Complete Rotax Spark Plug List

[gyropilot]

Back in December of 2003, I did a little research and made a complete list of NGK spark plugs available for the Rotax 447/503/582, etc. series of engines with their current street (Internet) prices (from www.rockauto.com ). Product descriptions are from NGK literature.

Basic size info. - 14mm threads, 3/4" reach, 13/16" hex, gasket seat

NGK brand

B8ES - Standard plug recommended by Rotax.
~$1.53 each

BR8ES - Same with resister for improved RFI suppression.
~$1.61 each

B8EV - Gold Palladium fine wire center electrode with resister.
~$4.15 each

NGK EV gold palladium spark plugs, have a fine wire (1.0mm) gold palladium center electrode for better ignitability, more power, and enhanced antifouling capabilities. Gold palladium increases durability. Traditional ground electrode.

BR8EV - Same as above with resister for improved RFI suppression.
~$4.33 each

BR8EVX - Platinum fine wire center electrode with resister.
~$5.73 each

NGK VX series are manufactured with performance in mind. The center electrode is platinum fine wire(0.8mm) for both long life and better performance. A fine wire center electrode requires less voltage thus creating a stronger spark from your current ignition system. A tapered cut ground electrode improves ignitability by allowing for larger growth of the flame kernel.

BR8EIX - Iridium fine wire center electrode with resister.
~$6.22 each

NGK iridium plugs represent the ultimate evolution of spark plug technology and performance. The iridium center electrode is both stronger and harder than platinum. This allows NGK engineers to design an ultra-fine (0.6mm) center electrode reducing the voltage requirement for spark. This allows for a brighter, stronger spark from your existing ignition system. The ground electrode has a tapered cut at the firing end which reduces quenching for better flame core growth and increased ignitability. The combination of fine wire center electrode and tapered cut ground will increase performance, improve acceleration, and fuel efficiency.

In the past, when I've replaced the plugs in my 503 with the stock BR8ES, the engine would start easier (normally the first pull) and would run smoother. However, this performance increase would last only a few hours then the engine would start and run more typically... usually 2 or 3 pulls required to start, etc.

This flying season I decided to give the expen$$ive BR8EIX Iridium plugs a try just as an experiment. I opened up the gap on these new iridium plugs (over the stock Rotax recommendations), because I felt the lower voltage requirement for the plug would allow this without putting a strain on the electronic ignition system. I'd hoped the easier starting and better running would last way beyond the first few hours after the plugs had been installed.

I'm happy to report "so far so good." At a minimum there doesn't seem to be any adverse effects. On the positive side, with about 15 hours on the plugs, the engine still starts on the first pull every time, it idles better, and it seems to still run quite smooth (subjective of course). My fuel economy also seems to be much better this year that last, but I'm not sure if I can attribute that to the spark plugs... doesn't seem to make sense. There could be many other reasons for that.

Just thought someone might find this interesting. If not... WELL EXCUSE ME!

John L.

 

[GyroRon]

Thanks for the info John, but a couple questions... One, what about the reccomended plug heat range? Two, do you plan to take the plugs your running now out and throw them away at 20-25 hours as most Rotax owners typically do, Or do you plan to leave them in there for 50 or perhaps 100 hours?

Last a comment. I personally feel that easy starts - " first pull " - have more to do with proper priming and throttle opening than what kind of plugs your running. John are you using a primer or do you use the stock Bing enrichment chokes?

 

[ToddP]

John,

I think this is great information. As a rule, us gyro people are tinkerers and this is just something else to give a try. I'm sure I'll be ordering some plugs in the next few days.

 

[ToddP]

John,

Do you know the difference between the BR8EIX and the BR8EIXSolid ?

 

[CLS447]

I been using the Gold Palladiums in my 447. No problems!

I've been searching for the best plug for my SUB. I started looking for the 4 prong Bosch Platinums, but since they don't make them for my engine , I've stumbled upon the Denso/NGK Iridiums ($13) . Thats what I'm getting. Some people laugh& say it's a waste of money but I've always wanted the best plugs....period.

John, I agree with Ron on the first pull issue.....You gotta get fuel to the plugs before you can get ignition. Either primed with a primer or a couple pulls with the switch off.

