LPG Spark Plugs - Fact or Fiction?

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LairdScooby
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LPG Spark Plugs - Fact or Fiction?

#1 Post by LairdScooby » Thu Aug 13, 2015 12:54 am

Being new to LPG i'm looking at all the various things for converting to gas and one of the big things are the spark plugs. OK, i know physically they're not that big but i've heard conflicting reports about whether you need to change to LPG-rated plugs or not.

To give a bit of background, i currently have a Jeep Cherokee 4.0 Ltd auto on LPG and i think it was converted by John Wayne Motors so i doubt it has LPG-rated plugs. However, aside from renewing the HT leads, dizzy cap and rotor arm which was necessary as they were disintegrating and the bits that stayed solid were corroded with some kind of white furry powder (not ash) i've not even looked at the plugs as it seems to be running fine.
I'm in the process of converting my other 2 beasts to gas though and for the purposes of this question, it's them i'm asking about.
The beasts in question are a pair of Rover 827s, both auto and one is still on the stock OE HT leads, the other has a set of home made Ferroflex Blue 8mm leads which have been on there a year now and are doing fine. Certainly worth spending the extra to get the Ferroflex cable in any case!

I keep both cars well serviced including changing the ATF, engine oil, antifreeze, brake fluid etc at the correct intervals at the longest, plugs as and when they need them (generally about 12-18k miles) and i have K&N air filter elements in place of the OE elements in both cars. Normally i run decat pipes/boxes through the year, only replacing the cat for the dreaded annual inspection.

So my question is this. The standard NGK plugs are BCPR6E-11 or BCPR6E set to 1.1mm gap. The specified LPG upgrade plugs on the NGK web-cat are LPG3 or 1498 plugs that come up at about £16 each on fleabay.
Given that i normally only pay about a tenner for a set of 6 standard plugs from my local auto factors, spending 9 times that amount just because i've converted to gas seems to be a contradiction in terms. Gas is meant to save you money, right???

So has anybody run a Rover 827 (or Honda Legend) on standard plugs or have they had to change to LPG-rated plugs?

Alternatively has anyone had any experiences (good or bad) from running on any sort of plugs when using gas?
Cheers,
Dave


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scottyf
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Re: LPG Spark Plugs - Fact or Fiction?

#2 Post by scottyf » Thu Aug 13, 2015 10:10 am

My car Alfa already use iridium tipped plugs (Twin Spark) the other in the cylinder is a normal bosch dual.
But its a wasted spark system and runs a lean burn so requires decent sparks (Basically is expensive to replace all 4 for a 4 cylinder car at roughly £70).

LPG being a gas is a dry fuel - So it runs a little hotter and its a bit harder to ignite. This means the coil packs and the Spark plugs have to work harder.

To be honest I can't see why anyone "Has" to change the spark plugs to run LPG.
But what does happen is it shortens the life of the ignition system.

My sparks are meant to last 60k on petrol. I'd expect them to only last 30k on LPG. They might last longer. But until I get to that mileage I won't know. I recently took the sparks out to have a look and they all look fine and they have clocked 19k Total, 12k on LPG and they are all working fine.

If I did 30k miles on them though I would have saved £3644.20 in petrol. So could probably afford to take another hit of £70 on a set of spark plugs in that time.


If I were you unless you "need" hotter running sparks I'd try the normal ones and see if they work or if they die pretty quickly.
If they don't and it just shortens lifespan then decide on the mileage.
If not try a one hit of the more expensive ones and see how long they last.

Some people on using turbo car's when tuning change to hotter / cooler running plugs because without it causes running issues or likely to burn a hole in the piston.

There will be more knowledgeable people on cars specific on your model that might be able to help with your car. But that's all i know regarding the physics with it.

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Re: LPG Spark Plugs - Fact or Fiction?

