Solutions for DI Engines?

[demarpaint]

Originally Posted By: shpankey
At 34k miles I've lost 3 - 4 mpg & very substantial power on my car from DI.



This is exactly what my mechanic buddy told me a few weeks back, he's had complaints from customers losing power and mpg in even fewer miles. I'm waiting on reports from someone who plumbed in an Inverse Oiler. I still believe that is one of the better preventative measures, but it has to be done early on before the carbon on the valves starts building up. Its a shame DI is here to stay, I think it will be a few years before they get the bugs out, and by that time they'll be on to another technology.

 

[A_Harman]

Originally Posted By: shpankey
At 34k miles I've lost 3 - 4 mpg & very substantial power on my car from DI.



Have you been using the old-school method of "blowing the carbon out" on a regular basis?

My dad used to take us boys out in the family station wagon and told us to look out the back for black smoke while he floored it for about a mile.

 

[Bill in Utah]

Originally Posted By: A_Harman
Originally Posted By: shpankey
At 34k miles I've lost 3 - 4 mpg & very substantial power on my car from DI.



Have you been using the old-school method of "blowing the carbon out" on a regular basis?

My dad used to take us boys out in the family station wagon and told us to look out the back for black smoke while he floored it for about a mile.


It would not help at ALL. In fact it could make the deposits WORST.

A understanding of the issue with DI would help here...

 

[SteveSRT8]

I am concerned with the focus on band aid solutions. Injecting ANY fluid into a modern dry manifold will likely result in uneven distribution and may cause other issues. Unless you put the 'cleaner' in at the intake valve for each cylinder I can't see this being effective.

Or you can simply dump in HUGE amounts and hope for the best.

I'm in the camp that thinks DI is still being developed. I am also watching carefully to see if Ford has solved this issue by using Variable cam timing to creat overlap conditions to deliberately expose the intake valves to reversion.

 

[GMBoy]

Originally Posted By: johnachak
Originally Posted By: JoeWGauss
Originally Posted By: GMBoy
[
There is no special coating inside the throttle body that can be harmed by carb cleaner like some vehicles..which was why intake cleaner was created.

.


INCORRECT!

There are some manufacturers that DO in fact use a coating on the inside the TB to reduce the amout of buildup that will stick to it.


They specifically state that using regular carb cleaner will destroy that coating.


Pray tell, Is Cadillac one of those?



No. No GM cars use a coating on the throttle bodies. Ford was big on that, however.

 

[SteveSRT8]

Interesting to note that my two oldest trucks, one with 200k miles and one with nearly 400k miles, and neither has any issues on the original TB.

 

[demarpaint]

Originally Posted By: SteveSRT8
I'm in the camp that thinks DI is still being developed.


I'm with you, and believe the end user is road testing the product.

 

[A_Harman]

Originally Posted By: Bill in Utah
Originally Posted By: A_Harman
Originally Posted By: shpankey
At 34k miles I've lost 3 - 4 mpg & very substantial power on my car from DI.



Have you been using the old-school method of "blowing the carbon out" on a regular basis?

My dad used to take us boys out in the family station wagon and told us to look out the back for black smoke while he floored it for about a mile.


It would not help at ALL. In fact it could make the deposits WORST.

A understanding of the issue with DI would help here...



Whatever the source of intake valve deposits, and I have yet to read a good explanation in this or any other thread of why they occur, the higher heat and acceleration loads put on the intake valves by an engine running at high speed and load may clean some of them off.

 

[badtlc]

Originally Posted By: A_Harman


Whatever the source of intake valve deposits, and I have yet to read a good explanation in this or any other thread of why they occur, the higher heat and acceleration loads put on the intake valves by an engine running at high speed and load may clean some of them off.


How can you comment on this problem and not know what causes it? The valve deposits on a DI engine are from oil vapor coming back through the PCV system and collect on the valves because no fuel is washing them off.

 

[A_Harman]

How do you know it's oil vapor and not something from the fuel?

 

[badtlc]

Originally Posted By: A_Harman
How do you know it's oil vapor and not something from the fuel?


Do you understand what direct injection is?

 

[A_Harman]

You betcha. The point I am making is there are no totally isolated systems in engines. Even though fuel is being injected directly into the combustion chamber, because of blowby, or poor atomization of fuel, small amounts of fuel can still get into the intake ports.

 

[PandaBear]

Originally Posted By: badtlc
Originally Posted By: A_Harman
How do you know it's oil vapor and not something from the fuel?


Do you understand what direct injection is?


For Lexus / Toyota the problem is mostly fuel vapor, not oil vapor.

 

[SteveSRT8]

It would seem unlikely that fuel vapor would deposit on the valves as a hard carbon like substance.

Doesn't this same fuel have additives to clean valves?

 

[kr_bitog]

Originally Posted By: SteveSRT8
It would seem unlikely that fuel vapor would deposit on the valves as a hard carbon like substance.

Doesn't this same fuel have additives to clean valves?


It is simply not all fuel contains same level additives around the world, and short trip low rpm driving tends to develop the deposits that then hardened due to high heat of modern engine nowadays. It may not exactly the same engine design, but I guess that's what italian tune up and MMO try to solve in the past

 

[wag123]

It was my understanding that the intake valve deposits in DI engines were being caused by the small amount of oil running down the valve stem and baking to the hot intake valve over time. On the exhaust side this oil is burned off. The valve guide seals are not 100% effective, they constantly allow a small amount of oil through to lubricate the valve guides. The valve guides would wear out astronomically fast if they didn't get some small amount of lubrication.

 

[kr_bitog]

One article on the issue
http://delphi.com/pdf/techpapers/2009-01-1495.pdf

 

[ffhdriver]

I see nothing in this article about intake valve deposits which is the main problem.

 

[bluesubie]

This was posted in the Interesting Articles forum:
http://www.autoobserver.com/2011/06/direct-injection-fouls-some-early-adopters.html

-Dennis

 

[Ursae_Majoris]

It is a good article.
The article did not mention that GM' DI technology was originally developed by Isuzu. One of the first DI vehicle on the market (actually second, after BMW, IIRC) was the 2003 Isuzu Axiom.