infinitepat

Do all 4 spark plugs fire every power "stroke"? Or does only one fire giving the other coil time to "recover" before the next power stroke? Normaly coil recovory time isnt somting you need to worry about, but at 9K rpm's it becomes a factor. Or even, does one fire slightly before the other to compensate for the spinning of the rotor?

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zoom44

they fire one after the other within a milisecond

Sputnik

And it's two per rotor, and like piston engines, they don't fire at the same time (they're cycles are offset).

---jps

wakeech

yeah, 2 plugs per rotor, and only two firing per half revolution... so i suppose yeah, 4 per rev.
60s/9000revs = 0.00666... s per revolution at redline.
not all four plugs fire at the same time, of course both sets of two are staggered by one half of a revolution (0.00333...s), and each plug of the two is also staggered (the lower, or "leading" plug fires first), with the "trailing" plug firing 10 to 15 degrees after the leading plug...

(0.0666s/360d) * 15d = <0.00028s (that is about a quarter of a millisecond for the digit-impared) between the leading and trailing plug firing...

now, in the 13B, each trailing plug had it's own coil because they had to be fired independantly of each other and the leading plugs (to get the timing right), but because of the position of the leading plugs, they both ran off of one coil together... the "waste spark" of the lead plug fires during the end of the combustion event, before the next compressing chamber has come around...

aaaanyhoo, all this said, the RENESIS's ingnition system will doubtlessly be able to handle whatever you can throw at it, rev wise. i wouldn't worry (look at what they can do in F1: 19K rpm on a 3.0L V10).

Cihuuy

does any1 know what kind of spark plugs they will be having... is it the same company NGK?? or is Mazda switchn to another company?? tanx in advance

maxcooper

I don't know for sure, but I would assume that NGK will continue to be the plug manufacturer.

And just to be clear about how often the plugs fire:
- each trailing plug fires once per eccentric shaft rotation
- each leading plug fires twice (becuase of the wasted spark setup) per eccentric shaft rotation

This assumes that the RX-8 will be using the same wasted spark setup that wakeech described that has been used on previous 13B engines with electronic ignition.

-Max

shahpor

I read somewhere that it had Iridium spark plugs.

not sure who manufactures them, though.....

wakeech

NGK, certainly.

Buger

Don't forget that when your tach says 9000 rpms, the rotors are only spinning at 3000 rpms...

wakeech

but there's one combustion event per revolution, so ignition timing is still in e-shaft degrees

eccles

The spark plugs come with a satellite phone?!?

inittab

hahaha.... I had one of those phones. "Had"

inittab

Here's an old post about the spark plugs. Looks like they just might be iridium.

http://www.rx8forum.com/showthread.php?s=&threadid=2011

P00Man

wouldnt it be 4.5k revs per rotor per minute? as it is dual-rotor not tri-rotor.
ofcourse i really have no idea, so im probably wrong.
________
Children Paxil

maxcooper

The eccentric shaft is rotating at 9000 RPM at redline. The rotors are rotating at 3000 RPM at redline (always 1/3 the speed of the eccentric shaft). Because each rotor has three combustion chambers, there is one combustion event per rotor per rotation of the eccentric shaft. Since there are two rotors, that's two combustion events per rotation of the eccentric shaft.

I think Denso makes the Iridium plugs.

-Max

wakeech

Denso does make irridium plugs, but i believe that the makers of these plugs specifically are made by NGK, as that's what i remember hearing, and NGK have always (uh, i THINK) made the plugs for Mazda's rotaries... there is obviously a huge margin for error on that statement about "all Mazda rotaries", but i don't ever remember seeing an RX-7 spec sheet with anything but NGK on them... (ya, i know there were others... so okay, it's a guess, but not a bad one :p)

wakeech

check out www.rotaryengineillustrated.com bro'... it's freakin' awesome, and the information ranges from super basic to fairly intimate, and has TONS of extremely cool animations if you still can't get it from the reading (i had to watch those animations for a while, then stared at them endlessly for hours once i got it )

Jeff20B

Those animations are great! I really like the one that illustrates one rotor face as it rotates around the rotor housings and when the L and T plugs fire. Notice the extra Leading spark right before the exhaust port opens? That's what so called 'wasted spark' looks like on a rotary. It's actually called simultanious firing when they both fire at the same time.

waterproofone

NGK has mad the majority of plugs for mazda rotary engines for some time. DENSO also makes a more expsensive(yes more expensive) than NGK. the rx-7 plugs were platinum and only about $6 - $8 bucks a pop while the current iridium plugs are still expensive and a rip off still but what can you do? Mazsport.net states you can install rx7 plugs in the rx-8 and it will also run just fine ( I do not see why it wouldn't) since it's still a 13b engine,,but I do not want to take the chance since for $20 bucks more I can obide mazda for warranty requirements..I don't want to have to argue with the shop if anything should ever come up.
Here is a hint that you can use if not sure simply by looking at a rotary engine spark plug to know if it's an rx-7 plug or an rx-8 plug.

Rx-7 plugs have no outer electrode..and they will stand-up on their own on a desk or whatever..they just have 4 slits near the center electrode hiding in the middle of the plug.

Rx-8 plugs have a platiunum outer electrode welded on the spark plug and a very very thin center electrode in the middle that you CANNOT gap...They will NOT stand up on their own.

currently I do not beleive any other maker (autolite, bosch, etc) makes a rotary engine plug.

Hope that helps.

nycgps

OMG !!!

damn n00b, before u reply, CHECK THE POST DATE ! Jeeeeze !

Jedi54

at least he was trying to help and give useful knowledge.
(unlike some thread ressurecting n00bs)

quazmosis

Reading this really cracked me up today.

mazdaverx7

let me clarify the misinformation. 79-80 RX-7 spark plugs use three gounding points and one electrode. the 79 plugs are a little different than the 80 plugs due to the points and condenser of the 79 model. 1980 added electronic ignition and the heat range went up slightly. from 1981-1985, not differeing by 12A or 13B, the RX-7's spark plugs went to a four ground one electrode type made by NGK (or you buy the identical Nippon Denso's). no platnium plug was offered from the factory. from 86-88 the RX-7's spark plugs were flat tipped with four slots cut into the plug's business end, so thus a four groung one electrode setup as well. heat range was different leading to trailing. the 93-95 RX-7 used an identical plug but were platnium, whic could be used on the 86-92 13B's as well.

autolite, bosch, denso, and champion did make plugs for the 79-85 RX-7. i would not use anything but NGK or Denso.

waterproofone

I was only speaking of 2nd generation plugs versus rx8's. I should have mentioned that. I am an avid 2nd generation owner but found them to be just to rare any more and finding a good one that is well cared for is out of my monetary reach so bought a new rx8. If they come out with a new rx7..I will try to get that instead.

nycgps

what does it matter now ... the dude who started this thread has only 14 post, probably Already sold the car or ... whatever.