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Old 07-29-2014, 12:26 PM   #13 (permalink)
FlyByGTI
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Quote:
Originally Posted by Mitco39 View Post
Im just curious as to what causes this to be an issue here but yet you can have a diesel with 500K miles and the valves will look ok (not good, but not coated like that picture by any means). Maybe there ports are designed in such a way to speed up the air entering the cylinder so that the air moves much faster around the valve? I know for a fact that the EGR systems on a diesel are way way more messy than that of a gas engine. All that soot goes into the intake tract. If you could find the difference between the two I think you would be well on your way to a solution. For all we know it could even just be a special coating on the valves.
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.
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