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-   -   What plugs do you reccomend? (https://rennlist.com/forums/944-turbo-and-turbo-s-forum/64382-what-plugs-do-you-reccomend.html)

Chris Evans 05-16-2003 06:43 PM

What plugs do you reccomend?
 
I've got a 86 951 with the Guru chips, reliaboost and 3 bar FPR. What plugs do you reccomend. Back in my Supra days, we used the cold Autolite plugs. I think we used 31-30's or 28-30's. Would a cold plug be better for 951's as well? If so what kind/#? Thanks

Luke 05-16-2003 07:34 PM

NGK heat range of a 6 stock.

I've been told 1 heat range colder for every 75 hp over stock.

champ 05-16-2003 11:34 PM

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Chris Evans:
<strong>I've got a 86 951 with the Guru chips, reliaboost and 3 bar FPR. What plugs do you reccomend. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Hi Chris - over the years I have always used Bosch WR7DS - these are silver electrode plugs and I have always been happy with them.

I was given a set of NGK IRIDIUM IX plugs by a supplier (BPR6EIX) which I intend to install some time in the summer. I will post my impressions on them at that time.

I suspect that the Bosch silvers are still the best plugs for our cars. A cheaper solution would be the copper electrode WR7DC as an alternative or the equivalent NGK "v" groove

Danno 05-17-2003 05:47 AM

I like the NGK or ND plugs in 1 range colder than stock. There have been problems with the Bosch platinum electrodes falling out. The Ferrari guys absolutely HATE Bosch plugs and loves the ND ones.

ringo951 05-17-2003 11:47 AM

Danno So that would be NGK or ND with heat range of 5 ?

Russ Murphy 05-17-2003 11:55 AM

The heat range numbers are inversely proportional to the "heat", which is the opposite of the Bosch numbers. I've got the NGK R BPRES 7's and 8's I believe (daily driving and track).

Luke 05-17-2003 11:58 AM

The computers at stores like 'murray's' and 'autozone' have us listed as a Wr7dc, but that is a typo. Those are for the 16v S cars. if you are going the bosch copper route, get the 6.

or buy both sets and see the difference <img border="0" title="" alt="[Wink]" src="wink.gif" />

I'm running a champion plug right now w/ a 4 heat range. Seems to be doing the job just fine.

how about plug wires though? Anybody make a set of Accell 10mm's?

Danno 05-19-2003 07:06 PM

"Danno So that would be NGK or ND with heat range of 5 ?"

My 1988 Technical Information book shows a Bosch-WR7DC for the 944 Turbo which cross-references to:

NGK-BPR6ES or an
ND-W20EPR-U

One plug colder would be:

Bosch-WR6DC
NGK-BPR7ES
ND-W22EPR-U

While I have personally used brand-B plugs with no ill-effects, I haven't noticed them to provide any performance benefits. The long-lasting platinum may be considered a durability and maintenance feature, but definitely not performance.

However, I've seen way too many examples of engine-damage caused by loose platinum electrodes. Just had a car in our shop for a blown headgasket and some digital-MAF tuning. Figured the gasket was blown from either improper tuning (too lean in upper-RPMs), or from an overboost-condition due to an improperly configured wastegate. However, once I took it apart, I realized the blown headgasket was caused by the plugs:
http://www.gururacing.net/ImagesMisc...BoschPlugs.jpg

The customer had reported that the car had blown several headgaskets in the past year and that this last time, it wasn't even under load (aha! a clue). The #2 & 4 compression-rings had signs of severe detonation and had been blown completely outwards. Closer examinations showed that the #2 & #4 plugs had extended their electrodes:
http://www.gururacing.net/ImagesMisc...X4plugsBad.jpg
http://www.gururacing.net/ImagesMisc...4plugsBad2.jpg

While the spark can easily jump the gap in the broken electrode, the problem is heat-retention in the broken section. Without being connected to the main ceramic body, the electrode tip will retain a lot of heat and work like a diesel glow-plug to cause pre-ignition and detonation in the chamber. Now it may very well be that the cause of these broken electrodes was detonation caused by overboosting and a lean air-fuel mixture.

Looks like the Honda guys don't like brand-B plugs either: NSX-Prime: Replacing Spark Plugs

EDIT: re-linked photos

Luke 05-19-2003 07:27 PM

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Danno:
[b][i]my 1988 Technical Information book shows a Bosch-WR7DC for the 944 Turbo which cross-references to:
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">i'm probably mistaken then Danno. I remember an article about this somewhere. I'm going to search.

I remember doing a test 2 years ago with both the 7dc's and the 6dc's. I feel the 6dc is a better plug for stock 944 turbo.

didn't they come w/ champions from the factory anyway?

ELLSSUU 05-19-2003 08:40 PM

Danno remind me to never play Porsche Jeopardy with you.

nine-44 05-20-2003 12:31 AM

I heard the plugs from the 928GTS were a good plug, don't remember the # off hand. What do you guys think? They are the ones with 3 electrodes.

Danno 05-20-2003 06:16 AM

"I remember doing a test 2 years ago with both the 7dc's and the 6dc's. I feel the 6dc is a better plug for stock 944 turbo."

Hmm, never tried the WR6DCs in a stock configuration. They do work better with an upgraded car at higher boost levels.

"didn't they come w/ champions from the factory anyway?"

Hmm, don't know. The book I have indicates the Champion-RN9YC or Bosch-WR7DC on the '88+ 924S/944 while the 944 Turbo only got the Bosch-WR7DC. The early low-compression 944NAs got the Bosch-WR8DC plugs.

fast951 05-20-2003 07:26 AM

For higher than stock boost, I prefer the WR6DC.

Perry 951 05-20-2003 11:30 AM

I have run the Champions (RN9YC) since i have owned it, and my car seems to love them.

To each his own, but no platnum. Besides the funky running, I have also heard what Danno proved, electrodes dropping out. Never good to have that bouncing around a 6K rpm!

Peckster 06-20-2003 01:41 PM

I installed some Bosch wr7d platinums because that's all I could find that fit my car at crappy tire. I know some say they have failure problems, but how often can that happen? Bosch is a pretty reputable company, you'd think they'd fix a manufacturing problem pretty fast.

Does anyone actually know someone who's had those problem? I wonder if it's like that rumour about Mobil 1 causing oil leaks.


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