Plugs for boosted Miata

So I'm putting the Miata back in Manic Mode™ and doing some maintenance while I have it apart. I figure I'll treat it to new spark plugs.

So what is the recommended plug for a Miata packing supernatural aspiration? It's currently pullied for about 10 pounds of boost. What about temperature range? That subject is a dark art for me - I don't really understand it.

Recommendations welcomed. Thanks.

BKR7E, or i believe FM likes the ZFR7F as well.

I've used both.

NGK ZFR6F is our street plug, we stopped using the 7 heat range a few years ago due to the potential for cold start fouling. We have a low resistance race plug that we use for maximum spark - it'll work fine on a street car, but there's the possibility of electrical noise in the stereo. Never had it happen, but it's a possibility.

Yep, NGK BKR7E.

FYI, the ZFR is an extended tip plug. Gives better combustion than the BKR in our opinion.

'Kay, thanks for the prompt answers, gents!

Suggestions on gap, please?

Depends on your ignition, methinks.

As much as possible. You'll be able to get more gap out of the race plugs.

Depends. I was gonna add to my post but for some reason couldn't do that from my phone. I'd try Keith's plug first and go colder if needed. Once this mornings' coffee kicked in, I recalled that's what we did with both my turbokars. You want as much gap and you can fire. On a stock coil, stick with .020-.025 so it doesn't blow out under boost. With a Jacobs or HK$ coil, I've run .035 or more to good effect.

I'm running .040 on ours i do believe.

Keith Tanner wrote: NGK ZFR6F is our street plug, we stopped using the 7 heat range a few years ago due to the potential for cold start fouling. We have a low resistance race plug that we use for maximum spark - it'll work fine on a street car, but there's the possibility of electrical noise in the stereo. Never had it happen, but it's a possibility.

Keith: I'm finally getting around to replacing the plugs and I have a couple questions concerning your answer above. In another thread, you had suggested the NGK race plugs to me.

1. You mention that you stopped using the 7 heat range plugs, but the FM description of the race plugs you suggest says they are 7 range. The Manic Miata is a street / autocross car. It starts pretty well, but NOT immediately and it is likely to sit for a month between starts, particularly in the off season.

2. For the race plugs, the FM description says "Not compatible with old Link ECU." The car has a Link, but in our previous discussions, I believe you mentioned it was the Obi-Wan Link. The PO was named Edward Trahan and he bought the Uber kit from FM. Can you confirm that (assuming the race plugs are what I want) that they are compatible with my ECU?

Thanks!

Jay_W wrote: Depends. I was gonna add to my post but for some reason couldn't do that from my phone. I'd try Keith's plug first and go colder if needed. Once this mornings' coffee kicked in, I recalled that's what we did with both my turbokars. You want as much gap and you can fire. On a stock coil, stick with .020-.025 so it doesn't blow out under boost. With a Jacobs or HK$ coil, I've run .035 or more to good effect.

I'm really liking the LS3 coils on mine, although they don't want to seem to do .035 at 27 psi. :)

The Obiwan is on the "old Link ecu" list, I believe. Stay away from the race plugs.

All right, thanks!

Back to the OP then - anything better than the NGK ZFR6F?

Not really, it's the right plug for the job. What you really want is some big burly coils backing them up.

Yeah, what's the most cost effective way to get them?

Find a well-maintained Miata, pop the hood and steal yourself a set.

Everybody's a comedian...

Or you could go to the guy who's been answering your technical questions about his product.

Most cost effective shipping would be via USPS, call to order.

Basically you've got four choices. Totally DIY something using random parts from a junkyard (cheap, but lots of work), junkyard Toyota COPs using various brackets and harnesses that are available (a couple hundred, but it's not all that much stronger than stock), the Fab9 coil kit (which I have no personal experience with, but haven't heard good things about), or FM's LS3 coil setup. Keith will sell you the whole thing with brand new guaranteed-genuine GM coils, or they also sell a kit without coils so you can source your own. Be aware that a lot of the "LS3" coils out there on ebay and the like there are counterfeits with inferior performance.

I have the FM set on my car. :) It's not the cheapest option up front, but it's cheaper than buying coils multiple times because you're unhappy with the first couple iterations.

Keith Tanner wrote: Or you could go to the guy who's been answering your technical questions about his product. Most cost effective shipping would be via USPS, call to order.

Oh, absolutely! I was just asking what FM's most recommended setup is. Not trying to abuse your generosity. Sorry if I came across that way.

But in looking at the FM Big Spark kit, it appears that the Link disqualifies me for that as well.

Sorry, it was a long day yesterday. I misinterpreted your statement. Although I have been known to steal plugs out of coworkers cars at the track when my Locost fouls a set Get the car running on the borrowed plugs, then swap my fouled ones into the hot combustion chambers one at a time. But I digress...

The Link does DQ you for the LS3 coils - that's why I didn't mention it earlier.