Spark Plug Shootout - The Results Are In
Discussion
So before I start this... these are the results of 10,000 miles running on LPG which is a notoriously difficult fuel to ignite, this characteristic puts the whole ignition system under huge stress. The best way to think about it is my 10,000 miles on LPG is like putting my whole ignition system, and especially the plugs, through a 50,000 mile test on petrol. So the results are as relevant to petrol drinkers as they are to gas sniffers like me, it's just the results have essentially been fast forwarded for you 
My car ('Ol Gasbag') is not exactly a standard Chimaera, it's not especially highly tuned, but here's my setup focusing exclusively on fuel & ignition to keep it all relevant to this post.
1. Canems Dual Fuel ECU alowing me to run both petrol & LPG
2. Wasted spark ignition (no distributor)
3. Ford Edis type coil packs - MSD performance versions with a different winding ratio than standard Ford Edis coil packs - 45,000 volts
4. MSD Superconductor HT leads - In my opinion these are the absolute mutt's nuts, and make the rubbish Magnecors look like speaker wire
The objective of the test was to compare two different NGK plugs:
1. BPR6EIX Iridium - £55 for a set of 8
2. LPG2 Iridium - £115 for a set of 8
Essentially I wanted to see if the ferociously expense LPG specific plugs were worth their astronomical price, both plugs sport an iridium centre electrode but that's where the similarities end. The key differences between the two are the LPG plugs have a special anti corrosive coating and a chip of pure platinum on the earth electrode which you can just see in the photo above, and boy do you pay for theses features...... but are they worth it?
I ran six LPG2s, three in each bank..... and two BPR6EIX, one in each bank for 10,000 miles.
First up here's an example of what happens to a BPR6EIX Iridium plug after 10,000 miles on LPG:
The formation of green corrosion on the surface of the terminal nut thread is not the typical air/water derived corrosion we are familiar with, it's the result of an electro/chemical reaction similar to that you might see on a battery terminal.
Look closer and you'll see tell-tail lines running down the ribbed ceramic insulator that indicate carbon tracking, this plug and the second BPR6EIX were clearly in real trouble, they were also the source of a very occasional misfire at low RPM/high load that prompted me to conclude my plug test and inspect the both types I've been running for the last 10,000 miles.
Now lets look at the standard nickel earth electrode on the BPR6EIX, clearly LPG was too much for it as the gap had opened up by almost 0.5mm.
It probably doesnt look as much as 0.5mm in the above photos but when the earth electrode is studied closely what you see is a dished area eroded into the soft nickel, it's like a miniature crater and it's when you take this into account it's clear the gap has opened significantly in just 10,000 miles.
The second BPR6EIX was worse still.
This time the sides of the crater had actually been completely blown out to reveal a step in the far cheaper nickel BPR6EIX earth electrode.
Obviously I took all the LPG2s out too, but quite simply there was no point in photographing them because they were completely corrosion free and all six showed absolutely none of the wear issues I'd suffered on both BPR6EIX, all six gaps on the LPG2 plugs were exactly the same as when I fitted them 10,000 miles ago.
I conclude these expensive LPG2 plugs are not marketing hype, that special anti-corrosive coating is definitely doing something and that chip of pure platinum solves all the premature wear issues associated with hard to strike LPG. Obviously I'm rather unique in running my TVR on gas but hopefully the results of my tests demonstrate where you might end up after 50,000 miles plus if you're running BPR6EIX Iridium plugs on petrol.
Don't get me wrong the BPR6EIX is a great plug, If I'd run the test with standard BPR6ES plugs no doubt they would look even worse than the BPR6EIX. The key takeaway from all this is a platinum earth electrode is a good idea, it works brilliantly in partnership with an iridium central electrode to give unparalleled service life even when pushed to the limit on LPG.
But those LPG2s are still £115 a set, and that's just nuts for 8 plugs, so taking everything I've learned during my 10,000 mile plug test into account, I'm now wondering if the Denso TT (£57 for a set of 8) could be the way forward. The Denso TT uses a fine wire iridium earth electrode like the BPR6EIX and others, but pairs it with a platinum fine wire earth electrode too.
Could the Denso TT be the ultimate combination of fine wire spark plug performance with rare metal earth electrode durability.... and for what amounts to a pretty reasonable price, especially when compared to my super expensive (but excellent performing) LPG2s
Let me test them for you on LPG, and we'll soon have our answer
My car ('Ol Gasbag') is not exactly a standard Chimaera, it's not especially highly tuned, but here's my setup focusing exclusively on fuel & ignition to keep it all relevant to this post.
