Even the mighty Porsche DI succumbs to deposits

[addyguy]

Would a 'cheap' fix be either water induction via the PCV valve, or sprayed into the intake on a hot engine every 10k miles or so? Seems to do a good job of 'steaming off' deposits....

 

[JoeFromPA]

This problem can be solved via a PCV bypass system and more aggressive driving. Edit: Also, I'm guessing alot of these engines are tested using euro-fuel and aggressive driving to beat the snot out of them and see how they hold up. How often are engines tested at low loads for long periods of time, hours and hours of idling, etc.? That's a serious question: I've never heard of a long-term idling test, but maybe it exists.

 

[pitzel]

 Originally Posted By: Anies

For a car that expensive, i'd change the oil 3k/3months. Not worth having problems. If you can afford a Porsche, you afford doing frequent maintenance.

That's exactly the problem! The oil is changed too frequently, hence the exact problem you're trying to avoid, ends up not only happening, but happens even worse! *sigh*, it just seems like common sense to me to not 'overmaintain' something. Think of new motor oil as being a sort of 'poison' to those intake systems, and all the instruments and bleed valves and actuators that sit within it. You wouldn't want to feed your expensive new engine more poison than it really needs, would ya? Just as an anecdotal comment of my own personal fleet, before I switched them to long drains (ie: 30-40k miles) on extended drain synthetics, I had problems with oil accumulating in intake plumbing. Made the change, and now when I take off the intake hoses after similar intervals, there's no oil to speak of, my oil cap don't accumulate any meaningful amount of contaminants on their undersides (they used to). That's because my engines only experience the nasty vapours from brand-new oil 1/10th as often as an engine that gets the '3000 mile' torture.

 

[saaber1]

 Originally Posted By: edhackett

Uh, guys, this is a direct injected engine. The fuel doesn't contact the back of the valves. That's what's causing the problem in the first place. How is the fuel or any additive going to make any difference? Ed

Also it should be noted that when VW redesigned the DI 2.0 FSI to the DI 2.0 TSI (avail. in the U.S. roughly mid 2008) they re-angled the fuel injectors so that some/more fuel is hitting the valves. That should help some I would think. For more info., see self study guide for the TSI here, about 1/3 of the way down the page: http://forums.vwvortex.com/zerothread?id=3749316&page=5

 

[RI_RS4]

pitzel, you have a hypothesis, but no actual science to back it up. You claim that if the oil were left it that the deposition rate would decrease. What do you base this on? Thus far NOACK volatility. However, NOACK volatility is measured on new, uncontaminated oil, not oil that has been fuel, ethanol and water diluted and degraded. There are currently no standard measures for the volatility and deposit formation properties of degraded oils. As a matter of fact, some of the RS4 engines in the UK that have had severe valve deposit issues had their oil changed per the manufacturers recommendation, with manufacturer recommend oil.

 

[RI_RS4]

 Originally Posted By: pitzel

 Originally Posted By: Anies

For a car that expensive, i'd change the oil 3k/3months. Not worth having problems. If you can afford a Porsche, you afford doing frequent maintenance.

That's exactly the problem! The oil is changed too frequently, hence the exact problem you're trying to avoid, ends up not only happening, but happens even worse! *sigh*, it just seems like common sense to me to not 'overmaintain' something. Think of new motor oil as being a sort of 'poison' to those intake systems, and all the instruments and bleed valves and actuators that sit within it. You wouldn't want to feed your expensive new engine more poison than it really needs, would ya?

pitzel, for an engineer, you are making unfounded assmuptions here. You assume that the problem is due to over maintenance, that intake valve issues do not occur with engines that have been maintained per the manufacturer's recommendations. In fact, quite a few Audi 2.0 TFSI, 3.2 FSI V6, 4.2 FSI V8, and 5.2 FSI V10 engines are coming into Audi shops across the country every day with intake valve deposits causing startup idle roughness and misfires. Most owners follow the manufacturer's OCI recommendations.

 

[ericthepig]

 Originally Posted By: RI_RS4

pitzel, you have a hypothesis, but no actual science to back it up.

If pitzel is pushing thoese OCIs and then taking data (which he states he is) - then I say he's got some real world science going. Not perfect test, but he's not making blind statements either.

 

[Anies]

Really? I really didn't think there would be an issue. 3k OCI's versus 6-7k oci's. So long as you run the engine hard high rpms once in awhile?. My TC loved being in the upper rpm ranges(sure its a poor mans car) where most of the import cars gain their performance or are tuned for.

