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Warning Brisk LPG spark plugs

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Old Jul 17th, 2011, 23:48   #11
Gareth83
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Default

Quote:
Originally Posted by classicswede View Post
The extra prongs are not there to increase life.

The idea is that they should give a stronger and broader spark. The effect of the stronger spark can give a small increase in power upto 2% and improved MPG upto 2%.
Quote:
Originally Posted by Clan View Post
The idea of multi prong plugs is indeed ONLY long life , basic electronics say the spark will always take the easiest path , it is impossible for the plug to have multi sparks on each prong at the same time unless it is fed with huge amounts of HT energy..
what happens is that the spark takes the path of least resistance which is the prong with the shortest gap , as this wears, the gap gets wider and eventualy the next unused prong is the easiest path and that one starts to get used , and likewise until that wears and the third prong starts to get used etc
, that is how volvo plugs last 72000 miles ..
You may choose your particular plugs that work right with your LPG, however if you use it on petrol often you will find the genuine volvo plugs give the best performance of all . Volvo ignition systems are and always have been very powerful and really should cope with lpg , they always did fine in the 1980s-1990's-2000's what's changed ? .. I guess genuine volvo plugs were not tried first on this problematic engine ..
This was my point they only extend plug life in reality. In theory 3 or 4 prong sounds great but they run no different in any situation.

Quote:
Did you know that there can ONLY be ONE ARC at a time when your spark plug fires????
Sorry, but you will NEVER EVER have two, three or four electrodes fire at once.
It's called " Physics". Take out a plug and lay it on your engine block and see for yourself. Just have a friend crank your engine and see. Go ahead.
Thats why a single electrode is the hottest most efficient source of spark.
The double sand quads only have an advantage if the plug becomes "fouled" on an electrode.
Then one of the others will be able to continue in a best case scenario.
My friend is an engineer for NGK. He's the one who told me all the skinny on this.
All of it is Marketing to sell more expensive plugs to people who are not informed.
Now you are informed.
Don't waste your cash.
I have also read on various forums multiple prongs particularly Bosch have snapped a prong and resulted in sticking valves. I'd rather stick to single prong but gap/change them more often
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Old Jul 18th, 2011, 17:14   #12
brodgar
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Default no fancy plugs

dutch installers (vogels) are adament NOT to install fancy sparkplugs

( 40 years of experience on lpg installation)
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Old Jul 21st, 2011, 14:54   #13
capt jack
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Default Plug ugly?

All that's been said about multi-point plugs certainly is borne out from my experience of running my 97 2.5 10v V70 on LPG for almost 200,000 miles now.

I've found that Volvo and Bosch multi-point plugs will certainly start to misfire within a few hundred miles.

Champion, NGK and Bosch superplus single point plugs are a bit better, but will still start missing before 10,000 miles are covered.

The plugs I've found work the best are Denso. I had to buy a set one time when the Bosch plugs in the car started playing up, and all the local motor factor had in stock were Denso plugs. It was a real stroke of luck because they have been consistently brilliant.

The Denso plugs I use are the bog standard basic copper-cored single point type K20PR-U. I set the gap at 0.8mm. Best of all these sell at our local Motor Factors for around £2-odd each. I change the plugs every 10k miles, but I reckon they'd probably go on much longer - even when they come out the gap is still good, and there's no obvious signs of deterioration at all.

Cheers

Jack
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Old Jul 27th, 2011, 09:26   #14
Joe Harding
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Default On a similar subject...

Our 340 1.4 with 32DIR carb has been plagued with intermittent poor idle, even stalling on occasions after a long motorway run. But it runs okay on petrol. Following this thread, I checked the plugs, hoping to find that they were multi-point. Finding they were single path simple beasties, that moment of hope died...

BUT THEN

whilst in the area I checked the distributor. Found that the rotor and receptor contacts had blossomed and corroded. Cleaned them off and hey! Perfect idle again.

So my method of comparing running on petrol and gas falls down here. Just because it runs on petrol, doesn't mean all is well. I see from the above contributions that gas needs a fatter spark. At crusing speeds this will be no problem, but at idle, any compromise in the spark intensity will be evident.

So thanks to all who have helped me on this one.
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Old Jul 30th, 2011, 12:43   #15
capt jack
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Originally Posted by Joe Harding View Post
Our 340 1.4 with 32DIR carb has been plagued with intermittent poor idle, even stalling on occasions after a long motorway run. But it runs okay on petrol. Following this thread, I checked the plugs, hoping to find that they were multi-point. Finding they were single path simple beasties, that moment of hope died...

BUT THEN

whilst in the area I checked the distributor. Found that the rotor and receptor contacts had blossomed and corroded. Cleaned them off and hey! Perfect idle again.

So my method of comparing running on petrol and gas falls down here. Just because it runs on petrol, doesn't mean all is well. I see from the above contributions that gas needs a fatter spark. At crusing speeds this will be no problem, but at idle, any compromise in the spark intensity will be evident.

So thanks to all who have helped me on this one.

100% correct! It's easy to forget the distributor end of things, but in effect the spark needs to be working properly at both ends of the plug lead! If the spark ain't even reaching the spark plug, no matter how many pins the plug does or doesn't have, it won't, well - spark! Petrol is far more forgiving of poor ignition than is LPG.

Jack
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