#3 Post by Gilbertd » Thu Aug 13, 2015 2:39 pm

Check for the NGK Iridium equivalent. I would only ever use NGK plugs in something running on LPG anyway as it is harder on plugs and they seem to work best. My Range Rovers run BPR6ES as the standard plugs, cost a couple of quid each and are good for 10,000 miles (I change them every time I change the oil). The Iridium equivalent is the BPR6EiX which cost around £6 each but are good for around 40,000 miles and then there is the 'special' LPG plug at £15+. If you look at the tech spec of the LPG plugs on the NGK website, you'll see that they bear a striking resemblance to the Iridium equivalent at a third of the cost. They appear to have a slightly wider heat range so there are less variants, but I wouldn't consider them worth the money considering standard ones or the Iridium equivalent do such a good job. The standard and Iridium for mine both run a 0.9mm gap so I would suspect if you gapped yours down, then you'd be fine with either. DO NOT get the Br**k silver ones, they seem to not work well in anything.
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93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
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LairdScooby
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Re: LPG Spark Plugs - Fact or Fiction?

#4 Post by LairdScooby » Thu Aug 13, 2015 3:01 pm

Thanks for the advice - i wondered about the NGK Iridium plugs as a compromise but knowing how good NGK plugs are to start with i doubt it would be a compromise. Reading between the lines on what you say about the tech spec of them, it seems they are probably better suited to running both LPG and petrol without any compropmise on either.

Reckon that will be the way i go although for now there is a near new set of BCPR6Es in both cars so i'll use them "just to get started" and replace them in the not too distant.
Cheers,
Dave


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Re: LPG Spark Plugs - Fact or Fiction?

#5 Post by Gilbertd » Thu Aug 13, 2015 3:44 pm

I ran a set of Iridiums in one of my Range Rovers for around 30,000 miles but then managed to overheat and well and truly cook the engine. When I put it back together decided that the plugs probably hadn't taken too kindly to it so thought I'd treat it to a new set. I could get the standard ones from my usual motor factors but would have had to order a set of Iridiums online. Being impatient, I got them from the factors with the intention of changing for Iridiums after 10,000 but never bothered. As said, I change the oil and filter every 10,000 so just bung a set of plugs in it while I'm at it. If they are a pain to get at, like they are on some more modern cars, then go for the Iridiums as it will save less skinned knuckles in the future but if they are nice and easy to access, then it probably doesn't matter.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


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Re: LPG Spark Plugs - Fact or Fiction?

#6 Post by LairdScooby » Thu Aug 13, 2015 5:26 pm

Well they're on a FWD V6 with the rear bank quite close to the bulkhead - not good for bad backs!
Cheers,
Dave


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Brian_H
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Re: LPG Spark Plugs - Fact or Fiction?

#7 Post by Brian_H » Thu Aug 13, 2015 11:18 pm

I've used NGK bkr7eix plugs on mine with gas - they ended up in there for longer than I'd thought (50k miles) and had started to give up at that point (worse on gas than petrol). On checking the book the recommended interval is 30k though so can't complain on that really!.

Similar to yours they are buried in the back of the engine so access not the best, I get more problems with the leads than the plugs to be fair though, was a lot easier the second time though as I'd used copperease on them when replaced before as they didn't want to come out the first time.

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Re: LPG Spark Plugs - Fact or Fiction?

#8 Post by LairdScooby » Fri Aug 14, 2015 12:31 am

What sort of car do you run Brian? I always put a smear of copper grease of some description on the threads and a dab works it's way onto the sealing washer too. A small pantbrush is good for putting it on, not too much is easily achieved as you can brush the excess off and use it on the next one.

Funny you should mention "Recommended Intervals" - had a similar conversion with a friend the other day about cam belts. Yes, they should be changed at the recommended intervals but many manufacturers "build in" a grace period for want of a better expression. For example, the interval on mine is 96k, i reckon it's probably good for 120k as the water pump is designed to leak at about 120k as it's a seervice item. This can throw the cam belt as the water pump bearings give up so the leak is the first warning. :wink:

With that in mind, a recommended interval of 30k probably means they're good for 45k or thereabouts. As for HT leads, i now build my own using Ferroflex cable. It's available in red, black and blue :

http://www.ebay.co.uk/itm/121056208202? ... EBIDX%3AIT

I also invested in a set of Ripaults HT crimping pliers to do it properly and bought the terminals from http://www.vehicle-wiring-products.eu/s ... -terminals and reused the OE boots and plug shrouds after thorough cleaning.
My car (Rover 827) has a reputation for giving HT leads a hard time. Pattern leads sets are available for about £30 upwards but only last a year or two. The OE ones, now only available through Honda, are about £200 a set - hence deciding to make my own! Had two sets (one was the first OE set at 18 years old! Second was a pattern set at about 18 months of age!!!) completely die on me with no prior warning - all 7 leads in both sets! Unreal!
Cheers,
Dave


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Re: LPG Spark Plugs - Fact or Fiction?

