Spark Lifetime?

[roulli]

Hi,

 

 

what is actually the typical lifetime (milage) of a standard plug (BP6ES) on Megajolt, with 1,2mm gap?

Is lifetime reduced due to the lost spark and /or increased gap ?

What are the symptoms, once they start to degrade?

 

Thanks for sharing your experience.

 

Cheers,

Patrick

[Nick Jones]

1.2mm gap is a bit too big? I think 1mm is maybe safer. I say this as Ford reduced plug gaps on their Focus models (and possibly others) from 1.3 to 1.0mm due to the number of HT lead and coil pack failures. The bigger gap means that the coil charges to higher voltages before the spark jumps increasing the strain on insulation.

 

I've no experience with that particular plug type (don't use them) but in general I'd say loss of response, flat spot on light throttle opening and maybe some hitching/hesitation at cruise - normally where mixture is weakest. Don't know if wear occurs quicker with bigger gaps due to bigger spark energy, but maybe the already large gap makes the increase due to wear more noticeable?

 

Quite recently had an issue with my wifes Focus with occasional misfires which turned out to be due to the plugs worn to a 1.9mm gap! Closing the gap back to 1mm solved the problem but the car now has new plugs.

 

I use triple electrode plugs, special favourites Bosch (as used on Mk2/Mk3 Golf GTI 8v) on all my Triumphs - they love them and the plugs last >20k miles.

 

Cheers

 

Nick

[roulli]

Thanks Nick for your fast response.

 

The standard plugs have at least 7000miles and the engine starts to hesitate, when hot at very small throttle opening, despite controlled carb ballancing. The car was running very smoothy before with that setup.

The compression test on the hot engine shows 15 to 15,5bar on all 6 cylinders, so it's basically healthy.

 

I will follow your advice and reduce the gaps to 1,0mm and report back.

 

Cheers

Patrick

[GT]

I'm told the plasma plugs run 50 000-60 000kms and still seem to be going strong....

[roulli]

According to the NGK tech-page, waisted spark ignition systems, like EDIS reduce lifetime of tradional plugs strongly. That's why this new electrode materials and multi electrode sparks have been invented.

Therefore I didn't want to mess around with +7000 mls standard plugs fitted by the PO.

 

So I bought some Bosch 4 electrode WR78 plugs, and the the engine runs smoothly without hesitation and hardly any popping at overrun.

 

Good investment!

 

Patrick

[Nick Jones]

My opinion is that the Triumph engines also like the "side electrode" nature of the multi-electrode plugs where the spark is directly exposed to the chamber.

 

Same would be true (and more so) of the plasma plugs which they also seem to like. Can see the plasma plugs lasting a very long time due to having what is effectively a continuous earth electrode.

 

Must try my set of plasma plugs again - had some bizarre interference problems with them on the Vitesse before (most likely my crappy leads to blame for that!) but lots has been changed since then and I can try them on the PI as well, which seems to want a richer mix to run cleanly.

 

Nick

[motov8id]

I've replaced a barrel full of platinum tipped electrode plugs at 60k mile service with no noticeable wear. Not sure of the metric equivalent of a barrel. I am not sure of the necessity of the multi electrode plug. The spark will only arc once and to one electrode when I had Lodge multi electrode plugs in my Alfetta years ago and thought they were unique. The ability of the coil to produce high voltage current flow in a Milli second is the important factor. I would gap ngk bp6es to .025 , .030 at the widest . .62 to .74mm

Edited August 22, 2012 by motov8id

[roulli]

Well, I bought a set of plasma plugs, as everybody is so fond of them, but I tried them twice now, but strangely they don't seem to work on my engine. Symptoms are like weak mixture, hesitation and popping in the exhaust.

 

I'd probably need to adapt the carburetors and Ignition to the sparks.

 

Maybe JC can try my plasma plugs once, to see if the 6 plasma ejector orifices make a difference to the 3 orifices of the original design.

