I'm just about to take my car in to be re-mapped and it occurred to me that I should see that my spark plugs are tip top condition.

I currently run relatively new NGK PFR7B Iridium Platinum plugs they have done <3000 miles since my new build. ( BKR7EIX are Iridium and cost about £8 each)

I looked on the Net to check the price of some replacements and was shocked to see that for 8 of these (I always keep a spare set for next service ) that I needed to pay over £100
compared to a set of NGK BCPR7ES which are the copper equivalents which for 8 are just £22 delivered.

Before hitting the pay button on these , has anyone ever Dyno compared the Torque/Bhp on new Copper spark plugs versus Iridium ?

( I'm not interested in comments on which ones last longer , I change mine with the oil )

 

use iridium they last , copper won’t , it’s worth the difference , plus saves having to change your plugs more often , if they have only done 3000 miles they won’t need changing for another 50k or so they say up to 60k miles , i normally change at 50k , i assume your question is not about the heat range of the plug , unless you are mapping for a lot of power again i’m sure they will be fine , i have 7’s in mine at 340 bhp and it’s fine

 

Again ( I'm not interested in comments on which ones last longer , I change mine with the oil ) I dont really care about them lasting even 20k ,

What I need is anyone who knows what happens on the Dyno , both NGK are rated heat 7
and I presume if I gap them 0.7 then a like for like , do both produce same power ? Graphs please.

If not then I am going to use whichever is better, otherwise it will be the CU version.

 

There's a thread somewhere about the copper vs iridium plugs and the only place where the copper plugs were inferior was durability. If you change your plugs every oil change I think you know the answer.

 

No offence intended by this but honestly why are you changing your plugs so often.

 

thread was not very clear you were after performance , looked like you were asking which was best copper or iridium , there will be no relevant performance benefit , you will notice more in performance on a cold day v a warm day by a long way v a change in plug , in higher output forced induction engines running twice the power of a scooby there is no benefit , there is talk of cooler plugs but that’s going to be very limited benefit too , by changing them more often you are leaving yourself up for risk around the fitting going wrong , crossed threads broken plugs wear on the aluminium thread where the plug screws into , more stress on ht leads or coil packs , put a decent set of iridium in and change every 50k or so

 

Thanks Joe I will try looking more for that thread ,

At the risk of boring everyone, here ( I didn't put this into General technical and kept it simple in the OP post for this reason)

My grounds to consider putting in some new NGKs in now are that I'm just about to fit some ported headers and do a mapping & dyno session ( On the day before and after check to see the effect of the single modification ),

I just want to be thorough , the plugs I have were from an older block and head combination. The older engine was using quite a bit of oil and had developed a misfire, The iridium Platin plugs that were in had been fitted by my garage in Germany as a possible cure
Compression was down a little bit on all 4 pots so I decided to strip it down , apart from oil fouled valves and worn valve guides, I discovered however some cracks around the spark plugs on all 4 pots ,
although this is common and fair few here have said don't worry about it I decided just to replace the heads and took the opportunity to do a forged upgrade.

The misfire that at the time we thought was due to oil fouling but persisted after the new build and was later diagnosed by Plymouth Engine tuner as a sticky Tumbler valve
( So I just had these deleted ) At the time of doing he new block and reworked S/H head build I had simply cleaned up the old "iridium Platin plugs" in petrol and salvaged from he previous heads.
And as the misfire was cured by the work at Plymouth engine tuners I continued to use them, By now have done a total of 6k miles in both the old and reworked new assemblies.

I have perhaps an old fashioned outlook to spark plugs and would normally have binned these plugs out of hand for new ones except that I knew they were expensive and supposed to last longer.
Spark plugs are (or at least were ) for me the best way to look at what is going on in the combustion chamber, I am used to checking them ( on NA cars ), looking to see if the fuel mixture is ok , or are they too hot , or oiling up and according to this taking steps to cure. The iridium' Platin s just don't give you that same feedback , unless things are not well (mine were previously a bit oily ) I can't really tell if they are in good health as the electrode is much smaller and the insulation is not as prominent so any colouring is very hard to see. ( also I wear glasses).

Here is the post I think Joe was on about , many thanks for the tip



I checked Andy Forest has NGK PFR 7B quoted in his site AFP Subaru these are platinum one but still cost a tenner each.
So yes piece of mind for 10k mile run on a 330bhp car with 1.5 bar boost so I definitely need to use the 7s.

However I have made up my mind I'm going to order BCPR7ES coppers and have them in "new" ahead of the next Dyno run .
If I make close 350bhp I'm done on the WRX anyway then I will just stick to my practice of doing my changes with the 6k oil changes
a 15 minute job whilst the oil drops out.

And this is a price I can certainly live with



I cross checked these stock gap is 0.9 mm , probably at higher boost levels it should be reduced further than our 0.7 - 0.8mm.

* The Saab and Honda forced induction boys both use them on boost ( 1.5 bar) applications
instead of the previous spec/'d 1.1mm gapped version BCPR7ES-11 which otherwise has to be gapped down on higher boost.

 

That is a post I'd seen but not the one I was thinking about. It was a back to back comparison and the copper plugs actually performed better than the others. On a side note I personally don't rate the iridium's at all I always use platinum's.

 

After some further research , and to finish this thread.

I checked advice from Bob Rawle "the plug gap should be as wide as you can go without it being extinguished".

According to the boost pressure that I intend to run which is the ECU TeK scaled max of 23 psi 1.55bar
I should gap at 0.6mm , if a misfire develops at full or if higher boost is mapped then per advice it will be reduced in 0.05mm increments.

I have gapped the NGK BCPR7ES coppers that I have just received and these will they go in now
I had hoped to post an update a dyno curve following just the plug change but due to Covid conditions Plymouth engine tune cannot do Rolling Road at present (non essential work)

However if anyone wants to follow you will eventually see Dyno progress with the fitted NGK BCPR7ES on my thread "Life before and after Ported headers"