Spark Plugs

decoupe

decoupe

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I'm just about to fire up the engine (hopefully Saturday) after converting carbs to EFI. What about the spark plugs?

The block and head are 80's 535i with a little work done to the ports, 282 cam, 9:1 compression ratio, fully programable ECU engine management and GM coil packs instead of distributor and coils. The combustion chamber is probably different as well (?) so this is neither CS or CSi. Closer to a 6 series motronic engine and ECU but fully programable like mega squirt would allow.

The common wisdom I've heard and practised when it was carbs and distributor was to use the Bosch WR9DS plugs. The advice I'm getting from the local European specialists is to go with Bosch Platinums.

AndyM, what did you use?

Doug
 
decoupe said:
I The combustion chamber is probably different as well (?) so this is neither CS or CSi. Closer to a 6 series motronic engine and ECU but fully programable like mega squirt would allow.

The common wisdom I've heard and practised when it was carbs and distributor was to use the Bosch WR9DS plugs. The advice I'm getting from the local European specialists is to go with Bosch Platinums.

AndyM, what did you use?

Doug
Click to expand...

If your combustion chambers are that of an 80's M30, you might benefit from using the longer projected nose WR9LS plugs that were typically recommended by the manf. That is a silver/silber plug. http://www.bavauto.com/se1.asp?dept_id=25 http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=WR9LS and http://www.ultimategarage.com/shop/part.php?cPath=&products_id=2066&osCsid=pxswxprovez (just three examples of so-called published spark plug application recommendations) I have never heard anyone complain about silver spark plugs, except for the price.
Since their introduction in 1985 by Bosch, Platinum plugs have a "mixed" reputation among the older M10 and M30 crowd. That may have more to do with the older-style conventional ignition systems in those cars and/or the fact that the design of the engine obviously preceded the platinum plug design by many years. Factory recommendations for early 80's M30's was the silver plug mentioned above or the copper. I have tried copper, silver and even Champion fine wire gold on various engines and have concluded that proper heat range is probably more important than the electrode composition. Now that time has marched on, iridium plugs may be the best choice, but I have no personal experience with these plugs in any BMW engine. Like the silver, the only major criticism seems to be price. (In my current Csi engine, which is fairly close to stock, 9.5:1 I tend to favor NGK's BP5ES or BP6ES or Bosch W8DC's and W7DC's (I believe Bosch has given these plugs a new designation and a slightly updated design PN: 7505?). Over the years I have used other brands too, including Denso, Delco and Autolite "64". I should also note having used platinum plugs of various stripes. My experiences have not been particularly negative. However, I never noticed any increased benefit to using them.)

Lastly, given your engine's upgrades, you are more likely to find a field-tested opinion on the boards focusing more on engines similar to your, i.e., E24s, E12s E23's and the like. Remember, you have to judge for yourself how reliable any of this information is. :wink:
http://http://forums.bimmerforums.com/forum/showthread.php?t=1101010 see: http://www.dtbmw.com/tips/SparkPlugChart.pdf

http://www.bimmerboard.com/forums/posts/479690



FWIW, there has been a fair amount of discussion regarding plugs here.
http://www.e9coupe.com/forum/showthread.php?t=5277

http://www.e9coupe.com/forum/showthread.php?t=4643

http://http://www.e9coupe.com/forum/showthread.php?t=112

Good luck.
 
Last edited:
Lloyd:

Haven't tried the e24 forum but went to boschsparkplugs.com and typed in several different 535i/635csi combinations up to 1992 and several Platinum +2 plugs consistently came up for the m30 + motronic series of engines. Oddly the m series s38 used an entirely different plug. I typed in the stock number of the Platimum +2 they shipped to me today and it came up as the recommended plug for a 1987 635CSi.

Typed in the 1973 CS and it gave WR8DP+ or WR8DC+ as recommended.

Thanks,
 
Bert Poliakoff said:
M30's do not run right on platinums. Go Bosch silbers, or even, better NGKs
Click to expand...

Obviously, opinions vary on the subject of platinum spark plugs. And this isn't just a BMW phenomenon (http://www.benzworld.org/forums/w124-e-ce-d-td-class/1248048-bosch-platinum-spark-plugs-w124-4.html )

As noted in my earlier post, I tend to share Bert's opinion, although maybe not with the same fervor. Nevertheless, since your engine is a bona fide hybrid, it might fare differently. I personally don't see much to gain by going platinum, even with the most powerful ignition system available. Yet, there's not much harm in experimenting - - - other than to your bank account. Suffice it to say, most of us have made the same experiment.
 
Thanks all for the discussions. WR9LS will be the starting point and once I get the car running and dialed in I'm going to try the Platinums for sheer morbid curiosity. I don't expect any performance improvements - just curious if the new technology will work with the m30. The combustion chamber design is the only part of this engine that isn't been changed - should have mentioned that the pistons are not OEM - forged Arias and I believe flat tops.

Doug
 
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