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I haven't tried the 6601s yet, but I did swap to conventional 11s in the trail, and the only effect thus far as it seems to smoke longer when cold, and needs to reach a higher coolant temp before it stops.
"it seems to smoke longer when cold, and needs to reach a higher coolant temp before it stops."
your observation is probably accurate. our motors are surprisingly cold on startup. it is common to see oil smoke initially from the unburned premix. a colder plug takes longer to warm. so far, my 4 6601s run a little ragged on start. it has been cold in the mountains of N Georgia recently. the idle smooths before warmup enrichment ends. they work fine underway.
keep in mind there are significant benefits for running colder plugs. your apex seals will thank you.
i do think something that Scotty305 posted has merit. if you don't have enough firepower to run 11s it might make sense to buy the proper coils and plug wires rather than eventually calling your engine builder.
that's of course if you are single turbo or are tracking your FD.
Update-- So I was able to actually drive the car today. Car runs fine with these plugs, maybe a touch smoother. I will have to plug in my laptop and pull a log. For some reason it looked as if my AFRs were slightly richer than before. Dont know if this is due to the weather being slightly warmer, fresh plugs or both. Currently running these plugs, without crush washer in leading and trailing spots.
i found in that different plugs wanted different idle mixtures, or were able to run different idle mixtures.
for instance the BUREQ's want a pretty rich mixture, but the Rx8 leadings were not happy, and wanted a leaner mixture.
so if you say had a stock car and just put Rx8 plugs in it (they are like the race plugs but in street heat ranges) it wouldn't run very well, but if you can tweak the idle mixture they run better.
so if the plug is better, less shrouded, closer to the chamber you might notice that at idle/low speed.
Wanted to provide any update as I was able to really run the car today. As I noticed, the car was running rich compared to the regular plugs. I can only speculate that maybe I am not getting as efficient burn because I am running stock coils with the Twin power. I did a 25 minute drive with light, medium and heavy load and there were a lot of cells that I needed to pull 5-6% fuel out of to hit my target AFRs. Below is a screenshot of FCTweak looking at the datalog and correcting the fuel adjustments. Green cells note the need to remove fuel to hit target AFR.
I will likely put the stock 9s back in until I get a marine coil setup and see if my results are different. I think with these plugs being shorter, the marine coils might be necessary to get the desired results. I dont know how else to explain the need to remove fuel to hit my target AFRs unless someone has a better suggestion.
Wanted to provide any update as I was able to really run the car today. As I noticed, the car was running rich compared to the regular plugs. I can only speculate that maybe I am not getting as efficient burn because I am running stock coils with the Twin power. I did a 25 minute drive with light, medium and heavy load and there were a lot of cells that I needed to pull 5-6% fuel out of to hit my target AFRs. Below is a screenshot of FCTweak looking at the datalog and correcting the fuel adjustments. Green cells note the need to remove fuel to hit target AFR.
I will likely put the stock 9s back in until I get a marine coil setup and see if my results are different. I think with these plugs being shorter, the marine coils might be necessary to get the desired results. I dont know how else to explain the need to remove fuel to hit my target AFRs unless someone has a better suggestion.
took note to knock levels? notice any difference i responsiveness?
but let me ask you this; if when the engine was being tuned the plug heat range was too hot, what do you suppose the affect might be on timing values? And then with colder plugs, what changes might be needed?
Because there are some people who assert nothing will change when swapping to a colder plug. I’d offer that they might be assuming too much without considering the possibilities fully.
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TeamRX8- So for my power level(probably 340rwp guessing) I have run 9s. I posted the photos of my leading/trailing plugs in the thread. I *might* be able to go to a colder plug, but I was able to find the R6001-9s for $50 shipped. I decided to take a risk and see what would happen based on others experience. I purposely did not want to change heat range, timing or anything just to simply see what would happen after installing the new plugs. For my power level, with the Twin Power, I am assuming that my spark is too weak to potentially take advantage of these plugs. As I have posted, my combustion cycle was not as clean(read richer AFRs) as the stock plugs that were 1.5 years old. Maybe the R6601s cant reach far enough into the housing to burn as clean or I would need the Marine Coil firepower for a hotter spark. Regardless, this was just my personal experience after experimenting for the past few days.
I just installed a new set of BREQ9s back in all 4 and after going back to my prior tune, the car feels a lot stronger and my knock has decreased. I will now say however that the R6601s did feel smoother at idle and across the RPM range under light/medium load.
I got my set of 11 R6601S and noticed they do seem not to sit in deep like a factory plug
my plan is maybe run denso 5720 (10 heat range) in leading and R6601s with washer? in trailing
a few power runs off the spring (breaking in motor). 8% less fuel. 507 rwhp at 16 psi w Garrett G40-1150. Knock readings around 50 down from 60 w the normal $30 plugs.
To make sure I understand correctly, when you say you have 8% less fuel, I assume that means that you too were seeing a lower(richer) AFR from the plug changeover? What is the cause of this? I was only speculating that these plugs were not burning off the fuel as well and therefore had to pull fuel out to hit the same target AFR. Please enlighten me if am assumption is incorrect.
Can't explain why my knock readings were slightly higher when yours are lower. Maybe when I swap to a single turbo setup with marine coils I can try the plugs again..
ok iceman, thought you went from -9s to a colder plug
the R6601 only has a 19mm threaded reach length as compared to 21mm. This is why some are attempting to run without the sealing washer and only a thin copper washer instead; to gain additional reach.
they are much shorter exterior length; the spark boots will be a lot closer to the housing.
or as someone referred to their appearance in another thread … lawnmower plugs …
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It's hard to do a good back-to-back test on something like a car engine since there are lots of environmental factors we can't control. How consistent were your log results before changing spark plugs, iceman4537? Did the car need 5-6% trims on different days, or was it consistently closer to the target?