#9 Post by Brian_H » Fri Aug 14, 2015 8:25 am

That one is an old 2.0 Ford galaxy. Engine is far from what youd call modern. Some of the issues were down to the vapouriser location. Was originally Sat right above the coils packs. I'd brought it as spares or repairs due to having half a dozen issues. Log being suspected as the cause which it wasn't in the end.
I've improved the bracket used for the vaporizer and relocated it so it doesn't foul the plug leads anymore. The way it was mounted had it attached to the engine and meant you had to disassemble the lot to change the ht leads.

Good tip on the paintbrush.

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Re: LPG Spark Plugs - Fact or Fiction?

#10 Post by LairdScooby » Fri Aug 14, 2015 11:11 am

Some people seem to fit things without regard to future maintenance! The set-up on my Jeep is similar, the main vapouriser solenoid valve is sited in just the right place to take out the underbonnet lamp (solved by fitting the later style underbonnet lamp which mounts in a different place) and the vapouriser is sited so that it obstructs the dizzy, HT leads and at least 3 out of the 6 plugs (inline 6) with what i consider to be a long gas hose from the vapouriser to mixer with the stepper motor/power valve positioned about 6" from the mixer!

The paintbrush can be used for other things too like the brakes, threads on exhaust clamps/manifold bolts and so on. Such a simple idea yet so effective, can't remember who gave me the tip in the first place but it was a long time ago! Makes the grease last longer as well as you don't have to wipe the excess off with a rag that you'll later bin!
Cheers,
Dave


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Gilbertd
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Re: LPG Spark Plugs - Fact or Fiction?

#11 Post by Gilbertd » Fri Aug 14, 2015 11:15 am

I've seen some pretty dodgy looking installs too, but one piece of advice. The length of the hose from vaporiser to mixer isn't too critical but the length between the mixer and the stepper is. It wants to be as close to the mixer as possible or the steeper will be constantly hunting up and down due to the delay in response from the lambda sensor.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


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LairdScooby
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Re: LPG Spark Plugs - Fact or Fiction?

#12 Post by LairdScooby » Fri Aug 14, 2015 3:17 pm

I was planning on making that as short as physically possible for that very reason - also thinking of altering it on the Jeep as well to improve response.
Cheers,
Dave


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Re: LPG Spark Plugs - Fact or Fiction?

#13 Post by LPGC » Fri Aug 14, 2015 7:35 pm

Plug life / misfires due to not good enough spark quality are 2 different subjects.

Iridiums will last longer than nickle (or platinum) in engines running on LPG but that doesn't mean to say they will give as good spark quality or not cause problems.

If a vehicle manufacturer recommends a few different plugs, e.g. a platinum as the expensive option and nickle for penny pinching, I usually prefer nickle - because they're cheaper, will probably give a better spark and may work out cheaper in the long run even if they were to need replacing more often.

There are so many ifs and buts when it comes to plugs. Same thread length, electrode protrusion, number of electrodes, electrical spec, heat range, etc, etc, may seem to come up with an equivalent iridium that in theory should work well but in practice might not on some models. Would be a shame to spend a few times as much on an 'equivalent' iridium only to find the iridiums don't work well...

Plugs are particularly difficult to get at on my Grand Voyager, but I still fitted nickle plugs. Thinking was, while checking plugs it's as easy to change them at the same time, while nickle plugs might give a better spark. That's me sorted for thousands of miles - no worries about having to remove an expensive set of plugs in case I found they didn't work properly. And next time I check them I will change them.

Platinums supposedly wear out at a much accelerated rate on LPG and most cars come fitted with them. In practice I find although they wear faster, they don't wear as fast as is sometimes believed. In these cases the standard plugs are usually a good bet, especially if the manufacturer doesn't recommend an iridium equivalent.

Some of the LPG branded plugs give terrible results on both LPG and petrol.
Some engines, such as some of the Vauxhalls with the factory fitted systems, are very plug fussy indeed... I wouldn't chance any iridiums in one of those...

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Re: LPG Spark Plugs - Fact or Fiction?

