Hi

 

Thinking of replacing my 1992 UK 300ZX twin turbo's spark plugs; firstly, what sized spark plug wrench do I need - 14mm? Think I only have a 10mm one at the moment...

 

Secondly, which plugs should I use? Looking around it seems NGK PFR6B-11 are recommended for a standard TT but NGK PFR6B-11B are better for a 'modified' TT.

 

Mine has the 70+bhp EPROM upgrade and Apexi air filter, no other engine mods... so am I better off with the B? I see they're different lengths though...

 

Cheers

 

Ross

You can't really buy the B in the UK, so the 11C is the jobbie to go for

smithy

I'll have a look for the 11C then... But I think you can get the B in the UK, or at least from eBay... Thought I saw some...

 

Do happen to know what size wrench I need?

16mm wrench bud, don;t know if your familiar with it but this may help if not

 

http://z32.wikispaces.com/Spark+Plug

16mm wrench bud, don;t know if your familiar with it but this may help if not

 

http://z32.wikispaces.com/Spark+Plug

 

lol.. entertaining...

lol.. entertaining...

 

What? It's a basic guide to changing plugs

Perhaps he found the bit around firing the spark plug into the bin amusing?

 

Anyway... that article seems to suggest that the PFR6B-11C has been discontinued but clearly it hasn't (can see them on eBay) yet the PFR6B-11B doesn't appear to be around (earlier comment about not being available in the UK perhaps being true!) so I guess it's PFR6B-11C for me then and a new 16mm spark plug wrench :)

 

Cheers guys!

Ah gotcha, I didn't scroll down further than the guide.

 

Get a long wrench the plugs are pretty deep and make sure you don't loose the balance bar O-rings when you remove it they are expensive to replace

Thanks eggs :)

Aye the 11b was only available in the US designed by Nissan for the difference in emission laws me thinks, however it protruded just ever so slightly morre which benefitted the UK cars running higher boost.

11C also designed by Nissan works well with both stock and higher boost, just not quite as good as the 11B that was all.

smithy

I'm pretty sure the 11B has a longer shroud (extended shell at the end of the threads), to protect the insulator and centre electrode better. For higher boosting engines it's preferable to reduce the projection (take the tip away from the combustion action) and close the plug gap slightly. Shrouding it more protects it and still allows the same projection for better low speed running. 11B was never officially available in the UK AFAIK, there may still be some knocking around in the USA or from unofficial importers in the UK.

H

I finally got round to checking my existing spark plugs the other week and found they were PFR6B-11C, and looked pretty new and in good condition so not going to bother changing them (I'm actually working step by step at trying to sort the dreaded hesitation and this was one of the possible causes).

 

Just a note on the spark plugs: my "10mm" wrench was fine; it's 10mm for the spark plug screw thread; and 16mm for the hex part at the top of the spark plug which the wrench turns :)

if u have a 10mm spark plug socket that will fit mate. need a long extension.

oh just see ya done it with 10mm they confuse ya lol.

Wrench manufacturer's drive me to distraction, they call a wrench that fits 16mm hex size 10mm (the threads of a 16mm hex size plug may be 10mm, 12mm or in our case 14mm). They call a wrench that fits a 21mm hex size 14mm (14mm thread dia). Why the heck they can't just call them 16mm or 21mm and stop confusing everybody.....!?

Edited October 25, 201213 yr by RobH

LOL, even worse, some 10mm/16mm wrenches are advertised as just 10mm, and some are advertised just as 16mm.

 

So I bought a '16mm' wrench when I already had a '10mm' wrench at home - and they're the same bl00dy thing :)

yep depends on who makes them, but has u found out 10mm the same.

 

stupid tools lol.

I run copper core BCR8ES in my Zed, and have run these plugs in all kinds of different cars. Some may think running grade 8 plugs is overkill, and they'll foul up under normal driving, but that's definitely not been the case. They're not the ideal plug for the Zed due to the design of the cylinder head (they have a shorter thread and non-projected tip), but the equivalent grade 8 projected plugs are NGK R7435-8 at £30 each.

