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 Post subject: Spark plugs?
PostPosted: Mon Mar 19, 2018 11:45 am 
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Joined: Sun Jun 21, 2009 4:14 pm
Posts: 465
Hi all,
What are the best spark plugs for a lpg engine?
I've been running iridium ones but have been reading that the tips can break off.

Thanks.

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 Post subject: Re: Spark plugs?
PostPosted: Mon Mar 19, 2018 2:58 pm 
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Joined: Wed Apr 09, 2008 9:00 am
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By tips do you mean the outer electrode or the thin centre one? The outer electrode could break off any plug if it was abused or poorly made. The centre electrode on an Iridium (and Platinum) plug is much thinner and erodes so if left far too long could look like it has fallen off when it actually hasn't, it just isn't there any more. The Platinum plugs in my Partners Merc should be changed every 50,000 miles but had never been changed in 98,000. A couple of them looked like the tips had broken off but looking at the others you could see that they had actually eroded to the point that the tip had disappeared.

Normal advice is to use whatever the manufacturer recommends for running on petrol but Iridium will last 3-4 times longer than standard copper. But they also cost 3-4 times more than standard copper electrode plugs so it just means you need to change them more often.

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 Post subject: Re: Spark plugs?
PostPosted: Tue Mar 20, 2018 12:28 am 
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Joined: Sat Apr 30, 2011 2:06 pm
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Location: ramsgate kent
After much [expensive] testing of iridium, multi electrode and brisk lpg im back to copper NGK standard plugs.
Economy, torque and acceleration best on standard, disappointed with brisk as affected low end torque very badly, multi electrode were worse everywhere and iridium the performance does tail off with a few miles on them, wont use them on my motocross bikes either being worse on 2 strokes than 4 strokes.
More regular plug changes also stop the plugs seizing as well, and whilst the bonnets up might as well change the oil and filters.


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 Post subject: Re: Spark plugs?
PostPosted: Tue Mar 20, 2018 8:53 am 
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All good advice from redvanman. I've used Iridium in the past but have gone back to standard NGK copper core plugs and change them every time I do an oil and filter change every 10,000 miles. At only 2 quid a time, an extra £16 every service is nothing too.

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'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.


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 Post subject: Re: Spark plugs?
PostPosted: Tue Mar 20, 2018 8:29 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
Posts: 3210
Location: Yorkshire
I also agree.... As long as the plugs aren't too difficult to access. If difficult then it could be better to fit iridium with single electrode.. but unless there's a vehicle manufacturer approved iridium plug it might still be better to stick to standard plugs.

I've converted a lot of Nissan Elgrands lately (almost the same engine as your Skyline) and it's normally a pita to change plugs due to lack of access but during LPG conversion it's easy to access plugs when the wiper mechanism and manifold (which is a different design to yours) is off.

I usually advise NGK but for your Skyline I'd advise Denso double iridium plugs.

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 Post subject: Re: Spark plugs?
PostPosted: Tue Mar 20, 2018 8:57 pm 
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Joined: Sun Jun 21, 2009 4:14 pm
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Copper NGK it is then!
Plug change can be done with removing inlet manifold.
Then again the manifolds got to be removed to sort out lpg leak and spark plug tube leak.

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 Post subject: Re: Spark plugs?
PostPosted: Wed Mar 21, 2018 9:28 am 
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Joined: Wed Sep 29, 2010 5:01 pm
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Location: Yorkshire
Much easier to access plugs on your Skyline than on Elgrands... so yeh the copper NGKs make sense.
I fit Denso IKH16 or VKH16 in Elgrands, these are a Nissan recommended iridium plug. The standard plug is NGK PLFR5A-11 which is only platinum and more difficult to source than iridium IKH16 or VKH16. You'll get copper / nickle plugs from anywhere though.

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Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
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http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240


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