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Ok, I've done a buttload of searching on this subject, and I just want a definite answer because it's bothering me.
I've gotten a few different answers on which type of NGK spark plug to buy (i.e. BKR6E, BKR5E-11, PFR6B-11, etc.) and from the massive response to the BKR6E plugs, I've concluded that these are best suited for the SR20, despite what NGK or various NGK dealers have listed as "stock" or "recommended" (Though, it does boggle my mind how two different Nissan dealerships can list two different types of plugs as stock or recommended, such as BKR5ES-11 versus BKR6E and so on and so forth). Case closed. However I need one question answered:
Is it the larger the gap, the more spark, and the more power, or is it the larger the gap, the further the spark has to travel, resulting in a weaker spark, and less power.
I know OEM gap is .044", however I also know that this is the gap for the PFR6B-11's (NGK Double Plats), which came stock in the SR20. Now I've read that if you switch to BKR6E's (NGK Coppers) that they are pre-gapped to about .032", and that you should keep them gapped at .032-.035". However, I've also read that it is wise to gap these back up to 0.44" for more power. Is this true? Will this result in a greater spark, and, ultimately, more power? I'm very confused on this subject as there have been hundreds of answers just on this site alone.
I run BKR6E-11 in all NA SR20's .. Its a Non Platinum 6 heat range plug , stock is listed as a 5 range, but a colder plug will be less likely to have preignition or pinging as its often called, 7 heat range is good for turbo Nitrous or on a major NA buildup....As far as gaps go I run all the Performance NA SR's at .047 in. , stock is listed in the NGK catalog in the platinum plug as .044 in. , and some where a BKR5E plug was listed thats a .035 in. gap , so alot of people run them at .035 in, Why would they use a .044 in. gap on one plug and .035 in. on the other, makes no sense ....
I have found a larger gap will make a larger spark, Hotter spark will make a larger explosion, causing more of the fuel to be burnt causing more HP , the stock coils on the SR's will make 45,000 volts easy !! At idle it only takes about 5000 volts to fire the plug , and even on the big built NA SR's I have done , I see mabie 40,000 volts at peak RPM with a .047in. gap .... so yea, the coil has to work a little harder, but its not at its limits ... With Boost or Nitrous , you need alot more Voltage to fire the plugs, thats why a smaller gap will help, the coil will not have to work so hard , and a smaller gap will require less spark to fire , so there is less likely you will get a missfire ....
I have run SR's and other cars at the track with up to .050 in. gap and they always run better, now I wouldnt suggest that for daily use, its tough on the coils and other ignition parts, but it works great for the short bursts at the track ..Even my brothers 400+ HP SR20DET we run them at .040 in. with MSD SCI and stock coil , and have seen good results.....
Everybody has there own opinions on plug gap , I am just stating what I have seen and where I have had the best results ... Most of all , try it yourself , get a set of BKR6E's gap at .035 drive a week, the get a set of BKR6E-11's and gap at .044 drive a week , then go to .047 , see which one you like better, The BKR5E-11 plugs are fine, but like i said , for Performance use, the 6 heat range is a better choice, oh and the 11 at the end is 1.1mm gap ( .044 in. ) , vs. no 11 at the end .032 in. gap ... Also, you dont want to gap the standard non 11 plugs anymore than .035, you will not get a good strait gap , the ground electrode has more length on the 11 plug for the larger gap ...
The only advantage to the platinum plugs is they last longer...60,000 miles , but the copper plugs seem to make a bit more HP , but require changing every 15,000 -20,000 miles ...
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Last edited by SHAWNATGERBROCK; 02-10-2005 at 02:04 AM.
Ok, I understand exactly what you're saying. Damn, I had it all wrong then. The only thing I had right was the difference between heat ranges, lol!
So a larger gap results in a larger spark and more power, but it pulls more volts from the coil and makes it work a little bit harder, whereas a smaller gap will put less strain on the coil and make a little less power. The BKR6E plugs are designed with a shorter ground electrode for a maximum .035" gap, and the BKR6E-11's are designed with a longer ground electrode for a larger gap, more spark, and more power. And there is a compromise between firing efficiency (or voltage needed to fire) and gap (or power). I guess my next question is are there any compromises between power and gas mileage and such with the larger gap?
