Spark plug gap & PFB6 vs PFB7
16 March 2017, 09:57 PM
#1
Spark plug gap & PFB6 vs PFB7
Hi All
No question just what I've found out. I have a classic with hybrid turbo to just over 300bhp / lbft.
Treated the old war horse to a little over due TLC. As had been suffering from misfire under full boost 1.3 bar.
Changed the plugs and still had misfire, so changed the coil and presto misfire gone almost.
New plugs are 0.8mm as they come and theres much ado about reducing gap to 0.6mm when increasing boost. My findings suggest its not just the gap but whole ignition system, well who'd have thought it.
Anyway my leads are relatively new and upgraded so should be helping as well.
I'm going to reduce gap to 0.7mm to try an eliminate the slight remaining mis.
Second thing I found: by accident I ended up with NGK PFB7s rather than 6s. Wasn't straight forward to find but the difference is the 7s are 1 grade cooler than the 6s.
A cooler plug conducts heat away from tip faster so the spark contact tips are cooler. You need a cooler plug when generating more heat ie when modified to keep the tips in correct operating zone.
Too cool a plug in a car may end up getting fouled with combustion deposits, it needs to be hot enough to burn that off. Its why old race car drivers rev the nuts of the engine before killing the engine in the paddock.
Too hot a plug is much more of an issue as the tips may melt. I did that in my Mini using standard 1000cc plugs in a modified 1300cc - only just remembered that.
NGK recommend 1 grade cooler plug for every 75-100 bhp so with 300bhp and PFB7s instead of 6s I'm now spot on.
I also used after market coil (97 car with single coil pack) £50 seems to be just fine and no need to spend £150.
Happy motoring all
Cheers
No question just what I've found out. I have a classic with hybrid turbo to just over 300bhp / lbft.
Treated the old war horse to a little over due TLC. As had been suffering from misfire under full boost 1.3 bar.
Changed the plugs and still had misfire, so changed the coil and presto misfire gone almost.
New plugs are 0.8mm as they come and theres much ado about reducing gap to 0.6mm when increasing boost. My findings suggest its not just the gap but whole ignition system, well who'd have thought it.
Anyway my leads are relatively new and upgraded so should be helping as well.
I'm going to reduce gap to 0.7mm to try an eliminate the slight remaining mis.
Second thing I found: by accident I ended up with NGK PFB7s rather than 6s. Wasn't straight forward to find but the difference is the 7s are 1 grade cooler than the 6s.
A cooler plug conducts heat away from tip faster so the spark contact tips are cooler. You need a cooler plug when generating more heat ie when modified to keep the tips in correct operating zone.
Too cool a plug in a car may end up getting fouled with combustion deposits, it needs to be hot enough to burn that off. Its why old race car drivers rev the nuts of the engine before killing the engine in the paddock.
Too hot a plug is much more of an issue as the tips may melt. I did that in my Mini using standard 1000cc plugs in a modified 1300cc - only just remembered that.
NGK recommend 1 grade cooler plug for every 75-100 bhp so with 300bhp and PFB7s instead of 6s I'm now spot on.
I also used after market coil (97 car with single coil pack) £50 seems to be just fine and no need to spend £150.
Happy motoring all
Cheers
