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plug recommendation?

Twin plugging my CIS motor as I write, Electromotive crank fire, C2 cams, 36mm intake port heads/intake manifold etc. what's a good plug to run and at what heat range? Is there any benefit (or liability) to running a cooler (or hotter) plug? Tanks!
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82 930 Pearl White 3.3 964 cams, K27 HF, Kokeln, fuel enriched, IA fuel head mod, wur mod, crankfire, 2X plug, Aase worked heads. 1bar, GHL, zork, 23/33 bars, low, loud
Old 07-28-2009, 06:38 PM
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Doug Siegel
 
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NGK racing plugs. Cheap and good.
R5671A-7 If you are not going to beat the piss out of her.
R5671A-8 if you are (colder)

When I tried to install Bosch WCS plugs in my lower 6, I had an unfortunate surprise. They were too fat. Couln't get'em in there.

Carquest has the NGK. Call ahead. They'll usually have them in a day. You need to do a google search to get the stock number. If memory serves me, the 8's are 4554 and the 7's are 7091. Carquest won't recognize the r5671a number.

Gap: 24-25
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88' blk/blk 930: Haltech EFI, Twin Plug, Pauter Rods, Nascar Bearings, custom crank work, dowel pinned case, ported manifold and heads, Kokeln I/C, SC Cams, Turbonetics ball bearing 62-1, BB headers, RARLYL8 Zork, additional 993 oil filter, plx/inyourface gage, RS style coilover, Fikse FM10-17 wheels, TIAL 46mm 1 bar. (where the heck did all my money go?)
Old 07-28-2009, 07:06 PM
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I 2nd that- NGK R5671A-7.. Gap-.040 with my MSD-6AL & MSD COIL. Best plug I used so far. IMOP.
Old 07-29-2009, 04:39 AM
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Quote:
Originally Posted by wjfk32 View Post
I 2nd that- NGK R5671A-7.. Gap-.040 with my MSD-6AL & MSD COIL. Best plug I used so far. IMOP.
+1. I went with those and gapped at .40 last plug change and am happy with it.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 07-29-2009, 04:45 AM
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Doug Siegel
 
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I'd like to hear others chime in regarding gaping. I was told that anything bigger than .25 on a turbo car is likely to extinguish. The bigger the gap, the bigger the spark, that is unless the boost pressure blows her out.
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88' blk/blk 930: Haltech EFI, Twin Plug, Pauter Rods, Nascar Bearings, custom crank work, dowel pinned case, ported manifold and heads, Kokeln I/C, SC Cams, Turbonetics ball bearing 62-1, BB headers, RARLYL8 Zork, additional 993 oil filter, plx/inyourface gage, RS style coilover, Fikse FM10-17 wheels, TIAL 46mm 1 bar. (where the heck did all my money go?)
Old 07-29-2009, 12:59 PM
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I've used the bosch W3dpo (expensive oem platinum sparkplugs) and bosch W4cs which have a silver electrode and I can't tell any difference.

NGK plugs are just as good.
Old 07-29-2009, 01:39 PM
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Quote:
Originally Posted by dsiegel360 View Post
I'd like to hear others chime in regarding gaping. I was told that anything bigger than .25 on a turbo car is likely to extinguish. The bigger the gap, the bigger the spark, that is unless the boost pressure blows her out.
Could be true with stock CDI ignition. With my MSD setup, if I recall even MSD suggested something larger than .40 (for NA cars).
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 07-29-2009, 02:32 PM
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If you are using Electromotive's coil packs, you'll need to narrow that gap. You should call Electromotive to get their recommendation. When I had them, it was close to .024 max. They do not have the power of CDI and you run the risk of blowing your fire out at high rpm. In addition, remember to use a good resister type plug and wires since its probably wasted spark.

Ironically, I bought the electromotive to gain spark control over the distributor. They didn't tell me that I was sacrificing significant spark energy with their wasted spark unit which ended up giving me relatively little gain given all the money I threw at this project.
Old 07-29-2009, 02:50 PM
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I have been running the Beru Silverstone S9's since having issues with the bosch plugs, have had a little (a lot) difficulty tracking them down however. The NGK's seem readily available although the plugs mentioned above as well as the ones listed for stock 930's are not resistor plugs, other than radio noise how might this affect actual performance?
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82 930 Pearl White 3.3 964 cams, K27 HF, Kokeln, fuel enriched, IA fuel head mod, wur mod, crankfire, 2X plug, Aase worked heads. 1bar, GHL, zork, 23/33 bars, low, loud
Old 07-31-2009, 06:45 AM
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from the NGK web page...

