Direct Injection problems

[Tallredrider]

I was telling a buddy of mine who is a real gear head (teaches automitive mechanics in college) about my new G23. I told him about the supposed improvements in torque and fuel efficiency, as I have been a little skeptical. He told me that I will notice for sure the improvements that have been touted on this website and elsewhere, but that there may be some pretty significant problems down the road. A simple google search of 'Direct Injection problems' brings up a lot of issues that have occurred in the automotive industry.

Here is one for example : http://www.consumerreports.org/cro/n...ines/index.htm

Any ideas how to prevent some of these issues from happening, or an explanation of what PCM has done differently so that those problems do not occur in our boats?

[Beg4wake]

I didn't quite read all of that article but I do know some about direct injection problems (these problems are discussed in great depth in the Corvette forums since the new C7 Stingrays are direct injected.) But I'm not 100% sure what kind of PCV set up a marine engine uses, but on most cars, a simple installation of a catch can can be used in line to catch most of the oil vapor that would deposit back on top of the valves causing "coking". I have installed one on my Stingray. However I don't think the marine engines use quite the same style of PCV system. Would have to further research this.

[swc5150]

We've had DI engines in our cars for years now, and have had zero issues. 2 are P cars, and the service tech at our dealership said if we're seriously worried about it, run them over 4,000rpms for a few minutes straight, and always run the highest quality fuel we can find.

[Beg4wake]

We've had DI engines in our cars for years now, and have had zero issues. 2 are P cars, and the service tech at our dealership said if we're seriously worried about it, run them over 4,000rpms for a few minutes straight, and always run the highest quality fuel we can find.

I don't think that would do much for the "coking" issue associated with DI engines. With port injection, fuel was always being sprayed above the valves and the detergents in the fuel would clean the oil deposits left on top of the valves from the PCV system as it passed over the valves. With DI engines, the fuel is shot in below the valves leaving nothing to clean off the top, hence the coking effect on the top of the valves. But in all honesty, you will get plenty of life out of the engine even with this effect. It will eventually result in a reduction of performance but will be barely noticeable. Also, the tops of the valves can always be cleaned back off. The coking issue has really only been a big problem for people who desire maximum performance at all times, which is why this is a big issue in the Corvette forums. I too worried a little about this when ordering my new G, but I figure with the amount of use a boat gets compared to that of a car, it will be LONG down the road before any action measures would need to be taken to correct any coking issues and that the added fuel efficiency and performance would far outweigh the possible cons of a DI engine!

[swc5150]

I also wondered what the fuel type would have to do with keeping the valves cleaned, but that's just what the service guy said. I think the issues Audi had with DI started the internet "panic", at least from the forums I go on. I'll admit I'm not familiar with any US built incarnations of DI or associated problems. I do agree, this potential and unlikely issue would not keep from ordering an H5 or 6 in a Nautique however.

[Beg4wake]

I also wondered what the fuel type would have to do with keeping the valves cleaned, but that's just what the service guy said. I think the issues Audi had with DI started the internet "panic", at least from the forums I go on. I'll admit I'm not familiar with any US built incarnations of DI or associated problems. I do agree, this potential and unlikely issue would not keep from ordering an H5 or 6 in a Nautique however.

Yeah Audi pretty much had the same probs as the American counterparts. One vehicle that had a lot of problems with it was actually the first generations of the Ford Edge. Just didn't hear much about it publicly. And a higher grade of fuel would help keep the valves clean, IF it were being sprayed on top of the valves, but not in a DI engine. I just didn't understand the running it over 4k RPMs part?!! I've never heard of that! Maybe that's a new trick, however I don't see how it would work, much less be good for a motor!! To me it would seem like that would only cause the coking process to be accelerated....haha, anyways.....

[swc5150]

You got me on the 4k r's too? I'd have to be hauling *** in the Cayenne or drop the gear to keep it over 4k for any period of time. They also said there were no issues with the flat 6, so drive as we so choose. In the end, I'm just not worried about it...nor would I be with a DI PCM