Spark plugs, hi-tech or low-tech?

Just thought I’d share this information with you. It’s Sunday morning and it’s this or the tax return. This wins..

Recently I had the chance to listen to a scientist responsible for a research program into low emission gasoline engines in an American research institute. His first job was to find the best ignition system and he presented what I thought was some interesting information. I’m not an expert so this is only how I understood it

Firstly they filmed the speed at which different types of spark plugs could ignite a mixture. They measured the flame area 5 ms after the spark event start :
Typical conventional plug...............150
Iridium thin wire electrode..............350
Double thin wire iridium electrode.....700

The reason why the iridium plug is better than a conventional plug is that a thin wire takes less heat out of the spark which leaves more for the combustion. The double thin wire, where it jumps from one to the other, is even better.

Must get some of those iridium plugs I thought.

He then went onto more esoteric stuff :
Plasma jet plug.........20 x faster than iridium
Laser plug.................5 times faster again
Corona jet.................even faster

The most novel of these was the corona plug which literally shoots out bolts of lightning towards the piston but cuts the voltage supply off before they get there. Great stuff, might be a little expensive.

Then onto the voltage systems. A conventional coil produces a spark that lasts 2 ms which is good. A capacitative system produces sparks which are far quicker which is bad. So you need a multi-strike system.

Picking his brains afterwards though, I was in for some disappointment.

Firstly iridium plugs have been developed because manufacturers are aiming for 100,000 miles plug service intervals. Not really necessary for my Ferrari then.

Ah, but the faster combustion must be good? Nope. These plugs are good when the conditions are tough and it is hard to get stable combustion, ie for very lean mixtures or high rates of EGR. If the mixture is anywhere near stoichometric, (and judging by my fuel consumption my Webers run somewhat richer) he had done further tests which showed no benefit of even iridium plugs over normal plugs. Just so long as it sparks…

So what do you think guys? Myself, I’ll be sticking to my good old Bosch plugs.

Now, Dear Mr Taxman, I'm sorry to say....

 

NGKBP6ES OR NGKBP5ES for me . they have worked great in all of my carb cars, and crane Technologies recommended them with my XR300 ignition in my 77 GTB. never had any luck with Champion or Bosch plugs in the carb cars.

 

The laser spark plugs have a lot of promise. The first experiment with them was back in the late 1970's.

A more recent experiment using a natural gas engine was flawed, in my humble opinion, in a couple of major ways (e.g. expected lean temperature direction, size of laser used, etc.): http://www.netl.doe.gov/publications/newsroom/backgrounder/mb-0006.html


Scroll down about half-way on this page for more: http://www.ornl.gov/info/news/pulse/pulse_v179_05.htm
(see "Laser spark plug outpowers current systems")
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The scientist's comment on laser plugs was also that they had a lot of promise. On the question of cost, which is obviously far too high at the moment, he thought that even the manufacturers did not know what it could be reduced to if it came to mass production.

To me it is hard to imagine laser plugs being viable but then, when you look at the amount of effort being put into low emissions, who knows?

 

Here's a bit on the plasma jet spark plugs:
http://www.directhits.com/tech/SAE_02ffl_204.pdf
http://www.findarticles.com/p/articles/mi_m3165/is_n7_v27/ai_11010153
http://www.directhits.com/AdvAutoIgnSys.html
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=4766855.PN.&OS=PN/4766855&RS=PN/4766855

 

Interesting info.

 

I've found it depends on the car. For example, I've tried the various "low-tech" and "high-tech" plugs on my Daytonas and found they run best with the cheap, under $2.00 per plug, 6ES or 7ES (cooler) for spirited driving. The 288 GTO, on the other hand, ran just great with the more expensive Iridium plugs. It did fine on the thin wire 9EV/9EVX plugs as well.

Steve

 

So, I've got an older car ('78 308), but with a newer ignition system (Electromotive DIS). Do you think I would benefit from new tech plugs or stick with the conventional NGK's that I've got in there now?

 

The trick with the laser plug is the lens. Even a cheap hand-held laser will ignite a gasoline-air charge if a lens can be mounted on its end that focuses the laser to a very small pinpoint on the piston at the right distance.

 

About the best thing that current commercially available plugs offer is unshrouding (e.g. the Bosch +4 plug doesn't cast a shadow on the piston when the spark fires).

 

Very interesting information.
In various tests , with a wide spread of car types, it was found that the combination of no resistance plug wires plus a 80pf capacitor in parallel to the plugs improved the mpg with 10 to 20%, and also gave a better cold start.

Why is not every car manufacturer using this easy and relatively low cost improvement, and why are the plug manufacturers not responding to this seemingly highly succesfull improvement ??

No-Doubt, it is probably not a coincidence that you could give us so much information, so do you have an answer to my above question ?

 

The answer that I've heard is that the plugs wear out far too fast (within hours) when you push that much juice through so fast.

In contrast, the automobile industry is trending toward longer intervals between services. Customers don't seem to want to change spark plugs with each fuel fillup.

...but, if you you were willing to change the plugs with each fillup and run with the capacitors, then yeah, you could bump up fuel economy by 10%.

 

I tried Bosch platinum in my carb 308 when they first came out but they fouled in fifteen minutes - a waste of $35, at a time when you could fill the tank for $20. Never had a problem with the Champions except I can't find them any more. I think the carb cars are so lo tech they just need a spark of any kind to ignite the mixture. Sophisticated engines with variable valve timing, computerized fuel mapping etc, may run better with the high tech plugs. To me low tech = low tech

 

Even then, the multistrike cuts out over 3000 RPM. A CD ignition is actually inferior to a properly designed inductive ignition. And that's the problem, too many manufacturers implemented mediocre inductive ignitions and Ferrari is no exception.

For a cost as no object ignition, the one designed by http://www.adrenalineresearch.com/ which is now owned by http://www.woodward.com/engine/gaseng/smartfire/smart.cfm goes for $22k.

 

I found another supplier, called Nology (www.nology.com), using the same principle as DirectHits who is supplying HotWire spark plug wire.
Many Dragsters seem to use Hotwire to get the ultimate achievable power.

These Spark Plug wires have an extra earth wire, and have the capacity build into the wire. You do not need capacitors on top of the existing plugs like DirectHits does.

About wear of the plugs, this is not too different from wear with standard layout. The flame is much more intens, but the duration is also much shorter, that's why.

 

My 79 308 GTB runs well on Bosch single electrode plugs (tuned on the lean side), though I have used NGK plugs for years in many breaker ignition cars with great success. I agree with the low tech concludions, if it lights the fuel, it is doing its job.

Has anyone tried Bosch +4's in a stock, breaker ignition 308? I have been afraid to try them with the stock set-up. With the stright at the piston plug orientation they should be ideal from a shrouding standpoint.