There are 3 new NGK Iridium ECS version spark plugs available for snowmobiles. These are the same as the other ECS spark plugs which have chamfered faces where the ground electrode is attached by welding. This chamfer was added to strengthen the weld and eliminate electrode burn off. The chamfer is also added to allow better flame propagation. The one with the -5 (must stand for 0.5mm) is for sleds that require 0.020" gaps. They are listed under Accessories on BRP site. Also listed is standard NGK ECS spark plugs. The plugs in Blue are the only plugs recommended by BRP for the Mach Z.

BR8ECSIX Doo Part No. 515176726 NGK Part No. 5886 gap 0.032"

BR9ECSIX Doo Part No. 515176728 NGK Part No. 5438 gap 0.032"

BR9ECSIX-5 Doo Part No. 515176729 NGK Part No. 6014 gap 0.020"

BR9ECS NGK Part No. 4677 .028-.032" gap solid top (Original Mach Z plug)

BR9ECS NGK Part No. 4771 .018-.020" gap solid top (Do not use in Mach Z)

BR9ECS NGK Part No. 3570 .028-.032" gap screw top (Aftermarket available)

BR8ECS NGK Part No. 4172.028-,032" gap solid top (Aftermarket available now)

You can buy 9ECS NGK No. 3570 from some auto parts stores (NAPA for one) for less than $4. The 8ECS is now available at aftermarket stores also. Below is a listing of NGK plug numbers.

DO NOT re-gap ECS plugs due to the way the electrode is welded to the plug ground. Bending the electrode will weaken the electrode weld. The ground is chamfered to improve the weld on the ECS electrode. If the gap is incorrect ask dealer for a new plug. Here is a pic showing difference between standard NGK plug and NGK ECS plug on the right.

Click to view attachment

If you look at the picture below, you can see that when you bend a standard spark plug (BR9EYA left) ground electrode you are not bending the weld. If you bend the electrode on the plug on the right (ECS), the force will be transferred directly to the weld. Per NGK tech, the ECS plug was designed for SDI 2 stroke engines to eliminate electrodes from being burned off and dropping in cylinder. When initially testing the SDIs, Rotax had issues with spark plugs.

Click to view attachment

Other spark plugs being used by members are.

BR9EIX NGK part No. 3089 gap to .032"

BR8EIX NGK part No. 6747 gap to .032"

BR9EYA NGK part No. 7548 gap to .032"

BR8ES NGK part No. 5422 gap to ,032"


The BR9ES, BR9ECS, BR9EYA and BR9EIX BR9ECSIX are all basically the same plug.


Here is an explanation of what the different letters and numbers mean.

The B stands for 14 mm thread diameter

The R means resistor type

The 9 (or number) is the heat range The larger the number the colder the heat range. The spark plug does not add heat to the engine other than igniting the fuel/air mixture. The heat range refers to the plugs ability to remove heat from the combustion chamber. The colder plugs remove more heat and therefore are less likely to detonate.

The E stands for 19 mm (3/4") reach

The S stands for standard electrode

The C stands for low angle ground electrode

The Y stands for v groove center electrode

The A stand for special design

The I stands for Iridium electrode

The X stands for booster gap

Now to explain the differences. The ECS is the same as the ES except for the chamfer and the ground electrode (see pics above) is welded more securely to the flat section. This was designed by NGK to eliminate electrodes from burning off in combustion chamber. I guess they had issues during initial testing of the SDI engines. The gaps can not be changed on the ECS because you would cause the electrode weld to bend and fail. The chamfer was also supposed to reduce hot spots near the center of combustion chamber therefore reducing detonation. Evidently the electrodes don't burn off under normal conditions, otherwise we would hear about it on dooTalk with all the different plugs being tested.

The ES and EYA are the same except for the electrode on the EYA is "V" grooved. The idea of the V grooved electrode is to force the spark to the outer edges of the ground electrode placing it closer to the fuel/air mixture giving more complete combustion.

The EYA and EIX are the same except the EIX has an Iridium electrode. Iridium is a very dense material and requires less voltage to spark. It burns very efficiently and sparks well at leaner fuel mixtures. Most Asian motorcycles perform extremely well running Iridium plugs. Very expensive and high performance. May not work well in the overly rich Mach Z.

The ECSIX is the same as a ECS but includes an Iridium electrode. It includes the chamfered section like the original Mach Z plugs.