Have to change spark plugs this weekend. I went to 3 FLAP and none of them carry Bosch W7CC. They have the usual AC Deelco, NGK, champion etc. Are any of these any good or should I stick to the Bosch? If Bosch is the best bet, who has the best price and shipping?
Thanks

Seriously? Ngk bp6

Based on recommendation of John at aircooled.net I'm putting NGK BP6ET in a 4 cyl I'm working on. These are triple electrode

+1

Triple electrode is just marketing BS. If the basic plug is a decent one, they work fine. If the basic plug sucks, adding more electrodes won't make it suck less. (I'm looking at you Bosch +4 plugs!)

There will only ever be one path that the spark takes. More electrodes serve as backup if the outer electrode gets fouled or damaged (if those happen the other outer electrodes will likely get it as well) and to shroud the flame front, reducing combustion quality slightly.

The NGK plugs should be fine, basic or multi-electrode. Just don't pay any more for the multiple ones.

--DD

Bosch or NGK only, the reason for not using champion is they have straight cut threads which will gall the aluminum and strip out the threads.
Only use copper core plugs, don't use platinum, etc., in an aircooled engine.

Bosch or NGK (also Beru) have rolled threads that are aluminum friendly.

Good advice. Now if I could just remember what plugs I used last time.

uh, pull one out

Don't want to hijack the thread , but which one when the 2.0 heads have been converted (improved) to 12mm threads long reach? 2056 engine.
Thanks

I hope this isn't hijacking, but it reminds me of a question about twin plug engines. How does that really help? If multiple electrodes are a waste (which I agree with), why are multiple plugs effective? If it combusts, how does it matter where it started? Or how does it matter if it starts in more than one place (if that's even possible once it started)? It's in the same chamber and combustion is combustion, right? Sorry if it's a dumb question, but I've never heard the answer.

I used to use NGK DP8EA-9 in my old 2270 with 12mm threads. Verified by McMark http://www.914world.com/bbs2/index.php?sho...;hl=spark++plug

In my old 1.7 with 14mm threads, I used NGK BP6ES.

Thank you for the information.

Now back to regular program.

it's what I use on my 2600cc T4 with 2.0 heads.

The whole charge does not just suddenly burn. It takes time for it to all burn. If you start the burn from two separate locations, the burn happens faster and in theory more evenly. The rule of thumb in 911 engines is that you can run a full point of compression higher in twin-plug engines than single-plug ones.

Modern cylinder head design makes twin-plugging less beneficial, as more care is taken to get the chamber shape to work optimally with the spark plug placement.

In some applications (e.g., aero engines) the two plugs are there for redundancy. Because if one spark fails while you're in the air, you really really really want to have another one there to light the charge.

--DD

The burn is like a wave, if it starts on one side it takes time to get to the other side.
If it starts at two points the wave from each point only has to travel half as far.
The more efficient the burn the higher CR you can run.

Modern heads the plug is in the center surrounded by 4 valves, like Dave said better chamber and piston top design, plus water cooled can run higher CR and leaner AFR due to more efficient cooling.

Thanks guys. I figured that was the reasoning, it's just hard to imagine because it happens so fast.

As it was explained to me years ago, the combustion cycle is like a slow grass fire starting with the spark at the electrode, albeit in real time, and at high revs, how slow is slow?

Pre-detonation (pinging) is caused if that grass fire is too quick ... the expansion of the ignited air/fuel mixture is burning faster than the mechanical components can handle.

I am curious of people's thoughts on another bit of conflicting info I have seen. I see the NGK BP6ES mentioned a lot, but the NGK application guide calls for BR6ES for the 4 cylinder 914 engine.

I know the "R" just indicates the ignition noise suppression, so my main question is the "P", projected tip, correct, even thought NGK says to use the non projected plug?

The projected tip plugs have a wider effective heat range...
They act like hot plugs at low loads, and cold plugs when under high loads.

Sounds like BS but its basic engineering applied well.

I don't think I have run non projected tip plugs in 25 years.

...And the copper/nickel triples are not BS, they last a lot longer before the performance goes south.
NGK BP6ET or #1263 (or Bosch W7DTC if you can find them, work same AFAICT)
These are a VW approved plug for a 914, BTW.
There is also a 5/8" hex version that's a bit easier to get in/out but I cannot recall the part#.

The multi-electrode platinums are junk IME, due to the fine wire electrode that erodes down the hole in the insulator after a few thousand miles.
An iridium version might actually work. I might even buy a set to try if they existed.
(OK, Nippondenso actually makes such beasts ALSO with platinum tips on the 3 ground straps, for $15... Just need o figure out desnos part# system...)

On newer cars that disappearing act kills coils, on older cars it just runs like garbage.

https://www.youtube.com/watch?v=jdW1t8r8qYc

Slow motion of the burn in a cylinder, ok its only a B&S single cyl but still interesting.

Yes that's a very cool vid. You can see how the flame travels like a wave front.
You also can see that it's wasted spark, firing each stroke. Absolutely zero effect on efficiency.

It would be real cool to see a FI batch vs sequential vid.

Thanks for the reply on projected tip. I had already gone with the non-projected tip plug and will keep this thread in mind for the next time I need to purchase plugs. The car runs pretty nicely so I don't see a need to replace them now.

Jim

I have tried different types of spark plugs to squeak out more power, multi electrode, copper, platinum! (indexing seems to have small effect) (a multi spark ignition seems to have some effect) I use platium single electrode in every engine I can get them for! Airplanes have two magneto's for safety but when you test them before flight and you turn off or ground out one system the rpm drops and has to be in an except amount for flight. Also the mags are usually timed a degree of timing apart. I have not tested the E3 spark plug. I would like to hear what Jake has to say about spark plugs!
My two Cents!

additionally...
when the factory started twin plugging their race motors.. they were pretty small bore
the 2.o pistons and combustion chambers on a 6 cylinder were a different design and shape than the later motors

so the tall piston shape was another barrier for the burn to cross... making the twin plug a great solution to start the fire on both sides of the pistons "ridge" or tall center

I believe starting with the 2.2, the combustion chamber was re-shaped and the piston as well, to help address this issue and assist the burn front in completing its job...

picture of a 906 2 liter high compression piston... and the ridge....