 

[Drew99GT]

I understand Pitzel's strategy here: let all the light hydrocarbons and volatile components of the oil burn off until you're left with thick tar for a lubricant. That way, nothing else can vaporize from the tar/caked sludge to contaminate the intake tract. BRILLIANT!

 

[Drew99GT]

 Originally Posted By: ericthepig

 Originally Posted By: RI_RS4

pitzel, you have a hypothesis, but no actual science to back it up.

If pitzel is pushing thoese OCIs and then taking data (which he states he is) - then I say he's got some real world science going. Not perfect test, but he's not making blind statements either.

The only data Pitzel has is his mega long 30,000 + mile oil change on Esso 0w-30 in a 3.1L V-6 n/a. I can't imagine the carnage on a DI turbocharged engine from such a long oil change.

 

[RI_RS4]

 Originally Posted By: ericthepig

 Originally Posted By: RI_RS4

pitzel, you have a hypothesis, but no actual science to back it up.

If pitzel is pushing thoese OCIs and then taking data (which he states he is) - then I say he's got some real world science going. Not perfect test, but he's not making blind statements either.

Eric, Right, but we're talking about DI engines in this thread, not a GM Manifold injected engine. There is a world of difference. He's not sharing any data that he has on DI, and is making some interesting conclusions that are not support by the facts available. DI engines are prone to intake valve deposits, which is a well-documented and researched phenomena. Audi/VW/Porsche DI engines seem to be extremely sensitive to this issue. Audi/VW engines have had this problem irrespective of whether or not oil was changed per the manufacturer's recommendations or earlier. Some Audi engines have had this problem even with the initial factory oil fill.

 

[ericthepig]

 Originally Posted By: Drew99GT

The only data Pitzel has is his mega long 30,000 + mile oil change on Esso 0w-30 in a 3.1L V-6 n/a.

Elementary calculus - let t approach infinity and a lot of real world truth will be exposed.

 

[pitzel]

 Originally Posted By: RI_RS4

you have a hypothesis, but no actual science to back it up.

Well the NOACK volatility test is predictive of how much an oil will vapourize when actually placed in service in an engine. Where do you suppose the components of motor oil that are 'lost' when oil is placed into service end up? Into the PCV system, and ultimately, deposited onto those exhaust valves.

 Quote:

You claim that if the oil were left it that the deposition rate would decrease. What do you base this on? Thus far NOACK volatility. However, NOACK volatility is measured on new, uncontaminated oil, not oil that has been fuel, ethanol and water diluted and degraded.

A chemical reaction, per se, does not occur between molecules of motor oil, and molecules of contaminants in such motor oil. If you dissolve one quart gasoline in one quart motor oil, you can, through the process of distillation, seperate the two components into their original constituents, ie: you're left with one quart gasoline, and one quart motor oil. The only exception to this is when you have combustion of the actual components, but this does not occur at the pressures and temperatures present in the crankcase. As for water, and ethanol, these substances don't exist in motor oil, at engine operating temperatures, long enough to cause any harm (such as emulsification). So what you're left with, in PCV vapour, is a mixture of blowby gases, and volatilized motor oil. Blowby gases, by definition, are gaseous combustion byproducts that don't cause much of any deposition (just look at the exhaust on a modern car -- there's extraordinarily little in terms of particulate matter deposited on exhaust components these days!). So what are you left with? Volatilized motor oil. We know that new motor oil is much more volatile than motor oil that has been in service. So much of the solution revolves around ensuring that the oil that is in service has the lowest volatility possible. Its no coincidence that a major part of the modern API oil specs, and a real driver towards the use of synthetic and semi-synthetic oils in manufacturers recommendations have been driven by volatility concerns. If one keeps changing their oil every few thousand miles, this is just ensuring that the oil that's in their crankcase is as volatile as it possibly can be, creating exactly the problems as described in this thread.

 Quote:

As a matter of fact, some of the RS4 engines in the UK that have had severe valve deposit issues had their oil changed per the manufacturers recommendation, with manufacturer recommend oil.

Maybe the manufacturer's recommendations are overly aggressive on oil changes. As we've discussed here extensively recommended OCI's are often not based on good science, but are rather, based on marketing or non-scientific criteria, good or bad.

 

[Art_Vandelay]

 Originally Posted By: pitzel

GC's not really an extended drain oil (and is really over-hyped), but if a true extended drain product were used (ie: Esso XD-3 0W-40, Amsoil 0W-30/40, etc., with dual gas diesel ratings and TBN to match), 25k with just a filter swap isn't really a stretch at all.

