1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Spark plugs after ignition swap

Old 08-16-15, 11:36 PM
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Spark plugs after ignition swap

I swapped a 81-85 distributor into my 79 today following various guides. Interesting experience.

I recently replaced my spark plugs with the stock BR7ET plugs. With the electronic ignition the BR8EQ-14*plugs are recommended. Are there any problems running the points plugs with an electronic ignition until they are due for replacement? As the plugs are fairly new I don't want to replace them unless I have to.
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Old 08-17-15, 12:54 AM
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I have no idea but I'll give you my experience.

Mine has a tfidfis ignition conversion and did have different bottom plugs from the top. I had to replace them and I ordered 4 of the ones mazdatrix has listed for my year (BR8EQ-14) not knowing the leading and trailing was different.

All I can say is I feel a difference in smoothness (I think), the new plugs feeling better. But that could just be because of the fact that they are new. No noticeable difference in power.

I know we have much different scenarios and I'm sure it's better to use the recommended plugs but for now it's working for me.

Last edited by Tylerx7fb; 08-17-15 at 12:56 AM.
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Old 08-17-15, 06:02 AM
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The points plugs are a hotter heat range to better deal with fouling with the weaker spark.

IMO the reason to convert to electronic is so you can run colder plugs, not the other way around. If you took out the points ignition without changing the plugs, all you did was move parts around to no benefit.

I always preferred the BR8ETs to the flat electrode style, personally. That's the 1980 plug.
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Old 08-17-15, 07:12 AM
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I'm running the rx8 plugs but its really dependent on the type of ignition you have. The stronger
the spark, the cooler the plug you can run. +1 on what PeeJay said.

Last edited by t_g_farrell; 08-17-15 at 07:18 AM.
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Old 08-17-15, 08:15 AM
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Wouldn't the rotary benefit from an overall hotter spark (ie using the earlier plugs with later igniton)? I would imagine that would clean up more of the unburned fuel that rotaries leave behind.
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Old 08-17-15, 09:03 AM
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Originally Posted by TheRX7Project View Post
Wouldn't the rotary benefit from an overall hotter spark (ie using the earlier plugs with later igniton)? I would imagine that would clean up more of the unburned fuel that rotaries leave behind.
you want a more powerful spark, but with a spark plug that runs at a colder temperature
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Old 08-17-15, 09:37 AM
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I guess I don't understand.

I always assumed a hotter spark meant a more powerful spark? What is the benefit of a colder temperature spark plug?
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Old 08-17-15, 11:02 AM
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Leaving the old plugs in was a matter of necessity as I simply didn't think about the plugs until I was well into the swap. My question is mostly about potential damage like the plugs running too hot and breaking up. If the plugs will work fine I'll leave them until they need to be replaced anyway. I daily my car so I'm not trying to squeeze every ounce of power out of. The swap was done mostly for driveability.
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Old 08-17-15, 11:36 AM
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Old 08-17-15, 12:55 PM
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That diagram pretty much covers it - thanks for posting.

The purpose behind a hotter plug is to retain more heat in the body of the plug to help burn off carbon deposits - it has nothing to do with the 'heat' of the spark, and running a plug too hot will result in ceramic electrode casing failure and broken bits of ceramic spinning inside your engine.

I've always run BR8EQ14's, and never saw a need to change colder or hotter, given the EFI nature of an -SE.
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Old 08-17-15, 02:40 PM
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That makes sense. I'm not even sure what plugs I'm running at the moment (they've been in the car for a few years now). I know I've got some new NGK BR8EQ-14's ready to go in, just haven't had the opportunity to work on my car (new baby at home).
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Old 08-18-15, 12:47 PM
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Originally Posted by TheRX7Project View Post
Wouldn't the rotary benefit from an overall hotter spark (ie using the earlier plugs with later igniton)? I would imagine that would clean up more of the unburned fuel that rotaries leave behind.
That's not what it means... the heat range of a plug is how much heat it retains vs. rejects, not a measure of spark energy. Colder plugs foul more easily but hotter plugs can result in high speed miss or even preignition.

Generally you want to run the coldest plugs you can get away with, without fouling. I'm running 10s and an MSD.
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Old 08-18-15, 09:25 PM
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Ok, I'll be more specific. I understand the heat ranges and that led to a good discussion on that topic. However, my question is what is the difference between the "ET" and "EQ-14" suffixes and is it a difference that will cause issues?
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Old 08-18-15, 09:31 PM
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ET have three straps, EQ have four flat ground electrodes.

Personally I like the ETs, but the EQs are easier to find. Usually. If you have an actual '79 engine then you will need a thinwall spark plug socket to use the EQs. Another point in fabor of the BR8ETs. I still remember the part number, too - 4221. Haven't used them since 2001...
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Old 08-19-15, 10:27 AM
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Originally Posted by peejay View Post
That's not what it means... the heat range of a plug is how much heat it retains vs. rejects, not a measure of spark energy. Colder plugs foul more easily but hotter plugs can result in high speed miss or even preignition.

Generally you want to run the coldest plugs you can get away with, without fouling. I'm running 10s and an MSD.
Thanks for clearing this up.
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Old 08-19-15, 12:20 PM
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Originally Posted by peejay View Post
ET have three straps, EQ have four flat ground electrodes.

Personally I like the ETs, but the EQs are easier to find. Usually. If you have an actual '79 engine then you will need a thinwall spark plug socket to use the EQs. Another point in fabor of the BR8ETs. I still remember the part number, too - 4221. Haven't used them since 2001...
Thank you. It is the original 79 engine so I'll keep using the ETs but get a cooler plug when I replace them.
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Old 08-19-15, 06:24 PM
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Originally Posted by peejay View Post
ET have three straps, EQ have four flat ground electrodes.

Personally I like the ETs, but the EQs are easier to find. Usually. If you have an actual '79 engine then you will need a thinwall spark plug socket to use the EQs. Another point in fabor of the BR8ETs. I still remember the part number, too - 4221. Haven't used them since 2001...
Thats the plug we use for our 1st Gens in the UK. BR8ET
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