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Boost and Spark Plug Gap....

36K views 59 replies 28 participants last post by  Kevin 
#1 ·
I am currently running the Greddy 15G setup.... I am running NGK BKR7E and they are gapped to .028 I was just wondering what everyone else is running? or what is the best gap in your experiences? Thanks!
 
#13 ·
my bkr7e's were .028 out of the box, i left them as-is and they are doing great for the past several months
 
#16 ·
your tune might be to rich at 20mpgs. haveing them gapped to big and the boosted air can blow out the spark and not ignigte the fuel. on the other hand having it to small of a gap, your not igniting all of the fuel and only getting a partial burn. i suggest opening them up a bit. try .028 and out of boost you should be getting close to thesame mpg's you had before
 
#17 ·
Most people will find that a gap of under .035" but not much less than .030" will work well for most setups making less than 200ft/lbs of torque. I prefer to keep my gaps as wide as posible, so I start at .040" and take them down if I experience any issues, but, I haven't messed with high boost, so, that is also a factor (under 11PSI, since I am using a stock MAP sensor).
 
#18 ·
.028 has been doing me good at 204ft/lb. Inconsistent misfire due to being waaay rich.
 
#27 ·
I would use what everyone else is using for 1 main reason it is proven.

there is no better way. trail and error

if it blows out at high rpm or higher boost, tighten it down a little and retry.

its not a big deal. once you find the optimal gap you know for ever :)
I've never had a plug blow out. What does it feel or sound like? Will I notice lol
 
#32 ·
car will start to misfire and buck on the dyno/street. its impossible to miss, lol
Word!
I will post what I end up gapping mine on. Perhaps we could make a new thread with a basic run of our setups than put what we have a our plugs gapped at so other peeps can have a good reference
 
#31 ·
I was running 10psi on a stock z6 at .025/.028 and it was perfect. I was blowing the plug out before i down gapped it , and it would rev, build boost to maybe 6-7 psi, and then just start misfiring until i let off the gas...gapped it down and wallah!
 
#34 · (Edited)
yep I agree ,
I run .030" on 4554's at 10psi. I made a switch from the bkr7's for some reason the plugs showed signs of being too hot in all 4 cylinder's no matter what ignition changes or fuel changes I made.
I had about 3 n 3 quarters of colour change around the threads, porcelain was a white not shiny except number 3 though, they were gapped at .028" , after I switched to 4554's gapped them at .030" nice brownish color on porcelain and only about 2 threads are changed in color. With the bkr7e I kept running a 14.5 , 14.4 first run after the spark plug switch and a few adjustments I ran a constant 14.3 after that :D i love the 4554's.
Hav'nt had a problem with freezing during datalogging with neptune. I think it froze once thats it but has been great ever since.
it runs great!
 
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