 

 

Patrick

[GT]

Well, I bought a set of plasma plugs, ... I tried them twice now, but strangely they don't seem to work on my engine. Symptoms are like weak mixture, hesitation and popping in the exhaust.

 

Try using MORE advance and (3 deg typical) and leaning the mixture right off.

(as you use webers, you may need to go down a size on main eg 125>120).

 

If you use a WLS go right to the end of the scale so it's struggling to read (15-16:1).

Lean it right off into this region, and you will see it goes cool and the torque comes right up.

 

You may need specific jetting.

(Nota:-It also depends what has been done to the head.)

 

Normally speaking you could gain as much as 2-3L/100kms, if you do this right.

Don't go over 10.75:1.

[spitfire6]

Hi, This link about plasma plugs was an interesting read. 44%MPG increase on one application claimed. http://www.hho4free....plasmaplugs.pdf

Edited November 1, 2012 by spitfire6

[pomwah]

Hi, This link about plasma plugs was an interesting read. 44%MPG increase on one application claimed. http://www.hho4free....plasmaplugs.pdf

 

Like all those claims, if they were any good car builders everywhere would be using them.

 

J2

[Nick Jones]

Interesting, but tend to agree with the above remark. Also not really sure why they are calling those plugs "plasma" plugs - really just different electrode design.

 

In contrast, Gareths plugs have a shaped chamber designed to eject burning charge (plasma) when fired.

 

 

 

Nick

[GT]

Like all those claims, if they were any good car builders everywhere would be using them.

Well I read the stuff about Kupra with obviously a lot of interest.

I'm afraid you're on a hide to nowhere trying to criticise him or "smoky Yunnick".

 

These 2 were seriously innovative people as was Nikola Tesla.

 

As for us, with the prechamber plug, I got a heap of rubbish (mostly hearsay) from a pair of Spanish students who seemed to set out to PROVE to Opel, the pre-chamber plug design was b....llsh..t.

 

What to say?

I went to enormous trouble with Prof Muoni no less (now name names), to TEST this (prechamber) plug.

The results were astonishing, and I sold a modified version for Jaguar HE engines (CR 12.6:1) to my friend in Tallinn, who today apart from me is the ONLY independent Jaguar specialist left in the country.

 

From cold running to general round town driving, fitting them was a transformation,but of course it is an "old style" 2V vertical inlet -horizontal swirl type engine, and far from efficient from the factory.

 

The only problems I had were:-

 

1/ The manufacturer who is highly unstable.

 

2/ The main and massive cylinder pressure gain we had was in a range that was not ideal for a road car.

In reality we had access to 2 university departments, 4 research engines on dyno and all of them on the proper Ricardo test machine with proper facilities.

 

Please, I would love to know of ALL the Triumph "specialists" throughout the world, never mind the after market dyno and test facilities up to the level of SCHRICK in Germany who has access to such multi million pound facilities as we did?

 

The conclusion was WITHOUT a shadow of doubt.

The Plasma plug was giving us immediately a rise of 10 BAR in cylinder pressure (from 60>70 bar in fact) but between 7500-12500rpm.

HC was up to 4 x lower, but was was astonishing was to see a 25bhp increase in power output on our laboratory engine, just changing the plug and optimising the advance.

 

What can i say?

I didn't invent the figures. It wasn't magic, it was normal behaviour as far as I am concerned, & I like to be objective.

 

Just now I am participating on a Jaguar XJS engine project where we aim to make this 24V 6 cylinder engine hit 50mpg.

RUBBISH! you say, can't be done...

Well the car is already doing 40mpg or better, so we're not so far away now.

Next we change the plugs and the exhaust for a proper 6-3-1.

 

Ask me how?

Just some people need to use their brains, not criticise things ignorantly.

You will be suprised what you can do by using some brains, it beats money 1000x over.

