Spark Plug Heat Range

patkeefe · 01-24-2019, 07:27 AM

Hi, for all of you running non-factory turbo setups, a question:
What spark plug heat range are you running in the engine for street use? I have NGK BP6 xxx I'm putting back in. I realize these are a bit hotter that normal, but I don't remember why I have them in there. I've had the car a part for a while, and am evidently suffering from CRS.
BTW, low boost (like 6 PSI, EFI)
TIA
Pat

mark houghton · 01-24-2019, 01:56 PM

Last time I ran NGK's I started out with 8's, then moved down to 7's. The burn looked good'er with the 7's.

gumba · 01-24-2019, 09:00 PM

I’m using Bosch w3cs in both 3.5 twin plug, and a modified 3.3 single plug

pkabush · 01-24-2019, 10:21 PM

Quote:

Originally Posted by gumba

I’m using Bosch w3cs in both 3.5 twin plug, and a modified 3.3 single plug

That’s good to know. I almost posted the question myself since I’ll soon be running twin plug ignition.

T77911S · 01-25-2019, 02:54 AM

BP6 is probably too hot. the plug can actually get hot enough to ignite the fuel WAY too early. this is pre ignition which is way more damaging than detonation.

I run BP8's and my plugs look great. I would like to try one heat range colder.

how you use the car also matters. on the track you are asking for trouble with a 6.

you need to inspect the plugs. start cold and work your way hotter.
if you are at an 8 and they are black you are probably running too rich.

the W3's are another common heat range for the 930.

xbmwguy · xbmwguy's Garage

Ngk bkr 8eix are a great plug for performance efi turbos twin plug

patkeefe · 01-25-2019, 07:12 PM

Quote:

Originally Posted by T77911S

how you use the car also matters. on the track you are asking for trouble with a 6.

you need to inspect the plugs. start cold and work your way hotter.

I think the reason I went to 6 is because I was having drivability issues using the 8's I had ran at the track. I'm going to put the 7's back in and see how this goes. I just restarted the car after a long down time (Gearbox rebuild). The damn thing is hunting at fast idle, so I'll be shaking out the fuel and ignition system tomorrow.

T77911S · 01-28-2019, 03:32 AM

6 is too hot for the track.

if you cant run an 8 then you have another issue.

you really need to look at the plugs to determine what you need.

patkeefe · 01-28-2019, 03:50 AM

6's may have had to do with the over-rich issues I was getting with the CIS. I'm going to go with 7 or 8 in conjunction with the fuel damper.

993Speedster · 01-28-2019, 04:55 AM

My 964 has a 7 range in N/A form. 930 has an 8. I'm starting with a 9 for my N/A 3.6 turbo build and then moving to an 8 if they foul out and don't look too hot. Most of the fouling has to do with the tune though and rich cruising conditions. Now that you're EFI and your part throttle areas of the map are hopefully cleaned up; it won't be an issue.

T77911S · 01-28-2019, 07:00 AM

hotter plugs are needed for idle and starting. that is where most foul.
cruise and WOT need a colder plug.
the heat is there only to keep the plugs clean.

8's in my car could be a little on the hot side based in how they look. I would like to try a 9.
as I said, if you have to go hotter than 8 you may be compensating for another issue.
too rich, not enough timing, bad rings.

also depends on how you check them, it is best to do a WOT shut down or even a cruise shut down. I don't usually do that, i just try not to let it idle much before shutting it down but i have let it idle for a while and the plugs still look good,

remember a hot plug can become and ignition source that ignites the fuel long before it should. that could result in catastrophic damage