PMag Spark Plug Guide

[jliltd]

I have been reading VAF and talking to folks who use NGK automotive spark plugs with their PMags. From what I have learnt I gather the following:

First and foremost we should use plugs with a solid post terminal (tip), not the equivalent model number with the screw-off tip. There have been issues over time with the screw off tips loosening and arcing leading to ignition trouble. There have been workarounds like crimping hard on the tips with side cutters etc. in order to alleviate the loosening but why not avoid the whole mess by sticking to the solid tip plugs.

Next, I gather that there are 2 poplular heat ranges....


For compression ratios up to 9:1

NGK BR8ES Part Number 3961 with solid/permanent tip – standard plug

Optional Upgrade: NGK BR8EIX Part Number 6747 with solid/permanent tip – Iridium

The 8 heat range is the suggested rating in the EMag Air installation manual.



For compression ratios above 9:1

NGK BR9ES Part Number 7788 with solid/permanent tip – standard plug

Optional Upgrade: NGK BR9EIX Part Number 3089 with solid/permanent tip -- Iridium



I also hear from folks who buy the cheaper standard plugs and replace them every second oil change or so (~ 100 hrs), whereas the Iridium models can go a few hundred hours (~500). The Iridiums cost 3 or 4 times more than the standard plugs.

I would like to hear comments about my understanding of the above.

Jim

[N941WR]

Originally Posted by jliltd

...
I also hear from folks who buy the cheaper standard plugs and replace them every second oil change or so (~ 100 hrs), whereas the Iridium models can go a few hundred hours (~500). The Iridiums cost 3 or 4 times more than the standard plugs.

I would like to hear comments about my understanding of the above.

Jim

We do not recommend running past 100 hours with any automotive spark plug.

The reason is that with an EICommander installed, the pilot will notice the deterioration of the spark event once past 100 hours. This is regardless of if the standard plugs or iridium plugs are installed.

The pilot will not notice a difference unless they have a way to "read" the P-mag spark events.

Since the cost is so cheap and it is good practice to inspect the plugs once a year, we recommend replacing them during the condition inspection or at 100 hours, whichever comes first.

[William Slaughter]

Originally Posted by jliltd

I have been reading VAF and talking to folks who use NGK automotive spark plugs with their PMags. From what I have learnt I gather the following:

First and foremost we should use plugs with a solid post terminal (tip), not the equivalent model number with the screw-off tip. There have been issues over time with the screw off tips loosening and arcing leading to ignition trouble. There have been workarounds like crimping hard on the tips with side cutters etc. in order to alleviate the loosening but why not avoid the whole mess by sticking to the solid tip plugs.

Next, I gather that there are 2 poplular heat ranges....


For compression ratios up to 9:1

NGK BR8ES Part Number 3961 with solid/permanent tip ? standard plug

Optional Upgrade: NGK BR8EIX Part Number 6747 with solid/permanent tip ? Iridium

The 8 heat range is the suggested rating in the EMag Air installation manual.



For compression ratios above 9:1

NGK BR9ES Part Number 7788 with solid/permanent tip ? standard plug

Optional Upgrade: NGK BR9EIX Part Number 3089 with solid/permanent tip -- Iridium



I also hear from folks who buy the cheaper standard plugs and replace them every second oil change or so (~ 100 hrs), whereas the Iridium models can go a few hundred hours (~500). The Iridiums cost 3 or 4 times more than the standard plugs.

I would like to hear comments about my understanding of the above.

Jim

I have a 10:1 compression engine and initially went with the BR9ES heat range plugs, but suffered from numerous instances of lead bridging shorting the plug. Switched to the BR8 heat range based on their successful use in Nigel Speedy's 10:1 engine. All good now. I went with the Iridium plugs. They are rather more expensive, but still quite reasonable in the overall scheme of things.

[penguin]

I have a regular compression O-320 and have been running one Slick and one E-Mag (then P-mag) since around 2005. Initially I used BR8ES exclusively, but found they wore quite quickly, although it was not an issue as I changed them every annual - around 40 to 50 hours. By that time the gap would be around 0.040" or more, having started at 0.035". I also found the plugs would load up with lead to some extent.

