Spark Plug Dilemma
 

i purchased some Denso Iridium plugs for my 05 rx8 thru sparkplugs.com

ive gotten mixed recommendations from forum members regarding yea's and nay's
so, i dont know whether to used them or not...

i just took out my OEMs today...compared them to the Denso's....they are both the same thread, size, HAVE A BEAM (the beam is the same)...but the oem has those groves around the rim...

here is a pic of the Denso Iridium leading plug...

http://img211.imageshack.us/img211/5491/pc250162ud6.jpg

i appreciate anyones thoughts on this...

:D:

The grooves are on the OEM plugs to reduce the chance of flooding.
Are you running OEM heat range? I though that boosted rotaries needed hotter leading plugs... or was that colder?

BTW, can you post pics of the old plugs please?

can you speak english, not mountie????

:lol:

i cleaned the oem plugs and put them back in...

i guess i should have taken a pic or two
:banghead:

I am speaking English.

What did you not understand?? Seriously...

Did your plugs look like mine?
https://www.rx8club.com/showpost.php...48&postcount=1

j/k on the english....although i dont understand the heat range thing...

only took out the leading ones...
they were mostly dark but not a lot of corrosion or build up as yours...just a little on the beam

my car had been runnin rich with the x...now its right where it should be with the flash....

Spark plug 101
http://www.ngksparkplugs.com/techinf...000&country=US

Some nice pics in this one
http://www.nightrider.com/biketech/s....htm#discussed

I love the description of my plug condition:
Light brown deposits encrusted on the ground and/or center electrodes indicate ash deposits. This situation is caused by oil and/or fuel additives. When the deposits are found on only one side of the spark plug core nose, it is usually considered to be a problem with the cylinder head (valve stem seals or valve guides). When they are found on both sides of the spark plug, it is often considered to be a problem sealing at the piston rings. This condition can mask the spark and, in some cases, contribute to misfire. Check for worn valve guides and valve stem seals and/or piston rings. The spark plug is the correct heat range and was a victim of the engine's condition, not the cause of it. We does not recommend the use of fuel additives which leave deposits on the core nose of the spark plug.

thx

at the risk of sounding totally illiterate, do those statements apply with the rotary engine?

Well some of them do. Obviously we have oil in our combustion chambers but it is there by design. It really means that the deposits on my plugs are normal for a rotary engine. Obviously they didn't consider our little engines when they wrote that.
Next time you pull out your plugs you can use this information to check how your engine is doing.

If the car has been running rich in the past, then the plugs would be evidence of this by having black carbon buildup on them. On the flip side, it's been my understanding that a plug that's tan in colour is one that's been in an environment where it's been run lean while under load and pretty hot. A sure-fire indicator of having too hot of a plug for a chamber environment is the electrode (very small center part) having been worn down and seemingly eaten away.

Spark plug heat ranges -- think of it like this: For a hotter combustion chamber environment, the engine needs a "colder" spark plug, meaning it needs a plug that's built for a hotter environment. Spark plugs have varying heat ranges as they're designed for specific environments when it comes to internal heat. A good comparative example of a hotter chamber environment would be a turbocharged 8 vs. a stock, non-turbo'd one. The non-turbo'd one won't run internally as hot (or won't have the potential to) compared to the turbo one. It's kind of on the same level as why running a hotter environment (like the turbo'd one) would need a higher octane, "colder" fuel and hence the reason why we'd run 91/93 on a turbocharged application instead of just 87 on a non-turbo. The spark plug will hold (x) heat until it runs the risk of becoming a defacto glow-plug which will cause all sorts of pre-ignition engine knock (instead of the plug initiating the burn when the computer tells the ignitor/coil to zap it at a specific time, it will be so hot that it will light the mixture at random times). Think of an environment for running a "hot" plug for a beater car like, let's say, a 3-cyl Geo Metro grocery getter that can barely keep up with the city bus when it's floored. Think of using a "colder" plug in something like a road-race car that's on the throttle for several minutes at a time with the engine running very hard.

If the plug in the engine is too "hot" for the desired load, then the motor will violently knock randomly and intermittently (the kind that shudders the entire driveline and shakes the car) when it's good and cookin' hot, increasing in frequency as the motor continues to load out, until it results in a catastrophic failure. I've seen this happen before first-hand three times, unfortunately.

If the plug is too "cold" for the environment, then the motor will have a hard time starting especially when cold, run more poorly, will foul considerably more easily and produce misfires, will be blackened on its entire surface, and will reduce gas mileage.

Btw, slick looking car!

Hope this helps,

B

shinx: how did you clean them? Our iridium plugs are kinnda fragile

i used a toothbrush....
as per suggested by CRH....i agree...they look pretty fragile..

ive done a little research and decided to use the denso plugs...my concern was the length...they compare to OEM in that respect...

thx everyone for the info....

:D:

Let us know what you think of the Denso's

I was thinking about trying Denso.

but after I found that on Ebay someone selling Leading plugs for 9 bux a pop .... I changed my mind and got myself 6 of them, and buying the trailing on maybe Amazon or sparkplugs.com

There are at least two members that posted using Denso's.

One person gave me a feedback and said they were good.

The post concerning the tan plug is in correct. Tan color is what you want.

A white tip is too hot and black tip is too rich.

To really check the condition of your plugs you need to remove them right after the load.

Unfortunately it's not as easy as a motorcycle. That's why we have different tools that measure A/F ratio etc..

You should run the throttle wide open on the road then shut off. Pull plugs and check. Then do the samething at mid throttle and idle.

If you run your car in traffic all the time and let it idle alot especially right before you pull the plugs... You will see the surrounding of the plug as being black. There is a good possiblility the tip could be black too, depending how long you let it idle before pulling the plugs.

The tip should be a tan color.

Our RX8's will always have black soot around the surounding tip as they are flashed to run pig rich for EPA. The tip it's self should be tan.

My car ran better with new Densos than with new NGKs (not the ones I just sold).

The denso plugs are like what, 40 bux a pop ?

kinda too much imo.

i got em for 35 at sparkplugs.com

still cheaper than what you get from the dealer :lol:

What liquid did you use? water?

no liquid Dom
just a soft toothbrush very gently...

dont tell anyone, but i scraped off some stuff with my finger nail...:lol2:

eventually i will get the new plugs in...
been busy with the fj cruiser...

i just changed out my plugs on my 04. the old ones had about 20k on them. they were caked with a tan residue. is that a sign that my seals are not sealing properly through the cycle? thanks.

LOL I still need a set :) PM me when you are going to place your next order so I can get a set.

i received my set today charles, i'll be putting them in tomorrow most likely. thanks.