I'm not a rotary expert or a tuning expert, but if you told me a 4-cylinder piston engine got richer after changing ignition coils I would conclude that is better (more complete) combustion with less misfires. If you disable one of your coils at idle to create a consistent misfire, the measured O2 will get leaner (not richer). If you fix that misfire the mixture gets richer.
@Rx8- correct. I removed the crush washers completely. I posted a photo of a stock plug next to these to compare length without the washer. The 6601 still doesn't reach as far into the motor.
Scotty-weather and temperature can absolutely change the tune. Just seemed like it need a larger change than typical. I also noticed slightly higher knock levels in some cells.
And I am by no means a tuner and just speculating. I would have thought opposite, that a richer reading would mean less complete combustion as there is more remaining fuel passing through the exhaust. Maybe a real tuner or Howard can comment either way.
A wideband O2 sensor is an indirect way of measuring the combustion efficiency. The actual measurement comes from the percentage of oxygen in the exhaust, and the wideband gauge assumes the exhaust air/fuel ratio based on how much oxygen was measured by the sensor. The O2 sensor can't detect the burned or unburned fuel, it detects how much unburned oxygen is left over after combustion and there's more unburned oxygen left over when combustion doesn't happen.
It's a somewhat common diagnostic test to disable each coil and disable each injector on an engine, to confirm that all the cylinders are doing work. Whether you disable a coil or an injector, the exhaust will show a leaner measurement because of all the unburned oxygen getting pumped straight through the engine without being turned into CO2+CO+NOx exhaust gases.
Don't take my word for it, you can try testing this yourself at idle or at light load. But I wanted to point out that misfires usually result in false-lean readings on the wideband O2 gauge. I suspect a richer mixture means the combustion is more efficient because more fuel combined with oxygen and burned.
Last edited by scotty305; Mar 26, 2023 at 11:47 PM.
lots of analyzing going on here and of course i admit to being one of the guilty.
since misfires have come up... i have no idea as to whether i am having any however:
a quick look at my acceleration shows it is just a hair better than my best time w the 9180. admittedly this is on a sort of straight mountain road and i am using 72 to 100 mph. at about 105 i am on the brakes and hoping i will make the turn. altitude 2650 ft.
this is also at much less boost than the 9180. i have less EMP and my crossover from neg to positive (to boost) is more than 200 rpm later.
based on my accel i don't think i am having any misfires
I was generally referring to the possibility of the combustion being more efficient in my reply to iceman, which is why it was also stated that there are ways to determine it for sure rather than make assumptions.
As Howard demonstrates, a simple comparison of data logs for speed vs. time under similar or same conditions is one such method. Dyno runs are another.
Not surprised by your recent results Howard. As we discussed, the G40 1.06 is larger than the EFR9180 1.44 A/R. Which is likely fine for straight-line speed runs with gearing to stay in the boost. Coming from full off-throttle out of a turn such as autox or on a tight track; my general focus, is likely quite different though.
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its really hard to quantify, but there are three phenomena with plug wires we need to be concerned about.
the first is "inductive cross fire". when a plug fires there is a wave of energy, and if there is another plug wire nearby it can fire that plug too. very common in V8's with cylinders that are both next to each other in the firing order and physically. for that engine its like advancing the timing 90 degrees on that one cylinder (rotary is like 180). which will break it. fix is either to keep the wires apart, the FD kind of does this from the factory, because they knew what they were doing. or to cross the wires at 90 degrees, which cancels the wave (like a stock FC turbo)
Second is Radio Frequency Interference, RFI. this is when the electrical noise from the spark jumping starts to interfere with other stuff, like the ECU or the stereo. its a bigger problem on planes and corvettes, because they aren't steel, but typically the plug wire is sheathed and grounded.
Third. Spark Leakage. when combustion chamber pressure goes up, the energy required to jump the plug gap goes up as well. Electricity will find the easiest path to ground. at some point the spark energy will leak out of the wire/boot and skip the plug. loose plug boots are a no go here....
Using Howard's pic, and sorry about the art skills...
What if Mazda or another company made the housing so that the spark plug hole itself is the ground and a special spark plug with just a center electrode could be used?
It could be very small, just enough to not foul, the gap would be set by the center electrode and housings surface, and could be done for both leading and trailing...
Less leakage, no mountain to skip over, etc. What do you think?
Using Howard's pic, and sorry about the art skills...
What if Mazda or another company made the housing so that the spark plug hole itself is the ground and a special spark plug with just a center electrode could be used?
It could be very small, just enough to not foul, the gap would be set by the center electrode and housings surface, and could be done for both leading and trailing...
Less leakage, no mountain to skip over, etc. What do you think?
That sounds like a brilliant idea WRT less leakage, though I think it would still be susceptible to spark plug mountain as you still have a heat retaining plug screwed into the housing that will want to expand, though perhaps less? Anyway, the only thing I can think of that might make it impractical for a production car is that you'll still have the normal carbon/plug wear deposits ending up on both the anode (positive/hot) & cathode (negative/ground) terminals of your spark plug, but now when you replace them, you're only getting rid of the deposits on the anode side. Whatever deposits are on the cathode/housing side would still remain on the housing when you change plugs.
