Acknowledgement of the Audi/VW FSI Deposit Issues

Status
Not open for further replies.
Joined
Jul 18, 2006
Messages
1,175
Location
Rhode Island
Directly from the technical staff of VAG is complete acknowledgment of the FSI intake valve deposit issue, and it's impacts, including: decreased performance, misfires, catalytic converter damage ... etc.

VW Patent on "Direct Injection Internal Combutstion Engine"

Quote:
"Gasoline engines with direct injection of the fuel into the combustion chamber, i.e., not into the intake port, suffer especially from the problem of the formation of carbon deposits on components. Carbon deposits form especially in the neck region of intake valves. A more exact analysis of how these carbon deposits form leads to the following result: Oil and fuel constituents first form a sticky coating on the components. These constituents are chiefly long-chain and branched-chain hydrocarbons, i.e., the low-volatility components of oil and fuel. Aromatic compounds adhere especially well. This sticky base coating serves as a base for the deposition of soot particles. This results in a porous surface, in which oil and fuel particles in turn become embedded. This process is a circular process, by which the coating thickness of the carbon deposits continuously increases. Especially in the area of the intake valves, the deposits originate from blowby gases and from internal and external exhaust gas recirculation, and in this process, the blowby gasses and the recirculated exhaust gas come into direct contact with the intake valve."

"Especially in the area of the neck of the intake valves, excessive carbon deposits have extremely negative effects for the following reasons: In the case of Otto direct injectors, the successful ignition of the stratified charge depends to a great extent on the correct development of the internal cylinder flow, which ensures reliable transport of the injected fuel to the spark plug to guarantee reliable ignition at the spark plug. However, a coating of carbon deposits in the neck region of the intake valve may interfere so strongly with the tumble flow that ignition failures may occur there as a result. Under certain circumstances, however, ignition failures can lead to irreversible damage of a catalytic converter installed in the exhaust gas tract for purifying the exhaust gas. Furthermore, the coating of carbon deposits in the neck region of the intake valve causes flow resistance, which can lead to significant performance losses due to insufficient cylinder filling, especially in the upper load and speed range of the internal combustion engine. In addition, the carbon deposits in the neck region of the intake valve may prevent correct valve closing, which leads to compression losses and thus sporadic ignition failures. This in turn could irreversibly damage the catalytic converter. There is the potential for small particles to break away from the coating of carbon deposits in the neck region of the intake valve and get into the catalytic converter. These hot particles may then cause secondary reaction and corresponding local damage of the catalytic converter. For example, a hole may be burned in the structure of the catalytic converter."

"Globular deposits are found especially on the valve stem downstream from a partition plate in the intake port. Due to the dripping of high-boiling hydrocarbons from the partition plate towards the valve neck or valve stem, globular carbon deposits eventually form there by the sequence of events explained above. These deposits on the valve stem can result in flow deficits due to undesired swirling and turbulent flow around the globular carbon deposits. This may persistently interfere with the formation of stable tumble flow from cycle to cycle."

"A possible solution would be to keep these sources of deposits away, for example, from the intake valve, by completely eliminating exhaust gas recirculation and the introduction of blowby gases into the intake port. However with the combustion behavior of modern reciprocating internal combustion engines, at least external exhaust gas recirculation and the introduction of blowby gases into the intake port are absolutely necessary for reasons of emission control and fuel consumption, so that this approach is not possible. "
 
Could they not cure the problem by putting a secondary fuel injector at the end of each intake runner (roughly where the injector would be on a normal EFI set up) to inject a small amount of gasoline that would wash the intake valve on the intake stroke?
 
Heck, they don't even acknowledge it as being a problem at the dealer service level. It does not appear that this new valve design has gotten into production yet.
 
Originally Posted By: RI_RS4
They could, but I believe the patent belongs to another company.


They could patent the secondary injector "cure" and get a whole new patent on the entire set up.
thumbsup2.gif
 
Originally Posted By: G-MAN
Could they not cure the problem by putting a secondary fuel injector at the end of each intake runner (roughly where the injector would be on a normal EFI set up) to inject a small amount of gasoline that would wash the intake valve on the intake stroke?


That would be acknowledging that FSI isn't ready for primetime and port FI is still the way to go. And of course, adds complexity.

The solution is an exceptionally good PCV system with a redesign of the path the crankcase fumes goes through the intake. I'm sure they'll figure it out eventually.
 
