Regarding intake valve desposits with DI..

[UG_Passat]

Originally Posted By: glxpassat
I believe Toyota/Lexus solved this problem by letting low pressure injectors spray a little gas on the valve like it's always been done, while still using DI for the majority of the gas charge. It seems like a very easy and reasonable solution to me.


Nope.

The Toyota D4-S system uses both port & direct injection.

Port & direct for low to medium loads

direct only for high loads.

the old multiport system Toyota used on many engine did have an extra injector to spray additional fuel during cold starts, aka cold start injector.

 

[cryption]

Originally Posted By: glxpassat
I believe Toyota/Lexus solved this problem by letting low pressure injectors spray a little gas on the valve like it's always been done, while still using DI for the majority of the gas charge. It seems like a very easy and reasonable solution to me.


Sounds like they are just adding one more system to break. Cars are just too complicated these days. They pack so much technology into a car, when really it just hurts the length a car will last.

Of course, cars are considered disposable by many now - lots of people lease or get a new car after 3 or 4 years.

 

[Audi Junkie]

I use 2C and Techron mixed in every tank.

 

[cryption]

But fuel additives won't do anything because no fuel goes over the intake valves. It will help your injectors, tho.

 

[MCompact]

The BMW valve deposit issue resulted in a Service Campaign in the mid '80s. One result of the problem was the BMW Valve Deposit test.

 

[OldBaldy]

Originally Posted By: cryption
But fuel additives won't do anything because no fuel goes over the intake valves. It will help your injectors, tho.


Exactly. No amount of fuel additive is going to clean the intakes and valves when the fuel does not go anywhere near them.

 

[m6pwr]

Originally Posted By: cryption
But fuel additives won't do anything because no fuel goes over the intake valves. It will help your injectors, tho.


Maybe not entirely true. In di engines, anything that's in the gas will to an extent get in the oil (i.e., fuel dilution of oil) and its the oil vapors (sucked up thru the CCV sytem) that I believe cause the deposits on the intake side. Whether or not any of the fuel additives succeed in treating this problem, I do not know.

 

[cryption]

Originally Posted By: MCompact
The BMW valve deposit issue resulted in a Service Campaign in the mid '80s. One result of the problem was the BMW Valve Deposit test.


But now BMW engines are direct injected. ALL DI ENGINES GET DEPOSITS.

 

[glxpassat]

Originally Posted By: UG_Passat
Originally Posted By: glxpassat
I believe Toyota/Lexus solved this problem by letting low pressure injectors spray a little gas on the valve like it's always been done, while still using DI for the majority of the gas charge. It seems like a very easy and reasonable solution to me.


Nope.

The Toyota D4-S system uses both port & direct injection.

Port & direct for low to medium loads

direct only for high loads.

the old multiport system Toyota used on many engine did have an extra injector to spray additional fuel during cold starts, aka cold start injector.


Not sure why you are disagreeing with me, as what I described is the D4-S system. Most cars are under light/medium load most of the time which would allow the port injection to clean the valves.

 

[Audi Junkie]

Originally Posted By: m6pwr
Originally Posted By: cryption
But fuel additives won't do anything because no fuel goes over the intake valves. It will help your injectors, tho.


Maybe not entirely true. In di engines, anything that's in the gas will to an extent get in the oil (i.e., fuel dilution of oil) and its the oil vapors (sucked up thru the CCV sytem) that I believe cause the deposits on the intake side. Whether or not any of the fuel additives succeed in treating this problem, I do not know.



So we're discounting valve lap now?

 

[cryption]

Calling saaber for correct information ... lol

 

[saaber1]

In terms of Audi/VW, as I recall when they changed from the FSI to the TFSI they changed the angle of the injectors so that some fuel hits a portion of the bottom of the valve. So in that sense fuel injector cleaner could possibly help a little in theory.

Another thing to think about is what effect does the cleaner have on the oil? For example does it affect the anti-oxidants? In other words is it contributing to increased deposit buildup by degrading the oil faster, creating cross-linkages with the oil, decreasing additives, or? We would need a tribologist to try to sort that out I think.

In terms of valve overlap, I would think it depends on the specific engine and also again the question of whether the overlap helps the deposits or whether the particulates supplied actually increase deposit formation.

I think fuel injector cleaner would have very little impact to the valve deposits in DI engines. Certainly they can help clean injectors. I know there are studies out there on fuel injected engines (not DI as far as I know)that show some cleaners increase deposits. Also I read one study where 3 different gasoline blends were tried (in engines with no engine oil component reaching the valves) that showed virtually no difference in deposits. When doped with used oil, those same 3 showed increased deposits.

We can speculate about minute ways of how it might affect the valve deposits but we would have to have the complete picture of both the positive and negative effects to do that IMO.

 

[MCompact]

Originally Posted By: cryption
But now BMW engines are direct injected.


Not all of them. See my post on page one of this thread
.
Originally Posted By: cryption
ALL DI ENGINES GET DEPOSITS.


Thank you for the helpful information...

 

[dwendt44]

I wonder if a catch can near the PCV valve would help any!?!?

 

[dparm]

The Audi FSI motors saw no improvement with that.

 

[Silk]

Originally Posted By: A_Harman
I haven't found an explanation for the mechanism involved in the formation of intake valve deposits. Can people out there in BITOG-land post their explanations or theories?


With Mitsubishi GDI engines from the '90's it was mainly caused by EGR - they used a lot of EGR to cut emissions.Here in NZ it was also blamed on our poor fuels,as they were never designed to run on the rubbish here.Later GDI engines were better,and then Mitsi finally stopped them.

 

[dwendt44]

As I recently ordered a new GM product this subject is of importance to me.
It appears that all, or at least most, GM 4 and 6 cylinder engines are DI, so we should be hearing of problems with these before long.
I wonder if short trip, stop and go driving are a factor.

 

[glxpassat]

I think the build-up will occur as long as gasses are feed back into the engine's intake. They may be able to slow it down until the warranty's gone, but unless they use something like Toyota's D4-S system, I don't see how the build up can be avoided.

 

[cryption]

And it seems to me that having two injection systems like Toyota is just asking for double the parts to replace when they wear, and more to go wrong.

 

[A_Harman]

Originally Posted By: dwendt44
As I recently ordered a new GM product this subject is of importance to me.
It appears that all, or at least most, GM 4 and 6 cylinder engines are DI, so we should be hearing of problems with these before long.
I wonder if short trip, stop and go driving are a factor.


I think your best course would be to religiously follow the Owner Manual recommendations for oil selection and change intervals. That way, if you have a problem in the future, they can't give you any guff about using a non-approved oil. With these DI engines new to the market, nobody knows more about them than the manufacturer.