Intake valve carbon build-up
#16
09-14-2013, 09:44 PM
I've stayed away from DI as long as I could, but my latest SUV trade took me from the good ole Jeep Hemi to a Cayenne 4.8 DFI. I'm hoping that Porsche has figured out how to remove carbon products from the crankcase vapor that gets recycled through the intake by the PCV system. It's my understanding that the PCV is the primary source of intake valve carbon buildup.
My take on DI is that all of the makers are perfectly aware of the intake valve issue and have little incentive to do anything about it, while having very strong incentives to adopt DI for efficiency purposes. Most consumers are likely unaware that the need for $500 maintenance is due to manufacturer negligence.
One more thing. I read the old post referenced by the OP, and someone claimed BMW was denying the issue on M5 V10's. That engine had port injection. I was sad to see it go, along with the E9X M3's port-injected V8. Wonderful engines--with no DI.
My take on DI is that all of the makers are perfectly aware of the intake valve issue and have little incentive to do anything about it, while having very strong incentives to adopt DI for efficiency purposes. Most consumers are likely unaware that the need for $500 maintenance is due to manufacturer negligence.
One more thing. I read the old post referenced by the OP, and someone claimed BMW was denying the issue on M5 V10's. That engine had port injection. I was sad to see it go, along with the E9X M3's port-injected V8. Wonderful engines--with no DI.
#17
09-15-2013, 07:05 AM
The upcoming VW Golf R and Audi S3 ( 2015MY) will have both port injection and direct injection. my understanding is that the DFI is used for idling and high loads while the port injectors are used much of the time ( cruising, etc.). This sounds like the solution. The engine in those cars are extremely powerful for their size by the way.
#18
09-15-2013, 09:16 AM
I suspect that then reason this has not been seen as an ongoing problem yet on the P boards has to do with the relatively low mileage many members run up compared with the daily driver types. Watch the road tests where they retest performance at 40k miles. I am reminded of a comment made by one tester to the effect that significant loss is "common with vw's". I would find it disheartening to think that my cars performance is deteriorating over time. Sounds too much like my health status 
#19
09-16-2013, 05:35 PM
I have seen comments from a reputedly knowledgeable mechanic, who said that there are dirty PCV systems and clean ones and that the 997.2 is a "clean" system with a different design from the Audi/VW ones. Please correct me but I think the only Porsche issues with carbon build up has been with the VW/Audi sourced engines for the Cayenne.
It is ironic that the people who seemed to be most concerned with purported carbon buil-up in the 997.2 don't actually own one!
It is ironic that the people who seemed to be most concerned with purported carbon buil-up in the 997.2 don't actually own one!
#20
09-16-2013, 07:50 PM
The problem is caused by not having the detergent and cleaners in the fuel wash off the valve. No matter what you put in the gas it does not help. If you remove the PVC system and EGR systems, you remove the problem, unfortunately that is illegal. Basically the fumes bake on to the hot valve which would normally be washed off by the fuel in the intake charge. Since there is no fuel in the intake charge with DI the valves build up crud.
This will eventually happen with any DFI car. That's why some manufactures are adding one port injector just to keep the valves clean.
My friend had a VW with this problem and didn't want to pay the dealer we tried a home made remedy. Seafoam sells an aerosol upper engine cleaner, we sprayed 2 cans into the intake tract and then shut the car off and let it work. 30 minutes later start the car and watch out, all the softened carbon is dissolved and burns off in huge clouds of smoke. Worked wonders, should be used before it gets really bad, and change your oil after.
This will eventually happen with any DFI car. That's why some manufactures are adding one port injector just to keep the valves clean.
My friend had a VW with this problem and didn't want to pay the dealer we tried a home made remedy. Seafoam sells an aerosol upper engine cleaner, we sprayed 2 cans into the intake tract and then shut the car off and let it work. 30 minutes later start the car and watch out, all the softened carbon is dissolved and burns off in huge clouds of smoke. Worked wonders, should be used before it gets really bad, and change your oil after.
#21
09-16-2013, 10:45 PM
Anyone seen this picture? It appears to show the DI occurring at an angle inside the combustion chamber that would also coat the open intake valve with fuel. The upper neck of the intake valve would still be suspect, depending on how good Porsche is at removing oil vapor, etc. from the PCV return. If they've managed a good job at creating a "clean" PCV system, and the DI is actually spraying the intake valve to some extent, then their solution might just be pretty good.
#22
09-17-2013, 12:23 AM
I have seen comments from a reputedly knowledgeable mechanic, who said that there are dirty PCV systems and clean ones and that the 997.2 is a "clean" system with a different design from the Audi/VW ones. Please correct me but I think the only Porsche issues with carbon build up has been with the VW/Audi sourced engines for the Cayenne.
