[boom]

I was discussing some things with Rob from Cobb the other day and one thing I asked about was EGR. My old car had an egr valve and piped it right into the intake manifold.

For those that don't know, EGR is exhaust gas recirculation and it is an emissions trick. If you pipe exhaust gas into a motor you it won't burn. The engine needs to open it's throttle more to compensate. An open throttle results in less pumping loss and a more efficient engine with less fuel consumption under cruise/light load.

The N54 does not have an EGR valve. It accomplishes the EPA required EGR by overlap of the intake and exhaust cams using double vanos. By overlapping the cams the exhaust valves and intake valves can be open in such a way as to recirculate exhaust gases back into the combustion chamber. EGR is no bueno for DI motors as there is no fuel to wash the valves clean. As a result we get carbon build up from it and the PCV system. If you look at BMW DI patents they even mention that there is no advantage whatsoever from EGR for DI motor.

Anyway, Rob said that Cobb had modified the cam phasing to significantly reduce this overalap on their tunes to improve response to throttle imputs. I would love to see the exact tables and am really hopeful they did this cam phasing at low and mid loads as it should have the additional benefit of reducing carbon buildup on the head. Of course this would be very difficult to verify but I'll take anything I can get when it comes to carbon buildup mitigation.

In short, I'm speculating that a quality catch can + the Cobb accessport are the best ways to reduce carbon buildup. Add meth and that's probably the best it will ever be.

Thoughts?

[MF80]

S

[rader1]

It all sounds plausible. I guess the only way to see what affect it has to compare cars making similar power, running the same gas, driving in the same manner and one running Cobb and the other running another tune and compare the carbon buildup.

[vasillalov]

Nope. You are still going to get carbon buildup because the crank case ventilation is dumped into the rear turbo inlet. ...and there is no catch can that can filter 100% of all oil fumes coming out of the PCV system.

[rader1]

Originally Posted by vasillalov

Nope. You are still going to get carbon buildup because the crank case ventilation is dumped into the rear turbo inlet. ...and there is no catch can that can filter 100% of all oil fumes coming out of the PCV system.

I think it serves to reduce the carbon buildup, not eliminate it. if you start out with clean valves: Cobb+ oil can+ meth+a routine of using fuel injector cleaner drawn in through a vaccuum line into the intake mani= semi clean valves.

[335iJWC]

Makes sense! Any that helps is an advantage. DI engines will never have 100% clean valves but the mods above will make a big difference

[boom]

Originally Posted by vasillalov

Nope. You are still going to get carbon buildup because the crank case ventilation is dumped into the rear turbo inlet. ...and there is no catch can that can filter 100% of all oil fumes coming out of the PCV system.

Read last paragraph of op.