Can anyone confirm if this spark plug heat range cross-reference chart I found seems accurate or not.




In my supercharged '79 I had been running NGK BR8ES plugs in my car and recently switched to Bosch. I thought the heat range for a Bosch plug in a standard 928 was a 7. Being supercharged, I went 1 range colder to a 6. Bosch #s get colder with the lower numbers whereas NGK plugs get colder as the number increases. With a Bosch 7 I though I was comparable to the previous NGK 8,but according to this chart, I'd need to be in a Bosch 4.

I don't think I've ever run this cold a plug in any of my cars.

If others (Eric, Dave, Carl, etc) have recommendations for my setup, I'm open to those as well

Thanks.

 

Since no one has responded yet, let me ask the question a different way.

What are the recommended NGK and Bosch plugs for a 16v 928 engine and what's the plug gap?

Anyone running a supercharger, and what plug and gap are you using with your setup?

Thanks.

 

I use a Bosch 5 and gap them at 30.

 

Thanks Sean and your car is supercharged too, correct?

 

Yup.