Hot_Wheels

iTrader: (12)

i got a turbo 1.6, what plugs are you guys running? i was told the ngk ifr6t11 i believe, i got those in there now i still have a little break up though, im thinking of changeing the cap and rotor. did the early miatas have a cap and rotor?

Joe Perez

iTrader: (8)

BRK7E and IFR8H


Yes, but they're part of the suspension and brake system, not the ignition.

gospeed81

iTrader: (51)

LOL


Try searching a little on spark plug gap...I found ~.024" to be just right on mine up to 12psi when still on stock (coil and ignitor) ignition system.

After you realize how much gapping down and still occasionally getting blowout sucks, then search on COPS. It looks complicated, but it couldn't be simpler, it's literally 4 wires.

Braineack

iTrader: (62)

< 6psi = BKR6E
> 6psi = BKR7E

although I think that there's probably a reason the 1.8L has a BKR5E from the factory and we are all running 1 step colder than we probably should.

Joe Perez

iTrader: (8)

Yes, it probably produced a fiftieth of a percent reduction in cold idle NOx emissions.

Now, granted, they continued to specify the 5 plug even for the MSM, which suggests that perhaps we're all a little over-paranoid about this, but on the other hand, I ran the IFR8H plugs for about two years as an experiment, and had no problem at all with them. When I switched out to a set of new BRK7Es just to do a back-to-back comparison, I noted no difference at all in performance.

As an additional Very Interesting™ datapoint: the specified plug on the non-turbo 1.6 323 (the 8-valve version of the B6) is the 5 range, however like us, they went one step colder and specified the 6 plug on the 323 GTX. Why did the 1.6 Miata also have a 6 plug stock? Enquiring Minds Want to Know.


Long story short- there's a pretty wide range of "acceptable" in spark plug selection. You're not going to contract herpes or start voting a straight democratic ticket if you go one or two ranges colder than stock.



Hot_Wheels: it's possible that worn-out muffler bearings can also produce the symptoms you describe, and they're pretty cheap, so pick up a set of those (there are three in total) while you're at the parts store.

shlammed

iTrader: (8)

i use 6's at 10psi and i havent had any pre-det or any of the harmful effects.

i have tried 7's and 8's as well...
8's blew out in boost no matter the gap.... i assume they just werent getting hot enough or something
7s work and i have a set in my armrest just incase (i drive with my tools in my trunk)

kotomile

iTrader: (24)

I dynoed with 6s at 14 psi without issue, but I run WI and 7s on the street for an extra margin of safety. Whether it's needed or not is probably arguable.

Splitime

iTrader: (24)

I've always found bkr7s to do the trick.

Braineack

iTrader: (62)

you really takes things one step further don't you? here I simply pose the question and you run with it.

shlammed

iTrader: (8)

i call prefectionist or some type of engineer.

We like to overthink the basic questions people have.

Braineack

iTrader: (62)

Joe is a Mad Scientist.

shlammed

iTrader: (8)

or that.

Hot_Wheels

iTrader: (12)

i put ifr6t11 in after talking to someone on clubprotege.com so far they seem ok but it still sonds like it breaks up at idle, it could be a cap issue, theres no boost control on the car im running of the stock wastegate which is set for 8lbs i believe, ive seen it spike to 15 though. should i pull these plugs and put a safer plug in or should these be ok?

Braineack

iTrader: (62)

no. your plugs are fine. albeit gapped too large.