I believe this to be a tuning specific topic so I put it here instead of the misc tech section.

what are the pro's and con's of the below plug types? and why?

BKR/BCPR - standard reach tip (GSR's)
ZFR - extended reach tip (almost all Hondas/acuras besides GSR's)

the only physical difference is the actual length of the firing tip. all dimensions of all other parts are identical. this basically just means that the ZFR type puts the spark exactly 2.2mm deeper into the combustion chamber.

the only pro/con I can understand is using the shorter BKR type on high comp motors to prevent piston contact.

what are the pro's and con's of the below plug types? and why?
and why do nearly all Hondas call for ZFR, while GSR's call for BKR? and why do most people use BKR's in their boosted Honda's, even when using stock pistons, when oem is ZFR style?

 

You run a colder plug for higher performance engines:

http://www.e3sparkplugs.com/news/hot...park-plugs/326

 

When too much of the ceramic and electrode is protruded in the combustion chamber, the hotter it gets.. If you stick those ZFR plugs in anything that makes decent power, the electrode will overheat and melt, and the ceramic will crack.

Pros of running a really hot plug would be great cold starts, great part throttle response and better overall fuel economy. Our engine condition changes, but we can't run one plug for low RPM and cruising, and another one when we make 300+ WHP. So there is a compromise, and we run colder plugs.

 

obviously. I'm well aware of what heat ranges mean, I am a tuner afterall, I'd be a pretty sh1tty tuner if I didn't know about heat ranges. please read before posting.

 

if the heat range is the same as the comparable BKR plug though, shouldn't they have similar characteristics in heat dissipation?
I used both (BKR and ZFR) in my car at 350hp and never had any issues, and the plugs always read identical. and using the standard v-power plugs, I never experienced one needing to be regapped any sooner than the other.
is there any rough power level where you'd expect to start getting damage to plug tips from using a ZFR instead of a BKR?

 

the plugs pictured are BKR7E and ZFR7F. this should theoretically make them identical in heat dissipation (heat range) as well as everything else.
I can understand a longer tip being thought to absorb more heat, or dissipate absorbed heat slower, but if the heat range is set correctly that shouldn't be a factor. At least I would think that should be the case, but having more ceramic surface area exposed does make sense for absorbing more heat, so thank you as that had never crossed my mind.

I'm still wondering though, what other pro's and con's there are to a standard tip vs protruded tip, mostly in reference to location of the spark in the combustion chamber?
which would be more ideal and why?: spark occurring right up against the head surface, or spark occurring 2.2mm deeper into the combustion chamber?
(this of course is assuming no damage to the plug tips occurs)

 

http://www.ngksparkplugs.ca/tech-info-spark-plugs.cfm

Here is a little write up from NGK on spark plug design.

 

yes, good info, I've read that multiple times over the last 10+ years or so. still unrelated to my question though.

the insulator length on the zfr and bkr plugs is rated for the same heat range and perform similarly in heat dissipation, as I mentioned above.

the question I'm asking here has to do with pro's and cons of having the tip closer to the head surface, or deeper into the combustion chamber. specifically the actual spark location; which is better and why.

and tony above did point out that the deeper prolonged tip is prone to absorbing more heat due to additional surface area openly exposed to combustion temps, which is unrelated to heat range because heat range has to do with heat dissipation, not heat absorption, so that was useful info I was not expecting but am glad he pointed out as stuff like that is also what I'm seeking.

 

http://www.briskusa.com/technical-in...cation-design/

Here is another little article on spark plug gap location and design with some nice charts. I don't feel like writing a novel so just trying to find info that I can link to.

 

now THAT is helpful, thank you. especially the temperature chart, showing nearly equal tip temps at high load, but longer tip having hotter temps than shorter tip at lower loads; which is a good thing when using a colder than stock plug in a daily driven turbo Honda that would much prefer stock heat range while cruising or light throttle. this is the 1st bit of info I was specifically seeking.

I also especially like the quote: "By means of shifting the insulator tip suitably out, i.e. into the combustion chamber of the engine, better access and ignition of air fuel mixture is achieved."
that's the 2nd part of the exact info I was wondering about.

the 3rd part I'm wondering about is how the flamefront propogates with a shallower tip vs a deeper tip. if the spark occurs closer to the center of the combustion chamber, does it combust more equally and/or efficiently, or with any stronger expansive forces, or smoother less pulsated expansive forces possibly with less turbulence? would it put more stress on the head due to initial combustion occurring further from the head surface, due to the combustion pulse gaining a bit of additional speed before reaching the surface of the head?
also wondering how spark depth affects combustion force and temp in the squish zone of the chamber?

 

Wow a lot of technical questions. May I make a suggestion as you are getting more in depth on the conversation. There are a couple of great books I would suggest you pick up and read. These are two books I own and everyone wanting to know about the internal combustion engine should own.

1. Internal Combustion Engine Fundamentals - John Heywood
2. Automotive Handbook - SAE published by Bosch

The second book deals with an automobile on a whole. While the first is on the Internal Combustion Engine.

 

I'll have to check them out, thank you for the suggestions.

 

anyone else with input or other resources regarding this, please contribute

 

gsr having different quench area so maybe has a different optimal spot to start the flame
in the dome instead of on top of the piston?

 

plus gsr also has an egr valve in euro models maybe its related.

im also curious now what spark plugs to use with built motors if clearance allows for either.

 

ZFR plugs have been know to touch the piston domes on particular setups... BKR's are approx 3mm shorter and provide adequate clearance.

 

exactly, I know that's why a lot of high comp setups use BKR. but if using stock pistons, or pistons with the same or lower dome height as stock, in an engine that calls for ZFR as stock plugs, I'm wondering if it'd be better to use a ZFR. so far everything leads to yes as long as the tip doesn't overheat and damage the porcelain.

I'm going to try it in my car and see if any damage occurs. and when I hit the dyno I'll be tuning on BKR, then I'll slap a set of ZFR's in and see if power and/or afr's change. that won't be for a week or two though.

 

so you think it wouldn't have anything to do with the gsr design (quench area, piston domes and intake manifold design?

 

I don't think it has anything to do with the quench area or intake mani design. I do think it has everything to do with the piston domes and clearance to them.

 

The design of the sparkplug determines how much heat it absorbs and how much of the plug is exposed to combustion. Heatrange number is just the amount of heat the plug can shed away.

I used to run a semi surface discharge plug (R6601-8) on my old 230 WHP NA build which had a decked block and a heavily milled head. I ran this type of plug with an 8-heatrange and it reported much better power on pump gas (at 13.0:1 CR) versus any other standard electrode plugs that I've tried.

Motoxxman summed it up pretty well, it has a lot to do with how deep the plug protrudes into the chamber, as well as how close it is to the piston.