What the truth about the 997.2 DFI engines and carbon buildup to the point of performance loss?

If there is an issue what can be done to prevent or correct it before it s a major repair issue?

Lot s of rumors on lots of forum s about the DFI engine. What s the truth as related to Porsche? Thanks for your time and efforts 411.

 

I was hoping someone else would give an answer.


This is a big problem facing every OEM, including Porsche. Not one OEM is immune to this problem. The cause is well known but the fix is at the regulation level not mechanical. In a nutshell, the cause of the deposits building up on the Valves is from all of the recirculated Oil and other emissions been sent back into the combustion chamber. with DI engines we don't have the washing effect of the fuel as we do with Port Injected engines.


Regulations imposed upon the OEM by Govts demand that unburned hydrocarbons and other emissions be redirected back into the Intake system. EGR systems are required to lower NOx in turn to run the engines at a leaner mixture level for both emission and mileage standards. A big mess. And we pay for this. You want a greener planet, belly up to the desk and pay for it.




There are devices fitted to these engines to try to eliminate the oil residue and other particulates but if they worked we would not seeing the repairs required. DI engines by nature will generate more carbon just as diesel engine do. It is a by product of DI.


The result of all of this is an error code created and the necessary repairs done in order to clear that code. Some may have had this done under warranty, but these repairs will continue as the engine get more mileage and runs out of its OEM warranty.


Will there be a fix? I have no idea as this is all uncharted waters brought on by regulation. I can only imagine the regulations becoming more not less.

 

411: you deserve a rep for that. Thanks.

 

Thanks, nice description

 

How many miles / years does it take to become a problem in the 911? What's the fix / repair cost?

ChuckJ

 

The engine has been out since 2009 I have yet to see a post about this problem actually occurring on a Porsche. I run my car to red line almost every day. This is how they test them that is how you should drive them. If not you might as well sell it. YMMV

 

I thought I read an article recently (maybe in Excellence) where Jake Raby said he had some concerns about the DFI engines washing the oil lubrication from the cylinder walls that he doesn't believe happens with the older non-DFI engines, like that in the 996s & 997.1 cars. Your response above seems to state the opposite or maybe I'm remembering Jake's statement incorrectly, but just curious. Thanks.

 

This is also a problem with GMs LS motors which I've used in a pro-touring Chevelle I sold a few yrs back. I added an oil catch can into the recirculation line and in season, not driven huge miles, would drain about a teaspoon a month out of it. Has anyone tried this on our DI engines?

 

A teaspoon of oil a month? From the crankcase fumes? Oh the horrors…

You do know that gasoline has oil added to it? About 1% by weight. It is there to help prevent rust forming on steel/iron fuel system components.

This DFI engine deposit rumor is seeking one isolated case to be blown up into the 997's IMSB.

There will be one along sometime. Given how sedately some drive these cars, use them, one that spent years lugging around town at barely above idle, hardly getting warm enough to register on the temperate gage, and probably doing all of the above on the cheapest goat **** imitation gasoline around, with infrequent oil/filter services will be the exception that everyone latches on to which be then be used to prove the case DFI engines are terrible.

 

A similar problem occurs with some supercharged engines .I am particularly familiar with the issue on Jaguars. As a previous poster mentioned,it is easily(but perhaps illegally ) solved with a catch can in the crankcase ventilation plumbing.
The trick is to use a small catch can with a drain hose on it that has an easy manual valve at the end of the hose. Drain off the oil periodically. Use a heat-proof can and fittings.
I suggest you don't give this task to someone who does not quite understand my explanation. It requires a bit of finagling and an understanding of the eccentricities of the engine. It needs to be concealed somewhat or look OEM because of the Smog visual check issue.And of course it would invalidate a warranty. So those who do this mod may be reluctant to discuss it publicly. Anyone who suggests a 'draft tube ' is 30 years out of date -but they did work!
If your environmental conscience is troubling you about this mod -of course you dispose of the drained oil(about a teaspoon a month!) responsibly. And think of the environmental issues/costs of dismantling both cylinder heads to 'de-coke' them as it used to be called. Then there is the $ cost. A little catch can sounds like a good idea now?
I hope this helps you decide to buy a DFI engined car.