects the spark plug's tip temperature * The higher the altitude, the lower cylinder pressure becomes. As the cylinder temperature de-creases, so does the plug tip temperature * Many mechanics attempt to "chase" tuning by changing spark plug heat ranges * The real answer is to adjust jetting or air/fuel mixtures in an effort to put more air back into the en-gine

Types of Abnormal Combustion

Pre-ignition

* Defined as: ignition of the air/fuel mixture before the pre-set ignition timing mark * Caused by hot spots in the combustion chamber...can be caused (or amplified) by over advanced timing, too hot a spark plug, low octane fuel, lean air/fuel mixture, too high compression, or insufficient engine cooling * A change to a higher octane fuel, a colder plug, richer fuel mixture, or lower compression may be in order * You may also need to retard ignition timing, and check vehicle's cooling system * Pre-ignition usually leads to detonation; pre-ignition an detonation are two separate events

Detonation

* The spark plug's worst enemy! (Besides fouling) * Can break insulators or break off ground electrodes * Pre-ignition most often leads to detonation * Plug tip temperatures can spike to over 3000°F during the combustion process (in a racing engine) * Most frequently caused by hot spots in the combustion chamber. Hot spots will allow the air/fuel mixture to pre-ignite. As the piston is being forced upward by mechanical action of the connecting rod, the pre-ignited explosion will try to force the piston downward. If the piston can't go up (because of the force of the premature explosion) and it can't go down (because of the upward mo-tion of the connecting rod), the piston will rattle from side to side. The resulting shock wave causes an audible pinging sound. This is detonation. * Most of the damage than an engine sustains when "detonating" is from excessive heat * The spark plug is damaged by both the elevated temperatures and the accompanying shock wave, or concussion

Misfires

* A spark plug is said to have misfired when enough voltage has not been delivered to light off all fuel present in the combustion chamber at the proper moment of the power stroke (a few degrees before top dead center) * A spark plug can deliver a weak spark (or no spark at all) for a variety of reasons...defective coil, too much compression with incorrect plug gap, dry fouled or wet fouled spark plugs, insufficient ignition timing, etc. * Slight misfires can cause a loss of performance for obvious reasons (if fuel is not lit, no energy is be-ing created) * Severe misfires will cause poor fuel economy, poor driveability, and can lead to engine damage

Fouling

* Will occur when spark plug tip temperature is insufficient to burn off carbon, fuel, oil or other deposits * Will cause spark to leach to metal shell...no spark across plug gap will cause a misfire * Wet-fouled spark plugs must be changed...spark plugs will not fire * Dry-fouled spark plugs can sometimes be cleaned by bringing engine up to operating temperature * Before changing fouled spark plugs, be sure to eliminate root cause of fouling

Part No Applications: NME3011, NME3010

Article Date: Mar 08, 2006
Car Accociations: NEW_MINI
Hits: 631

Order and Shipping Information

Worldwide Shipping Charges
Shipping Address Policy
Worldwide General Shipping Information
Shipping Schedule
When Will I Get My Order?
Entering APO/FPO Addresses
Backorders

World-Wide Shipping Charges

How can I get a shipping estimate?

Just click "Buy Now" on the product page to add it to your cart. Continue shopping and when ready for the shipping estimate, begin the checkout process. Shipping charges for most items are calculated and displayed during order checkout. You will NOT need to log in or create an account to use the 'shipping quote' button.  If you're not ready to order, simply use you browser's "back" button to return to previously viewed pages.

Shipping Methods appropriate for your destination are displayed to you during order checkout. Once you've decided on the items you'd like to order, consider how quickly you would like to receive your shipment(s), evaluate the shipping cost displayed, and choose a shipping method.

What if no shipping charges are displayed?

Shipping charges are calculated at time of shipment based on the actual package weight and dimensions. In some cases, we may not have weights or dimensions in our computer system for one or more of the items you ordered. In this case, shipping is not quoted. The amount you will be billed is the carrier's standard charge. We don not charge any handling fees. The cost of shipping your order will be sent to you in a confirmation email message at the time of shipment. No action is required on your part.

