It's been suggested that I change plugs every ~6k mi. or so. This recommendation came after a discussion regarding tuning I've been doing and some knock I was getting in 4th gear. I was at about 7,500 mi. at the time, so I figured I would swap them with my next oil change. Here's what I found:


BR7ES

I would add that the next feeler size up was 0.036", and the 0.032" in the picture had a touch of wiggle, so my actual gap was probably more like 0.034". The electrode itself looked healthy and the plug overall was in good shape. That gap, though... It was at 0.026" when it went in the car.

This is with fairly vanilla driving. No racing and only a handful of non-tuning WOT pulls.

I'd say this is a pretty good endorsement for every ~6k mi.

Wow, that is a big difference! I am thinking of switching out to Iridium plugs next time. I have nearly 50K miles on my Iridiums in my Evo and I run E-85 at 28psi

I'd be interested to know what, if any, con's switching to an irridium plug might present. I've only ever heard BR7ES and BPR7ES.

I remember the old days of when people were really against running iridium plugs. Now these days when I see my buddy's running 11.5:1 compression and 20+psi in their 5.0s, I don't mind running iridium in my 4G63

It depends on what you want. I like to pull plugs and swap them often, so I recommend the 1.50 NGK plugs. I will put a fresh set in, make a pull, pull the plugs and check the timing line to get a better picture of the cylinders running conditions. Then a new set goes in after any tuning with timing. You can't really do this with Iridium, mostly because of cost. With Iridium, they last long, but at a much higher price.

Never seen such a gap growth in a car after so little mileage. Crazy. Iridium is great to use, but you don't want to swap them out often, unless you rich and have nothing else to buy.

I had nothing but issues with iridiums. NGK or denso. I switched to race plugs and have had no issues.

Which race plugs? Brisk?

Denso.

/ubbthreads/images/graemlins/rofl.gif

Quoting G:
I had nothing but issues with iridiums. NGK or denso. I switched to race plugs and have had no issues.



To go with your "race cam"? /ubbthreads/images/graemlins/rofl.gif

/ubbthreads/images/graemlins/rofl.gif

good call. maybe I'll check mine. I always run the $2 NGK plugs in my cars.

I guess I should check mine. I've put on a bunch of 2nd & 3rd pulls at this point, and I had to go to a .022 gap to make the car happy. at .032 my car misfires and runs like sh*t over 8,000.

I actually was just checking my plugs, this should be a habit that everyone here should have. I was beating the dog sh*t out of my motor this past weekend street racing so I just had the plugs out this afternoon. I just remembered they are iridiums but race version. I was having issues with the standard iridiums. I usually go back and forth between ngk's and these densos.

I've found that the non-projected NGK plugs seem to be a bit happier in our cars. Try the BR7ES instead of the BPR7ES. I'm running them gapped tight but also running ~26psi on a T67...

Yes, those work great as well. I'm only pushing 24-25 psi max out of my tiny turbo. I'm sure once i'm in 35psi land with a bigger turbo It will be a different story.

Quoting slugsgomoo:
also running ~26psi on a T67...



soon....very soon... /ubbthreads/images/graemlins/banghead.gif

Quoting slugsgomoo:
I've found that the non-projected NGK plugs seem to be a bit happier in our cars. Try the BR7ES instead of the BPR7ES. I'm running them gapped tight but also running ~26psi on a T67...



That's exactly where I'm at. Evan suggested I switch to the non-protruding NGK's after I got my tune over 22psi and started getting some misfire. Happy ever since.

Quoting slugsgomoo:
I've found that the non-projected NGK plugs seem to be a bit happier in our cars. Try the BR7ES instead of the BPR7ES. I'm running them gapped tight but also running ~26psi on a T67...



I too run the non-projected BR7ES in 1837. They perform great.

I've only had issues with iridium plugs. Aside from longevity, what other benefits are there? I'd probably care about how long my plugs lasted in a DD or something, but not in anything I'm beating the sh*t out of. As much as I pull the plugs to check them on 1837, I just spend the $10 bucks and throw in a new set of copper cores every few thousand miles.

WTF makes a spark plug a "racing" spark plug?

In a 950whp 2G we look after it runs BPR9EIX plugs gaped to 0.018" (Has MSD ignition setup though) In my car I run BPR8ES gaped to 0.026" And have no breakup issues to date, though boost is quite low do to only running 25psi on 91. Brothers Evo again runs BPR8ES gaped to 0.022" (Stock ignition setup). Haven't had any problems with ignition with his current setup going on 3 years.

Also another thing to take into consideration is your plug wires. Best would be to replace them every 2 years with a moderately powered car that see's decent amount of miles. Last night for example, I was helping diagnose an engine noise in a local 2G when trying to start it one of the plug wires decided to take a sh*t. Really it had no spark at all on one cylinder. Replaced it with a spare and fired right up.

I replace plugs every oil change.