Rub20B

crap I am pulling the heat ranges around in my head. so the 2 we run where the coldest bosch plugs available at the time at our parts guy. now the 08 you listed is for sure 0.8, might be worth a try in a turbo'd engine..

stickmantijuana

iTrader: (1)

I'm running 20b with gt 4202r. I just installed haltech 2500, and it will be tuned to 20psi. I have 9 range NGK plugs on both leading and trailing, then I saw this thread lol.

will the 9 range spark plugs be okay for my setup? I see people using ngk br10es or autolite ar3932. I'm ok going colder to lessen heat retention by the plugs, but not sure about using one without the flat surface which would exacerbate gas blow-by..

what's the latest consensus for spark plugs for 250-350whp per rotor build? honestly, ngk 9 series have been working ok for me.... but I don't know what it's doing inside. this is mostly a street car but occasional/frequent onramp pulls. it will be tuned for approx 800whp.

Howard Coleman

iTrader: (6)

your post re 9 heat range plugs in a 553 hp 2/800 3 rotor got me to thinking (often a bad thing) and produced the following thread in the 3rd gen section:

"when Mazda added turbos to the 13BREW it was a game changer.

thanks primarily to the 50 mm peripheral exhaust port the engine can breath in a different zipcode than a piston engine of similar displacement.

taken to extreme, running methanol the 1.3 L 80 cubic inch motor can produce over 1100 rwhp! Ok, admittedly that's crazytown (but true) so let's take another approach to better understanding our motors.

i have posted some of this here and there so maybe you are rolling your eyes thinking here goes Howard again... feel free to turn the page.

here's a list of the heavy turbo and supercharged hitters for 2017 or thereabouts:

2017 Corvette supercharged 552 rwhp 378 cubic inches 1.46 hp/cu inch
2017 Camaro ZL1 supercharged 544 rwhp 378 cu in 1.44 hp/cu inch
2017 Nissan GTR Nismo twin turbo 510 rwhp 232 cubic inches 2.21 hp/ cu in
2017 BMW twin turbo I4 211 rwhp 122 cubic inches 1.73 hp/cu inch
2016 Ferrari 488GTB twin turbo 562 rwhp 238 cubic inches 2.36 hp/ cu inch
2017 Mclaren 570 twin turbo 477 rwhp 232 cubic inches 2.05 hp/ cu inch
2017 Porsche Turbo twin turbo 493 rwhp 232 cubic inches 2.12 hp/ cu inch

1993 Mazda RX7 217 rwhp 80 cubic inches 2.71 hp cu inch
1993 Mazda RX7 400 rwhp 80 cubic inches 5 hp/cubic inch
1993 Mazda RX7 500 rwhp 80 cubic inches 6.25 hp/ cubic inch
1993 Mazda RX7 600 rwhp 80 cubic inches 7.5 hp/ cubic inch

consider that the world of 100K+ supercars is ULTRA competitive, yet even in the 2017 world of titanium connecting rods and supercomputer ECUs the lines between hp greed and warranty expense cross.

it looks like they cross around 2.25 hp/ cu inch.

now consider our 13BREW powerplants... updated to FD spec around 1992... that would be 25 years prior. what type of smartphone were you using in 1993?

so if the line cross around 2.25 hp/ cu inch how do we now consider our "moderately" modded 5 hp/ cubic inch 400 hp motors?

hint: better consider them very very seriously.

what's that you say, you don't need AI because you are only running 400

no matter what power level FD you have, even stock, you have a beast that requires lots of respect."

10s should work well for your app gapped around .023 ideally w IGN1-A/AEM Smartcoils and a set of Magnecor wires. our motors generate lots of combustion chamber pressure and are always a challenge to properly light especially w the 2 cycle reducing dwell time.

i like BR10ES or AR3932.

Howard

jsnow82

iTrader: (3)

Hi Howard. I see that you still like the ar3932 plugs. I was under the impression that you gave up on this plugs because they would crack the porcelin. Also the br10es, fill me on on these plug. They are 19mm vs the 21mm ngk plugs.

Are the NGK 7420-10.5 and NGK 7420-11 still the best plug for the rotary community running high horsepower?

thewird

iTrader: (8)

I tried the ar3932 plugs on a customer car and they were ****, car lost like 100 hp on the same tune (on a car making 54x rwhp). Popped the NGK 7420 back in and the power was restored. Even tried gapping them and playing with timing, made no difference.

thewird

Howard Coleman

iTrader: (6)

"Hi Howard. I see that you still like the ar3932 plugs. I was under the impression that you gave up on this plugs because they would crack the porcelin. Also the br10es, fill me on on these plug. They are 19mm vs the 21mm ngk plugs.