A few years ago I switched to BR9ES after talking with NGK tech support (at an auto show) and reading their advice on the web. I have found much less wear and less lead deposits. One year I only flew 20 hours - hardly any wear. I still change the plugs each year or two ( 50 to 70 hours typically).

I do lean aggressively as soon as I throttle back after take-off & climb, and usually fly between 2000' & 4000' cruising between 140 & 150kt.

I have come to the conclusion that there are more variables than just compression ratio, and one that is difficult to quantify is operating "style". The only advice I would give is to try a higher (cooler) plug if the wear of your plugs is higher than you would like.

Pete

[D Weisgerber]

Originally Posted by penguin

I have a regular compression O-320 and have been running one Slick and one E-Mag (then P-mag) since around 2005. Initially I used BR8ES exclusively, but found they wore quite quickly, although it was not an issue as I changed them every annual - around 40 to 50 hours. By that time the gap would be around 0.040" or more, having started at 0.035". I also found the plugs would load up with lead to some extent.

A few years ago I switched to BR9ES after talking with NGK tech support (at an auto show) and reading their advice on the web. I have found much less wear and less lead deposits. One year I only flew 20 hours - hardly any wear. I still change the plugs each year or two ( 50 to 70 hours typically).

I do lean aggressively as soon as I throttle back after take-off & climb, and usually fly between 2000' & 4000' cruising between 140 & 150kt.

I have come to the conclusion that there are more variables than just compression ratio, and one that is difficult to quantify is operating "style". The only advice I would give is to try a higher (cooler) plug if the wear of your plugs is higher than you would like.

Pete

I agree that there are more variables, I run 1 E Mag and 1 Mag since 2001 or 2002. I think 1 other variable is if its fuel injected or carb. I think the fuel injection distributes the fuel more evenly

[smokyray]

Originally Posted by jliltd

I have been reading VAF and talking to folks who use NGK automotive spark plug
I also hear from folks who buy the cheaper standard plugs and replace them every second oil change or so (~ 100 hrs), whereas the Iridium models can go a few hundred hours (~500). The Iridiums cost 3 or 4 times more than the standard plugs.

I would like to hear comments about my understanding of the above.

Jim

Jim,
I bought Jeff Rose's first 0-320 Electroair system for my RV4 back in 94'. Since then my HR2 and current RV6X use both a P-Mag and a EI system. In all these years NGK is my least favorite plug and the only plugs I have had fail inflight.

What are my faves?

Autolite 386 Great heat range, sold at NAPA and need no inserts.
Denso L-14U Also a great heat range and same thread as the Autolites.

Lots of years and hours on both, highly recommended.

V/R
Smokey

[Omega232Devils]

Originally Posted by smokyray

Jim,
I bought Jeff Rose's first 0-320 Electroair system for my RV4 back in 94'.


Autolite 386 Great heat range, sold at NAPA and need no inserts.

Smokey

Smokey,
I too had the original Jeff Rose (Prior to Electroair), great ignition but eventually gave out, so I switched to PMags. I used the Autolite 386 plugs in the Jeff Rose and worked like a charm.

Am I understanding you correctly that you use the Autolite 386 with your PMags? Any issues or comparison to the NGK BR8ES? I would take the 18mm Autolite 386 any day if this is the case.

Cheers,

Dan

[Skysailor]

There are four RV's I know running Autolite 386 plugs with the PMAG including mine. All report excellent results.

[birddog486]

Apologize if I missed it but do the Autolite 386 plugs come as a solid cap version? I did a quick search but only found them with removable caps.

[Jonathan Alvord]

I've been chasing some pmag issues over the last few weeks. 1st noticed as my RPM was jumping around and then just stopped working. We cleaned all the contacts and then it appeared to be working well again, but soon started bouncing again. There was no change when doing run ups an checking mags. Last week I replaced the plugs (clearly the gaps were off) when I took the plugs to NAPA I was given a replacement plug and told it would be good, needless to say the plug was 1/2inch shorter thread, and 1" longer top (Obviously not a replacement). The original plug was NGK R 3035 BR8ECM, which is interesting now as I read the above and there is no mention of that number. I'm still trying to figure out which PMAG it really is, and how to service it. The RPM's are reading normal but jumping occasionally to a higher RPM. Any insight would be great.

Jon