I was thinking about getting some Iridium spark plugs for my N/A 300.

 

Loads of claims are made about more power (up to 10bhp more etc).

 

Do they really make any noticable difference or would I need a dyno run to actually tell they were there?

 

 

 

:hyper:

Crraaaiiiggggg Daaaaayyyyvvviidddd ; Bo!

Hi Craig

 

I have these in my TT.

 

IMO they don't give any extra bhp but they are more durable than platinum so should stay at peak performance for longer. Also they would be better than stock plugs if you drove a modded car. So overall I would say they are better :)

 

When I replaced mine I did notice an improvement in the overall running of the car but put that down to the fact that the originals had been in for a long time and were past their best.

 

If you log onto

 

http://www.sparkplugs.co.uk

 

you can get iridium jobbies for way less cash than a stock set

 

Richard :cool:

 

you can get the iridium

Personally I wouldn't touch irridiums with a barge pole.

 

There is a host of problems associated with irridiums on tt.net, irridiums where a source of detonation on my S13. Do a search on tt.net and on this forum for the huge debates that gone on in the past.

 

I would personally use NGK PFR6B-11B if running a higher boost, and gap them to .9mm! Get them from Cos at CZP!

 

But there again there are a host of people who have used irridiums with no problems.

 

But there are none who have had any probs with platinum!!!!

What grade and brand spark plugs are recommended for my 1992 Jap N/A auto ? My car is stock, except for the K & N Induction Kit, so I am just looking for a standard (platinum I guess) plug, and where is the cheapest place to get them.

 

Thanks

 

John

I would NEVER go back to stock plugs after I fitted the HKS.

LOL Spark plugs don't give you power, they only lose it! If you have a good spark, you have a good spark, full stop. If you notice a difference fitting a different kind of plug (ok heat range is different) then your old plugs were shagged - fitting new plugs of the old type would give the same difference. No arguement.

LOL Spark plugs don't give you power, they only lose it! If you have a good spark, you have a good spark, full stop. If you notice a difference fitting a different kind of plug (ok heat range is different) then your old plugs were shagged - fitting new plugs of the old type would give the same difference. No arguement.

 

I use them because of this........................

 

The Iridium electrode is more suitable for tuned engines due to the iridium electrode having a high melting point (2454°C) when compared to platinum (1769°C).

So the plug lasts longer under detonation, really f'ckin things up ;) If you melt a platinum plug then there's something seriously wrong...

I can only say, that as an NA driver, possibly the most powerful NA on the forum, I have run mine for the last year on copper. In the belief, correct or otherwise, if things get silly the copper will melt before the piston does. Preparing to be pelted, and lambasted for not buying a proper car with turbos :)

I run ZFR7F-11 coppers (0.8mm gap) and they're fine. Most big tuned US/JAP cars use these too.

I've put Iridiums in mine - they seem to do the job. No more - no less. You pays yer money and takes your choice. My car is stock.

Most of the problems I've heard of with use of Iridium plugs are due to using the wrong type. All common 300ZX (Z32) use an ISO standard plug - I know some people have fitted JIS standard plugs - these are longer, Z coil packs weren't designed for use with JIS types. It's not usually a problem where simple plug caps are used but where coil packs are on top of the plugs you can see where it may be a problem. Quite a lot of folks seem to buy from US suppliers on Ebay and the like (good luck to you) - IMHO the US guys don't give a monkey if they sell you the wrong type. They may believe they've sold you the correct plugs but don't forget they're selling to the US market with different driving styles/fuel grades and hence often a different required heat range. People are also often unsure about selecting the correct heat range when going from say NGK to Denso.

 

More of an issue is fitting an ISO plug to a JIS designed coilpack (as with all turbo Skylines and I suspect earlier model 200SX - never seen under the bonnet). There may not be sufficient contact between coil pack and plug terminal therefore creating an auxiliary gap which may be a little too much under high load.

 

John, ZFR7F-11 is an unusual choice, being extra projected - put's the fragile bits right in the firing line. It's usual to go less projected when a colder plug is needed. BKR7E-11 would be a closer copper replacement and even cheaper (I'm not endorsing this though!)

