Topic: Modern Audi's direct injected V6 and V8 Carbon build-up issues.

[aquadorhj]

so, it seems, judging by  browsing thru Audi forums, that modern Audi's direct injection larger displacement engines suffer from quite a lot of carbon build up on valve trains on intake valves regardless of fuel used or driving styles.

this is a concern i have, as i thought the RS4 or R8 would one day make its way into my garage....
for those who were interested in it, i think you should know.

http://www.audizine.com/forum/showthread.php/336352-Audi-FSI-Engine-Carbon-Build-up-Megathread

i saw someone write that modern Audi is like a magical car...  mysterious things happen on Audis and nobody can explain why.

[HeliDriver]

It's not just Audi: There's been the same complaints with the 2.0T in VW cars.

I don't think there's any mystery to it: it's going to be a concern with any direct injection engine that doesn't get a cleaning spray of fuel over the intake valves.

[ktm525]

Land Rover is struggling with this as well in the 5.0L (Jag V8). Enough to make me look for a 2009 LR3 with the trusty old 4.4.

[johngenx]

I understand that is why some manufacturers (ex: Toyota/Subaru on the new DI 2.0L) are using a combination of DI and conventional injection.  Through variable vale timing and injection mapping you get the best of all worlds, including the power/economy of DI and the cleaner operation of port injection.

[rrocket]

I understand that is why some manufacturers (ex: Toyota/Subaru on the new DI 2.0L) are using a combination of DI and conventional injection.  Through variable vale timing and injection mapping you get the best of all worlds, including the power/economy of DI and the cleaner operation of port injection.

The D4S system has been in use since 2006 on the IS models...with no issues whatsoever.

[vdk]

Would Shell gasoline with nitrogen Enrichment stop carbon build up in those engines like Shell claims?

[aquadorhj]

Would Shell gasoline with nitrogen Enrichment stop carbon build up in those engines like Shell claims?

it wouldn't help, because fuel/air mixture never washes or touches the intake valves in the vw ag. engines. 

[rrocket]

Would Shell gasoline with nitrogen Enrichment stop carbon build up in those engines like Shell claims?

it wouldn't help, because fuel/air mixture never washes or touches the intake valves in the vw ag. engines. 

Correct.

[articsteve]

it's going to be a concern with any direct injection engine that doesn't get a cleaning spray of fuel over the intake valves.

The jurys still out this issue.  Some pretty "popular" brands have gone heavy DI and in a few years there might be some serious blow back.  Lest I can only hope. 

[Flinter]

I understand that is why some manufacturers (ex: Toyota/Subaru on the new DI 2.0L) are using a combination of DI and conventional injection.  Through variable vale timing and injection mapping you get the best of all worlds, including the power/economy of DI and the cleaner operation of port injection.

The D4S system has been in use since 2006 on the IS models...with no issues whatsoever.

This system does seem to be the best of both worlds. Is it used in any other 3.5L equipt. Toyota/Lexus vehicles?

Does the complexity of the system limit aftermarket support much?

[PJungnitsch]

The way I understand it the issue is more dirty breather/egr systems on some engine designs. Stop dumping carbon and oil onto the valves and the problem goes away. What was an acceptable level of 'recycling' in a port injection system is not good enough for DI.

[tpl]

^^^   Need to find another way to do EGR or even better...not do it at all. It is a left over from the early days of emission controls. According to Wiki Chrysler have a new engine with no EGR.


Also to stop using the inlet as a source of low pressure to purge the crankcase of fumes.

[rrocket]

This system does seem to be the best of both worlds. Is it used in any other 3.5L equipt. Toyota/Lexus vehicles?

Does the complexity of the system limit aftermarket support much?

They use it in their V8s also...and now in the new Subraru BRZ/FR-S.

It indeed will limit forced induction tuning to some extent.  You'd need to have a VERY savvy tuner and would need to be running 12 channels for injectors (for a V6) for optimal tuning.  Otherwise, some companies have made a specials piggy-back ECU to work with the system.  There are some turbo IS-F running that seem to be doing OK.