Direct injection engines and fuel dilution/carbon

[The motor guy]

Ive heard these new direct injection engines have problems with carbon buildup on the intake valves and fuel dilution. Well my question here is diesels have pretty much always been direct injection and they don't have problems with carbon buildup on the intake valves. Why do these gas engines have that problem? Also since its direct injection does that mean combustion temps would become cool at idle causing fuel dilution like on a diesel when idled in cold weather well technically all weather.

 

[electrolover]

most diesels on the road dont have egr systems which is where the deposits come from. they had their problems tho, the old mechanical cat injectors were really bad about clogging ports and changing the mixture. plus the heat from combustion would actually pit the needle valves and seats.

(when i was a kid i worked at a diesel fuel injector shop)

 

[Shannow]

Originally Posted By: electrolover
most diesels on the road don't have egr systems which is where the deposits come from.


Ya reckon ?

I don't see many without EGR these days.

 

[chubbs1]

I believe part of it is the better quality of ULSD. We have lousy gas, lets face it. I really think that makes a difference.

EGR systems are standard equip on most diesels I see nowadays.

 

[JHZR2]

My 82 MB turbodiesel has EGR and they go hundreds of thousands of miles without much issue. Open up an intake and you will see deposits though.

Perhaps it is more of an imagined issue in that regard (fuel dilution and some of the others not so much...)?

 

[Silk]

Early indirect injection diesels with EGR didn't have a lot of intake deposits,they were there,but the engine could run it's whole life without any problems. The modern common rail direct injection diesels do have considerable intake deposits from EGR.

 

[MrCritical]

I don't know the answer, but the problem is that now you see significant accumulations at low mileage.

A few auto manufacturers are paying to remove the deposits. Most are not.

 

[demarpaint]

Diesel vs gas are two different animals. There was a pretty good explaination of why it works better in diesel engines here on Bitog, I can't find it. DI in gas engines is a problem looking for a solution. I also think that gas has more of a negative impact when it gets into oil than diesel fuel does.

 

[mechtech2]

Carbonless diesels? Really?

 

[ffhdriver]

It's is reported that the problem is deposits from the PCV and not the EGR system.

 

[Silk]

The Nissan ZD30 diesel engine has separate inlet tracts for both valves,and separate butterflies for each. One intake does PCV,the other EGR - the PCV tract has just oil in it,the EGR has thick deposits.

 

[Shannow]

Not anymore Silk, not anymore.

And disabling the swirl/egr butterfly has made it a really nice drive as well (will break traction at idle on snow now, rather that herky jerky part throttle take-offs)

 

[Silk]

I'd like to disconnect the EGR on the Tritons,but Mitsubishi would frown upon it,and customers don't really care - they like to complain,but not to do something about a long term fix. At least I've got the guys to stop using CI-4...but too late to make a comparison.

 

[dparm]

Originally Posted By: Shannow
Not anymore Silk, not anymore.

And disabling the swirl/egr butterfly has made it a really nice drive as well (will break traction at idle on snow now, rather that herky jerky part throttle take-offs)


That's illegal in pretty much every state...

 

[Silk]

I don't know about Australia,but we have no emission testing in New Zealand,so EGR systems are often removed.