Spark plugs Options

[Mark Henry]

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.

[jvmarino]

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.

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

[porsha916]

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! (IMG:style_emoticons/default/beerchug.gif)

[brant]

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?

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

(IMG:style_emoticons/default/agree.gif)
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.

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...

[brant]

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