I've been doing a lot of researching. The point of indexing your plugs is to position the ground so that you can achieve the most efficient burn. The most accepted way is to position the opening towards your intake ports where the fuel is coming in. In the n54, wouldn't we want to position them towards the injectors, but I've read that sometimes this causes spark blow out. Anyone have some insight?
I just had this very conversation with someone on Facebook. Can't remember if it was you or someone else. But generally speaking, the open side of the plug is best to face the Intake ports. I've done some (non-scientific) testing through the years and when it comes to DI you need to take into account the ultimate direction that the injector is spraying.
On the N54 i've seen better idles and less studdering with the plugs indexed towards the intake ports. But on other DI engines, i found better results indexing towards the exhaust valves away from the injector. The later was mainly due to the positioning of the injector pretty much firing DIRECTLY at the plug face. And seemed to increase the chance of plug fouling when spraying a lot of fuel. On the N54, the injector points straight down. So plug quenching is theoretically decreased wehn spraying a lot of fuel. so indexing toward the injector/intake valves seemed to give the best results.
If you follow the torque spec, and assuming your threads are in good shape, isn't this already dictated by where the threads begin? Once seated there are only a set number of turns and unless you've got some other issues I think to a large degree the spark plug will always point in the same direction, no? Unless there are plugs where the electrode portion can be rotated that I am not familiar with?
Not at all. Maybe if you were dealing with an OE plug with a single ground electrode where the OE specified the thread start location in relation to the ground electrode. But our OE plugs are multi-prong. And most people are using generic NGK plugs. How does NGK create a plug that indexes correctly for an N54 DI engine where you want the gap pointed at the injector which is (for sake of argument) 10deg from the thread start....but have that same plug fit a whole different engine with a different index?
That's where indexing washers/spacers come into play.
OEM or aftermarket, threads never start and end at the same spot. And just because a plug is OEM to a car from the manufacturer. Best believe they are just rebranded or made by one of the major spark plug makers and also were made to fit other engines so the same still applies. Threads start and stop at different places which will affect the index position.
The very best way to index plugs is to buy double you need and try to get them indexed how you want without spacers. because spacers affect plug cylinder depth.
EDIT: indexing plugs for me, was and is never done for power gains, but mainly to promote better combustion and reduce the chance of misfire.