#14 Post by Brian_H » Fri Aug 14, 2015 10:15 pm

LPGC wrote: Some of the LPG branded plugs give terrible results on both LPG and petrol.
Some engines, such as some of the Vauxhalls with the factory fitted systems, are very plug fussy indeed... I wouldn't chance any iridiums in one of those...

Simon
The other thing seen reported here several times with the ones mentioned above is that they have had a bad habit of falling apart with the potential for damage being caused.

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Re: LPG Spark Plugs - Fact or Fiction?

#15 Post by LairdScooby » Sat Aug 15, 2015 1:19 am

All interesting stuff - i remember back in 1982 my dad had a brand new Cavalier 1.6 GLS company car and as it came up for its first service (600 mile/1000km) it started to misfire like a pig, cut out as and when it felt like it, wouldn't cruise - all down to the plugs!
New plugs fitted at the service and within a few hundred miles it was doing the same again! As his girlfriend commented "it's like being inside a giant vibrator!"
So back it went to the Vauxhall main stealer who diagnosed the plugs. Again!

However this time instead of fitting the AC Delco branded (Champion made?) plugs, they fitted Bosch - problem solved for the next 20000 miles!
Luckily he took it back to the same dealer and they were on the ball having made a note ot only fit Bosch plugs. Whether this had come as a result of a Technical Bulletin (like Ford issued for the CVH engine in the then new Mk3 Escort - same problem, Motorcraft aka Champion plugs misfiring, solved by using Bosch) or not i never did find out.

Seems like dodgy plugs in new cars has been a problem regardless of fuel type for a long time!
Cheers,
Dave


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Re: LPG Spark Plugs - Fact or Fiction?

#16 Post by LPGC » Sat Aug 15, 2015 6:11 pm

In my above post I should have included...

especially if the manufacturer doesn't recommend an iridium or nickle equivalent.

Say you've got a Beemer with 6 platinum multi pronged plugs which have lasted 20000 miles on LPG and given good performance. There is no equivalent plug listed.. So do you chance a supposedly equivalent iridium or nickle plug, or do you fit the same model platinum plugs that worked well? I might be tempted with the nickles but would likely just fit the same manufacturer recommend plugs that gave the good results.. full in the knowledge they would give the same good results, no worries about having to immediately do the job again in the event the replacements didn't work properly.

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Re: LPG Spark Plugs - Fact or Fiction?

#17 Post by tom-madbiker » Sun Aug 16, 2015 11:12 pm

i only use ngk plugs and i also find that single pronged plugs seem to work better with lpg the rover has iridium at the moment (they are reccomended for the engine) and personally i cannot tell the difference between them and non iridium although i have not changed them for 40000 miles and they are still fine the thing that seems to make the most difference is good quality leads personally i like magnecore stainless wound ones but they are expensive

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Re: LPG Spark Plugs - Fact or Fiction?

#18 Post by LairdScooby » Sun Aug 16, 2015 11:57 pm

tom-madbiker wrote:i only use ngk plugs and i also find that single pronged plugs seem to work better with lpg the rover has iridium at the moment (they are reccomended for the engine) and personally i cannot tell the difference between them and non iridium although i have not changed them for 40000 miles and they are still fine the thing that seems to make the most difference is good quality leads personally i like magnecore stainless wound ones but they are expensive

Which Rover do you run Tom?
Cheers,
Dave


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Re: LPG Spark Plugs - Fact or Fiction?

#19 Post by tom-madbiker » Mon Aug 17, 2015 6:58 pm

Rover 25 1600 the iridium tipped ones last a good while but they are a Tenner
each

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Re: LPG Spark Plugs - Fact or Fiction?

#20 Post by LPGC » Mon Aug 17, 2015 9:38 pm

tom-madbiker wrote:Rover 25 1600 the iridium tipped ones last a good while but they are a Tenner
each
Easy to change on that motor and could buy 4 sets of nickle plugs for same cost...

Point here easy to understand and similarly applying to long lived tyres - Good that you don't have to change them so often, unless some other problem occurs such as punctures (particularly in tyre sidewalls) or kerb damage (case of some drivers). I prefer to change plugs during servicing anyway, less chance of them being stuck when it comes to changing, gives opportunity to check if cam cover gaskets are leaking oil into plug chambers.

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