Yes, I re-read my last post and I did have it backwards. Switching the terms "leading" and "trailing" will correct what I meant to say. The trailing plugs are two heat ranges colder than the leaders because they spend more time in a heat soak. See, this is why I hate these ultra-detailed discussions..... You should have seen how long it took me to type all this junk.

I think combining Yaw's page with the NGK website makes for some great info.

Can we get back to making power, now?

CRH

 

Hope you don't mind me digging this thread, since I am thinking of changing plug soon.

Saw some HKS product for the rotary, not sure they are for RX-7 or RX-8. They have heat range from 9, 10, 10.5 and 11.
Then couple of pages later in the magazine there is a FEED RX-8 that sells the FEED spark plug having a NGK eqiv rating 10 and 11 .

From what you are saying I understand. It may be a short term benefit for the 10 and 11 plugs but it won't last long --- right?

 

Oh that is a useful table, I think

 

Is there any protential problem running all 9's????

If not so, is there ANY benefit?

I am tempted to change to the HKS RE series plugs but they only have 9, 10, 10.5 and 11.

All 9s is ok?! RG will say yes but elaborate, please ?

Another extremely stupid, but confirming question: So I need 4 new plugs? (I told you it is stupid .... :p )

 

I could suggest a theoretical answer but RG can answer you based on experience so I'll wait for him. If he doesn't chime in I'll respond.

 

This is going to be a very untechnical answer. I drive my car alot harder than the average person does since it is a play car. I just don't go through 9's as fast as I do 7's. I once experimented with some 6 heat range plugs and had the ceramic element break and fall through the engine! Bad news. If I were to drive the car more civilized or on the freeway more where the engine isn't being worked as hard, I'd probably stick to 7's on the leading. When I had a turbo, I only ran 9's.

FWIW: I swa a test of all the different types of rotary engine plugs from both the factory and aftermarket. I don't know where the website is anymore. Bsically it showed that many aftermarket plugs just weren't worth it. Strangely enough out of all the options available over the years, the RX-8 plugs seem to be the best. I'd switch over to them if they weren't so expensive. No need to go with HKS.

 

It seems like HKS (in Japan), Denso (in Australia) and the NGK (in Australia) are the same price ($50 AUD), but I heard NGK and Denso in Australia's dealer carries is not as good as the NGK or Denso in Japan, thats all. It may be a rumour but I can't take the risk for my priced machine. I can not source any JDM NGK or Denso, but I can find HKS easily in Hong Kong.

That is why I took the step for the HKS and the car is weekend car (with highways) and go to track 3 times a year. So if you think 9's on the leading plug is ok then I will take the punt.

 

This may be a stupid question, but I'm famous for them at this point. Do the stock NGK trailing plugs (with the 9 heat level) fit in the leading holes (where the stock heat level is 7)?

 

The plugs are the same size.

 

Yes perfect... I think all 9s for me in the next service. I rather have HKS plugs than the inferior than stock NGK (Australia) plugs

 

Just wondering but is clearance an issue with the 8's..I just checked my plugs today and man did they look hidious! As RG had said busted off ceramic is not good but Ive survived..In all this I did notice the length differs between leading and trailing plugs..RG if you can give me a ideal set up for my(our) 8's..I drive hard but right and like the theory made in regard to durability..Makes sense..Any input would be appreciated.

 

Fujita Engineering supplied mine ... I think it is NGK racing 10 in the front and 9 at the rear.

I doubt they last very long

 

i previously had a set of the Mazdaspeed leading plugs (really just NGK units 1 heat range colder) & they felt great. I switched to the Denso iridiums one heat range colder on both leading & trailing & the car feels a bit rougher with them. I think I will be switching back the next time around. About the only problem I found with the colder plugs is the fouling gets a bit more than with the hotter plugs.

 

http://www.silverbulletrx7.com/plugs/ this guy has done his homework, good read

 

He has updated hence like 2 years ago... I wish I can fastforward for a few years and see what he thinks.