 

Mr Duff (hi!), valid point, but relatively speaking you're looking for the most efficient spark you can get. If you could induce a more perfect spark then you would be getting better combustion - compared to a platinum plug there is a difference in power produced. Doesn't every engine component lose you power if you look at it that way??

 

I have no axe to grind, I'm just as happy selling Platinum as Iridium :-) - best thing about Iridium being the availability of colder heat ranges for tuned engines.

 

Didn't mean to give a lecture but there you go - sorry!

 

RobH

According to NGK, ZFR7F-11 is the closest dimensionally to PFR6B-11B, which was a plug nissan had designed specifically for this engine.

I was lead to believe that the projection is an important aspect on this head, as the PFR6B-11C / BKR7EIX-11 don't project far enough to get the spark right into the mixture and are masked slightly.

The only other one they recommended was a surface discharge race plug, but it was an 8 range.

Hi John, PFR6B-11C is a special for the VG30DETT engine - PFR6B-11B is a revision reputed to have been made for the North American market and lightly tuned or hard driven cars, running slightly cooler. Not available from NGK in the UK and no longer available in the US (at least last time I tried to get some). Both of these plugs have an extended shell which allows the spark to be placed more toward the centre of the combustion chamber while still affording the ceramic insulator and centre electrode some protection. From what I can make out the '11B has an even more extended shell but I don't have one to compare unfortunately.

 

ZFR7F-11 will put the spark in a similar position but without the shell protection of the PFR6B-11C/11B. The extra extended centre electrode and insulator also means an extra extended ground electrode - not a good thing in a high performance or tuned engine.

 

Only putting my 1/4p's worth in because plugs is something I actually feel qualified to comment on.

 

Ciao!

The -11B does have a much more extened shell, in fact the ceramic is almost completely covered, the overall length is also a little longer.

I'll go have a look at a -11C, ZFR and EIX as I have one of all these lying around for comparison.

Other thing to remember is that the PFR6B-11X is not available in a 7 heat range which is really what you should be running in a tuned Z. The -11B is a colder plug for the US because their stock one is PFR5B-11B.

Thanks Rob

 

John

When I had Iridiums put in I noticed the ride was much smoother - the old ones were still in fairly good nick. That's all.

Don't get me wrong John Dixon (a bit confusing John Dixon and DixonJohn posting on one thread) if ZFR7F-11 work for you then that's great - just a bit of an unusual replacement for the standard recommendation that's all.

 

A word about durability - NGK's Iridiums should last up to 60000 miles (same as double platinum PFR plugs), Denso (aka HKS) recommend a 30000 mile replacement schedule. Plugs (Iridium and platinum) are well past their best a long time before this. Some of Denso's blurb actually recommends 20000 to 30000 kms (!).

 

The only way to get Denso Iridium performance and extended service life (60000 miles) is the hideously expensive VK20PR-Z11, Iridium centre and platinum ground - over £20 per plug.

 

Cheers!

 

RobH

hey guys!

im looking to get a uprated set of plugs as im gonna be running 400bhp odd,

thinking of going for the denso ones instead of splashing out on ythe pricey HKS!

what is the correct code and heat range for the denso plugs!! cheers guys!!!

Don't get me wrong John Dixon (a bit confusing John Dixon and DixonJohn posting on one thread) if ZFR7F-11 work for you then that's great - just a bit of an unusual replacement for the standard recommendation that's all.

 

A word about durability - NGK's Iridiums should last up to 60000 miles (same as double platinum PFR plugs), Denso (aka HKS) recommend a 30000 mile replacement schedule. Plugs (Iridium and platinum) are well past their best a long time before this. Some of Denso's blurb actually recommends 20000 to 30000 kms (!).

 

The only way to get Denso Iridium performance and extended service life (60000 miles) is the hideously expensive VK20PR-Z11, Iridium centre and platinum ground - over £20 per plug.

 

Cheers!

 

RobH

... if ZFR7F-11 work for you then that's great - just a bit of an unusual replacement for the standard recommendation that's all.

 

RobH

 

ZFR7F-11 are a copper plug. They don't last long but some people think they give a fatter spark and if you are running a lot of boost they are rumoured to give some detonation protection as the detonation eats the plug rather than the piston. They are also very cheap. I use them too.