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Spark Plug Resistance Gurus....talking 1k Ohm or 5K Ohm plugs.

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
I've been running a 5k Ohm plug for ever (NGK PFR7B)...and I am contemplating a switch to a 1k Ohm plug (PFR7Q).
I notice one of the NGK (stock/OE plugs) is also a 1k OHM plug (PFR7S8EG).
Another popular plug is a 5k Ohm plug (BKR7EIX).

I have been looking into the whats and whys on the two, the 1k and 5k Ohm plugs. I understand the 1k Ohm plugs will allow a hotter arc. But I was hoping to find a spark plug guru who would explain more thoroughly as to why you choose one over the other. I do know of the other resistance factors which are applied to the overload figures. But with our OE coils having a 3.3 M Ohm secondary winding...I don't expect lowering the plug resistance to exceed this and burn coils often. That is, if I correctly understood what I have read up to now.

I did see an episode on some car thing/show (@ 8:00 in the link below) where they modified a MK7 Golf R. At the end they switched to the PFR7Q-1k Ohm plug used in the RS6 and gained more than or near 30 HP. I know not what they removed though...and granted, they mention tweaked the tune along with the RS6 plugs...but why? is the question. Was it for a more efficient combustion and to burn fuel more efficiently?
 
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clockwise33

New York Giants Fanatic
Location
NJ
I tried a bunch of different plugs and gap last year trying to fix a high rpm misfire. NGK PFR8S8EG performed the best at the time. They are 1k ohm plugs made for VAG (B8 S4 3.0SC). Eventually my issue was resolved with a tune update to APR K04 v1.3 “Rich Fix”. Before it was requesting 0.75 AFR, the updated beta file requests 0.80 and it runs perfect.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
For years I've been curious why all these recommendations of switching to higher resistance coils and plugs. I myself was told by DM (Bronson) to try PFR7B (5k Ohm)...and yes, it worked. Many others have been recommended BKR7EIX (5k Ohm) and it works. And there's the "reduce the plug gap" suggestions as well. More recommendations for R8 coils (5.31 M Ohm) or others (resistance unknown), but I bet this too was to add resistance to ignition. It's as though they are chasing the problem rather than asking why, or providing a real explanation. People having some stumbling at high revs and high load....so, cool the arc with higher resistance plugs and coils. But why not, as you did and I may soon do, stick with a hot arcing plug, with a good amount of gap and with more cooling"?" I'm certain I will try the PFR7Q (1k Ohm)...and if it stumbles I can move on and try the PFR8S8EG. Obviously our ignition was meant to be hot with these coming with 3.3 M Ohm coils and 1k Ohm plugs. I never understood why it was best in fighting stumbling issues, once tuned and adding more boost and fuel (more heat during combustion), by adding resistance (lowering the current) and closing plug gaps (due to the decrease in arc strength). Any way...this has been a curiosity thing for me lately.

Thank you for your input.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
NGK tech responded with this: Hello Brad, Had to contact our technical team for this. The following is their reply; "So the resistance is to eliminate FRI, so 5k ohm resistor plugs should be used. The most important part of the plug/coil combo tune is the spark plug gap. Since the coil is putting out a higher voltage than the stock coil, the gap should be adjusted accordingly and the tuner should be able to see where the “sweet spot” is according to the tune and boost level."

So I was responding, in text, because my points weren't completely addressed in their response. So in the midst of typing...I decided instead to phone them ather than type it all out and hope all of my points were addressed. I actually reached the NGK person who responded in the text and we talked a good bit and they were very king and helpful.

What I got from the call was more clarity and understanding in that; The higher voltage coil they mention in their response is that of the R8 5.31 M Ohm which I mentioned in my initial message to NGK. The R8 coil has more resistance_lower current_and higher Voltage. So with that they recommend the 5k Ohm resistor plugs. Also, more coil resistance; lowers current but delivers higher voltage for ionizing the arc across the plug gap. Higher resistance and voltage coils should allow one to run a larger gap on the plug (Not sure yet why folks are reducing gaps with them).

And so the OE coil, with its lower resistance equals_higher current_and lower voltage...and may require a reduction in the plug gap if it stumbles at high load after boost and fueling is increased from tuning etc.. The gap should not be reduced much in any case, so to allow the kernel to grow uninterrupted while arcing. Perhaps reducing plug gap affects the kernel in some way, but this doesn't explain why higher voltage coils require a reduction in plug gap. I asked why then with higher voltage coils, people still reduce the gap. The only thing they could think of was the nature of combustion, based on boost, fueling, and heat etc., may require a slightly smaller gap. They suggest no more than 0.004"....otherwise they said to try a higher resistance coil for more voltage and then to open the gap again.
 