1. Canems Dual Fuel ECU alowing me to run both petrol & LPG
2. Wasted spark ignition (no distributor)
3. Ford Edis type coil packs - MSD performance versions with a different winding ratio than standard Ford Edis coil packs - 45,000 volts
4. MSD Superconductor HT leads - In my opinion these are the absolute mutt's nuts, and make the rubbish Magnecors look like speaker wire
The objective of the test was to compare two different NGK plugs:
1. BPR6EIX Iridium - £55 for a set of 8
2. LPG2 Iridium - £115 for a set of 8
Essentially I wanted to see if the ferociously expense LPG specific plugs were worth their astronomical price, both plugs sport an iridium centre electrode but that's where the similarities end. The key differences between the two are the LPG plugs have a special anti corrosive coating and a chip of pure platinum on the earth electrode which you can just see in the photo above, and boy do you pay for theses features...... but are they worth it?
I ran six LPG2s, three in each bank..... and two BPR6EIX, one in each bank for 10,000 miles.
First up here's an example of what happens to a BPR6EIX Iridium plug after 10,000 miles on LPG:
The formation of green corrosion on the surface of the terminal nut thread is not the typical air/water derived corrosion we are familiar with, it's the result of an electro/chemical reaction similar to that you might see on a battery terminal.
Look closer and you'll see tell-tail lines running down the ribbed ceramic insulator that indicate carbon tracking, this plug and the second BPR6EIX were clearly in real trouble, they were also the source of a very occasional misfire at low RPM/high load that prompted me to conclude my plug test and inspect the both types I've been running for the last 10,000 miles.
Now lets look at the standard nickel earth electrode on the BPR6EIX, clearly LPG was too much for it as the gap had opened up by almost 0.5mm.
It probably doesnt look as much as 0.5mm in the above photos but when the earth electrode is studied closely what you see is a dished area eroded into the soft nickel, it's like a miniature crater and it's when you take this into account it's clear the gap has opened significantly in just 10,000 miles.
The second BPR6EIX was worse still.
This time the sides of the crater had actually been completely blown out to reveal a step in the far cheaper nickel BPR6EIX earth electrode.
Obviously I took all the LPG2s out too, but quite simply there was no point in photographing them because they were completely corrosion free and all six showed absolutely none of the wear issues I'd suffered on both BPR6EIX, all six gaps on the LPG2 plugs were exactly the same as when I fitted them 10,000 miles ago.
I conclude these expensive LPG2 plugs are not marketing hype, that special anti-corrosive coating is definitely doing something and that chip of pure platinum solves all the premature wear issues associated with hard to strike LPG. Obviously I'm rather unique in running my TVR on gas but hopefully the results of my tests demonstrate where you might end up after 50,000 miles plus if you're running BPR6EIX Iridium plugs on petrol.
Don't get me wrong the BPR6EIX is a great plug, If I'd run the test with standard BPR6ES plugs no doubt they would look even worse than the BPR6EIX. The key takeaway from all this is a platinum earth electrode is a good idea, it works brilliantly in partnership with an iridium central electrode to give unparalleled service life even when pushed to the limit on LPG.
But those LPG2s are still £115 a set, and that's just nuts for 8 plugs, so taking everything I've learned during my 10,000 mile plug test into account, I'm now wondering if the Denso TT (£57 for a set of 8) could be the way forward. The Denso TT uses a fine wire iridium earth electrode like the BPR6EIX and others, but pairs it with a platinum fine wire earth electrode too.
Could the Denso TT be the ultimate combination of fine wire spark plug performance with rare metal earth electrode durability.... and for what amounts to a pretty reasonable price, especially when compared to my super expensive (but excellent performing) LPG2s
Let me test them for you on LPG, and we'll soon have our answer
Edited by ChimpOnGas on Saturday 17th February 08:56
The LPG2 is rated as 6 but apparently the heat range is wider than a regular 6, the idea is to cope with the higher combustion temps of LPG but still be within range when you switch to petrol.
The BPR6EIX is obviously a six.
In theory this wide heat range means the expensive LPG2 plugs could also be ideal for boosted applications, as the challenges of igniting LPG are similar to those experienced when striking an air/petrol mixture when cylinder pressures are high..... as is the case with forced induction
The BPR6EIX is obviously a six.
In theory this wide heat range means the expensive LPG2 plugs could also be ideal for boosted applications, as the challenges of igniting LPG are similar to those experienced when striking an air/petrol mixture when cylinder pressures are high..... as is the case with forced induction
Boosted LS1 said:
Have you any close up shots of the earth electrodes?
