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Another FWIW, a friend recently had his motor scoped when in for other service. His car has a lot of miles. The valves were reported as clean.
Whatever the truth about DFI motors, it seems that the 9A1 is well designed to be pretty immune to carbon build up.
Sure does from the graphic. Maybe Porsche figured it out by having the fuel wash the back of the intake valve during the intake stroke. I wonder where the injector is positioned in the other types of DFI motors that are famous for carbon buildup, like the BMWs. I also wonder if my DFI 09 Cayenne turbo has a similar design to the 997 9A1 motor since both DFI motors were developed for the 2nd generation Cayenne (957 series in 2008) and 2nd generation 997 (997.2 series in 2009) around the same time.
I might need to post that graphic in the Cayenne forum and let someone who has had one of the 957 DFI motors apart respond.
Looks like the same technology is used in my Cayenne 4.8L DFI motor. I actually have a PDF copy of the 957 generation Technical Release Document to Porsche Service, that includes a similar graphic on the Cayenne DFI engine that shows the injectors spraying the backside of the input valve - here's the page (31 of 108), so it looks like Porsche employed this technology in all of their first generation DFI engines, which I think is great news for those of us who have heard horror stories about carbon buidup on the back of intake valves in DFI engines. I think this makes the use of a Techron treatment prior to the last oil change even more effective at maintaining the vehicle's drive train.
Techron works in DFI engines. Techron as a liquid and vapor phase. When fuel with Techron is injected into the engine any thing the Techron as a liquid comes in contact with -- including the injector nozzles -- is cleaned. During combustion the Techron turns to vapor. Since some exhaust gas can flow back and contact the intake valve the intake valve being "cold" causes any vaporized Techron to condense on it and then liquid (again) Techron can loosen/remove deposits on the valves.
If you want to run Techron periodically my advice would be to run it a tank or two *before* an oil change. I would use Techron according to directions. Well, I cheat a bit. A bottle I buy treats 20 gallons but I use the entire bottle even though the gas tanks of both of my cars only hold a bit over 16 gallons.
Unless the bottle of Techron is sized to treat just 4 or 5 gallons of gasoline I would *not* use a bottle of Techron that treats 20 gallons or whatever in just 4 or 5 gallons of gasoline.
Just use Techron according to directions and it will work just fine.
Originally Posted by Petza914
Looks like the same technology is used in my Cayenne 4.8L DFI motor. I actually have a PDF copy of the 957 generation Technical Release Document to Porsche Service, that includes a similar graphic on the Cayenne DFI engine that shows the injectors spraying the backside of the input valve - here's the page (31 of 108), so it looks like Porsche employed this technology in all of their first generation DFI engines, which I think is great news for those of us who have heard horror stories about carbon buidup on the back of intake valves in DFI engines. I think this makes the use of a Techron treatment prior to the last oil change even more effective at maintaining the vehicle's drive train.
Nice post. I didn't know that the earlier v6 base 3.2 liter was not DFI, but DFI came out with the 957s then. We have a 2009 Base we are very happy with, as it came with a lot of options. Can you post that document. I can look through press releases and such but haven't located a technical document such as you have.
Nice post. I didn't know that the earlier v6 base 3.2 liter was not DFI, but DFI came out with the 957s then. We have a 2009 Base we are very happy with, as it came with a lot of options. Can you post that document. I can look through press releases and such but haven't located a technical document such as you have.
I have been using Techron for about 30 years in my 1985 911 because it was recommended by Porsche. Every 3000 miles, a couple of tanks before an oil change, and this car runs unbelievably well after about 116,000 miles. Is it a coincidence? I don't know, but I won't stop. I also use it in my DFI 997 because it should at least help keep the injectors clean, and might keep the valves clean. Plus there is the placebo effect. Mike
Thanks for reposting this picture. That's always been my understanding, that the back side of the valve gets "washed".
I am not an expert but if I recall correctly valves rotate in the process of being used so unlike the dark side of the moon the valve's front side is constantly rotating to become the washed back side. (good strategy for showering also)
In my prior Porsche life I recall always scouting out Chevron for my fill ups. Additionally, a concentrated Techron flush - one bottle to 3-4 gallons before every other oil change was recommended. And a normal mix before a long trip at highway speeds.
I am not an expert but if I recall correctly valves rotate in the process of being used so unlike the dark side of the moon the valve's front side is constantly rotating to become the washed back side. (good strategy for showering also)
In my prior Porsche life I recall always scouting out Chevron for my fill ups. Additionally, a concentrated Techron flush - one bottle to 3-4 gallons before every other oil change was recommended. And a normal mix before a long trip at highway speeds.
In addition to Chevron gas, Texaco gas also includes Techron additives.
Interesting. Would love to have this nugget re-confirmed. Thank you.
Ha ! I learned this in high school - the idea that the rocker arm was slightly off center and forced the valve to rotate ever so slightly. (kind of happy when my memory hasn't failed me again)
Ha ! I learned this in high school - the idea that the rocker arm was slightly off center and forced the valve to rotate ever so slightly. (kind of happy when my memory hasn't failed me again)
Interesting. Would love to have this nugget re-confirmed. Thank you.
The valves indeed tend to rotate due to the action of the spring, unless the keepers have been ground down. Just like piston rings rotate on the piston (except when they are pinned as Porsche did on the 2nd piston ring).
Nice post. I didn't know that the earlier v6 base 3.2 liter was not DFI, but DFI came out with the 957s then. We have a 2009 Base we are very happy with, as it came with a lot of options. Can you post that document. I can look through press releases and such but haven't located a technical document such as you have.
I agree, very nice post. One can also infer that with considerable control over both valve timing and injection timing, they could have designed in a "cleaning cycle" periodically. Especially if the valve/injector timing for cleaning isn't optimal for overall performance.
Goddam clever that would be, especially for the 2009 model year when everyone was still trying to sort DI out.
12-04-2017, 11:33 PM