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Chumeta

Passed Driver's Ed
Location
Vitoria-España
Hello again ROH, as always it is a luxury that there are people like you in this forum. After reading a lot about this topic, I totally agree with what the Ngk specialist tells you and the conclusion that I draw is that the best way to go is the red R8 coil or Okada plasma high versus black oem. This is what I found that you have seen it, I repeat in terms of coil:

COILS

1) These coils can be used on your FSI/TSI engine at ANY level of modification. They function just as well on a dead stock car as a highly modified one.

2) They are NOT the same coils with red housings. The secondary circuit on the R8 coils has a higher resistance (more windings) than the stock coils. In fact the secondary circuits were slightly closer to the Okadas we tested than the secondary of the stock coils.

3) We tested these between 12 and 16 volts (remember if your alternator is charging properly the input will be right around 14). We tested them between 200 and 16,000rpm. The stock coils started to misfire at a much lower rpm than the R8's with a stock spark plug gapped @ .032".

4) The spark was visibly brighter and more intense on the R8's when compared to the stock coils @ every rpm we compared in the stock rev range. We didn't compare anything under 1,000rpm.

5) We were able to open the gap on the plugs much further with the R8's than the stock plug with out misfiring at the same rpm/voltage.

6) Here is what we were finding as an AVERAGE on the secondary circuit for each of the coils.

Stock black : 3.3 M ohms
5 cylinder coils: 4.75 M ohms
R8 red: 5.31 M ohms
Okada plasma competition : 6.2 M ohms

SPARKS PLUG for this type of coils:

OEM: BKR6EIX (iridium)

Stage 1: BKR7EIX

Stage 2- 2+ : BKR7EIX - PFR7B (double platinum)(normal use)
BKR8EIX - ( for competition or track day, prolonged operation, high rpm etc..) *

Stage 3 : : BKR7EIX - PFR7B
BKR8EIX- ( for competition or track day, prolonged operation, high rpm etc..) *

* The thermal degree will depend on the out side temperature and operation at high r.p.m.
* Check electrode coloration

GAP:
It is super important, the larger the spark plug gap, the longer the arc will be generated when ignited. It is easierto ignite the gas mixture in the gas cilinder, and naturally the kinetic energy will be higher. The specific spacing of the spark plug is mainly determined by the redundancy of the output voltage high voltage coil. In theory, the larger the gap, the longer the arc, the higher the ignition energy.The gap increses within a certain range, which leads to increased ignition energy. However, the larger the gap, the greater the voltage required to descompose the air when ignited, so open it to adapt the voltage and resistance to that situation.

So a gap of 0.032 with these coils is great, even a little more, especially with the Okada competition. In the past, the problem came with black oem coils, as they traveled many km and the electrodes were wearing out, they incresed the gap (changes every 60.000km according to the official agency) and made the coils work very hard, causing ignition problems and failures. It is not a good idea to hold spark plugs for so many km, no matter how platinum they are. I prefer to change every 20.000 to 25000 km like the coils, it is not very expensive.
 

Chumeta

Passed Driver's Ed
Location
Vitoria-España
Partly from the Seat leon mk2 cupra and the vw golf mk5 gti English championship. The summary is that a spark plug and coil of 5k Ohm or more, and spark plugs of 5K Ohms is what you have to carry. as well as a gap of 0,032or more if we carry Okada
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Thanks, yes, I've seen all of that. And happy to have a bit more understanding.
I will likely run a genuine R8 coil in the future with; BKR7EIX or FR7BHX-S with them. PFR7Bs have been great and would likely be fine with higher voltage coils. I would likely install coils first so to know if the PFR7B work well or not, before trying a BKR7EIX or FR7BHX-S. Just because of the PFR7B lifespan of 90k miles is much greater than the BKR7EIX iridium's 50k....making the price value of the BKR7EIX not as appealing. The PFR7B gap of 0.028" would likely still be compliant if increased to 0.031". I would prefer a combo allowing more gap. NGK is not yet confident on the mileage for the FR7BHX-S, so they posted a mileage range of 60k-120k miles. We'll see if that changes by the time I pull the trigger on replacement coils.

APR's new coils seem like a great option, but they only mention on their site that their coil does only provide 10% more energy output (mJ/ms) than OE coils. But they do not show the volts as we are always shown → So is the OE coil a 30k, 40k, or 50k voltage output. Not quite worth trying until I understood more of the energy output of mJ/ms to volts. Going to phone APR Monday to find their stock energy output findings so to know what theirs is.
apr coil.png


Thanks for all of your input.
 