Shipping Address Policy

When you order product using your credit card we initiate a process to check the address information you enter to see if it matches the address that your credit card issuer has on file and matches your billing address. If they do not match then the issuer of the credit card will not approve the transaction 100%. This is because much of credit card fraud occurs by having products shipped to the address of the person who stole the credit card instead of to your address – the billing address. The fraudster steals the credit card, orders products and has those products shipped to the fraudsters’ address and you don't know anything about it until you get your credit card bill.

This works great for those people that have products shipped to their home address and their credit card bill is also mailed to that same address. But some people use a PO Box or their personal credit card to order products for business. In those cases they want the product shipped to their office but the statement (billing address) is still being mailed to their home address or PO Box. This normally would be a rejected transaction because of the two legitimate, but different, addresses.

The way to get around this is with an Alternate Shipping Address. You can add an Alternate Shipping Address to your credit card so that orders will be accepted at both addresses. The alternate shipping address does not have to be your business address but is used here simply as an example.

Simply use the toll-free number on the front or back of your card to contact your credit card company and create an Alternate Shipping Address which is simply a note on your account authorizing purchases that are delivered to a destination other than your billing address. With the Alternate Shipping Address feature in place you can have credit card orders shipped to two different addresses but your credit card bill will continue to be mailed to the original billing address.

Add the Alternate Shipping Address to your credit card account before placing your order. After your credit card company has updated your credit card account you can then order products with your credit card and have them shipped to the alternate shipping address you have on file with the credit card issuer.

* Please note that on your initial order items must be sent to the billing Or ‘Alternate’ address as registered with your credit card company. See this Policy for more details or contact our sales staff at 800-946-2642.

Mini Mania, Inc. primarily uses FedEx, UPS and the US Postal Service to ship orders world-wide, each of which may be available only in certain areas. Truck freight items may be shipped using our choice of a variety of motor freight carriers. The customer pays shipping costs unless stated otherwise.

When choosing a shipping method, remember that carriers charge considerably more for expedited delivery. Expedited delivery also generally requires the package be signed for at the time of delivery. Check with your selected carrier locally if you or your authorized representative may not be available to sign for the package at the time of delivery.

For some destinations, we offer the choice of Mail (USPS). While often less expensive, remember that items shipped via Priority Mail, while insured, are not always reliably delivered and cannot be tracked. By choosing Priority Mail, you accept responsibility for your order once it leaves our facility.

Customers outside the domestic United States should exercise particular care when selecting a carrier or expedited shipping methods. If in doubt, consult with your potential carrier for information about shipments to your country. Import duties, local taxes, customs charges, etc. are the responsibility of the customer. If Mini Mania is invoiced by any carrier for import duties, local taxes, customs charges, or similar fees, the customer's credit card on file will be charged immediately for these fees, and an invoice explaining the charges will be sent to the customer.

Shipping Schedule

Most orders phoned in to Mini Mania before 12 noon Pacific Time are shipped the same day; orders received later usually ship the next day. If you must receive your order by a specific date, please make this clear when placing your order.

Most Internet orders are processed the next business day and are shipped within 1-2 days.

If there is more than one item in your order, we will ship your items as they become available.

Depending on availability, your order may be sent in more than one shipment. You will be charged shipping for each shipment.

You may choose to contact us by phone or e-mail before placing your order in order to ascertain availability.

When Will I Get My Order?

For Ground shipments, see the maps below for approximate delivery times. For expedited shipping choices, please see your chosen carrier’s web site for details, terms and conditions. Note that in all cases, shipping times do not include the day the order ships, weekends or holidays.