It is ironic that the people who seemed to be most concerned with purported carbon buil-up in the 997.2 don't actually own one!
It is ironic that the people who seemed to be most concerned with purported carbon buil-up in the 997.2 don't actually own one!
#23
09-17-2013, 09:38 AM
Thinking about it, if the picture above is accurate, then owning a GTS, where the valve lift is increased by 1mm, means my intake valves should be cleaner than the non-GTS valves. Woohoo, and unadvertised benefit!
More seriously, if the intake valve does get some fuel sprayed on it inside the combustion chamber due to the angle of the injector relative to the valve, then the "Italian tune up" could have some benefit.
More seriously, if the intake valve does get some fuel sprayed on it inside the combustion chamber due to the angle of the injector relative to the valve, then the "Italian tune up" could have some benefit.
#24
09-17-2013, 11:14 AM
Ah, yes. The Italian Tune Up. A great way to decrease carbon build up while having fun for about 45 minutes....hehehe.
Thinking about it, if the picture above is accurate, then owning a GTS, where the valve lift is increased by 1mm, means my intake valves should be cleaner than the non-GTS valves. Woohoo, and unadvertised benefit!
More seriously, if the intake valve does get some fuel sprayed on it inside the combustion chamber due to the angle of the injector relative to the valve, then the "Italian tune up" could have some benefit.
More seriously, if the intake valve does get some fuel sprayed on it inside the combustion chamber due to the angle of the injector relative to the valve, then the "Italian tune up" could have some benefit.
#25
09-18-2013, 07:09 AM
Why should someone have their valves inspected if they're not experiencing any issues?
#27
09-18-2013, 10:32 AM
As an Audi RS4 owner I've become well versed in the world of direct-injection carbon buildup issues on intake valves/runners/flaps on pretty much every DI motor (Porsche Cayenne, Chevy's 2.0L, anything under the VW umbrella... even Toyota had to rethink their direct injection engine due to bad carbon bulidup[they were the first to include both port injection and direction injection in order to keep it clean and smooth out cold startups]).
Who here is cleaning it themselves? (I've done one, ugh)
Who's taking it in for cleaning? What are you paying?
How is the dealership treating the issue? Denying it? Boroscoping the intake to see the buildup then cleaning?
I know for a while Audi was saying there was no issue, then they started giving people a fluid to add to the gas tank(even though the fuel doesn't even touch the intake runners on a DI engine, awesome), finally they started popping the engine and cleaning it out. Recently, Audi has started sending out letters stating they are extending warranties on certain DI-engined cars for free carbon cleaning(RS4 didn't make the cut, grrr)
A friend went through the exact same ordeal on his BMW 335 and Porsche Cayenne a year or two ago. (He got rid of both after that)
I'm curious how Porsche is approaching this now.
Who here is cleaning it themselves? (I've done one, ugh)
Who's taking it in for cleaning? What are you paying?
How is the dealership treating the issue? Denying it? Boroscoping the intake to see the buildup then cleaning?
I know for a while Audi was saying there was no issue, then they started giving people a fluid to add to the gas tank(even though the fuel doesn't even touch the intake runners on a DI engine, awesome), finally they started popping the engine and cleaning it out. Recently, Audi has started sending out letters stating they are extending warranties on certain DI-engined cars for free carbon cleaning(RS4 didn't make the cut, grrr)
A friend went through the exact same ordeal on his BMW 335 and Porsche Cayenne a year or two ago. (He got rid of both after that)
I'm curious how Porsche is approaching this now.
#28
09-18-2013, 11:27 AM
It's strange. The .2ers response to this discussion is often one of indignation. "How dare you" Just accept it, he is NOT going to have this issue with his car. I hope not but in reality it makes not a rats **** of difference to me At 36 k miles and 7.5 years I may have my # 6 cylinder scoped next service. Just saying.....
At 36 k miles and 7.5 years I may have my # 6 cylinder scoped next service. Just saying.....
#29
09-18-2013, 01:46 PM
Why should someone have their valves inspected if they're not experiencing any issues?
#30
09-18-2013, 03:34 PM
I've written on this before. Our Audi A4 3.2 Quattro had this same issue early on in the DFI engine history. Carbon build-up, CEL light. The dealership didn't know what to do and even suggested it was our fault for using cheap gas - which we weren't. We got no joy from the dealership who claimed they had no idea how to "fix" the issue. (Although at one point I was talking to a service rep I knew who used to work at the related Porsche service desk. He told me that this Audi service department was seeing these problems intermittently and had no idea how to fix it.) Anyway, after the car was in the service department for the qualifying period of time we sued Audi under the California Lemon Law and they settled very quickly for about 2/3 the cost of the car (and told us to keep it). My take: corporate knew of the problem and was doing everything they could to keep it under wraps.