Wow, fantastic info!

After RL_RS4's last post showing the deposits on the Euro car, I requested a bid to convert my pcv system to a "slashcut" system, which will send pcv gunk to the exhaust and not to the intake manifold. Simple and effective solution and cranckase gases are still pulled out under vacuum.

slashcutcopy.jpg
 
This is a classic case of a system designed for the race track having problems in the "translation" to street use.

Anyone who has ever looked at the inside of a typical port injected/EGR intake manifold upstream of the injectors would have been able to predict this problem. The same sort of deposit accumulation, except with DFI all the way to, and including, the intake valves.
 
hehe I was right..screw the emissions

"A possible solution would be to keep these sources of deposits away, for example, from the intake valve, by completely eliminating exhaust gas recirculation and the introduction of blowby gases into the intake port. However with the combustion behavior of modern reciprocating internal combustion engines, at least external exhaust gas recirculation and the introduction of blowby gases into the intake port are absolutely necessary for reasons of emission control and fuel consumption, so that this approach is not possible. "
 
What about an physical EGR block-off with an aftermarket software upgrade to make it work?

This is exactly what the turbodiesel guys do. If I'm not mistaken, there is plenty of aftermarket to achieve this for those turbodiesel trucks.
 
A catch can system would be of great benefit to those DI engines.

The problem for a mfr. is that it relies on the consumer to empty it rather frequently. Anything that relies on the consumer is automatically faulty.
 
Last edited:
Originally Posted By: G-MAN
Could they not cure the problem by putting a secondary fuel injector at the end of each intake runner (roughly where the injector would be on a normal EFI set up) to inject a small amount of gasoline that would wash the intake valve on the intake stroke?


Toyota's 2GR-FSE motor has direct injection & port injectors.
 
What about other brands with DI engines(toyota excluded), do they have similar intake/valve deposits as audi/vw?

also why we don't see this problem on diesel cars, they too have direct injection so no fuel get on their intake valves?
 
Last edited:
Originally Posted By: zoomzoom
also why we don't see this problem on diesel cars, they too have direct injection so no fuel get on their intake valves?


Now that EGR is being put on a lot of diesel engines, I would not be surprised if we don't start seeing the problem with them as well.
 
this is probably why diesel doesn't have such problems

more info here:
Good study of fuel caused deposits

• Gasoline 87: As you can see from Figure 4, gasoline 87 deposit on SS304 has the highest carbon signal with a temperature program oxidation (TPO) peak at 800°C. On SS416 deposition from gasoline 87 gave three TPO peaks at 350°C, 400°C and 450°C. The lowest carbon signal for gasoline 87 deposit was found on Inconel 718 with a TPO peak at 400°C. Overall gasoline 87 produced the highest amount of carbon deposits.

• Gasoline 89: Gasoline 89 deposits on SS304 gave two TPO peaks at 400°C and 450°C as can be seen in Figure 4. Gasoline 89 deposit on SS416 also gave two TPO peaks, one at 350°C and the other at 500 °C. The lowest amount of carbon deposit formed from gasoline 89 was found on Inconel 718 with a TPO peak at 500°C.

• Gasoline 93: As can be seen on Figure 4, gasoline 93 gave overall the lowest amount of carbon deposit out of the three gasoline samples. Gasoline 93 deposit on SS304 produced a TPO peak at 400°C. Gasoline 93 deposits on SS416 have the second highest carbon signal with a TPO peak at 450°C. Out of the three metals tested with gasoline 93, Inconel 718 collected the lowest amount of carbon deposit with a TPO peak at 450°C.

• Diesel fuel: The deposit from this fuel gave the lowest carbon signal out of all the fuels that were tested. With all three metallic surfaces that were tested there are barely any TPO peaks. Overall the diesel fuel sample leaves the least amount of carbon deposit on all the surfaces tested.
 
Last edited:
Originally Posted By: G-MAN
Originally Posted By: zoomzoom
also why we don't see this problem on diesel cars, they too have direct injection so no fuel get on their intake valves?


Now that EGR is being put on a lot of diesel engines, I would not be surprised if we don't start seeing the problem with them as well.


It's a real problem for many modern diesel trucks. Why Duramax owners should block EGR Pics:

Block that EGR
 
Status
Not open for further replies.
Back
Top