This is very interesting information. So basically, due to the platinum plug's design, it performs about the same gapped @ .044" as the copper plug gapped @ .035", so they both give about the same power output (I wonder why the smaller gapped BKR6E's perform a little better than the larger gapped PFR6B-11's?). So if you want more power on the platinum plug, you can raise the gap, but .035" is the maximum gap allowed on the copper plug due to it's inefficiency when gapped past this point. If you want to raise the gap without using the platinum plugs you should use BKR6E-11's, which were designed for a larger gap. Does this all sound right? It's late, so if I made a mistake anywhere, please feel free to correct me. This is a learning experience for me, and I would rather gain vital knowledge than defend an ego. lol
I think it's sort of ironic that the SR20 benefits more from using stock GA16 plugs than using it's own plugs! lol (No offense to any GA16 owners )
I also think that it's ironic that after 2+ years of working on cars, after removing engines and transmissions, replacing clutches, fixing suspension components, removing entire engine bay systems, and modifying cars, that I never stopped to learn about such a simple thing as a spark plug! LOL
I think it's all starting to fall into place now. Thank you very much for your input! A+
just for reference, in a turbo application, the spark can be "blown out" if your plug gap is too big. Therefore, to run high levels of boost, you have to make the gap smaller sometimes.
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Khiem
'96 SE-R.... boost, brakes, suspension, etc... sold
'05 Evo
'05 CBR 600RR
From Mike K on se-r.net "The SR20 has a powerful stock ignition that can fire through turbo boost and NOS. Gap the plugs at 0.045". If you experience misfire under squeeze or high boost (and the rest of the ignition system is in good condition, like the cap, rotor and wires) you can close the gap down to as small as 0.020" to prevent it. Go down in 0.005" increments until the misfire stops. Higher cylinder pressures cause by big NOS or high boost requires smaller gaps with the stock ignition. The smaller gap loses a little power but this trick can tide you over until you can get that snazzy turkey roaster ignition."
Basically run a larger gap for more power. If you get misfire, then you need to shorten the gap.
I use to run Platium 4 plugs in my SR which gave me good performance for the first couple of weeks, then it strarts stutter at idle. so now I'm looking for the correct type of plugs to use. thanks guys.
Having worked in the auto parts industry for about 6 years, i learned that almost ALL imports require a .044 gap That's what i gap my plugs too in my NX and SE-L.
Generally, I believe the wider the gap, the hotter the plug will fire (and the hotter the cylinder temps will be) and the smaller the gap, the colder.. Look at it as heat generated by a big lightning bolt as opposed to heat generated by a smaller lightning bolt.
-nathan
edit: da_linkwent I use regular NGK's. they work like a charm.
get the bkr6e-11's all the time. there cheap and u can even change them every month if u want.
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The plug gap is based on the dynamic cylinder pressure and the current capacity of the coil/ignition circuit.
The larger the gap the more current required to bridge the gap.
The higher the dynamic cylinder pressure the more current required to bridge the gap.
High boost or high CR will generally warrant a smaller gap if the OEM ignition is marginal in terms of current capacity.
No electrical circuit will generate more "power" than is just enough to get the job done.
A 100hp motor only makes 100hp and draws full running amps when the load is sufficient to warant it. So does the ignition circuit. It only EVER draws as much power as is needed.
If the plug is fouling, cold or hot, it's usually carbon tracking across the inner electrode via the ceramic insulator (carbon conducts electricity) to ground. In this instance the higher the spark energy the more the plug fouls up as the arc seeks the past of least resistance, ALWAYS.
High Voltage coil marketing is a ploy on ignorrance to sell the ultimate "Hot Coil".
The challenge is dwell time on the primary winding of the coil more so as average rpm has increased on the moder car. This is the only reason we have wasted spark and coil on plug systems, it's to gain dwell time by splitting up the duty cycle on more than one coil.
Old American V8 iron is where all this came from, V-Plug, Splitfire, Multi Spark etc, it's all because flame propagation in the heads is/was poor and all sorts of tricks were used to compensate for bad design. Just think of the real reason the Hemi was so impressive, it's combustion chamber was better and flame propagation was better.
Finally, if you run wasted spark, or know someone who does do the following;
Remove all the plugs from the head, keep them on the leads.
Ground only one plug so it can fire.
Crank the motor and look at how tiny and weak the spark is.
Ground the next plug fed by the same coil and try again.
Big, BLUE, spark on both plugs.
Reason: The Wasted Spark circuit requires that the circuit be terminated back to the coil. It must go through Gap#1 in the correct polarity, then Gap#2 in REVERSE polarity.
That being said, the point is, here are your 500, billion, 3 gazillion volts firing two plugs out of phase (one cylinder is always in polarity, the other is always in reverse).
But Mr Coil Seller is telling you you need 600 billion, 4 gazillion volts just to fire one plug.
The other thing is that the highest current draw is just prior to the gap being bridged, thereafter the air between the gap is ionized and therefore conducts electricity, so the required current drops until it gets to zero as the secondary coil winding voltage goes to zero.
Plug gap does not give more power and bigger bang and higher temperature.
The Nissan Catalog shows heat range 6 or 5 based on the climate and ambient air temperature.