 

If you're running decent boost, I would fit some projected copper plugs, eg. BCPR7ES. I'd be wary of running grade 6 plugs in anything other than a completely stock car. I generally don't run iridiums in modified cars, either. Thick copper tips dissipate heat whereas the fine iridium tips retain heat, which in turn can promote pre-ignition and/or damage the ceramic insulators. Downside is, you need to change them more often for peak performance, a bit of a pain with the Zed. They're good for 10000 miles, although I change mine after half that at the most.

I was only going to change the spark plugs as a possible cause of the 'hesitation' issue I get, but reading through some details on this it sounds like spark plugs would only be the cause at higher revs, my 'stumble' is at lower revs and only for the first 10 mins or so when the car is cold. I've been working my way through the list of possible causes and have already ruled out:

 

PCV hose/values

Air flow meter - voltage fine

Throttle intake valve clean

Voltage check TPS - adjusted to 0.47V

Cold start temp sensor voltage check

 

The PTU is a common cause - I have a series 1 so have ordered a second hand Series 2 PTU from the states on eBay, had hoped would have arrived by now but have had to pay a £13 import tax plus another £13 'handling fee' from Parcelforce, what a rip off!! But will hopefully have that soon and will fit and see if that helps... if not I'll post a more detailed new forum question up to see if anyone has any other ideas.

i.e. it's not at boost I'm having the stumble probs else perhaps a grade 7 plug would be better for my slightly higher boost

BKR7E is a closer match to the recommended plug for the 300ZX than BCPR7ES, 'BC' type plugs have a ceramic body 2.5mm longer than 'BK' types - shouldn't be an issue either way, but the idea is that the direct fire coils (often incorrectly called coil packs) are designed to use a plug with a specific body length.

 

It may be worth changing your plugs - even if it's just for some cheap, temporary replacements, it's worth £20 or so to rule the plugs out as the issue. Most plugs of the correct size will work fine initially, it's only with time that they may wear badly or foul up.

 

The heat range of the part number indicates the ability of the plug to conduct heat away from the firing end - regardless of what material and how fine the electrode is. A copper plug in an NGK '7' heat range will have the same conduction property as an Iridium plug in a '7' heat range.

 

TBH it sounds more like a bad connector or intake air leak that's the problem.

Cheers

H

Thanks... will see how we go when the PTU turns up and then at least that's one more thing ruled out :)

BKR7E is a closer match to the recommended plug for the 300ZX than BCPR7ES, 'BC' type plugs have a ceramic body 2.5mm longer than 'BK' types - shouldn't be an issue either way, but the idea is that the direct fire coils (often incorrectly called coil packs) are designed to use a plug with a specific body length.

 

 

BCPR7ES work fine with the VG COP system, the ceramic section is identical, there is a couple mm difference in the middle seat section IIRC (I've not got any to hand).

 

Here is a rundown of the relevant nomenclature:

 

'B' = 14mm thread diameter

'K' denotes a 5/8" hex diameter and ISO thread taper.

'C' denotes a 5/8" hex diameter and thread to Japanese Industrial Standards (JIS). 'P' simply denotes a projected insulator (again, 1.5mm); R= Resistor-type; hence BKR7 (ISO) = BCPR7 (JIS).

'E': ONLY when this is the final symbol does it denote a V-shaped electrode (which is 2.5mm diamter, but not specified) with a 1.5mm insulator projection, in place of the 'P' symbol. (Note: BKR7E doesn't have a symbol specifying the thread reach, which is approx. 19mm(3/4") )

'E' when followed by 1 or more symbols denotes a thread reach of 19mm (3/4")

'S' denotes a 2.5mm centre electrode diameter

 

The lengths of the ceramic sections are identical for BKR7E, BCR8ES, BCPR7ES and the BPR8ES which have a 13/16 hex diameter (perfect for Evos & Saabs, no use for most). The symbols aren't always directly comparable across the range of NGK plugs.

 

The heat range of the part number indicates the ability of the plug to conduct heat away from the firing end - regardless of what material and how fine the electrode is. A copper plug in an NGK '7' heat range will have the same conduction property as an Iridium plug in a '7' heat range.

