Spark plug heat range?
 

I believe the engine on my Carrera 3.2 was rebuilt. The ODO shows 165k, but the engine has 0-1% leak down, the Motronic has a custom high RPM chip, etc.), but the PO who only had it for a few years did not know anything about it (did not know much about cars in general).

Since I don't know how the engine was built, I don't know if I should go with the stock heat range or not.

The spark plugs I pulled out are Bosch W7DC, Bosch heat range 7. Looking at various heat range mapping, I see that a Bosch heat range of 7 is equivalent to an NGK heat range of 6.

Therefore I'm thinking of going with NGK Iridium BPR6EIX plugs...heat range 6 to match the heat range of the Bosch plugs that were in the car.

Is this the right plug and the right way to think about it?

NGK 7 seems to be the sweet spot for a stock 2.7/3.0/3.2 in my experience and from what I've picked up here over the years. I run the BKR7EIX in my 3.0.

Remember that the heat range numbering of NGK and Bosch spark plugs are opposite oriented. NGK: the lower the heat index the hotter the spark plug. Bosch and others are the opposite!

http://forums.pelicanparts.com/uploa...1728384882.jpg

Refer to the manual or the Porsche tech spec book for further details on what your engine is best. W7DC seems to me the original recommendation from the user manual. There are cross reference tables available on the web.
E.g.
https://plugspecs.com/ngk-spark-plugs-cross-reference/#ngk-spark-plugs-cross-reference-chart

Following their information the BPR6ES is the 1:1 replacement for the W7DC.

Here's another chart showing the heat ranges of the vendors:
https://vasttuning.com/spark-plug-selection-and-spark-blowout/

Thomas

Also depends on engine type. Bosch plug for Carrera engines is WR7 DC or DP for US engines but WR4 CC or CP for RoW engines (930/20). According to the cross ref above, NGK plug BR8ES is the replacement for WR4 CC or CP.

Correct. Here an excerpt from the tech spec book for Carrera from 84-87:

http://forums.pelicanparts.com/uploa...1728402956.png