Excellent explanation bigtoe. I think I was able to grasp the basic concept of what you were explaining. I didn't do so well in physics lol So, basically, from now on I'll just use standard BKR6E-11 plugs gapped @ OEM gap unless I start running either nitrous or boost, in which case I'll run a 7 heat range and close the gap a bit. Thanks for all the input, guys! It's greatly appreciated!
Plug gap does not give more power and bigger bang and higher temperature.
I always thought that a longer arc will have more surface area, making a larger flame kernal quicker than a smaller spark would. I agree with you on spark voltage, it has nothing to do with making power in the cylinder - it merely allows you to arc a longer distance, i.e. bigger plug gap. I've always felt that you could gap it as big as it could tolerate before misfiring - anything less was a waste of having a bigger coil than you needed (any thoughts on this?)
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The bigger the gap the more enrgy required to bridge the gap.
The energy available to bridge the gap is a function of the dwell time of the coil primary winding. As the duty cycle increases (rpm) the available dwell reduces. As rpm increases and available energy therefore decreases the requirement for plug gap MUST reduce. This is why Capacitive Discharge systems cannot provide a multispark output past 3.5 to 4k rpm.
Once the fuel mixture is ignited, the flame front propagates as a function of the pressure profile within the combustion chamber. At 19,000rpm on a 96 x 41mm 3000cc F1 V-10, running on "pump gas" at 12:1CR the flame front propagation is not even close to being in the realm of the chemical reaction (burn) speed. Basically at even these high rpms you are not limmited by how quick combustion can take place.
If the density profile of the compressed charge is varied (due to swirl, over fuel, poor combustion chamber design, poor fuel atomisation etc) then the possibility exists that the spark energy required may vary dynamically within the same cylinder over multiple combustion events. In such a case then, again the energy required will be drawn form the secondary winding of the coil as required, once of course it's available.
This is mostly why the pent roof, or hemispherical combustion chamber was designed, with the spark plug in the center. The density profile within the compressed charge is geometrically dictated by a symetrical change in volume relationships within the chamber, also the plug is at the focal point of the dynamic pressure wave.
The bigger the gap the more enrgy required to bridge the gap.
The energy available to bridge the gap is a function of the dwell time of the coil primary winding. As the duty cycle increases (rpm) the available dwell reduces. As rpm increases and available energy therefore decreases the requirement for plug gap MUST reduce. This is why Capacitive Discharge systems cannot provide a multispark output past 3.5 to 4k rpm.
Once the fuel mixture is ignited, the flame front propagates as a function of the pressure profile within the combustion chamber. At 19,000rpm on a 96 x 41mm 3000cc F1 V-10, running on "pump gas" at 12:1CR the flame front propagation is not even close to being in the realm of the chemical reaction (burn) speed. Basically at even these high rpms you are not limmited by how quick combustion can take place.
If the density profile of the compressed charge is varied (due to swirl, over fuel, poor combustion chamber design, poor fuel atomisation etc) then the possibility exists that the spark energy required may vary dynamically within the same cylinder over multiple combustion events. In such a case then, again the energy required will be drawn form the secondary winding of the coil as required, once of course it's available.
This is mostly why the pent roof, or hemispherical combustion chamber was designed, with the spark plug in the center. The density profile within the compressed charge is geometrically dictated by a symetrical change in volume relationships within the chamber, also the plug is at the focal point of the dynamic pressure wave.
Keep you money in your pocket. Gap the plug with the minimum gap needed at full load and peak rpm. Be honest with you plug choice. If you NEED a cold plug go up in 1 unit steps. If it fouls around town and is clean on the idle after a good run, then it's too cold for the around town driving. If it idles all day just fine and after a hard run starts to misbehave, then it's probably too hot. Hot = lower number on NGK, Cold = higher number on NGK.
I have been told by some Honda Agent people that the plugs in the Honda or Nissan or Mitsubishi box, are identical to the off the shelf parts place plugs, however the OEM packaged plugs go through a higher level of random batch testing at NGK and have a higher quality of build. Generally they claim that the EOM packaged plugs internal resistor last longer. BS or not, I do not know.
ok, I got a question. I'm thinking of getting 2 sets of plugs. One for daily and one I can pop in for track and such. What do you think:
Daily driving:
PFR6B-11, Platinum, heat range 6, gapped at .044". I sorta drive the car hard, even on the road. Think 6 heat range is good?
racing and dyno:
BKR6E-11 or BKR7E-11, copper, gapped at .048". Not sure if a 7 heat range is too much or if I should stick with a 6.
