Iridium spark plugs or platinum?

I am due to change the plugs on the RX-8. I have had a bit of sticker shock, $38 each locally or $24 each on line. Am I wrong to consider the plugs from a 93 RX-7? They are about $6 each. I realize the Iridium plugs can go more miles between changes, but I do not mind changing them more often. Any opinions will be appreciated, Thank you.

Well I think you answered your own question. The only advantage of platinum and iridium plugs is greater longevity, and you said you don't mind changing them more often...

Plugs that sit for years tend to corrode themselves in place, destroying the part they come out of. Especially aluminum.

I've seem reports about the wonders of iridium and its variants that are all over the board. My own experiences are that it was not amazing, and I did ultimately have pretty substantial degredation over time. The plugs looked fine, but didn't work well.

That's wild. I bought a set of NGK Iridiums for the integra for 6 bucks each a few months ago. After eating up plugs left and right with nitrous in our first challenge car, somebody recommended these, and I think the same set is in there several years and several dozen drag passes later. I run them in everything now. Then again, I'm apparently a "hon-duh fanboi," so YMMV.

pilotbraden wrote: I am due to change the plugs on the RX-8. I have had a bit of sticker shock, $38 each locally or $24 each on line. Am I wrong to consider the plugs from a 93 RX-7? They are about $6 each. I realize the Iridium plugs can go more miles between changes, but I do not mind changing them more often. Any opinions will be appreciated, Thank you.

Get over to RockAuto. They're $16 each there. At that price, depending on how many miles they last, i might consider that worth it.

$38 each though? HELLLLLLLL NO.

In reply to poopshovel:

Well since HonDUH fanboi's have no earthly idea that a rotary spark plug might be different...

They're expensive because they're weird, the Iridium part really doesn't have much to do with it.

In reply to Javelin:

But presumably the $6 FD plugs are just as weird as the Rx-8 ones, no?

Surface gap plugs are only weird to automobile folk, they are common as dirt to outboard motor folk. Price matches to, they are far cheaper and more available at Boatersworld and such.

Ran the wrong plugs in an old RX7 of mine once. Only thing I could get my hands on. Standard Champion plug. Engine loved it. Later learned this was a quiet secret in the RX7 world. Don't know if that would apply to the RX8 world.

In reply to codrus:

Actually, they are not. Although most RX-7 plugs are odd, they are basically the same for all of the early Mazda rotaries (12A, 13B, etc). They are also usually of a "normal" electrode (as opposed to Iridium).

With the Renesis in the RX-8 (and it's different ports), the plug designed changed making for very different looking leading and trailing plugs. Not only are they more difficult to manufacture, but the market is a lot smaller (far less Renesis's out there than 13B's).

I would not recommend any 12A/13B plugs in a Renesis (nor visa-versa for that matter).

Just et the $16 ones from Rock Auto.

I definitely would stick with RX-8 specific plugs. Racing Beat has a write-up on their website about what plugs they recommend. I think there are some colder plugs that you can get which give a few more hp, but tend to foul a lot.

Racing Beat RX8 Ignition Tips

Thanks for the advice. If I can get the proper plug for $16 I will do that.

Braden

To second the motion of specific RX8 plugs. Most of the RX8 racers I know have told me that other plugs don't work as well in the Renisis in the RX8. The Iridium is only part of it, there's more to it. Reach is involved and I seem to remember someone said internal resistor/capacitor or something like that is the biggest reason the plugs are more expensive. Could be wrong about that, OK maybe most likely wrong but hey it sounded good though. They have gone up in $, the last time I changed plugs in my RX8 they were $21 a piece.

Why does a rotary need spark plugs? Doesn't the magical triangle make it's own fire?

Only for those who know the secret handshake. Obviously you are not among the anointed.

Speaking of making it's own fire, I wonder what it would take to make a compression-ignition rotary. Sounds interesting... and like it would blow out apex seals to no end.

I seem to recall that the rotory was originally designed to be a diesel...

My mechanic friend told me that a lot of newer cars with coil over plug ignitions will run into problems when running old style plugs. He says the resistance in the plug is different and it can cause problems with the ignition coils.

I don't know how or why, but that is his practical experience.

Javelin wrote: In reply to poopshovel: Well since HonDUH fanboi's have no earthly idea that a *rotary* spark plug might be different... They're expensive because they're weird, the Iridium part really doesn't have much to do with it.

DURP!

JohnyHachi6 wrote: Speaking of making it's own fire, I wonder what it would take to make a compression-ignition rotary. Sounds interesting... and like it would blow out apex seals to no end.

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