Spark Plug Recommendation
 

I'm looking for spark plug recommendations for a 1980 930 and thought I would toss it out to the group. My previous mechanic was all gung-ho on Champion because that is all he had ever used but I would expect there may be better plugs available.

The car is set up for full time DE and PCA Club Racing in Prepared-Stock and is bone stock except for reliability mods. The closest thing to a performance mod are custom exhaust headers and an open exhaust. At the moment the ignition is stock but that is subject to future change as PCA allows for non-standard ignition.

When the car is being run it is on boost (.8 bar) most of the time.

Thoughts, recommendations and learned experiences are appreciated and thanks.

Jim
1980 930
1995 993

The origonal Bosch W3DPO.
The coldest and most durable plug possible, especially if you're going to be running it hard on a track.

I too was told this by a worthy 930 tuner.

The only reason to use a different plug is if you are going to do a lot of driving on the street in traffic or you simply want to save money as the platinum W3DPO plugs are expensive.

NGK BP8ES...

now get to work on that fuel system!! kidding, glad to see your getting back to work on that old beast!

As other members have suggested, Bosch plugs are the way to go.


-Dmitry

Ditto that. They're fine for street driving and the occasional lapse of pedal judgement.

NGK BP8ES is a great plug, for a mid-'80's Honda. Skip Starbucks for a week and buy the W3DPO's. Platinum 0.8mm electrode vs Nickel 2.5mm electrode.

Bosch are overpriced junk. NGK all day everyday... :)

Yeah, and they work great in my early 70's two stroke MX too.

What I eventually settled on was NGK R5671A-7 which worked well with my MSD ignition.

Years back when I was playing this plug game, for me at least the W3DPO was a tad too cold. Different strokes, different tunes, different folks.

NGK, Bosch, Champion, yadda, yadda, yadda.

Actually, use whatever YOUR engine requires. As you hinted to before, running a stock ignition system, vs a higher power aftermarket one, will require different plugs. (mostly in the change of heat range). Some of the other factors as others have mentioned are, heavy track use, heavy street driving, aftermarket parts, higher boost, C/R, EFI, CDI, etc, etc

I have the race M&W CDI ignition on my car, and I run NGK. They work best for my application, but are not that cheap ( $12 a piece x12)

Chris Carol at Turbokraft recommended NGK Iridium BKR8EIX Spark Plugs to me a couple years ago so I got some.

They work great so now they are my favorite. They have a very wide heat range and would work good in any 911 motor.
Read the reviews... everyone gives them 5 stars.
You can get 4 of them off ebay for around $32 shipped or $27 shipped on amazon when you buy $35 of stuff. 2 more of them is just a little more so I guess they are around $40 for 6 of them.

4 x NGK Iridium IX Spark Plugs BKR8EIX Colder Heat Range 8 for Race Tuned Modifi

https://www.amazon.com/NGK-Iridium-Spark-BKR8EIX-2668/dp/B00332810I

These are the plugs I use as well, in the P car and the plane. They work great, and are cheap enough that I don't even bother cleaning, just replace with new every oil change.

it depends on which ones you get.

I had the bosch platinums in my mazda PU. for some reason I put in something like an autolite. ran MUCH better and my gas mileage went up 2-3 mpg.
yes those bosch plat's are crap.
bosch coppers in a 911 though

W3DPO for the 930.
also been told the bosch CS
I have copper NGK in there right now.

track and hard driving you want the 3, around town you can do 4.

OK for the inductive setups that Chris builds. Resistor plugs ar No Bueno for CDI ignition. Analyze the engineering, not the person.

Okay guys, now I am scratching my head period changing my plugs but I can't remember what I ran as a gap. Running NGK plugs with M&W pro CDI.... twin plug.. 16psi boost on pump gas, and target of 26 psi on E85

Ha!
Sorry I can't help with the question, but.
Welcome to getting older and developing CRS. Time to get a notebook.

Read the tech article on Performance Developments web site about spark plugs.

performancedevelopments.com – Engine Design. Read that you should then know what to do.

Don't let anyone tell you what to use. Your engine and the way you drive it may be different and spark plugs are not something to take for granted. Air cooled race engines don't give you much of a safety factor and can hurt themselves every quickly. With summer coming and hot days, these engine don't like over heated spark plugs. Engine rebuilds are expensive.

I wrote this sometime ago paraphrasing what is written in that article.

The best plugs to use are ones you can readily buy.

The choice is based upon what the engine wants not what I may say or anyone else. I suggest you run what you have already and do a plug check. Then read the plug and it will tell you what plug to use. If you have not run the engine yet start off with a cold plug and work up, hotter from there. Any of the main plug manufactures can help here.

From the description of the other plug suggested, that seems a little to warm for a track engine and it has a firing end not the best for a race engine. Air cooled race engines run hot head temps and over the the length of a race, the plug will have issues trying to dissipate the heat back into a hot head. You have to think about the heat over an entire race length. This often requires a plug temp range cooler than what you think and what the plug reads. Multi ground electrodes are for emissions reasons making sure the plug fires in all directions to burn the most or more complete mixture. Remember the plug only fires on one electrode at a time. Not all three at once. Within the cylinder the plug will fire in the direction of the less pressure or least Resistance.

That plug also has a thick center electrode which requires more energy to fire. You state you have Inductive coils so the energy released is all about battery voltage, coil winding's and the dwell settings. A fine wire plug will require far less energy to fire. Battery voltage and or Alternator condition are all helped by a fine wire plug. The precious metal electrodes, Iridium are better for wear as well. They will last longer than the old fashioned copper or Platinum plugs. Go with a single ground and you open up the flame front and will gain faster combustion. The more electrodes the more you plug up the flame travel.

I'd suggest a colder plug and if the piston clearance is there, go with a projected type to start. I only know NGK so a 9 heat range would be a good place to start. Go with a fine wire Iridium and a projected firing end, and choose one that has a wide gap. They are already gaped so don't touch them. And do not use any anti seize on the plug. Then do a plug check and read the plugs. If you are unsure of what to do, there is a good read about spark plugs on performancedevelopments.com – Engine Design web site in their tech papers.

To run a plug that is too warm can cause all sorts of problems. It will cause pre-ignition type detonation and will rattle the rings first. As the piston comes up to TDC under compression and the firing event happens the top ring is twisted in the groove. It turns down under pressure to help the sealing against the liner walls. If the pressure between the fire band and the top ring becomes larger than overall cylinder pressure from pre-ignition detonation, it bounces the ring back and forth within the groove under very high frequency. This is what breaks the ring. Often the engine still runs or seems to for average owner, and appears to use a little more oil and breathes a more heavier. Broken rings cause damage to the Cylinder walls and pound out the ring grooves.

Choose carefully and let the engine tell you what it wants, not me.

^^^^ Thank you M42!! Yes, I remember reading that article that Neil had. Thanks for your input as well. Its just been a minute since I have read this, and wanted to make sure about this info.
I also remember something about having the gap smaller, the more boost you run.