Why did you "feel" like you wanted to stretch the gap a bit? Is this a good idea even with the better plugs?

 

[MMorgan]

Hey guys,

I agree with Ron and Chris.

I have a 503 with the standard B8ES plugs. It starts most times on the first pull after a couple of shots with the primer. Even hot I prime it one time.

 

[gyropilot]

Spark Plug Questions

Spark Plug Questions

One, what about the recommended plug heat range?

Ron,

With an NGK spark plug, the "8" in the part number of our plug indicates the heat range. The basic heat range of all the plugs I listed is therefore the same.

Two, do you plan to take the plugs your running now out and throw them away at 20-25 hours as most Rotax owners typically do, Or do you plan to leave them in there for 50 or perhaps 100 hours?

With these expensive plugs I will definitely clean them (using an abrasive cleaner) and reuse them. How long will I use them? Don't know yet... probably until performance decreases or the ground electrode shows signs of obvious wear.

Now before you or others start screaming about abrasive cleaning, I know full well that Rotax specifically warns against it. If not completely removed after cleaning, abrasive particles left on the plug could find their way into the engine cylinder causing damage. I don't leave abrasive particles on my plugs after cleaning! Also, abrasive cleaning can wear down the otherwise sharp edges of the center and ground electrodes resulting in a higher plug voltage requirement. With platinum and iridium plugs, this isn't an issue with the fine wire center electrode. In the case of the softer ground electrode, I carefully touch up with a small ignition file (to sharpen the edges) and then regap. Good as new!

Of course, when using a standard plug which costs $1.53, there's not much point in bothering with all that cleaning work... just toss 'em and install new ones! I'm well aware, that with the exception of inverted engine installations, there's no really good financial justification to use iridium spark plugs which cost $6.22 each when good $1.53 spark plugs are available! It's just something fun to spend money on... and they do seem to work a little better.

Last a comment. I personally feel that easy starts - " first pull " - have more to do with proper priming and throttle opening than what kind of plugs your running. John are you using a primer or do you use the stock Bing enrichment chokes?

I mostly agree... and probably didn't elaborate about what I meant. The iridium plugs seem to have been giving me more *consistent* first pull starts this flying season.

I have both the carb enrichment system on my engine and the primer system. I use the primer (when needed) and almost never have to touch the enrichment levers unless it's *really* cold outside (sub-freezing temps).

Fly safe,

John L.

 

[gyropilot]

Solid vs. Threaded Plug Terminals

Solid vs. Threaded Plug Terminals

Do you know the difference between the BR8EIX and the BR8EIXSolid ?

Todd,

Are you asking if I know of a solid terminal version of the BR8EIX? I don't.

I use the threaded terminal type, but before putting it into service I carefully lock down the terminal with pliers after applying high strength Loctite to the threads. I've never had one come loose yet.

Regards,

John L.

 

[gyropilot]

Plug Gap

Plug Gap

Why did you "feel" like you wanted to stretch the gap a bit? Is this a good idea even with the better plugs?

Chris,

All else being equal, the voltage required for electrical current to jump the spark plug gap increases as the gap widens. The voltage requirement also increase as the edges of the electrodes wear smooth or become contaminated with deposits.

I presume the small plug gap Rotax specifies (0.4mm to 0.5mm / 0.016" to 0.020") is due to the somewhat anemic ignition voltage capabilities. Small gap = lower voltage requirement. Unfortunately this tiny gap makes the plug more susceptible to getting fouled from carbon deposits and it also mean a smaller (weaker) spark.

Now the following is my theorizing... I'm not an electrical engineer or a spark plug designer... you'll want to do your own research and come to your own conclusions...

According to NGK, the fine wire electrode of the iridium plug requires a lower voltage to generate a spark compared to a standard plug. This would mean that the ignition system has to generate less voltage to fire an iridium plug when set to the same gap as a standard plug.

My goal in slightly increasing the gap on the iridium plugs was not only to reduce the possibility of deposits bridging the electrodes, but also to create a longer (better) spark at the cost of increasing the voltage requirement back up to about the *same* level as the standard plugs would have been.

Regards,

John L.