Are the NGK 7420-10.5 and NGK 7420-11 still the best plug for the rotary community running high horsepower?"

as mentioned in post one, Lance Nist originially suggested the AR3932X when i was looking to replace my platinum/iridium plugs w copper nickel. the "X" has a nose similar to the stock FD plug. in my prior road racing piston life i had always used Autolite and so i gave them a whirl. they ran fine over 500 but we were starting to get some modest break up around peak torque and on up. the problem is the gap isn't adjustable and is around .030.

so we switched to the sister single ground strap plug the AR3932. Autolite's largest selling race plug. we were dynoing for the Oct 2013 Texas Mile and did 3 runs on the dyno to 203 mph in 5th gear... around 575 hp, 26/27 psi boost on E85. zero breakup at .023 gap and 4.5 mS dwell.

here's a log of the run to 203:



i did lose a fuel pump fuse on the second run around 160+. i flattened my corner seal springs and lost porcelain on one of the lead plugs. i decided to switch to a similar NGK plug.
BR10ES. it has done well in many of my engines. a year or so ago i heard that someone lost some porcelain from the NGK plug so now i am of the opinion that it was probably wrong to have abandoned the AR3932... probably most plugs would have failed given the circumstance.

nevertheless, one of my customers made 614 at 25.5 psi boost w the BR10ES, runs it very hard and has had zero problems so i will probably stick w it.

as to thewird's experience, all i can say is it does not mirror mine.

Howard

GoodfellaFD3S

iTrader: (213)

I would not want to be running OEM 9s at 20 psi--- for that you want 10 heat range in all six plugs, and with an expensive engine I'd go for the good ones. Full length with resistor, like the NGK 7420s.

Would suck to hurt the motor running basically stock spark plugs on your setup.

800 rwhp demands some respect in all things, including spark plug choice

gxl90rx7

iTrader: (1)

its dumb to run all 9's and think you are better off than running factory plugs. the trailing is naturally hotter, if you went from 7 to 9 in the leading only you didnt change anything. and i would not run the 3292 only because it has no resistor and can cause pickup noise which is instant engine killer. if you wnat your engine to last every little bit counts and it adds up

Howard Coleman

iTrader: (6)

"i would not run the 3292 only because it has no resistor and can cause pickup noise which is instant engine killer."

thanks for bringing that up as it is a legitimate and important point and probably is why i run the BR10ES as they are resistor.

thewird

iTrader: (8)

This was my experience with AR3932 all around vs old faithfull R7420's... Wasn't quite 100 hp but a lot of power to lose from just swapping to a different plug. Power lost across the board. Even more power was made when I was experimenting with 2 stages of water/meth but then decided not to use it due to inconsistency but will probably revisit it in the future (the 2nd picture). I only tried the AR3932 to see if I could smooth out the graph, so that is my experience.





thewird

jsnow82

iTrader: (3)

How do the br10 series plugs compare to the 7420 plugs? Seem a lot cheaper. Worth it or not?

cewrx7r1

iTrader: (2)

When are we going to start being factual about the 13B-REW engine?

Comparing intake air flow to a 4 cycle engine, our engines are not a 1.3 liter but a 2.6 liter.

Grow up rotary world!

GoodfellaFD3S

iTrader: (213)

You're speaking of b10egv or b10eix?

They're shorter in length, have less physical ceramic, don't thread in as completely into the rotor housing (leaving exposed threads inside the housing that can collect carbon and in theory leading to an increased change of detonation) and don't have a resistor, which as mentioned earlier in this thread is not great for a car running a CAS and susceptible to pickup noise.

Many years ago I had a long convo with Ari of RX7.com fame and he was pretty adamant about running the 'proper' full length resistor race plugs for higher power levels for all of the reasons mentioned above. I'm talking NGK/Greddy heat range 10/10.5/11 depending on boost and power.

I've also torn down more than one engine running the snowmobile plugs that showed very bad horizontal 'wing' cracks at the spark plugs holes, making the rotor housings paperweights. Power levels of 400-475 rwhp with either road course use or many highway pulls.

It's nuts to dump thousands (or tens of thousands) of dollars into an engine bay and then run inferior $5 spark plugs over $35 spark plugs to save a little bit of money. My opinion

RotaryEvolution

iTrader: (30)

i agree, there is really no cheap plug for high power that we have found yet, at least in the leadings. the trailings aren't super important and can be cleaned periodically.

TwinCharged RX7

iTrader: (14)

So what's the best plug for $35. And where is the link

GoodfellaFD3S

iTrader: (213)

I should also say I believe it comes down to the driving you plan on doing as well. If you're at around 400 rwhp and it's a street car that you don't beat the hell out of constantly, then perhaps those plugs are cool to use (no pun intended) ...... better than standard 9 OEM trailing plugs all around? Not really sure if that's been proven or not. I admit that spending 150 bones on a set of plugs isn't fun. For hard driving making a shitload of power in a tiny engine, if you wanna play you gotta pay

GoodfellaFD3S

iTrader: (213)

Support your forum vendors.... I'm currently rocking the Denso and a happy camper

Spark Plugs 93+ RX-7

jsnow82

iTrader: (3)

So, how about a differences between denso and ngk. Any real world experience?

