Anyone tried Bosch W6DC plugs?

[Gunter]

If you have, what type engine, CR and octane?

Thx.

[T77911S]

are you thinking of going to a colder plug?
i put in a set of USED W4's just to test. i have put about 2000 miles on them including a 1200 mile round trip to nashville. i expected to foul them since they were so cold, plus i run a tad on the rich side. i was using W7's. i can not tell the difference except i think the oil temp runs a little hotter and is quicker to go up, although it has not gone over 210. paulporche went to a hotter plug and i think his temp went down. i think the reason for the higher temp with cold plugs is that the extra heat from the plug is now going to the heads.
i was hoping i could get away with 87 octane gas, but it did not seem to help.
when checking the plugs, they came out black,( expected), except the center electrode was clean, (not the porcelin part). therefore the no fouling.
after 600 miles of hiway driving i checked them and they looked very good!
in the end i plan on using W5's, or the NGK equal.

[Paulporsche]

Gunter,

This is some of the info I was looking for in a post a couple of days ago.

In your case, wouldn't that be hotter for you? I seem to remember you were running 5s. I've run 7s in my engine , which is somewhat similar to yours, for about 18 years. My mech recently put in 8s because they were black, but I'm thinking that is only because my mix was too rich, compensating for a bad WUR. I use Sunoco 94 w/ 10.1:1 CR.

The spec for stock 78/9 is 8s. The spec for stock 80 is 5s. That's a big difference. My engine is an 80 originally, w/ a 78 WUR. I'm going to look @ my 8s soon. I think I may go back to the 7s. My driving is mixed; about even between highway and city.

[Gunter]

As I understand it, W6 is a hotter plug than a W5.
Higher heat values indicate colder plugs. For example W225T30 (W5DC) is a colder plug than W145T30 (W8DC)

Bosch and NGK heat ranges run reverse.

Bosch W6DC is a hotter plug than W5DC. (W5 = higher heat value)
NGK BP7 is hotter than BP8.

T77911S:
What CR do you have?
87 octane has a much greater possibility for detonation than 90+
IMHO, if a close inspection of the porcelain tip with a magnifier shows tiny cracks, or any damage, a hotter plug is in order.

[Paulporsche]

Why are you considering the change? Did you find cracks, etc?

[T77911S]

Originally Posted by Gunter

As I understand it, W6 is a hotter plug than a W5.
Higher heat values indicate colder plugs. For example W225T30 (W5DC) is a colder plug than W145T30 (W8DC)

Bosch and NGK heat ranges run reverse.

Bosch W6DC is a hotter plug than W5DC. (W5 = higher heat value)
NGK BP7 is hotter than BP8.

T77911S:
What CR do you have?
87 octane has a much greater possibility for detonation than 90+
IMHO, if a close inspection of the porcelain tip with a magnifier shows tiny cracks, or any damage, a hotter plug is in order.

W6 is hotter than W5

yes, bosch and NGK are reversed. W5 bosch = BP7 NGK, i think. check NGK's site, they have some good info of plug heat range. also do a search on "reading sparkplugs".
i have a stock 77s, 8.5 CR. the general rule is the higher the CR, the colder the plug. 930's use a W3 or W4.
if your porcelain has cracks, it is most likely due to too much heat.
if you are not sure what heat range to use, i would start cold and work my up to the best heat range.

[T77911S]

this is from NGK's site.

Pre-ignition: is defined as the ignition of the air/fuel mixture before desired ignition timing

Detonation: is a spark plugs worst enemy. It can break insulators and ground
electrodes. Spark plug temperatures can reach in excess of 3000 °F.
Detonation, in simple terms, is a violent uncontrolled burn of the air/fuel

mixture, which occurs when excessive heat and cylinder pressure causes the air/fuel mixture to spontaneously ignite.

By examining the insulator firing nose color, an experienced engine tuner can determine a great deal about the engine's overall operating condition.
In general, a light tan/gray color tells you that the spark plug is operating at optimum temperature and that the engine is in good condition. Dark coloring, such as heavy black wet or dry deposits can indicate an overly-rich condition, too cold a heat range spark plug, a possible vacuum leak, low compression, overly retarded timing or too large a plug gap. If the deposits are wet, it can be an indication of a breached head gasket, poor oil control from ring or valvetrain problems or an extremely rich condition - depending on the nature of the liquid present at the firing tip.




The temperature of the spark plug's firing end must be kept low enough to prevent pre-ignition, but high enough to prevent fouling. This is called "Thermal
Performance", and is determined by the heat range selected. A colder heat range is necessary when the engine is modified for performance, subjected to heavy loads, or is run at a high rpm for a significant period of time.

However, when compression is raised, along with the added power comes added heat.

Since spark plugs must remove heat and a modified engine makes more heat, the spark plug must remove more heat. A colder heat range spark plug must be selected and plug gaps should be adjusted smaller to ensure proper ignitability in this denser air/fuel mixture.

Typically, for every 75-100 hp you add, you should go one step colder on the spark plug's heat range. A hotter heat range is not usually recommended except when severe oil or fuel fouling is occurring.

It is a common misconception that spark plugs create heat. They don't. A heat range refers to how much heat a spark plug is capable of removing from the combustion chamber.

