AlexL.

I know there are dozens of postings on plugs which I have reviewed but none have answered my question entirely. I have a '88 944 Turbo "S" with a weltmeister chip, Test Pipe, Lindsey Boost Enhancer, K&N cone filter. With these mods I suspect I am gaining approx. 50-75hp over stock. With these mods do I need to run a colder plug? I have heard NGK makes a great plug so I purchased 4 BPR6ES plugs which are the recommended plugs for the stock car. Do I need to go with the BPR7ES plugs or do you recommend a different plug altogether? Thanks in advance.

Danno

Get your car dyno-tuned. I suspect you're around 250-260rwhp @15psi (+30-40hp). Yeah, you should go to one plug colder than stock if you have boost-increasing upgrades:

Bosch-WR6DC
NGK-BPR7ES
ND-W22EPR-U

Did you see these threads on plugs?
Cool Spark Plug Info
What plugs do you reccomend?

Also for those who are thinking about it, multi-electrode plugs are a marketing gimmick. It's impossible to gap each and every electrode exactly the same, so the spark will end up arcing to the closest electrode and that's it. Once the air-fuel mixture is ionized between that electrode, the resistance drops dramatically and the rest of the spark will simply go through that one electrode.

tazman

Should you still gap them to stock specs?

951and944S

Exactly Danno, the objective is to remove, not introduce areas that can get hot enough to cause pre-ignition.
When building a cylinder head, you *should* insert the plugs you plan to use and remove any spark plug thread not in use from the cylinder head casting for just this reason.

Terry S.

Mike1982

Yea, I heard that if you gap the plugs just a little wider it helps improve mpg and performance, is this true anyone??..

Danno

Hmmm, increasing the gap will cause a higher-voltage spark to jump across, provided your ignition system/coil can deliver the required voltage. I've run them as large as 0.050" but haven't noticed any differences and I've had to run some cars at 0.025" to prevent high-RPM misfires (coil may be going bad). The only time I've been able to improve MPG and performance has been with tweaking the fuel & ignition-timing maps on the chips themselves.

Bengt Sweden

I thought the idea of multi electrode plugs was to improve the longevity of the plugs. When the favored electrode gets a bit worn the next will be used and so on until you are back at the first one?

Bengt

86944turbo

It's also important to insure that the plug of your choice, is not extended into the comb. chamber. This, for the reasons mentioned above and others. Sounds simple, but you would be surprised. My motor uses a fairly wide spacer to insure this. Replaced the W2CS with some ultra exp. Bosch plugs recently. Do not have the #'s at hand. Probably not pertinent for your app. Single electrode and those Beru wires are just fine. Been told and believe that the Nology wires do not produce enough HP gain to carry their own weight.

J Chen

Hi,
Anyone out there have experiences with the iridium plugs ?
If so are they any good ?

adrial

I just picked up some plugs from Powertech (somewhat local Porsche shop)...and the turbo guru gave me some WR5DC plugs...

I'm not sure if that was a mistake or not because he said they were 1 step colder than stock...which is WR7DC....

RJP 951

I've been looking for the colder plugs (NGK, Bosch or ND) locally and just cannot find them. Are you guys buying these at the local auto parts stores? Mail order?

Thanks
Ron

adrial

I couldn't find even the standard plugs at local auto parts stores...check the local Porsche mechanics along with the dealer...

951and944S

Adrial, I thought I've seen that WR7dc's were the "standard" plug for 951's but after looking over a Chilton's manual today, they list WR6DC as standard so there's some conflicting info there on what the specification is.

The guy you spoke of gace you 5DC's, one step colder than what my information says is the required plug but I've also seen it many places that the 6DC's would put you one range colder.....?

Let us know if you run into any problems with those 5's....

Terry S.

adrial

Terry,

According to the Porsche factory manuals the WR7DC is the standard 951 plug.

Bill

I just installed a set of NGK iridiums, one step colder than stock. I only have about 200 miles on them, but so far so good. Idles and revs smooth. The thing I like the most about them is the small electrode. It reduces the possibility of a hot spot in the combustion chamber and thus is an additional feature to help combat pre-ignition. I am running 18psi of boost.

The electrode is made of iridium and is 4 times harder than the common electrode, thus should last longer. But that would only be a bonus, as I am more concerned in combating pre-ignition.

I purchased them from www.sparkplugs.com and they have a good technical write-up on the iridium plugs.