Barry Bordes

The closer to the housing surface the better... as jsnow indicated.

Also Yamamoto's research indicated surface gap plugs had fewer misfires. (see attachment 1)

Our big problem, well one of them anyway, is a slow burn-rate. This can be somewhat mitigated by a shallow ignition point (in relation to the housing) and of course strong ignition energy.

The initiation of the spark and subsequent kernel starting to burn can be captured by combustion testing equipment. (attachment 2)

I would like to test the ig1a coils to see if they make a difference from my HKS twin power set-up.

And Chuck, I wish we had another 1300cc to which to spread the pressure and heat. The only people that think it is a 2600 cc engine are the sanctioning bodies. They must penalize the rotary because of it's superior breathing from it's unobstructed ports as they do 2 strokes.

Barry Bordes

I use the Denso IRE01-31 and have good luck with them. .4 mm center electrode

Howard Coleman

iTrader: (6)

Barry,

as usual a high value post.

i primarily switched from noble metal plugs to nickel after having an out of the blue detonation incident when i was running 3000 CC per minute of meth as AI along w my base pump gas.

platinum and other noble metals are routinely used to catalyze various alcohols. according to an OE research paper this reaction could cause detonation. at that time i was switching from CD to inductive ignition which also fits well w nickel. i had been running NGK high dollar platinum plugs.

while i understand re the shorter reach of the BR10ES and AR3932s i will say they work. i see no evidence of misfires w zero smoothing on the dyno around 575 hp and as mentioned i have many engines running them around the 600 level.

that said, i like the Denso recommendation, especially since they are avail in a spread of heat ranges. the BR10ES comes no colder than 10.

here is the list of Denso IRE01 options:

Denso # 5720 IRE01-31 heat range 10
Denso # 5721 IRE01-32 heat range 10.5
Denso # 5722 IRE01-34 heat range 11
Denso # 5741 IRE01-35 heat range 11.5

generally available around $29 per.

Howard

RotaryEvolution

iTrader: (30)

flat faced plugs would be ideal, like the OEM NGKs. too bad the autolites are the only ones who stepped up in that area. because autolite is hot garbage of the spark plug world.

gxl90rx7

iTrader: (1)

a note on surface discharge plugs, i would like to see what you guys think.. ive tested both semi-surface and true surface discharge type plugs on a bench with an oscope, and its interesting. the factory plug sometimes but fairly regularly discharges deeper within the plug instead of on the surface. when this happens, spark duration changes for that event, as if it took different voltage to bridge the gap. not sure why it doesnt always hit the surface. but this is probably good for fouling resistance, if the surface gets fouled, it can discharge deeper within the plug. but i would think this is bad for consistent spark, especially if your tune was closer to ragged edge

i also tested the R6712 which i use, which is true surface discharge with resistor, and it always had consistent spark on the oscope, probably the same for all true surface discharge type plugs, because the spark can only go on the surface. problem is they are hard to find in colder heat range than NGK 9

the 6712 is only available in 9's and 10's though and reach is short. but.. if you remove the sealing washer, it gets closer to factory reach. i havent tried running them like that though. the pics are factory plug, R6712 with washer, and R6712 without washer

mannykiller

iTrader: (93)

Ive used quite a few different types of plugs. OEM Rx8 Plugs (good bang for the buck if you're in a bind, they usually carry these at autozone. The Denso IRE01's are good as well..but I had problems finding them,..also haven't tried looking in a couple years as i've been happy with NGK plugs. Autolite 3932 & X versions Which I didn't like at all. Could tell the difference immediately from the older NGK 6725's at start up. And 2 out of 4 of the Porcelains cracked. Threw them, along with the other couple sets I'd purchased in the garbage. I always tell people if they don't want to spend money on NGK7420's....the Stock RX8 Plugs are an excellent compromise. ONly thing is they're still 22 bucks a pop...and not in the preferred heat range. I gap all my plugs. run Direct Fire, E85 and Swear by the NGK R7420. 17-20PSI reving out to 9650 on a Semi PP engine will def expose weaknesses... and also reinforce confidence in the parts that are working. NGK R7420 is the best plug out there for rotaries making power....and or on the track. I'm with Mr. Goodfella....Spend the money on good plugs. Protect your investment.

Also, I will say that I AM in fact an NGK Sponsored Driver...So you could say I'm partial...but before that. ...I was experimenting with all sorts of different plug types. Eventually landed on the NGK6725...and then the R7420 and haven't looked back.

Gilgamesh

I just scored some Denso IRL01-31s off Amazon for $11.88 each with prime shipping.

these have:
.4mm iridium tipped center electrode
.8mm platinum tipped ground electrode
the proper 21mm reach