Fouling Plugs On My Rb30

[BAMR33]

Just a thought it could be the plenum design thats at fault. As you've stated it's the last three cylinders that have been fouled this is an indication that there is A) too much fuel being delivered to these cylinders B) to little air being received by the last three. Chances are you're not going to have 3 faulty injectors feeding too much fuel, even more unlikely 3 faulty injectors that happened to be from cylinders 4,5&6.

I read this somewhere 'It's not when the car is on boost you have to worry about uneven air distribution, it's when it's in vacuum'. This makes sense as it's when the car is in vacuum that each cylinder scavenges for air and first three are obviously going to scavenge more than the last three especially with a plenum design that is really narrow and low in volume. This scavenging effect is only going to get worse until positive boost is generated, where it doesn't matter a shit anyway because the air just gets feed in there.

Many, many people I know and have read about on this forum have had problems with custom plenums and idling issues and I think a lot of it can be put down to uneven air distribution. A tune is never going to completely fix this unless you some how tune each injector relative to the amount of air that's entering that camber. Alternatively you can 'trial and error' tune each injector until a stable idle is found. New design or standard plenum FTW.