No, sadly not, my phone camera simply isn't up to the task.However, what I can tell you is the crater I refer to is clearly visible when you invert the plug and study the underside of the earth electrode, the crater seems like it's formed by the very intense and directed spark leaving the sharp pointy shaped iridium centre electrode, the crater therefore appears directly under and in line with the iridium centre electrode.
Just like NGK Denso offer a range of iridium plugs, one of which shows a slightly different approach to earth electrode design where the cheaper nickel material is used (as with the NGK BPR6EIX):
Their Iridium Power plug has a 0.4mm iridium center electrode, however the cheaper but erosion prone nickel ground electrode used has a U-groove and tapered cut, Denso say this design gives high performance and the ultimate running results but I doubt it'll last well with LPG.
However, their Iridium Tough range, which are £95 for a set of 8, has the same 0.4mm iridium center electrode but this time they use a chip of platinum at the ground electrode right where my two BPR6EIX showed the crater shaped wear, the Iridium Tough is therefore the same design as my super durable LPG2 plugs which cost £115 a set of 8, Denso say the Iridium Tough is a high performance plug with an emphasis on longer life which my NGK tests would support.
Denso also offer their Iridium plus range shown above, this plug also caries a chip of platinum at the earth electrode but the chip is smaller than you get with the Iridium Tough or NGK LPG2, it would seem cost is heavily influenced by how much or little platinum you get which in turn has a direct impact on longevity and service life.
Finally there's the Denso TT range that not only has a fine wire iridium centre electrode like all the others discussed, but this time the platinum earth electrode is also formed in a fine wire shape, this is Denso's latest design and has only been on the market for 3 years. A set of 8 Denso TTs for the Rover V8 are £57, the twin fine wire design is very interesting as I can see it offering excellent performance, and the use of platinum for the earth fine wire should also deliver excellent longevity.
I'd love to try a set of these new Denso TTs, but the thing is I invested heavily in my set of NGK LPG2s which are performing brilliantly and look like they will easily last the 60,000 miles NGK claim they will in an LPG powered car. So perhaps someone else will try a set of the new twin fine wire tech TTs, I can see them giving fantastic performance, with the fine wire earth being constructed from platinum I also predict they'll deliver a superb service life that could easily reach 100,000 miles on spark plug friendly petrol.
Who will be the first to try a set of these Denso TTs? The part number you'll want for the Rover V8 is IW20TT, and the cheapest place you can buy them is here:
http://www.ebay.co.uk/itm/8x-DENSO-IW20TT-IRIDIUM-...
Actually what I'd really love to see is someone who's still running the highly inappropriate, too cold, and shrouded electrode NGK B7ECS as specified by TVR...
And switching straight to the Denso TT.....
I'd put money on them enjoying a massive improvement to their idle quality and throttle response
Ok so how much money???? re yu willing to put on this? 
Now as I need a spare set of plugs will check out some things:-
1) can we get them here?
2) Price of course here?
In the meantime will possibly order a set to be delivered to a friends house to go with the rest of the stuff in my trip and breakdown kit to go along with the jump starter, tools, punture kit, European break down kit etc.
The problem is of course that Heath fitted new plugs in when he serviced her and she has done almost no miles since then. Only the run ups and being moved around the storage place to keep everything moving and lubricated. So doing a comparision will be impossible really
but as mentioned I do need some spares.
Now as I need a spare set of plugs will check out some things:-
1) can we get them here?
2) Price of course here?
In the meantime will possibly order a set to be delivered to a friends house to go with the rest of the stuff in my trip and breakdown kit to go along with the jump starter, tools, punture kit, European break down kit etc.
The problem is of course that Heath fitted new plugs in when he serviced her and she has done almost no miles since then. Only the run ups and being moved around the storage place to keep everything moving and lubricated. So doing a comparision will be impossible really
but as mentioned I do need some spares.Edited by Brithunter on Monday 19th February 19:15
What plug gap were you running? In general coil packs run a larger gap than single coil which could account for your burnt contacts.
Are all the plugs showing the same burn? In wasted spark 2 plugs are fired at the same time with the spark going 'centre to earth' and the other going 'Earth to centre). due to this there should be a difference in the burn pattern.
Steve
Are all the plugs showing the same burn? In wasted spark 2 plugs are fired at the same time with the spark going 'centre to earth' and the other going 'Earth to centre). due to this there should be a difference in the burn pattern.
Steve
Steve_D said:
What plug gap were you running? In general coil packs run a larger gap than single coil which could account for your burnt contacts.
Are all the plugs showing the same burn? In wasted spark 2 plugs are fired at the same time with the spark going 'centre to earth' and the other going 'Earth to centre). due to this there should be a difference in the burn pattern.
