Low Boost

[DK77]

What steve said is that the code for the plugs indicates their pre-gap. (i.e. BKR6EIX-11 would be gapped at 1.1mm, while BKR6EIX-8 would be gapped at .8mm)

Next part he claims that the smaller the gap is, the better the plug will work, which is true to a certain extent. At some point, you will not have enough of a spark to burn the entire air/fuel mixture and you lose gas mileage.

And AFAIK, the "stock" gap for both turbo and N/A is 1.1mm, however as parts wear and boost gets turned up, the easy fix for a turbo car with spark blowout is to make the gap smaller so it doesn't take as much energy from the coils to make the spark since the spark has less distance to jump. Hopefully this makes sense to everyone.

[dpartinvr4]

But the spark only starts the combustion, Once it's started , it burns by itsself. The advantage with a bigger gap is that the combustion starts quicker(bigger flame front) and finishes quicker so takes less time overall (needs less timing advance). The disadvantage with a bigger gap is that it takes more volts to make a spark and the nessecary volts aren't always available under high cylinder pressure/ high boost/ high rpms.
So a smaller gap needs slightly more timing advance due to combustion taking ever so slightly longer to complete.

Hey that's how salesmen used to sell sparkplugs. Do a dyno with old plugs with wide gap and misfiring, do another with new plugs at the correct gap.
Instant more HP. It's the gap/timing advance that does it, not the new plugs. It's one of the oldest scams out but not the only one.

Steve

Who would waste their time setting up a car on a dyno and then changing plugs to run it twice just to sell spark plugsto somebody?

[DK77]

Spark plug companies i.e. NGK