DI and engine power loss over time

[Sport-Tech]

Interesting article on Daily Tech today looking at the potential for power loss over time in DI engines due to carbon buildup on intake valves:

http://www.dailytech.com/Direct+Inje...ticle21962.htm

The article provides dyno readouts for an Audi RS4 when it was relatively new and then before and after engine cleaning that show a dramatic power loss which was then reversed by the clean. A good discussion follows.

It's claimed in the discussion that the use by Toyota of port injection at low power and idle alongside DI in its current DI engines allows the cleaning agents in the fuel to wash the valves regularly so this may not be an issue for the FR-S.

[colHolm]

This is true. On the 4GR in the Lexus IS 250, there are issues with carbon build-up that over time can cause the check engine to light up. This engine has direct injection only. The 2GR in the IS 350, which uses Toyota's D4-S injection system has no such issues.

[ichitaka05]

Hm... interesting article. Thanks! I learned something

[markitect]

I don't think we will have a problem with the combination port and direct injection.

My question is, why aren't the people claiming it is carbon build up using a cleaner in the air intake?

[bigbcraig]

^ wut?

"why aren't the people claiming it is carbon build up using a cleaner in the air intake?"

Do you mean, "why aren't people (who think carbon is building up) using a cleaner in the air intake?"

I don't think it would have much affect. The stuff will get pretty caked onto the intake valves and a short burst of whatever you put in wont do much -- but it will confuse the shit out of the ECU and, if you don't spray it in enough downstream, can really mess with your MAF.

I know recently I saw a picture of a porsche (?) intake valve that looked quite nasty but can't find it. The buildup was attributed to DI.
As has been said before, the D4-S system that uses port and direct should amke this a complete nonissue, and make tuning much easier / power potential higher (pretty hard sometimes now because there aren't many replacement direct injectors).

[70NYD]

think about this. arent all (most) of the cars you mentioned here turbocharged?
apart from the turbo feeding some oil in to the intake, what else could possibly cause carbon buildup?? there is nothing in air that is flammable

[Random_Art]

Originally Posted by 70NYD

think about this. arent all (most) of the cars you mentioned here turbocharged?
apart from the turbo feeding some oil in to the intake, what else could possibly cause carbon buildup?? there is nothing in air that is flammable

Oxygen is extremely flammable, yo. But is it oxygen causing the carbon buildup? no.

[Snaps]

Originally Posted by 70NYD

think about this. arent all (most) of the cars you mentioned here turbocharged?
apart from the turbo feeding some oil in to the intake, what else could possibly cause carbon buildup?? there is nothing in air that is flammable

That's the same thing I thought when I heard about the problem...

As a guess - maybe the exhaust gases aren't fully evacuated out of the cylinder when the exhaust valve closes, then the intake valve opens and some of the exhaust gases escape into the valve port/valve area, and then cakes itself onto the valves over time.

That's just a guess though, I'm not sure how much (if any) exhaust gases would be left in the cylinder, let alone be able to escape against the fresh air coming back in when the intake valve opens...