Kevin Michael

What's the recommendation on these?
Thanks,
Kevin

jorj7

I would recommend them. They work in my 90 s/c.



(I use the stock ones).

AO

Funny George... LOL!

I think most people are running plugs one range cooler (I don't remember what that was).

Jim R.

I've had a set of Beru Silverstone in one heat range colder than stock for about 2.5 years. I think S7, but I'm not positive. Nice tan color whenever I pull a few to check. I don't know if they work any better than stock, but they have worked well so far.

Jim

Bill Ball

Some of the SC guys use one heat-range colder, some don't. I did based on the kit maker's recommendation and it seems to be fine that way.

SwayBar

It becomes more important as max boost increases, but the safest plug to run is as cold as possible without fouling, and/or the engine missing at idle/cruise which is a plain nuisance.

Todd in Green Bay who built my wet-sleeve motor gave me plugs which are 3 heat-ranges cooler than stock, and I've had no issues with fouling running NA. Also, those plugs do not have a protruding electrode either which is safer yet.

So I am sure you can run the same, and not have any drivability issues, while having a cooler/safer plug in while under boost.

Kevin Michael

I need a part # cause I am totally stupid about spark plugs! The part store said the computer came up for Bosch Platinums, but my better sense says I need a copper plug, Just don't know which one/heat range to get.
Thanks,
Kevin

V2Rocket

Bosch copper

Kevin Michael

Thanks V2, know what heat range for a boosted shark?
Kevin

SwayBar

The plugs I have are NGK, but I don't know their number offhand, so when I get home I'll get their number for you.

Kevin Michael

Thanks, Sway!

hacker-pschorr

Many places don't even carry the copper plugs anymore - they like pushing the platinums.

I've been running one range cooler Bosch Copper in my car since it was boosted, no issues.

Sway is right on you should run the coldest plug possible without fouling or rough running. So it can really depend on your driving style and where you are. For example, if 75% of the time you are in stop / go traffic plugs become easier to foul.

Stock Spark Plug = Bosch WR8DC (for the 4.5 liter motor, all others WR7DC)
The 8 is the heat range. Bosh plugs are colder as the number drops. So one range cooler is WR7DC.

NGK plugs are the exact opposite. As the number increases the heat range drops.

Bosch WR8DC = NGK BPR5ES
Bosch WR7DC = NGK BPR6ES
BOsch WR6DC = NGK BPR7ES

Some conversion charts show the NGK BPR6ES crosses over to the 6 & 7 Bosch plugs. They are not an exact cross over.

The plugs Sway is using are the same NGK part number with the "P" removed. The "P" stands for "protruding electrode". These are actually high performance snomobile plugs. I know many tuners using these in high boosted motors. One in GB is a 711whp Eclipse running pump gas.

Example:
NGK BR5ES = Stock heat range with non protruding electrode
NGK BR6ES = One range colder with non protruding electrode

Any one of the above plugs will work in a 928. How cold you can go will depend on a few things. Mr.Murf has been running stock plugs since day one. Since his #1 goal is tuning for a kit, he likes to keep everything 100% stock that he can. This makes it easier down the road for people to maintain the car.

Tim had hesitation & idle problems with the non-protruding electrode plugs on his 87 (what Sway is using on his track car). So they may not be the ideal setup for a street car. Todd is sticking with them (and 2-3 ranges colder) for safety. He's pushing his car much further than anyone else I know of (24psi with one motor) and colder plugs do help fight off detonation.

EDIT - Stock factory plugs for 4.7 - 5.0 - 5.4 liter cars is Bosch WR7DC. I was confusing my above info with the 4.5 plugs.

Kevin Michael

Erik, That right there is a solid piece of thorough information! You da man. Stock in an 87 is Bosch WR7DC, so I am thinking I need Bosch WR6DC or NGKBPR7ES. Is that right?
Thanks,
Kevin

hacker-pschorr

Whoops - stock plugs on the early OB's are WR8DC. Had those on the mind.

Like I said with the NGK conversion, some site list the BPR6ES as a replacement for both the 6 & 7 Bosch plug. They must fall somewhere in the middle of each other. You will not hurt anything running too cold of a spark plug. Just check them often & if they start to foul, go one hotter.

Did you fix your running problem?

Kevin Michael

BTW fellas, should of mentioned it before, I pulled the plugs and 3 were nice and tan, and the other 5 were sooty black. Makes no sense to me,any of you ever seen this?
Kevin