neanicu

It's not my illustration,it's Porsche's. If they've misinterpreted it then I did as well. Nobody knows how Porsche programmed their sequence. Technically you are correct,but bear in mind we're dealing with Variocam(variable valve timing) here,high pressurized fuel and a boxer engine design. So...is there any chance that at some point,high pressurized fuel can make its way on the back of the intake valve?

RajDatta

Have 142K on my 2008 DFI engined Cayenne S. Had the HPFP changed twice (once under warranty) but besides that, the engine is still running strong. I did see carbon buildup on the intake ports when changing the vacuum pump (needed to remove intake manifold), but nothing different that other engines that recirculate oil fumes/blowby back into the intake.

neanicu

Good to know. Perhaps Porsche is using a better PCV system...

neanicu

I won't go back and read,but I believe I've stated this in the past : the solution is simple and many manufacturers are already implementing it. Have a second set of port injectors that spray when the computer demands it on the back of the valves. Or use a water injection system like the one on the M4 GTS,that cools the charge in the same time making more power.

erik_plus8

It's been some (many...) years since I did engine calibration myself but I would assume that the injectors can be open also during the intake stroke, to acheive full atomization/mixture during high load/high speeds. (where time is short in only doing it with closed valves)

neanicu

That's my thought as well : if even every once in a while a bit of fuel ends up on the back of the intake valves,we might never have carbon build up issues in boxer engines where the position of the direct fuel injector is set up at the angle seen in the illustration.

Targaone1

would the intake injection of the 2009 987.2 caman base be a better option ??? shopping for a 2009 or 2010 2011 to get the 9a1 engine.

jorligan

No issues with intake injection regards to carbon build up in the intake but you also lose out on the advantages of direct injection.

Pcar81

Any update here?

How is the 9A2 design?
same issue?

Maverick11

Not sure about .2 gt3 engine but in the newer 3.0 engines the fuel injector is back on top vs off to the side like the original DFIs. Dont know if that design kept the valves cleaner or not but we are basically back to hoping porsche has done the design work to keep build up from happening longer term. Good news is I haven't really heard of any 911s having carbon build up problems. Time will tell...