rex

iTrader: (2)

I was browsing the RX-8 workshop manual online (I poneyed up for 24 hours of access) and found the following interesting reference to spark plug fouling in the engine specs:

Type NGK Leading side RE7A-L*4 (RE6A-L)*5
Trailing side RE9B-T*4

Plug gap Standard (mm {in}) 1.15-1.25 {0.046-0.049}
Maximum (mm {in}) Leading side: 1.5 {0.059}
Trailing side: 1.4 {0.055}

Resistance [25°C {77°F}] (kilohm) 3.0-7.5
Tightening torque (N·m {kgf·cm, in·lbf}) 12.8-17.7 {131-180, 114-156}

*4 Standard equipment
*5 Hot type plug: Available only for customers who often drive their car at very low speed which causes the plugs to foul easily.

Note the option of a hotter leading side plug (RE6A-L) as a plug fouling remedy.

My Rx-8 hasn't flooded yet, but several times my RX-8 has nearly stalled when I've tried to set off after being stuck in crawl along traffic with the engine idling.

MEGAREDS

Is there a down-side to using the hotter plug? Is it something those of us that have flooded should demand?

rex

iTrader: (2)

I'd ask your dealer about the redesigned plugs and use the hotter plugs if the new ones aren't available. Do this on a trial basis to see if it clears the flooding problem you're running into. I'm assuming that a hotter plug may not perform as well at high rpms, but I'm just guessing - the plug runs hotter, so may suffer pre-ignition? Any experts care to check my logic?

ashmason

Hmm, there are some complaints on the forum about engine rattles at high revs along with a loss of power, I just experienced it in mine too, or rather my wife did. Seems like this could be a plug fouling issue. I duplicated the problem once, then couldn't again, then my wife drove the car and hit the same snag. Again I drove it and couldn't replicate it. She sits on the 405 everyday in nose to tail traffic, I tend to grab the car by the scruff of the next and chuck it around and have fun. I guess it doesn't like going slow.

I called my dealer, they have never heard of the problem, I noted the hotter plugs in the workshop manual, he said he didn't have access, huh? I asked him if he was saying he didn't have access to the RX-8 Workshop manual? He asked me to hold, 5 mins later he came back and said he couldn't find any reference, personally I don't think he looked very hard, or maybe went for a coffee!

Let us know how you go on. I am not going to take it in unless I can replicate the problem reliably, otherwise I know they are going to tell me there is no problem.

rex

iTrader: (2)

Hi ashmason, fwiw, the hotter spark plug reference is in the Engine Specification section of the RX8 Workshop Manual. I cut and pasted the first post in this thread from the online manual.

JCC

Just wanted to add some general info to this thread. Mazda for years listed optional heat range sparkplugs in the Miata manuals. A change of one thermal nunber does not make a large difference but can help with short trips, trafic jams and light footed drivers The leading plug has the most effect at low engine speeds and one thermal number hotter should be fine for high octane gas and street driving. If preignition started happening the RX-8 knock sensor would kick in, something the early Miatas didn't have.

rex

iTrader: (2)

I'm cross posting the following because it describes potential problems with the hotter plug and wanted to make sure anyone reading this thread was aware of it:

blivets

I just got mine back from the third trip to the dealer for a check engine light problem I've had since day 1. They believe they fixed it this time by replacing both oxygen sensors. And so far, the light hasn't returned, but I'll have to see.

I've had no discernable problems with hard starting, detonation or flooding. They did find the plugs to be fouled, so they replaced them. It does seem to run a bit better after all this, but it seemed fine in the first place.

Anyway, I drive a mix of highway and back roads, and I tend to be on the aggresive side of moderate (70 -> 80 on the highway; 5 -> 10 mph above speed limits elsewhere).

The service manager said to stay away from Mobil and (I think) Shell, and recommended Sunoco, Getty, and a few others. I've since been using Sunoco.

I've been careful to obey the recommendation of running @ 3000+ RPM at some point during each run.

Not sure what else I can do except keep an eye on it.

DaveT

Well, blivets, your service manager is wrong. Basically all brands of gasoline come out of the same pipeline. Some brands add some "proprietary" ingredients, some don't. Personally I run Shell 93 octane in all my vehicles, but only because I know the dealer and have never had a bad tank of gas from him. Your biggest worry should be getting water with your gasoline. and/or buying your fuel from an "unknown". If you stick with major brand fuel you shouldn't have a problem if you use a high volume dealer.

rex

iTrader: (2)

I just heard from a friend in Japan that dealers are getting DENSO IRE01-27 plugs to replace the standard NGKs in the RX-8. The plug doesn't look very exotic to me - I was expecting something more radical looking based on what people have said elsewhere on the forum.

If you're looking at using alternative plugs to remedy the plug fouling problem, you might want to check with your dealer to see if this is the correct part number. I don't know how the heat range of this plug compares to the NGK RE7A-L and RE9B-T standard plugs.