Steve
Steve, the purpose of the test was to see how the BPR6EIX iridiums stack up against the far more expensive LPG2 plugs, which like the BPR6EIX have an iridium centre electrode but unlike the BPR6EIX have a chip of pure platinum on the earth electrode instead of it being plain nickel. Are all the plugs showing the same burn? In wasted spark 2 plugs are fired at the same time with the spark going 'centre to earth' and the other going 'Earth to centre). due to this there should be a difference in the burn pattern.
Steve
The car was run for 10,000 miles on LPG with a mix of the two types plugs all gapped to 0.8mm, after the 10,000 miles the two cheaper BPR6EIX had opened up from 0.8mm to 1.2mm while the LPG2s with their more durable platinum tipped earth electrode remained at 0.8mm.
It doesn't matter what plugs you use with LPG, BPR6ES, BPR6EIX or I suspect even the expensive LPG2s, once the gap goes over 1mm you are likely to experience misfires. I replaced the two worn out BPR6EIX with two of the clearly far more durable LPG2 and gapped all 8 to 0.75mm... test complete.
The point of the post is to show while as we already know iridium plugs work well, combining them with a platinum earth gives them a far better life expectancy especially when running LPG. People may be saying so what, but the test does show it's worth seeking out a plug that has both iridium and platinum if long life is important to you... even if you're only burning petrol.
At £57.20 a set the Denso TTs look to be the best value plugs that give you an iridium central electrode and a platinum earth electrode, which may also offer additional benefits as the platinum is formed into a fine wire shape.
Who will be the first to try a set of these Denso TTs? The part number you'll want for the Rover V8 is IW20TT, and the cheapest place you can buy them is here:
http://www.ebay.co.uk/itm/8x-DENSO-IW20TT-IRIDIUM-...
For £57.20 a set I'd say they are well worth a try
Denso are a Jap quality brand and neck and neck with NGK/NTK , they are also an OE ecu/ecm manufacturer for various Jap brands inc Suzuki motorcycles I have always exclusively used NGK plugs on the tools daily since 86 so you can imagine how many plugs I have fitted inc a long stint at a Honda dealer (NGK OE for Honda back then) however in recent years I have used Denso seeing they have become more widely available and alternate between both brands I have yet to see a faulty Denso although its early days and only ever witnessed 2 faulty NGK plugs in my career now that is some track recored I can tell you when you consider how many I have fitted over a 30+ period 
now thats faulty rather than worn out 
every plug as its lifespan , probably useless information but just my contribution to this thread 
seq ignition (pencil coils etc) fitted to 99% of modern cars & motorcycles are kinder to these Iridium/platinum plugs due to a lower duty cycle cant comment with LPG use Dave as covered that 
I have always exclusively used NGK plugs on the tools daily since 86 so you can imagine how many plugs I have fitted inc a long stint at a Honda dealer (NGK OE for Honda back then) however in recent years I have used Denso seeing they have become more widely available and alternate between both brands I have yet to see a faulty Denso although its early days and only ever witnessed 2 faulty NGK plugs in my career now that is some track recored I can tell you when you consider how many I have fitted over a 30+ period now thats faulty rather than worn out every plug as its lifespan , probably useless information but just my contribution to this thread seq ignition (pencil coils etc) fitted to 99% of modern cars & motorcycles are kinder to these Iridium/platinum plugs due to a lower duty cycle cant comment with LPG use Dave as covered that Edited by Sardonicus on Tuesday 20th February 11:02
SILICONEKID 345HP 12.03 said:
The BPR6ES are a massive improvement over the ones TVR specced .
Is there a better plug for my engine setup ?
8 plugs cost me 15 quid .
Probably not Is there a better plug for my engine setup ?
8 plugs cost me 15 quid .
Depends on how often you change them I suppose.
I’m looking at 20,000 before I replace mine.
I’m not sure if it’s the Iridium tips or the slightly hotter grade that does it but my engine runs sweeter on a 6 grade plug from the moment it starts.
that tickled me SILICONEKID 345HP 12.03 said:
The BPR6ES are a massive improvement over the ones TVR specced .
Is there a better plug for my engine setup ?
8 plugs cost me 15 quid .
I run NGK Irridium plugs in a 7 rating as they work better on the track. Does mean I need to do a bit of spirited driving on the road every now and again to keep 'em clean Is there a better plug for my engine setup ?
8 plugs cost me 15 quid .
If I didn't do trackdays and only did London driving I'd probably try a 5 rating (NGK scale).
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