DI hidden carbon problem??

[ProfPS]

I had a meeting this week with several service managers from a major auto manufacturer (not GM). One of the SMs raised the question whether any of the others have experienced any problems with DI engines? He went on to say that he has seen carbon buildup on the valves (didn't specify intake or exhaust, suspect exhaust) and that the carbon enters the piston cylinder area thus increasing piston/cylinder wall wear because the carbon is like sandpaper.

So far BITOG'ers have been concerned with DI fuel dillution, are there more DI hidden concerns?

 

[Pablo]

I think most active BITOGians are very aware of just how nasty DI engines are on oil.

Take a short tripper DI engine, running on high EtOH fuel - that is a nasty combination for engine oil right there.

 

[demarpaint]

Carbon and fuel dilution, are going to be MAJOR problems facing owners of DI engines. I think it should be back to the drawing board for the DI engine.

While reprogramming the OLM for shorter OCIs might help with fuel dilution, the carbon destroying the cylinders is something that isn't going to be resolved by changing oil early. I think an Inverse Oiler might help [a little anyway], but try telling that to someone who spent all that money for a new car with a state of the art DI engine.

 

[beanoil]

Carbon is building up on the intakes because there is no fuel washing over the stem to keep it clean. Changing oil too often makes the problem worse, but you can't wait very long either because the oil is diluted with fuel. The manufacturers are supposed to be looking into how VVT and overlap can be tuned so some fuel washes up the intake port to help. Can you say Catch 22?

 

[Rickey]

Does anyone anywhere know of an ACTUAL PROBLEM created by DI in a GM engine?

There are lots of them in service now.
Surely some problems would surface by now, given the wide variety of service these engines must be subject to.

In light of the almost immediate problems some imports have had with DI and GM's non-problem. GM must be doing something different and correctly I might add.

 

[sciphi]

Note how GM went back to port injection on the 1.4 turbo in the Cruze while using DI on the 2.0 turbo Ecotec. Maybe they know something us average Joes don't.

 

[Rickey]

I'd speculate the use of port injection on the Cruze is a cost cutting measure.
42 MPG EPA with a small turbo'ed 1.4!!
DI would be icing on the cake.
DI would probably raise the cost past their target.

 

[PandaBear]

Originally Posted By: sciphi
Note how GM went back to port injection on the 1.4 turbo in the Cruze while using DI on the 2.0 turbo Ecotec. Maybe they know something us average Joes don't.


It is only part of the reason. DI with no stratified spray pattern will actually be worse in fuel economy than port injection in low duty cycle (part throttle, low rpm, etc). That's why the Lexus IS350 has dual injector to compensate for the low duty cycle, while its 2.5L brother IS250 uses only direct injection.

Also with turbo you usually have to run fairly rich, so port injection is probably sufficient.

 

[GMBoy]

Originally Posted By: Rickey
Does anyone anywhere know of an ACTUAL PROBLEM created by DI in a GM engine?

There are lots of them in service now.
Surely some problems would surface by now, given the wide variety of service these engines must be subject to.

In light of the almost immediate problems some imports have had with DI and GM's non-problem. GM must be doing something different and correctly I might add.



Agreed. Not that the potential doesn't exist for the issue..I just haven't seen or heard of any problems yet.

I own a 2008 CTS with the 3.6DI and it's been fine so far. I do spray intake cleaner thru the air intake at every oil change to wash the valves so "if" there is a problem I think I am atleast controlling it.

 

[SteveSRT8]

Newer DI motors have excellent dispersal of fuel spray pattern at any engine speed. Their outrageously high fuel pressures guarantee it.

If there is going to be widespread problems you'd think we'd know by now. Many times the automakers concentrate on extreme durability testing and forget about "I'm just going to Publix" driving!

 

[Sayjac]

The DI carbon build up issue is what kept me away from a Sonata 2.0 Turbo purchase recently. And Bitogers have discussed the carbon build up concern, perhaps just not as much on the pcmo board.

The current BG Fuel Test on an Ecoboost Taurus has been mentioned and posted here many times. Many correctly point out, that BG has a vested interest in the DI carbon build concern. I'd say, as also do the auto makers have a vested interest in showing the opposite results.

Also it has been suggested, that one should just purchase a DI vehicle and let the manufacturer's sort out any issues while under warranty. In Hyundai's case that warranty time is substantial. However, I don't see the carbon build up concern as a complete engine failure issue, but rather a gradual loss of performance and efficiency/economy. For an owner, that is something difficult to prove without extensive testing and expensive diagnostic tools like the boroscope and dyno used in the BG Test.

So, perhaps DI carbon buildup is much ado about nothing, then again perhaps not. Owners will be the ones testing the current crop of DI engines in real world use to find out.

 

[demarpaint]

Originally Posted By: sayjac
Owners will be the ones testing the current crop of DI engines in real world use to find out.


This is true, and happens with some automotive products, like oil filters for example. A mile/time in service use is assigned to an extended drain oil filter for example, then changed when problems pop up. That's one of a few examples that come to mind. I feel sorry for the people who followed the directions and didn't have a problem, yet. I think the DI engine problems will slowly appear as you mentioned, and the mfg will deal with the problems as they pop up and learn in the process. Hopefully the problems occur during the warranty, if not I feel bad for those people too if the problem pops up later on, and hits their pocketbook! The DI engines on the road now, are the test engines for improved designs that will come later. As a result of their problems in real world use, the mfgs will scramble to make them better. JMO

 

[spasm3]

If i bought a DI engine, i would probably make some sort of catch can for the pcv system. Something i could take on an off so its not there for warranty work!

If you trade or lease , i would not worry about it. IF you plan to keep it 10-15 years then i would make the catch can system.

 

[demarpaint]

I'd hook up my Inverse Oiler if I owned a DI engine. They feed cleaner via a vacuum line in hopes to clean them up. I figure if I feed it MMO via the vacuum line when new, that might keep it clean. The jury is still out on DI engines. I don't own a DI engine and probably won't be in the market for anything new for at least another 2 years. By that time the bugs will either be worked out, or we'll have more data on what is helping to reduce or eliminate the carbon problems.

 

[Finklejag]

BMW knows about this problem. They now recommend that DI owners bring their cars in every 15K for treatment. They use crush walnut shells to clean off the valves.

I own a 2010 VW GTI. I will be doing the BG GDI cleaning every 15K.

 

[mechtech2]

There are problems already with some DI engines.
Valve deposits are #1. This is a very real problem.
They have not been out long enough to amass a lot of real world long term data.
But the idea has flaws that the car mfrs. are addressing with various methods. One is an additional injector upstream!

 

[marek0086]

Crushed walnut shells?!?!!?

And how exactly do they clean the valves with crushed walnut shells??

 

[marek0086]

Upstream injection??.... doesnt that defeat the whole purpose of DI ?!

 

[MarkM66]

Originally Posted By: marek0086
Crushed walnut shells?!?!!?

And how exactly do they clean the valves with crushed walnut shells??


Remove cylinder heads, remove valves, clean and re install.

I would guess..

 

[Kestas]

Crushed walnut shells is a commonly used grit blast medium. It removes deposits without leaving harmful abrasive residue. Soda and CO2 pellets are another.