Really?
is it just because performance is off?
Those plugs in which my performance fell off , upon inspection show deposits on them, but the electrode has no visible wear, the insulator is intact, the ground stap has no visible wear and the resistance specs out normal.
So what makes this plug unable to provide the performance as it did 5K miles ago?
WHy cant they just be cleaned and brought back to near new performance?

Is there no way to pull a plug on a rx8 engine and be able to say--this one is going bad--- better replace it. I can do that on recip engines pretty good but not the rotary.
What the heck "wears out" on a spark plug that cant be seen or measured?[

 

I don't know about your plugs, but my center electrode goes away pretty quickly.

 

So are you saying the gap is opening up pretty quickly on the OEM plugs? You are probably not NA.

 

 

Hmm. Probably not...

 

 

thats just it
under 10x hand held ant killer, the center electrode on my leading and trailing iridium plugs still looks good as does the grounding strap. dirty with deposits---yep. but once cleaned they appear ok and the resistance seems ok per voltometer?
I havent ran the flat tops long enough to evaluate.
Does your trailings also erode fast?

 

If the electrodes are intact and the gap is adequate, then the other thing that can deteriorate is the ability to insulate the spark so that it jumps the gap instead of being shunted to ground. It doesn't take much for a path to develop either on the insulator surface, or internally. Difficult to test because it's hard to replicate the conditions under which the plug must operate -- high voltage pulse in a pressurized air/fuel atmosphere.

Nothing wrong with cleaning and re-gapping, just be careful to not damage the insulator. That means no wire brushing, and also abrasives can be damaging (sand-blasting, etc). Ideally, plugs are self-cleaning in service and shouldn't need attention, other than possibly re-gapping, until it's time to replace them. The other reason to remove is for periodic inspection and to ensure the threads don't seize (anti-seize compound is important for the rotary).

 

Heres what I do:

1--I can tell my plugs needs attention--if i free rev the engine to around 2K and listen for an aubible very slight single, intermediant "skip". This skip seems to disappear after 2K and car is running fine. I lot of people cant hear it, but i also have had race teams tell me they do the same thing --at times.

2- I pull the plugs and look at them. With my tune etc i dont have much of what is commonly known for us as the black looking crust/deposits. i do have a dark/light brown crust on the leading and on the trailing it is darker. Its easy to tell the flame travel from these deposits.
The last 2 threads of my plug confirm my heat range is ok.

3- the grounding strap usually has some deposits on it(all over) but the tip is clean. it is gapped per oem. i used to run a closer gap before i installed the hks twin power.

4- the electrode is clean --a little discoloration ( no deposits) on it but the tip ---again---is clean.

5- the insulator is unreadable due to smaller grained deposits. These deposits are uniform the lenght of the insulator per ant killer.

Ok--since the plugs have a normal appearance in my engine I get to work and clean the body of the plug, plug end ring and grounding strap, use a dremel with a copper brush. cleans up good.
I clean the electrode tip/insulator with brake cleaner and a cloth with a wooden toothpick.
It cleans up pretty good.
I then test the resistance and it usually specs out fine.
I check the sparkplug wire boot/tip and the tip of the plug for fitment etc.
then I MAY regap the plug down from oem to about a 36-38.
Car will usually respond well and no more little delusional (meh) skips. (ob2 not showing misfires)
For about 1-2 weeks ===approx 300 miles.
Then it comes back. After a day or 2 of cussing -----I then get new plugs.
I have currently been running the Denso 27's and 31's since Aug /09.
About 6K on the clock--no tracking on these.
Reminds me when i was running a 11.5 compression ratio big block chevy. they would destroy plugs in 1-2 weeks. Course they didnt cost $80 either.

 

$80 for plugs?
You only need to change the leading.

 

Yep. Even with the cost of the Iridium plugs, probably not worth the time cost of futzing around trying to "fix a spark plug". And testing resistance with a 9v battery doesn't tell you how it's going to handle 50,000 volts at 10 atmospheres.

If they're running ok there's no reason to mess with them. If there's a miss, then a cleaning probably isn't going to give thousands of miles of extra service. The one exception might be if the plugs are badly fouled due to some other engine condition. Once that's fixed, it can make sense to clean the plugs of oil/carbon and return them to service so the excessive deposits don't bake on.

 

My first four RX had to have spark plugs cleaned gaped or changed every 4K so I'm happy with 37K! Rotary engines are very hard on spark plugs but spark plugs have improved immensely. The gap on plugs wore much more 40yrs ago but with Iridium now after 37K on a N/A engine very little gap change. Some people on here have more then 50K on there's but if your know your car you can notice a slight hesitation as the gap opens up and gunk builds up. You should have seen the led build up 40yrs ago it was BAD. After it was removed from gas I was surprised how clean they were but the gap still opened up. Then the tips went through many changes of design and materials.

 

We can tell if the coils are good by electrical resistance testing, and the cables by inductive, but there's really no way to evaluate the 'plugs other than visual inspection and of course a noted drop in performance. They can be cleaned and continued to be used if the insulator is intact and the anode/cathode parts have enough matter to still afford a spark (probably need a regap tho'). As most electrical components they work right up to the point of catastrophic failure. But as they're relatively cheap.... why are we even having this discussion?

 

^ yeah, I knew that would be the comeback even as I typed it. I think Olddragger is expressing frustration that there's no real empirical way to know if the 'plugs are going south, except for obvious visual cues with which he's well experienced. There are of course expensive test rigs that can measure all sorts of things and thereby pretty accurately predict reliability, but nothing we would acquire for the sake of an $80 set of 'plugs.

 

yep that's what I've been doing as well .

 

The trailing are pretty well shrouded.
The leading are the plugs that seem to wear and they're only $3 - $7 each.
I just swap them out every couple of months.

 

Funny this thread came up...

I just pulled the plugs from my car and the engine I'm selling this weekend (both got compression tests)

The plugs out of my car are over a year old and probably 25k miles
They were fairly clean as far as spark plugs go, but the local that compression tested me also tested them with his Fluke voltmeter...

The spark plugs out of the donor engine are; age unknown... visually, more build-up than my plugs. But then I switched them into my car to test them... they worked fine, and tested on the fluke at the exact same as my plugs.

So, I just wire brushed mine lightly to clean them off a bit, and stuck them back in.

 

Made the mistake of ordering some from a stealership recently
NZ$42 each for BUR9EQPs .

 

jeff is smart
wish i had a 5 ms dwell time.
OD

 

Can you please tell us where are you getting them so cheap?
The cheapest I've seen so far is 18$ each...

 

http://www.sparkplugs.com/