Tech Tip No. 16
Originally published in the quattro quarterly
Wrong Spark Plugs
Over the years I have traveled to many Quattro Club track event and
safety seminars. Usually at each event the following scenario takes place.
Says the owner of the Quattro, "I just can't believe it.
I had a tune up a few days ago to prepare for the event and now the engine runs terrible. I find it hard to start and it misses under load."
I and a few knowledgeable owners will reply,
. . . bet you're using Bosch platinum plugs.
We open the hood and sure enough there are five clean Bosch WR7DP
plugs. Usually someone has a set of old plugs that they're carrying around in some tool box. The used but correct plugs are installed and the engine runs perfectly.
The Bosch WR7DP platinum spark plugs just do not work in the turbo
application. I've talked to some Bosch employees, but they've not heard of the problem, but were willing to listen.
What spark plugs should you use?
The smart thing is to use what is recommended in your owner's manual. Audi has done a lot of testing to determine the correct plug, and the Bosch platinum is not one of them.
What do I recommend?
On Audi 10-valve turbocharged engines I recommend the following:
These are a long life plug with three ground electrodes that enable
the plug to last up to three times as long as standard plugs. But, here is a bit of trivia about multiple electrode plugs. Multiple electrode and platinum plugs of any type to not work with the Jacobs
If your budget can afford it use the better spark plug that is used
on the Audi 20-valve turbocharged engines that was not available when the 10-valve engines were made:
These plugs have a pair of platinum electrodes that are side
gapped, but have a price hovering around $20.00 each!
On my 400+ hp 20-valve turbo engine it was beyond the
recommended time to replace these plugs even though the car was running well. Upon examination the plugs looked as good as the $20.00 plugs I was installing.
I put the old plugs into my daughter, Marni's, 4000S quattro as an experiment, and they've been running well for three years.