Chris Evans

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

NGK heat range of a 6 stock.

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

champ

</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

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

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

Russ Murphy

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

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

"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:


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:



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

</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

Danno remind me to never play Porsche Jeopardy with you.

nine-44

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

"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

For higher than stock boost, I prefer the WR6DC.

Perry 951

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

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.