[Steve.breen@dinan]

Many of you have kept up with Johnnyr135's situation, where it was discovered that fouled spark plugs were the cause of misfires in his car. Since lots of us are driving high-output engines, it's worthwhile to explain in greater detail why this happened.

A higher output motor requires a colder plug, the higher the colder. This is to prevent the plug from glowing red and causing a hot spot in the combustion chamber, which would lead to detonation. Often misinterpreted, the heat range of a spark plug does not refer to the heat of the spark, rather it refers to the amount of heat retention and thereby the plug's ability to clean off the fuel that gets deposited on its porcelain insulator. The conflict here is that the hotter the plug, the better it cleans itself but the more it detonates, while a colder plug will detonate less but foul more easily. A plug fouls when it doesn't clean itself, leaving fuel deposites which cause the ignition to conduct across those deposits and not bridge the gap.

Lastly, since an engine's air/fuel ratio is richened for cold start, plugs are more susceptible to fouling when a car makes many short trips because there isn't sufficient time for them to clean themselves.

There's much more to spark plugs, but I hope this helps. Let me know if there are any questions.

[Bubbles]

Originally Posted by Steve.breen@dinan

Many of you have kept up with Johnnyr135's situation, where it was discovered that fouled spark plugs were the cause of misfires in his car. Since lots of us are driving high-output engines, it's worthwhile to explain in greater detail why this happened.

A higher output motor requires a colder plug, the higher the colder. This is to prevent the plug from glowing red and causing a hot spot in the combustion chamber, which would lead to detonation. Often misinterpreted, the heat range of a spark plug does not refer to the heat of the spark, rather it refers to the amount of heat retention and thereby the plug's ability to clean off the fuel that gets deposited on its porcelain insulator. The conflict here is that the hotter the plug, the better it cleans itself but the more it detonates, while a colder plug will detonate less but foul more easily. A plug fouls when it doesn't clean itself, leaving fuel deposites which cause the ignition to conduct across those deposits and not bridge the gap.

Lastly, since an engine's air/fuel ratio is richened for cold start, plugs are more susceptible to fouling when a car makes many short trips because there isn't sufficient time for them to clean themselves.

There's much more to spark plugs, but I hope this helps. Let me know if there are any questions.

Good info, I just posted this question. So if you drive short distances for a commute, you should expect your spark plugs to have a reduced useful life.

[f30er]

Great info, thanx!!

[M3EST]

Interesting info.

[NPDAN]

Hey Steve, thanks for the info.. Do you suggest upgrading the spark plugs?

[Jake C]

And if you do suggest upgrading the spark plugs. What do you suggest as a good replacement spark plug?

- J

[ezatnova]

With all the warning/notification gizmo and gadgetry that our cars have now (no oil stick, electronic brake pad warning, etc etc) it would be nice if somehow the car told us if the spark plugs needed replacing. I know that's kind of tough...I'm just saying, it'd be nice and take some of the guesswork out of a poorly running car. It's one thing in a car that takes 10 minutes to check all of the plugs, but, we all know it's not like working on a GM engine with these cars

[hotrod2448]

To my knowledge there are still no replacement plugs for this engine just OEM plugs. Has that changed?

[sajakh]

Originally Posted by ezatnova

With all the warning/notification gizmo and gadgetry that our cars have now (no oil stick, electronic brake pad warning, etc etc) it would be nice if somehow the car told us if the spark plugs needed replacing. I know that's kind of tough...I'm just saying, it'd be nice and take some of the guesswork out of a poorly running car. It's one thing in a car that takes 10 minutes to check all of the plugs, but, we all know it's not like working on a GM engine with these cars

The N54 DOES tell you on the maintenance menu. I got mine changed at 42K miles. It is not (to my knowledge) an iridium plug but a platinum one so expect a change every 40-60K miles.

[ezatnova]

Originally Posted by sajakh

The N54 DOES tell you on the maintenance menu. I got mine changed at 42K miles. It is not (to my knowledge) an iridium plug but a platinum one so expect a change every 40-60K miles.

That's just a time/milage thing. That doesn't actually "detect" fouled or poor condition plugs.

[Mr. 5]

I would love to change my plugs out with a colder plug.
I'm not worried about the plug not cleaning itself. If I want to clean the plug then I'll just take it to red line a couple times.
I'm just waiting for someone to come out with one.

[sajakh]

Originally Posted by ezatnova

That's just a time/milage thing. That doesn't actually "detect" fouled or poor condition plugs.

I thought it was based on plug condition since my dealer was surprised at the computer saying to replace the plugs so soon. My car was the first for this dealership. I don't do a lot of short trips and most of my mileage is hwy. I could be wrong though

[Sniz]

Originally Posted by Mr. 5

I would love to change my plugs out with a colder plug.
I'm not worried about the plug not cleaning itself. If I want to clean the plug then I'll just take it to red line a couple times.
I'm just waiting for someone to come out with one.

+1

[Nyulak]

My car needed plugs around 45k miles as well. The maintenance standard for the 335i calls for spark plugs at 60k miles. My car was also the first car with the N54 to have its spark plugs changed at my dealership. I was notified by the car to have the plugs changed.

[Sniz]

I changed my own spark plugs at about 25k miles, the car was noticeably smoother after I changed them out. It wasn't the placebo effect, my GF actually commented on the car being smoother without me telling her I swapped them out.

BMW is obviously trying to push out the maintenance as far as possible to minimize their costs in the free 50k zone.....screw that. I bought this car and I believe in preventative maintenance.....

[stimpy]

Originally Posted by Jake C

And if you do suggest upgrading the spark plugs. What do you suggest as a good replacement spark plug?

- J

Dinan Spark Plugs - $2000.00.

I kid I kid ... Thanks for the info!

[ybbiz34]

Nice. As always, thanks for the info.

[down4it]

I changed my plugs due to misfires on the dyno if you guys recall, i was at 17k miles... I will change my plugs every 15k on this car since i run so much 100oct... Here's what the plugs looked like when i pulled them out:

http://www.e90post.com/forums/showthread.php?t=123236

[Sniz]

mine weren't that bad at 25k ^

[down4it]

Originally Posted by Sniz

mine weren't that bad at 25k ^

I use a lot of 100oct and a while back V2 put me at 16-24psi at times, im sure that didnt help and for the majority of the time that i have had my car it has been running at 15psi so that and the combination of octane could be why they fouled faster...

[leftcoastman]

Originally Posted by stimpy

Dinan Spark Plugs - $2000.00.

I kid I kid ... Thanks for the info!

Don't give them ideas!

[Steve.breen@dinan]

Nope, stock plugs are fine.

Originally Posted by NPDAN

Hey Steve, thanks for the info.. Do you suggest upgrading the spark plugs?