So what the spark plug of choice these days?
I'm running a 3.5 liter, with dual Weber 38's and Crane electronic ignition.
I'm running a 3.5 liter, with dual Weber 38's and Crane electronic ignition.
Plugs of choice?
- Thread starter Jellobmw
- Start date
I run Bosch Silbers, WR9LS, in both my 2800CS and my 3.5 powered e12. Great results in both. The WR9DC also works well, costs half of what the Silbers do, but doesn't last quite as long. My e12 is a daily driver and the plugs are almost 2 years old and look great.
re Velocewest's recommendation
Velocewest touts WR9LS as his plug of choice with WR9DC as an optional choice. Based upon Velocewest's opinion and the fact that I have a number of WR9LS's, I intend to try them - but have not yet done so.
For what its worth, I have been fairly satisfied with W7DC W8DC (Bosch) BP6ES and BP5ES (NGK) plugs. Colder plugs for freeway - hotter for mostly city driving. This has also been my experience with a bavaria, coupes, 3.0Si and several 2002's.
Velocewest sounds very knowledgeable and if he is listening, perhaps he could explain any quantifiable performance or economy advantage(s) to the extra long extended nose plug (WR9LS) over the standard extended nose (W9DC). Likewise, other than avoiding radio interference, what is the advantage for the resistor plugs? Please bear in mind that most of our applications involve old school carburetors as well as the famous DJetronic - neither of which have computers that may require this resistance for feedback to operate efficiently.
Thank you in advance.
Velocewest touts WR9LS as his plug of choice with WR9DC as an optional choice. Based upon Velocewest's opinion and the fact that I have a number of WR9LS's, I intend to try them - but have not yet done so.
For what its worth, I have been fairly satisfied with W7DC W8DC (Bosch) BP6ES and BP5ES (NGK) plugs. Colder plugs for freeway - hotter for mostly city driving. This has also been my experience with a bavaria, coupes, 3.0Si and several 2002's.
Velocewest sounds very knowledgeable and if he is listening, perhaps he could explain any quantifiable performance or economy advantage(s) to the extra long extended nose plug (WR9LS) over the standard extended nose (W9DC). Likewise, other than avoiding radio interference, what is the advantage for the resistor plugs? Please bear in mind that most of our applications involve old school carburetors as well as the famous DJetronic - neither of which have computers that may require this resistance for feedback to operate efficiently.
Thank you in advance.
Re: re Velocewest's recommendation
I don't know how knowledgable I am, but I know what has worked. A mechanic I trust (that's a very small population) who has been wrenching on BMW's almost as long as I've been alive (he's not the youngest mechanic) told me I should use the WR9LS in the e9. I did, it works. The car has not had the plugs changed in about 5 years because circumstances have limited its mileage in that time to about 3,000 miles. This may be a better endorsement than saying I got 2 years on a daily driver -- sitting around not running is a good way to get fouled plugs.
Re the use of the Silbers in the e12 -- the engine in that car started life in an e28, has the Motronic DME, and the WR9LS is the factory recommended plug.
On a pseudo-technical note -- if you look at the placement of the plug inside the comustion chamber in an M30, you'll see that it sits right next to the intake valve, right in the path of the incoming A/F mix. Since the combustion chamber is the same on all M30 heads from the first 2500's up through the M30B34 in 1988 or so, BMW must have found a good reason to start recommending the long reach plugs. The additional 2mm of extension of the electrode of the "L" plug does put the spark further into the path of the incoming mix, which I suppose helps get a better combustion event. For the record, it doesn't put the electrode appreciably closer to the piston, due to the shape of the combustion chamber and the angle of the plug hole. You know, Dreikurbelwirbelwannenbrennraum... :wink:
And, y'all can call me Tony, it's much easier to type.
PS: Related Thread More spark plug talk
I don't know how knowledgable I am, but I know what has worked. A mechanic I trust (that's a very small population) who has been wrenching on BMW's almost as long as I've been alive (he's not the youngest mechanic) told me I should use the WR9LS in the e9. I did, it works. The car has not had the plugs changed in about 5 years because circumstances have limited its mileage in that time to about 3,000 miles. This may be a better endorsement than saying I got 2 years on a daily driver -- sitting around not running is a good way to get fouled plugs.
Re the use of the Silbers in the e12 -- the engine in that car started life in an e28, has the Motronic DME, and the WR9LS is the factory recommended plug.
On a pseudo-technical note -- if you look at the placement of the plug inside the comustion chamber in an M30, you'll see that it sits right next to the intake valve, right in the path of the incoming A/F mix. Since the combustion chamber is the same on all M30 heads from the first 2500's up through the M30B34 in 1988 or so, BMW must have found a good reason to start recommending the long reach plugs. The additional 2mm of extension of the electrode of the "L" plug does put the spark further into the path of the incoming mix, which I suppose helps get a better combustion event. For the record, it doesn't put the electrode appreciably closer to the piston, due to the shape of the combustion chamber and the angle of the plug hole. You know, Dreikurbelwirbelwannenbrennraum... :wink:
And, y'all can call me Tony, it's much easier to type.
PS: Related Thread More spark plug talk
Re: WR9LS
It has been at least 12 months since I last pulled the plugs in this coupe and found they were all lightly dusted tan and perfectly servicable. Swapped the W7DC's for the WR9LS and noticed very little difference until upper RPM level (+3500) mucho pinging. Pulled the plugs and discovered they were perfectly white - so unfortunately - for this particular application (high compression CSI) - it appears we need a colder plug or we need to retard timing.
Put old plugs back in and pinging is gone. Guess I 'll try them on a 2002 next.
Tony, could you please opine regarding your use of resistor plugs? As an aside, I read somewhere that the extended nose plugs and multi-electrode plugs may be slightly advantageous to the extent they occupy more space in each combustion chamber and therefore increase the compression. On the other hand I recall hearing from the purported bench flow experts that sticking a plug in the middle of the chamber may promote flame expansion at the expense of overall gas flow.
Thank you again for your thoughts on the subject.
It has been at least 12 months since I last pulled the plugs in this coupe and found they were all lightly dusted tan and perfectly servicable. Swapped the W7DC's for the WR9LS and noticed very little difference until upper RPM level (+3500) mucho pinging. Pulled the plugs and discovered they were perfectly white - so unfortunately - for this particular application (high compression CSI) - it appears we need a colder plug or we need to retard timing.
Put old plugs back in and pinging is gone. Guess I 'll try them on a 2002 next.
Tony, could you please opine regarding your use of resistor plugs? As an aside, I read somewhere that the extended nose plugs and multi-electrode plugs may be slightly advantageous to the extent they occupy more space in each combustion chamber and therefore increase the compression. On the other hand I recall hearing from the purported bench flow experts that sticking a plug in the middle of the chamber may promote flame expansion at the expense of overall gas flow.
Thank you again for your thoughts on the subject.