Why and when run a colder plug?
Thread Starter
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
Why and when run a colder plug?
Why and when would you run a colder plug.
I was reading today about AC Delco Rapidfires for 113d-port L98 heads. They recommend RF #5, or for more aggressive street driving and racing #9.
Sooooo, when do you go with which.
Downsides?
TIA
I was reading today about AC Delco Rapidfires for 113d-port L98 heads. They recommend RF #5, or for more aggressive street driving and racing #9.
Sooooo, when do you go with which.
Downsides?
TIA
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
I run the RF 9's in the ZR1 due to the fact that with 11 to 1 compression it calls for 93 octane and we only have 91 octane available here. RF 5's would work fine for normal driving if 93 octane was available. One caution, if you go to a colder plug let that puppy warm up to operating temps before driving or you may experience plug fouling. Later, 84 CF 91 ZR1
Racer
Joined: Aug 2004
Posts: 379
Likes: 170
From: Buffalo Grove IL
I think the most simple description would be:
- Colder plugs foul easier
- Hotter plugs can cause preignition (knock)
So, if your plugs foul quickly, try a hotter plug. Conversly if you're having problems with knock counts, try a colder plug and see if that helps
Ben
- Colder plugs foul easier
- Hotter plugs can cause preignition (knock)
So, if your plugs foul quickly, try a hotter plug. Conversly if you're having problems with knock counts, try a colder plug and see if that helps
Ben
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 60
From: Fremont Oh
USAsOnlyWay,
I wouldnt really go more than a step or so colder... if your normally aspirated
I'm running a supercharger with about 9 pounds of boost with 91 octane it was nesessary as above mentioned to keep me out of spark knocks. I'm currently at 4 steps colder.
Primarily it slows the burn process to help reduce detonation. Under racing situations the car is going to be running hotter and you would be on the throttle most of the time which would be a perfect scenerio for spark knock or pre detonation. It will help you also get a bit more advance on the high end but as with anything it becomes a balancing act...
Hope this helps!
mo
I wouldnt really go more than a step or so colder... if your normally aspirated
I'm running a supercharger with about 9 pounds of boost with 91 octane it was nesessary as above mentioned to keep me out of spark knocks. I'm currently at 4 steps colder.
Primarily it slows the burn process to help reduce detonation. Under racing situations the car is going to be running hotter and you would be on the throttle most of the time which would be a perfect scenerio for spark knock or pre detonation. It will help you also get a bit more advance on the high end but as with anything it becomes a balancing act...
Hope this helps!
mo
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
Originally Posted by USAsOnlyWay
Ok, good to know.
So how do I find out how many steps colder a plug is?
So how do I find out how many steps colder a plug is?
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Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
Originally Posted by USAsOnlyWay
Oh!
Doh, I guess I could have put two and two together.
Alright, thanks guys, looks like I will try a #6.
Doh, I guess I could have put two and two together.
Alright, thanks guys, looks like I will try a #6.