Q: When should I use a resistor spark plug?

A: NGK "R" or resistor spark plugs use a 5k ohm ceramic resistor in the spark plug to suppress ignition noise generated during sparking.

NGK strongly recommends using resistor spark plugs in any vehicle that uses on-board computer systems to monitor or control engine performance. This is because resistor spark plugs reduce electromagnetic interference with on-board electronics.

They are also recommended on any vehicle that has other on-board electronic systems such as engine-management computers, two-way radios, GPS systems, depth finders or whenever recommended by the manufacturer.

In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion.
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82 930 Pearl White 3.3 964 cams, K27 HF, Kokeln, fuel enriched, IA fuel head mod, wur mod, crankfire, 2X plug, Aase worked heads. 1bar, GHL, zork, 23/33 bars, low, loud
Old 07-31-2009, 06:46 AM
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Wo ist die Rennstrecke?
 
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In a wasted spark ignition system, a resistor plug and wires are used because one plug fires on the compression stroke and the opposite plug fires on the exhaust stroke (hence the name, wasted spark). The higher the compression in the chamber, the more power is required to fire a plug. If a coil is firing two plugs, all the energy will find its way down the path of least resistance - the plug on the exhaust stroke (no power). In order to make each path equal, a resistor plug and resistor wires are used - in theory, there is no path of least resistance and each plug is fired with equal energy. At high rom and boost, your effective compression ratio could approach 12.0:1 - now add forced induction (swirling air in the chamber) with high compression, and you'll need a stout spark. The only way to accomplish this on wasted spark is a small gap on the plug. If you try to run a hotter plug to off-set the small gap, you'll invite detonation by creating a glow plug. By the way, I used to run Bosch DTCFR5 plugs with good results on my wasted spark.
Old 07-31-2009, 04:16 PM
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Doug Siegel
 
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Quote:
Originally Posted by slyguy View Post
from the NGK web page...

Q: When should I use a resistor spark plug?

A: NGK "R" or resistor spark plugs use a 5k ohm ceramic resistor in the spark plug to suppress ignition noise generated during sparking.

NGK strongly recommends using resistor spark plugs in any vehicle that uses on-board computer systems to monitor or control engine performance. This is because resistor spark plugs reduce electromagnetic interference with on-board electronics.

They are also recommended on any vehicle that has other on-board electronic systems such as engine-management computers, two-way radios, GPS systems, depth finders or whenever recommended by the manufacturer.

In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion.
I just spoke with NGK. They suggest their iridium plug/resistor type for EFI applications. I've got a fresh box of R5671a-8's. 12 of em still in packaging. Anyone wanna buy'em?
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Old 08-06-2009, 11:31 AM
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NGK iridium in my car with a wasted spark CDI system.
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Old 08-06-2009, 01:30 PM
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Quote:
Originally Posted by DonE View Post
By the way, I used to run Bosch DTCFR5 plugs with good results on my wasted spark.
nothing like digging up an old post but it's still relative.

I'm going to try a set of these in my car. EFI / Wasted spark
Old 08-24-2011, 12:06 PM
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FR5-DTC- 3 PRONG-COOPER

My mechanic has a 996tt-EPL-24/18 turbos-running 1.3-1.4-boost...Was running NGK-Iridums..having trouble on top-end...Couldn't figure it out..Epl recommended NGKS
After more testing and switching to Bosch-FR6LDC-(2 prong copper)What a difference and no miss..

My wrench--said u can take those expensive NGKS and blah--blah...
I know this story is comparing to apples to oranges...Both Bosch plugs are quite similar.
GL
Walt
Old 08-25-2011, 04:54 AM
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bpr8es, nice and cheap.
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Old 08-25-2011, 05:50 AM
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In the twin plug crowd, does anyone else have 12mm thread (vs. std 14 mm) in the second plug hole? Mine were set up for 12mm to leave a bit more meat in the head and to help the smaller plug wrench to clear the head barrel nut.
I have done a thread search on plug recommendations, but looking for some help on the 12mm plug.
Thanks!
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Old 11-29-2011, 01:41 AM
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NGK (6684) BPR8EIX no issues so far (1000km) on my SDS EFI 930
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Old 11-29-2011, 03:09 AM
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Thanks Roland. I did not know how many people would use 12mm plugs.
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Old 11-29-2011, 05:06 AM
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Quote:
Originally Posted by bahnzai View Post
Thanks Roland. I did not know how many people would use 12mm plugs.
I've heard of some in cause of poor space there, but haven't seen in real
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Old 11-29-2011, 06:37 AM
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