 

This is very far from actual fact. Material properties & simple physics dictate that Cu has a much higher thermal conductivity than Ir (421Wm-1K-1 against 147Wm-1K-1). 0.4mm Ir tips retain heat a great deal more than 2mm Cu tips, which is a potential engine killer due to pre-ignition & brittle fracture of the plug material from overheating. Ir plugs are used as OEM components due to the amazing wear resistance & hardness of the material (370HV as opposed to 50HV!!). 40k+ mile capabilites without serious erosion which maintains performance between increasingly long service intervals. Great for lazy people, no place in a performance engine. A thick electrode with Cu composition conducts the heat away from the tip much faster than an Ir tip, Cu electrodes are malleable which won't break off if detonation becomes an issue, much greater heat range etc etc. Oh.... Platinums are just utterly pointless :blink:

 

Not saying you can't run Ir/Pt plugs quite happily, but I fail to see any benefit whatsoever to them, other than that they are actually cheaper in the long run than Cu plugs.

Edited October 31, 201213 yr by Noz

Well here is different view on Iridium plugs in Z32's from Greg at Specialty-Z:

 

http://www.twinturbo.net/net/viewmsg.aspx?forum=general&msg_id=1913149&forum=general&dtSearch=7

 

although he posted that back in 2006, he still stands by his comments:

 

https://specialtyz.com/shop/300zx/ngk-iridium-ix-spark-plugs.html

 

-Andrew

Edited October 31, 201213 yr by AndrewG

Just a couple of notes, BCR8ES appears to be ISO standard (agreed that it's the overall upper length that is different to JIS, the metal section rather than the ceramic portion, never bothered to measure before) therefore NGK have performed a classic plug manufacturer's trick and not applied their own coding system. In other words BCR8ES is the correct size for the Z32, BCPR7ES are technically not the correct size but that doesn't mean they won't work. I'm using a JIS size race plug at the moment. There are a number of plugs which are classed as JIS standard but are actually ISO length (most notably some NGK race parts).

 

Not disputing the figures you have quoted but Ir in it's pure form would be completely useless as an electrode material, far too brittle with poor electrical and heat conduction. That's why an Iridium alloy is used, usually Rhodium, to greatly improve strength properties, resistance to oxidation and conductivity. 'Copper' centre elctrodes are usually (but not exclusively) Copper-Nickel alloys therefore the conductivity figures you've quoted are out of context. (I'm just being a pedant)

 

The overall picture for Iridium is of a plug that does a better all round job than a copper plug. I have to say that having sold tens of thousands of Iridium plugs over the last 10 years or so the only issues with damaged centre electrodes have been through careless gapping or incorrect installation. Almost all applications benefit in some way from using an Iridium plug if a suitable part is available. A lower spark voltage is required, this means misfire is less likely when the ignition system would otherwise be reaching its maximum capacity. The best/easiest spark is created from a sharp edge, sharp edges don't last long on electrodes so the next best thing is a fine point - hence the finer the better for ignition efficiency, Iridium alloy being the current finest option. Consider it a trade off of thermal transfer against a whole raft of benefits...

 

Detonation issues generally (and logically) come from the ground electrode, obviously much longer than the centre electrode hence the longer heat path. Iridium plugs most often use the same ground electrode configuration as a 'standard copper' plug. Both types generally use a copper core. You'd use a shorter or less projected ground if you really wanted to avoid detonation. It does raise the question of why you'd be close enough to the det threshold for the spark plug config to make a difference though.

 

I doubt that both NGK and Denso would have chosen Iridium alloy as their best option for racing plug centre electrodes without good reason ;) . Race plugs are deisgned so as to be as unaffected as possible by vibration and to reduce the possibility of structural damage in critical applications. Not solely designed for performance but that is a major additional consideration.

 

Each to their own I guess. I stand by the statement that the heat range is set by the manufacturer and that's that, if the thermal transfer properties were different the manufacturer would apply a different heat range number, or rather they design their plug to have specific thermal transfer properties and number it accordingly. Take a look at your copper plugs and let me know if you still think the centre electrode is more likely to retain heat and cause det than the ground electrode. A couple of mm of Iridium alloy tip welded onto a copper core centre electrode is not going to retain significant heat relative to the ground electrode.

 

H

Yes Lisa... Daddy's a teacher now.