UPS Ground Delivery Transit time Map for Domestic Customers

FedEx Ground Service Delivery Map

Entering APO & FPO Addresses Correctly

Having trouble entering an APO or FPO address on our order form? Following these steps should help:

• Enter the recipient's full name and address in the relevant fields.
• Enter "APO" or "FPO" in the City field.
• Enter "AE" in the State/Province/Region field if the recipient is stationed in Europe, Canada, Africa, or the Middle East. Enter "AA" if the recipient is stationed in the Americas. Enter "AP" if the recipient is stationed in Asia or the Pacific.
• Regardless of where the recipient is stationed, select "United States" from the Country drop-down menu.

  Following these steps will ensure that you're charged the correct shipping amount and that your order will be delivered in a timely fashion. All shipments to APO/FPO addresses are sent via U.S. Priority or First Class Mail. We estimate 5 to 7 business days for delivery once the order has been shipped; however, some destinations may take up to 21 days.

  
  
  
  
  
  

  Backorders

  We endeavor to stock most of the items we sell. The automatic shipment notification email you receive will identify backordered items and indicate the approximate date we expect to receive the item at our warehouse. Be sure to contact us if you wish to cancel your backorder to avoid unnecessary shipping and restocking charges once your backordered items are shipped.

  
  
  

We will match the published price of any US supplier* -- even their current sales prices! If you find an item advertised at a lower price, make a notation in your online order, call or email us your price match request (see terms and details below). We'll sell you the SAME item at the SAME price! If you've already purchased the item from us, we'll even price match (for store credit only) as long as you contact us with your request within 10 days of placing your order.

This offer is restricted to identical items offered for sale in writing or on the web. When making your price match request, you must provide us with a link to the competitor's Internet URL for the item, a copy of the written ad or written quotation, which must include suppliers part number, description and price.

Price Match Terms and Fine Print

We may choose not to price match in some cases; here are some reasons why:

• The competitor's product is not an exact match (identical manufacturer & model) with ours.
• The competitor with the lower price does not have the item in stock at their warehouse.
• The competitor's total price (including shipping, handling, rebates, taxes, etc.) is higher.
• The competitor's product is used, refurbished, reconditioned, or a display model.
• The competitor is not selling in US dollars.
• The product is a clearance or closeout item.
• The item is not found within the first 10 items listed on major search engine results.
• The competitor is not manufacturer authorized or has advertised below the manufacturers minimum allowed price for the item.

* Qualified U.S. Suppliers are established businesses that routinely and regularly sell the item to be matched from an established physical storefront or warehouse.

While we endeavor to maintain the accuracy of item availability, descriptions and availability, we reserve the right to correct errors. We reserve the right to choose not to honor this offer.

How to Request a Price Match

Place an order on-line and leave a comment at checkout. Provide the competitor's name, part number, item description, URL link to the exact item and the competitor's price anlong with your request to price match. If we agree to match the price, your order will be processed at that adjusted price. In the event we cannot match the price, we will notify you by email. We will hold you order for 3 business days.

Alternately, you may call us with your request. We'd love to talk with you. We will generally respond to price match requests within one business day.

SHIPMENT PROBLEMS?

Claims for missing items or error in shipment must be reported within 5 days of order receipt .

BACKORDERS

We endeavor to stock most of the items we sell. For Classic Minis, parts are frequently in limited supply and are difficult to keep on hand. the automatic shipment notification email you receive will identify backordered items and indicate the approximate date we expect to receive the item at our warehouse.

Be sure to contact us if you wish to cancel your backorder to avoid unnecessary shipping and restocking charges once the item(s) you’ve ordered is shipped.

Some items are made available on a Special Order basis. These are typically items with very low demand that we choose not to keep in inventory, or items that are custom built or built to order. These items are ordered from their suppliers solely to fulfill your order. As such, these items require a 100% non-refundable deposit at the time the order is placed (power-unit orders require a $1,000 deposit before work begins). Because of the nature of Special Order items, your order cannot be cancelled once your order is accepted and deposit taken, nor can returns be accepted once the item has shipped.