Generally speaking, the HARDER you drive your car the COLDER you want the plug. But beware, colder plugs don't burn off carbon deposits as fast as hard plugs so they foul quicker. But NGK's are inexpensive (as long as they're the copper ones) HARD driving would include an engine modified for performance, an engine under heavy load, or an engine run at high rpm's for extended periods of time. Also engines utilizing turbos, supercharger, or nitrous must also run colder plugs (due to the higher internal cylinder pressures). A hotter plug can contribute to detonation in all these cases.
Alternatively, the EASIER you drive your car, the HOTTER you want the plug (to OE recommendations of course).
Another interesting tidbit of info: According to NGK the higher you increase your timing, the hotter you make the tip of your spark plug. They indicate that an increase of 10degrees in timing results in an increase of 70-100 degrees Celsius to the spark plug tip. If this formula also holds true for lower increases in timing then if we bumped our timing up from 15 to 19, we'd be looking at an increase in spark plug temps by 28-40 degrees Celsius (82 to 104 fahrenheit for we U.S. peeps). hooooooooooooooot. yikes.
Generally speaking, the HARDER you drive your car the COLDER you want the plug. But beware, colder plugs don't burn off carbon deposits as fast as hard plugs so they foul quicker. But NGK's are inexpensive (as long as they're the copper ones) HARD driving would include an engine modified for performance, an engine under heavy load, or an engine run at high rpm's for extended periods of time. Also engines utilizing turbos, supercharger, or nitrous must also run colder plugs (due to the higher internal cylinder pressures). A hotter plug can contribute to detonation in all these cases.
Alternatively, the EASIER you drive your car, the HOTTER you want the plug (to OE recommendations of course).
Another interesting tidbit of info: According to NGK the higher you increase your timing, the hotter you make the tip of your spark plug. They indicate that an increase of 10degrees in timing results in an increase of 70-100 degrees Celsius to the spark plug tip. If this formula also holds true for lower increases in timing then if we bumped our timing up from 15 to 19, we'd be looking at an increase in spark plug temps by 28-40 degrees Celsius (82 to 104 fahrenheit for we U.S. peeps). hooooooooooooooot. yikes.
-nathan
OK, cylinder pressure does not have direct implication to the selection of hot or cold plugs. The temperature of the ceramic insulator as a function of combustion chamber temperature is what is critical.
If you ever ran or run leaded fuel, you would see the the tail pipe near whitish grey after a hard run, browninsh to redish when run around town, or black and sooty if left idling or over rich. The temperature of the tail pipe, as a function of mass flow out the exhaust pipe along with the final gas temperature is what accounts for the color change. White means the tail pipe is hot and the carbon does not settle out, or chemically, electrostatically bond to the tail pipe and other carbon particles. Darker colors indicate cooler tail pipe temperatures and thus carbon build up. The farther up towards the ex. port you go the cleaner and lighter colored it becomes.
Same for the electrode and face of the steel body of the plug.
The heat range is controlled by controlling the void area round the insulator.
More void, hotter plug....meaning it will maintain a higher average temperature in a lower load, lower mean temperature combustion environment...thus not allowing carbon deposits.
Colder Plug means less void, more material to discipate heat to the cylinder head. It will try to stay cool in the hotter mean temperature environment, this is why they will foul easily at off cam, or low load on a motor that is used to race.
Hot/Cold is arelative thing.
Finally, the cylinder pressure is only relevent to the the spark energy required to bridge the gap and may not necessairily influence the heat range of the plug.
Temperature effect of ignition on the tip: Increasing timing (advance) allows the flame front to start propagation earlier, the intent being to optimise peak cylinder pressure as the gasses burn/expand at a point after TDC (usually somewhere between 12 and 18° ATDC. This is an engine reciprocating assembly geometry issue and fuel RON/MON issue.
As you retard you push the optimised cylinder pressure peak later on in the ATDC sectors and effectively lower the drive force on the piston. Turbo motors or nitrous motors more often than not have to do this because the fuel cannot sustain the rapid rise in flame front leading edge pressure and they suffer pre-ignition. So they retard and basically throw potential power out the exhaust valves.
Now as the ignition advances and the combustion event takes place earlier the mean time of the actual combustion cycle increases. More heat is generated, more heat has to be discipated and consequently everything will run hotter. The plug tip being very tiny relative to all else has very little mass and therefore has little heat capacity compared to say the piston, SO, the tip temperature rises up to the point where it either melts or burns or reaches equilibrium, with sufficient heat transfer over it's duty cycle, to the insulator and then on to the plug body.
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HARD driving would include an engine modified for performance, an engine under heavy load, or an engine run at high rpm's for extended periods of time. Also engines utilizing turbos, supercharger, or nitrous must also run colder plugs (due to the higher internal cylinder pressures). A hotter plug can contribute to detonation in all these cases.
