Carbon build-up in DI engines

Originally Posted by FlyByGTI

Looking around it seems like there are a few things with the Diesel direct injection that are interesting. Apparently the biggest issue facing those engines is idling. The recommendation (and this may explain why cummins drivers seem like d-bags all the time), is that to combat the build up in diesel engines you should floor it 10-15 times a drive. Apparently the way that the EGR is setup, it closes during full fuelling which means that flooring it should blast away all the crud and gunk. It doesn't seem like the Gas Direct Injection has that same setup on them. It looks like the smaller displacement turbo cars should have an easier time avoiding carbon buildup because they are more likely under heavy load for longer periods of time.

Originally Posted by Mitco39

Thats not entirely true. I have seen the inside of diesel engines on farm trucks driven by old farmers with nothing out of the ordinary in terms of build up. I mean you always will have some but nothing to affect performance a noticeable amount or anything like that. Surely nothing like that picture. I suggest deleting the external EGR where ever possible, its just not a good setup. Most new cars just have a internal EGR by changing the cam degrees with respect to each other.

I bet if there was a way to turn this off on the Z you would see both fuel mileage and power gains from it. The Z does not have external EGR system on it, so it only leads me to believe it is controlled by the VVEL.