You are saying that German Castrol meets the BMW Long Life specs but isn't an extended drain oil? Would Mobil 1 EP qualify?

 

[RI_RS4]

 Originally Posted By: ericthepig

 Originally Posted By: Drew99GT

The only data Pitzel has is his mega long 30,000 + mile oil change on Esso 0w-30 in a 3.1L V-6 n/a.

Elementary calculus - let t approach infinity and a lot of real world truth will be exposed.

Unless, of course, the system is non-linear.

 

[Anies]

Basically the design of the engine is at fault here? I know the VW/Audi's had problems with sludge regardless of interval.

 

[ericthepig]

RI_RS4 - I wasn't trying to launch into an apologetic defense of Pitzel's post. True he has a hypothesis. And true he has to extrapolate out of his known data points (Esso, 3.1L, long OCI). And it sounds like there's other variables he didn't take into account (eg, known Audi problems from the pt of factory fill). BUT, everything I just pointed out above is true in most all real world science - and I haven't seen data (on this thread) that would indicate Pitzel is patently wrong.

 

[saaber1]

 Originally Posted By: saaber1

Also it should be noted that when VW redesigned the DI 2.0 FSI to the DI 2.0 TSI (avail. in the U.S. roughly mid 2008) they re-angled the fuel injectors so that some/more fuel is hitting the valves. That should help some I would think.

rom the new TSI engine study guide

 

[raytseng]

 Originally Posted By: pitzel

 Originally Posted By: RI_RS4

you have a hypothesis, but no actual science to back it up.

Well the NOACK volatility test is predictive of how much an oil will vapourize when actually placed in service in an engine. Where do you suppose the components of motor oil that are 'lost' when oil is placed into service end up? Into the PCV system, and ultimately, deposited onto those exhaust valves.

 Quote:

You claim that if the oil were left it that the deposition rate would decrease. What do you base this on? Thus far NOACK volatility. However, NOACK volatility is measured on new, uncontaminated oil, not oil that has been fuel, ethanol and water diluted and degraded.

A chemical reaction, per se, does not occur between molecules of motor oil, and molecules of contaminants in such motor oil. If you dissolve one quart gasoline in one quart motor oil, you can, through the process of distillation, seperate the two components into their original constituents, ie: you're left with one quart gasoline, and one quart motor oil. The only exception to this is when you have combustion of the actual components, but this does not occur at the pressures and temperatures present in the crankcase. As for water, and ethanol, these substances don't exist in motor oil, at engine operating temperatures, long enough to cause any harm (such as emulsification). So what you're left with, in PCV vapour, is a mixture of blowby gases, and volatilized motor oil. Blowby gases, by definition, are gaseous combustion byproducts that don't cause much of any deposition (just look at the exhaust on a modern car -- there's extraordinarily little in terms of particulate matter deposited on exhaust components these days!). So what are you left with? Volatilized motor oil. We know that new motor oil is much more volatile than motor oil that has been in service. So much of the solution revolves around ensuring that the oil that is in service has the lowest volatility possible. Its no coincidence that a major part of the modern API oil specs, and a real driver towards the use of synthetic and semi-synthetic oils in manufacturers recommendations have been driven by volatility concerns. If one keeps changing their oil every few thousand miles, this is just ensuring that the oil that's in their crankcase is as volatile as it possibly can be, creating exactly the problems as described in this thread.

 Quote:

As a matter of fact, some of the RS4 engines in the UK that have had severe valve deposit issues had their oil changed per the manufacturers recommendation, with manufacturer recommend oil.

Maybe the manufacturer's recommendations are overly aggressive on oil changes. As we've discussed here extensively recommended OCI's are often not based on good science, but are rather, based on marketing or non-scientific criteria, good or bad.

Prediction: New hot thing on BITOG will be now to "burn-in" motor oil on a beater car for 1k mile before draining and transferring it to the main car for real use.

 

[pitzel]

 Quote:

You are saying that German Castrol meets the BMW Long Life specs but isn't an extended drain oil?

I'm not going to get into an oil war here, but TBN has been an issue on GC that has consistently prevented its use as a long drain (ie: 25k+ miles) oil. TBN's have always been low on GC. As for why a particular manufacturer would call it "Long Life", that might depend on their definition of "Long Life", or it might be in reference to the use of lower-sulfur fuels which do not place the same degree of acid loading onto a motor oil.

 Quote:

Prediction: New hot thing on BITOG will be now to "burn-in" motor oil on a beater car for 1k mile before draining and transferring it to the main car for real use.

Exactly! If contaminants such as dirt, underbody sand, etc. can be kept out, of course!