Is MazdaSpeed ones labeled NGK Racing Competition? I have ones that are in Japanese translated RE Iridium R7440A-9L R7440B-10T, so it is 9 leading and 10 trailing. Could you tell me more about the "fouling"?

 

[QUOTE=takahashi]He has updated hence like 2 years ago... I wish I can fastforward for a few years and see what he thinks.

no, he has see
This page was last updated 02-26-2006.

 

The ones I got were labeled RE8A-L for the leading plugs. When the plugs are colder it allows more of the burned material/gunk to cake onto the plugs, as opposed to the hotter plugs. Definition of it :

If the nose of the plug is not hot enough (colder plugs), it will gradually accumulate deposits, known as fouling. During normal engine operation, residue from the combustion process hits the insulator nose. This may include carbon, unburned fuel and oil, and chemical additives present in both fuel and oil.

If the insulator nose and electrodes are hot enough, the combustion deposits will be continuously burned off by the heat of the plug. The ideal situation is to have the deposits burned off as fast as they accumulate, so the insulator nose stays fairly clean and free of deposits.

If the deposits accumulate on the plug because it is not reaching a high enough temperature to burn them off, the gradual accumulation will eventually short out, or foul, the plug. The fouling is electrically conductive and forms a path along the insulator, which connects the center electrode to the metal shell of the plug.

The spark current will flow along the fouling path and will not jump across the spark gap . The engine stops running, but all you have lost is a spark plug. Fouling due to a too-cold plug is much better than pre-ignition due to a too-hot plug."

Usually they say just rev it up several times, and also might have to buy new plugs more often.

 

[QUOTE=Daver] My bad english.. I meant this page was first seen 2 years ago and I just saw it updated.

So what sign do I look for before taking the plugs out. You know I am lazy.
Thanks

 

Any kind of hesitation or stuttering, if your car doesn't feel as responsive, but in geeral need to pull them once in a while.

 

how do you find the result of using these RE Iridium R7440A-9L R7440B-10T?

 

Good thread. Lots of information and I have followed most of the posted links except for the NHK link. I am looking for how to handle my situation. I drive 5 miles to work each day. 1800 miles since early November. Recently, my car flooded and my mechanic removed and cleaned the plugs telling them they needed to be changed. He then gave me a lecture that included driving my car harder. "the rotary needs to be run"

EDIT

Anyway, from this thread it is clear I need hot plugs for my daily driving. But I also will be doing some hard track days this spring and summer.

Also, I am still confused about the alternatives. Assuming I want a hot plug, is there one that is better than the OEM plug for my situation? DENSO \ NGK etc.?

e.g. short daily commutes but with monthly track days through the fall?

Thanks guys!!!

 

Bump

 

They are from Fujita Engineering.

Yes I found them very good. My home track is Sandown Raceway in Melbourne Australia.
http://www.sandownraceway.com.au/Images/CircMap.gif

As you can see from the map, there are long straight and long back straight. From Turn 5 - 6 it is all up hill. When I had the old plugs, the car used to hesitate a lot at 4 gear around 6000rpm. And I took it out after 23000km. It is not bad at all - so it is functioning not fouling.

See below These are stock plugs after 23000km

http://www.step-hen.com/rx8/leading%...%2023500km.jpg
http://www.step-hen.com/rx8/trailing...%2023500km.jpg

Since I used the colder plug, plug cord, and v power from Fujita - those hesitation is gone and the car drives very well!

I know from the reading that it does not last as long as the hotter plug, and I have to rev it high occasionally to keep the carbon deposit away.

I have it for 11000km now and I am planning to change it again soon. Or at least take them out when I do my brake and brake oil next time.

 

It's not that hard to change the plugs. Best idea is to run the factory heat range normaly then have a set one range cooler you put in at the track. This way you know you are getting the most performance at the track with a clean set of plugs.

5 miles is enough to keep your plugs clean on the street. Just let it warm for 2 min before you drive off. Then gradually press it a little harder and rev it more as you get to work. You will be fine.

 

What would do you if you have to drive 7 hours to a race track? Change it at home before you go? or Change it at the track?