[s-cars] Which spark plugs

[Taka Mizutani]

I would take Scott's advice on the plug intervals as well as plug choice.

I've experienced what happens when the electrode separates from the plug-
that was an expensive fix to the tune of $5k and that's without replacing
the cylinder head and that was on an A4 1.8T engine, for which it is much
easier to source parts.

Iridium definitely seems like the way to go- most tuners for watercooled
Porsche turbos, GT-Rs and other stuff also use Iridium plugs.

That is a first about the service interval, though- I wonder when they
changed the interval to 25k- I thought it was 60k?


On Sat, Mar 22, 2014 at 9:57 AM, Scott Justusson <qshipq at aol.com> wrote:

>
>  Well, save yourself 22$ and just buy a copper plug if that is your
> presentation?  Any plug will work. I suggest you get a copy of the Denso
> Iridium White Paper (1999) to test some of your opinions and observations.
>  Audi calls the Service Interval of the F5DPOR to be 25k on the 20vt
> engimes/  I personally suspect that is to help reduce the amount of
> secondary voltage and dwell issues of a 7200rpm redline turbo engine.
>  Certainly if you are running a 20vt at 100k, you are risking spark issues,
> even at stock boost.  Will the engine *fire* that plug to 200k?  Ok,
> probably.
>
> When I did this research years ago, the iridium High Performance .4 vs
> .7mm electrode was my plug of choice, my first swaps were to my 3B engines
> because the required secondary voltage published in the paper dropped 5kv.
>  Not as key as the AAN COP, but significant even with COP.  Add in a 50%
> better wear resistance and a 25% increase in temp resistance, the Platinum
> Plug really became obsolete in a turbo application 15 years ago.
>
> Just about any turbo tuner regardless of marque, will use a HP Iridium
> Plug...  Or just copper.  I would say for a COP either is fine, because the
> 'flameout' issues in a copper just don't appear to be present with a COP
> application.  I'm a bit more reluctant to say the Copper is 'better' in a
> single coil application, but I routinely keep sets of copper plugs around
> to diagnose ignition problems in all 20vt engines.
>
> I will further opin two things on the F5D,  If you use it, make sure you
> replace it at 25k - period.  The combustion temps those plugs are exposed
> to mean degredation and failure of the plug increases exponentially past
> this (Audi Factory) Service Interval.  Second, if you insist on using it,
> and lose an electrode, your best hope is it either burned up (unlikely) or
> it exited the chamber without damaging vital engine components.
>
> This isn't an oil thread or mountains of opinion...  Iridiums in non
> boosted applications are as overkill as an F5DPOR is.  However in the world
> of boost, especially high boost, ignoring the benefits of the iridium
> technology seems stubborn.  I say there are many reasons *not* to use the
> F5DPOR in the I520vt - stock, and especially, boost tweeked.
>
> This thread has been bounced around a while, but it is not 'rumor' or
> opinion, I believe the bad rap the F5DPOR got is from the guys that work on
> more than 'just a couple'...  Because it doesn't take many experiences to
> ascribe that plug less than stellar.
>
> Cheers, HTH and my .02
>
> Scott J
>
>
> e
>
>
>
>
>
> -----Original Message-----
> From: Mike Miller <mikemilr at blackfoot.net>
> To: s-car-list <s-car-list at audifans.com>
> Sent: Sat, Mar 22, 2014 1:07 am
> Subject: Re: [s-cars] Which spark plugs
>
>
> I ran F5DP0R's in my 91 200q's without issue - swapped one set out after
> 100k+ miles just because. They still looked good and ran fine.
>
> In the current UrS6, running over 25psi boost, I'm using FR5DTC which
> seem to be doing OK. Not a lot of miles on them yet - maybe 5k.
>
> --mike
>
> On 3/21/2014 10:21 PM, Scott Justusson wrote:
> > Er, ok add me to the list of those *not* using FD5POR *ever* again,
> because
> when I had my shop, I have seen too many fail from the box, blow a pin
> hole in
> the ceramic and or just lose the electrode all together on high boost.  I
> had
> really good luck with NGK Iridiums for a while, but have recently just been
> content with a plain old Porsche Turbo app triple copper plug.
> >
> > FYI, that FD5 is supposed to have a 25k service interval in a stock 20vt
> engine, so beyond 30k (IME) you are asking for coil pack issues from a
> resistance problem.  I know I am not the exception to the opin that the
> FD5POR
> is hardly first prize at the spark plug county fair.  Bet you won't find
> m-any
> I5 tuners using that plug.  Lose and electrode once, you won't swear *by*
> them
> ever again.
> >
> > Just sayin
> >
> > Scott J
> > 7 x 20vt engines = 0 x FD5POR equipped
> >
> >
>
>
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