[spitfire6]

Hi, The missing text is here now. Nevermind.

Edited November 2, 2012 by spitfire6

[Nick Jones]

Interesting.

 

Why advance the ignition - would have thought the pre-chamber plugs would promote faster burn? Or is this only in conjunction with considerably leaned off mix - which will burn slower.....?

 

Nick

[GT]

Why advance the ignition ?

TBQH when you get a counter intuitive result, it's usually the most interesting moment.

 

I suspect a strong interaction between droplet size and flame propagation.

There are large differences in flame propagation between many of the popular induction methods.

Here are some generalisations.

 

As the venturi opens up on a SU type carb, the droplet size becomes (somewhat disastrously) larger.

This kills the top end & increases HC emissions the larger the venturi gets.

It becomes disastrous once you start running the smallest carbs with the largest engines.

(eg. Jaguar XJ6 S2 3.4L which only has HS6 carbs).

 

In practice the best results are obtained on SU carbs when the inlet manifold has been optimised and some level of damping introduced (eg. length and size).

In practice the Austins and Jaguars are the perfect illustration of worst practice.

 

On a lower pressure asyncronous EFI system, droplet size is pretty uniform but is poorly distributed at low CR and intake velocity.

(So you need very limited valve overlap).

Very little REAL work has been done to show the actual performance of such systems, alhough it appears they hit a very different sweet spot compared with optimised carbs.

The Jaguar 4.2L Series 3 was one of the first British cars to be fitted with this kind of EFI.

 

On a high pressure mechanical multi butterfly syncronous Pi system the particle size is supposed to be smaller, but the low RPM and part throttle behaviour are compromised by the difficulties of metering and emission control*.

(This makes for quite "dirty" emission at low RPM)

This is the system that Jaguar and Triumph adopted in the 50s/60s with their competition cars,and eventually in mass production in Canley.

 

On a Weber or Solex carburettor the droplet size is heavier than on say a Dellorto.

Traditionally an oversized throttled down Weber gives the best overall result for peak power, because (I suspect) it hits the droplet size sweet spot better than the Dellorto, particularly at high RPM.

(This is counter intuitive, I know.)

 

Emission control is hard to adopt with any of the above systems & the fixed jet carbs DH or DC have to be run rich or they don't work at all. That is part and parcel of using horizonal fixed jet carbs, so it's yet another compromise.

 

In practice very few people are prepared to go to the trouble to optimise anything.

When someone like Burgess recently came across a set of these plugs in an engine, the automatic reaction was "what's this rubbish", and throw them away, not to check if altering the advance or leaning off the mixture (weber carbs again) actually made the whole thing work better.

Of course some ignorant TR register people then started to leap about calling names and "snake oil".

This appears to be normal behaviour for those old fogeys.

 

So here we have an interesting situation of accelerating flame propagation with this plug, in several planes in the stratified charge area above the piston before it reaches TDC.

This chamber depth is highly variable, dependent on the bore/stroke ratio of the engine as well as the shape, and who the heck worked on the head last, and if they were any good.

(at least on this Triumph head)

 

To give some idea of the variations that could be expected* it's very clear, once squish, swirl and CR are accounted for, you can get as much as 40bhp more out of the same engine, using almost identical fuel delivery curves.

So where is the extended torque range coming from?

 

I did prove you could get 20-35bhp differences in power output with exactly the same CR, on several occasions with the SAME camshaft and not changing any other parameters- ONLY the head/chamber work.

 

Again I strongly suspect an interaction between higher swirl coefficient, alterred squish value and droplet size.

Both engines tested, used Lucas high pressure Pi, which as already mentioned is known for its excellent droplet size.

 

Those results are in the public domain.

 

As always, it's fascinating to run things in controlled conditions and say "why did this happen"?

 

The fact is, very few people even know what constitutes a controlled environment and are even less willing to understand.

Then you have the band of group thinkers who insist on running over the nearest cliff.