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ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Ordered NGK BKR7EIX plugs. While waiting for them to arrive I checked my wire gap-gauge with my caliper. Oddly, my gap gauge set comes; 0.6mm__0.7mm__0.75mm__0.9mm__1.0mm....and no 0.8mm. So I filed one side of the 1.0mm wire gauge to 0.8mm. The caliper shows the gauges; 0.7mm to be 0.67mm and the 7.5mm to be 0.72mm. The plugs arrived and I checked their gaps. They are supposed to be pre-set to 0.8mm, but were all 0.7mm, or there about. They were between 0.67mm and 0.72mm. So I opened them to fit my newly adjusted/filed 0.8mm gauge.
bkr7eix.png
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
I installed the new APR coils today along with new BKR7EIX plugs. I will likely return to using the PFR7Bs because the Platinum do last longer than Iridium. Have only gone on a gentle errand run and can only say at the moment I can report; that making 29 mpg running around town was done so quite easily.
apr coils1.png

apr coils2.png
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
*Update*
My LTFT (idle), before, was always 1.0% to 1.5%...and it is now at -0.4%. Not sure why it has gone to slightly rich at idle. There's one factor change to consider; being I did also install a catalytic converter. When before, it was catless. I wonder if tany of this will eventually affect LTFT (partial). LTFT (partial) was still at 7.0% and may take time to some any adjustment, but I will report any future findings.
 
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ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Curious to know...while I am reading more on the topic, I see the higher the resistance of the plug...the less coil energy(volts) reaches the gap of the plug. And the lower the plug resistance...the more coil energy(volts) reaches the gap. All understandable, right? The coil resistance is to resist the energy output of the secondary coil, but why resist it more with a plug with higher resistance? I cannot find any sort of information as to which resistance plug to use with a higher resistance and voltage of a coil-on-plug. Trying to sort out why and when to upgrade either of the two is some sort of secret. I have seen it said; that higher energy reaching the gap helps with smooth idle and makes more power, but may cause rough running or misfires at high rpms. I have experienced this when running the higher boost tune and switching to a 5k Ohm plug with reduced gap helped. I suppose now, since mine was running great with OE coils, there was no need to change to APRs. And I may have even been able to run a 1k Ohm plug again with OE coils. What I understand so far is; it is pointless to change anything unless there is a reason to do so. My tune is done with OE coils and a 1k Ohm plug and would probably run better, with more power, if I reverted back to them. Hmm?
 
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ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
I had another conversation with NGK yesterday, in order to try and summarize the whole 1k Ohm and 5k Ohm situation.
To summarize it they said:
"...there may not ever be any difference noticed between the 1k or 5k Ohm plugs when stock tuned and equipped with stock coils.
But when it is tuned, *and this depends on amount of increased boost and heat levels*, they said this:
1) with "OE stock coils" you 'MAY' (I assumed meant; or may not) need to reduce the gap of a 5k Ohm plug before you would a 1k Ohm plug.
2) with upgraded "higher-voltage coils" you 'MAY' (I assumed meant; or may not) need to go one plug cooler with the 1k Ohm plug before you would with a 5k Ohm plug."

Basically, either will work without noting any differences when stock. If tuned, then all of the variables come into play; the boost, fuel, and heat. From there, if problems arose, you would try reducing plug gap whether the plug is 1k or 5k. If the problem persists, upgrade the coil to a higher voltage replacement and run 5k Ohm plugs....reducing the gap, down from OE spec if needed. Which is where I am at currently; running APR coils (only slightly more voltage then OE according to APR) and running BKR7EIX plugs at 0.8mm gaps.
 

clockwise33

New York Giants Fanatic
Location
NJ
Not sure what issues you are/were having but this was my “ignition” problem-resolution:

My APR K04 tune started having a high RPM choppy/hesitation/misfire after installing an intake. I tried many different plug and gap combinations some made a difference but none fixed it 100%. I finally contacted APR and they informed me of a beta file that could resolve the issue. I flashed to this tune about 2 years ago and it completely fixed any issues and it’s been running great ever since. Comparing logs it seems they just adjusted lambda from 0.75 to 0.80. My theory is that the richer mix of the original tune was blowing out the spark.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Not sure what issues you are/were having but this was my “ignition” problem-resolution:
Mine isn't having an issue. This was just meant to be more of an inquiry for information on the differences between the 1k Ohm and 5k Ohm plugs.

I kept seeing on the BKR7EIX plug being recommended. Only difference I was seeing is the BKR7EIX has a smaller center electrode of 0.6mm, has 5k Ohm (more resistance) and it is Iridium coated at the center electrode but not the ground (which is nickel). I was initialy thinking more resistance meant less flow...which it does. But I didn't know flow = current = amps. And I didn't know it was volts need to make the arc/spark. So I was just trying to get to the bottom of; "why" switch.

When I did the DM K04+ tune from 2014 to 2016...mine too stumbled initially while running the stock 1k Ohm plugs. Bronson, of DM, told me to try PFR7B, which is another NGK 5k Ohm plug. The one thing NGK never mentioned is more resistance means higher voltage.

And so now I believe tuners (R-Tech in U.K.__APR__DM__Rowe Tech here__and probably more) are recommending the PFR7B, BKR7EIX or BKR8EIX because they need a plug with higher voltage to work well with their tuning. And if they really increase boost, then they recommend reducing the gaps of the 5k Ohm plugs.
 
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