Selecting a spark plug with the proper heat range will insure that the tip will
maintain a temperature high enough to prevent fouling yet be cool enough to prevent pre-ignition. selecting a spark plug in the proper heat range will ensure that the spark plug itself is not a hot spot source.

ignition timing directly affects the firing end temperature of the spark plug.
Advancing the ignition timing prolongs the time to compress the burning gases. The pre-ignition temperature also elevates gradually, since the pressure and
temperature of the combustible mixture is low before ignition. Advancing your
timing elevates firing end temperatures.

the by-product of increased compression is the elevation in cylinder temperatures.

NGK Spark Plugs recommends dropping heat ranges and altering Air/Fuel mixtures and timing as needed. It is very important to dissipate the excess heat from the
combustion chamber in order to prevent pre-ignition.



Air/Fuel Mixtures seriously affect engine performance and spark plug operating
temperatures.

Rich air/fuel mixtures cause tip temperature to drop, causing fouling and poor
driveability
Lean air/fuel mixtures cause plug tip and cylinder temperature to increase,
resulting in pre-ignition, detonation, and possibly serious spark plug and engine
damage

Higher Compression Ratios/Forced Induction will elevate spark plug tip and
in-cylinder temperatures. As compression increases, a colder heat range plug,
higher fuel octane, and careful attention to ignition timing and air/fuel ratios
are necessary. Failure to select a colder spark plug can lead to spark plug/engine
damage

[Gunter]

So, back to the original question: Has anyone tried W6's?
On what engine-type and CR?

[jbrinkley]

yes I did run them in my turbo 3.2, stock CR. Also, used wr5, and wr7, probably doesn't help you much.
dynamic comp. gets up there a bit. 93 oct always

930 uses w3dpo i think. most of them go with 4's. carreras are 7's stock and I'm almost 100% sure the equivalent to a bosch 7 is NGK 6 and a champion 8
and like they said bosch low number is cold, ngk low number is hot
I didn't like the 5's. I settled on the 6's, i put miles on all three and chose what I thought best.
they are cheap, try them all.

[Paulporsche]

Gunter,

What symptoms are you getting?

[Gunter]

Paul:
Have you tried W6's ?
Did you ever list details of your engine?
Year/type: 930/??
CIS: What year/type ??
Compression Ratio: ??
Distributor Bosch number: ??
Vacuum advance/retard connected ??
OEM or re-curved?
If recurved, to what specs??

[Paulporsche]

Gunther,

I've always used Bosch 7s in my engine, which I've had for something like 18 yrs/80,000 mi.

It was an 80, so I think it's a 930/7.
1980 CIS w/ no lambda control using a 78 WUR w/ vacuum (045)
CR is approx 10:1. It is set up for twin plug but I'm only using single, so I use Sunoco 94.
I'm using a 74S distrib w/points, so there is vac retard only. I don't know the number.
It apparently has been recurved, reaching total advance @ 2000 rpm.
Timing is set @ 0TDC @ idle, which gives me 32 total advance (I think. I'm not 100% sure on that).

[Gunter]

US '80 would be 930/07; it should be stamped on the case to the right of the fan-post to confirm.
Sounds like it has some mods.
How do you know CR is 10.1 ?
What crank and P/C's?

Someone must have changed the gear on the crank for the 74-distributor to work.
Vac retard only? You mean advance?

I would be concerned about it reaching full advance at 2k.

[Paulporsche]

Gunter,

I've got a little investigating to do. I'll get back to you on this.

I can confirm 930/07, gear swap to allow opposite diz rotation and retard only.

[Gunter]

O.K. see what you can find out.
Never heard of a retard-only distributor.....................but, maybe there is.
At first glance, it seems to make no sense, IMHO.

[Paulporsche]

According to poster psalt, the retard was used to reduce HC emissions @ idle by about 15%.

[unclebilly]

On a 2.7, 9.8:1 compression, webers with 34mm venturis and 140 mains, and DC40 cams, MSD Blaster and 6-AL what plugs should I be running?

WR5DC or the W5DPOs? I can get a delco cross over to the W5DPOs - thoughts?

[Gunter]

Hard to say.
W5DC worked for me on 9.8 CR with CIS and Bosch CDI but that may not be good for your set-up.
MSD requires a larger gap on the plugs, I think.

I am trying NGK BP6ES and will have to see how they work out.

The standard test is that you go for a hard run, shut down, take out a plug and check.
You don't want to have them look too white.
The easiest plug to reach is either #4 or 5.
I use Never-seize on the threads and ~20 ft-lbs torque.

[Steve@Rennsport]

Originally Posted by unclebilly

On a 2.7, 9.8:1 compression, webers with 34mm venturis and 140 mains, and DC40 cams, MSD Blaster and 6-AL what plugs should I be running?

WR5DC or the W5DPOs? I can get a delco cross over to the W5DPOs - thoughts?

First,....IMHO, 140 mains are pretty darned lean for a high-compression 2.7 like yours. Be careful as the consequences are not inexpensive.

One of the biggest advantages of using an MSD is the ability to use large plug gaps (.040-.050) that are key for best idle, drivability and more HP. The Bosch DPO's cannot be opened up so I use either DC's or DS (silvers). NGK's are also very good, as well.

I've always had poor luck using Yankee plugs so I stick with Bosch or NGK.

[unclebilly]

Steve,

I am at 3400 feet elevation. I also have 150 jets and 36mm ventries if i have to make a change.

How much gap should I be running on NGK BPR7ES? I am going to try 0.050" - does this seem about right?