silver_tt

Reviving a old thread trying to get more factual information and understanding of modes of failure that can kill a 9A1. I already understand bore scoring very well so will leave that alone....

But it seems folks here don't measure their timing chain "stretch". I am perplexed. Why? Timing chain wear is a major issue especially in DFI engines because of soot. I know Porsche revised the timing chains but I would have thought people would be paying close attention to this -- especially since you can monitor in software as an approximation.

I understand this engine utilizes an oil pump with a oil control solenoid. This seems like a very bad design to me to squeeze out more emissions gains. Has anyone seen failures related to this?

Anything else I am missing that can brick this engine on the spot?

Flat6 Innovations

Bore scoring is really about the only thing that has been taking the 9a1 out. I’d say that 95% of failure reports with the 9a1 has been related to bore scoring.

The oil pumps don’t really give issues unless something passes through them as foreign object debris. Usually that’s the very tip end of a valve spring that chips off and floats in the oil, finally being sucked up by the scavenge side of the oil pump. When it passes through it will seize the pump, or damage it. I’ve seen this failure more than any other singular issue, but it is still not common.

Timing chains do stretch, and soot is a huge contributor. I have developed a mechanical means of measuring chain stretch and shops will soon have the tools to measure this in their tool boxes. Relying on electronic data through camshaft deviations is not accurate, since more can create this than simply worn chain(s).

These engines have been better than I expected. Some odd issues have been experienced, and those were fun to solve. The remain my least favorite Porsche engine to modify, and I simply hate working with them. The cylinder heads alone are 3x more time consuming than any other engine I work with.
We built the first performance 9a1 to 4.2L in February of 2010. After 12 years I thought that we’d finally get used to working with them, but that hasn’t happened. I don’t think it ever will.

silver_tt

Hey man, thank you very much for the information; very helpful as always. IMHO people should be paying close attention to their timing chains (say once an OCI), much more so than I see now, especially as these engines get into higher mileage. I know software is just an approximation and you could have worn guides or other stuff going on, but it's literally free if you own a Porsche scan tool and takes just seconds. I always cut open my oil filter and look for bits of plastic or metal, this can offer clues especially for the guides that won't show up in oil analysis. The summer before last I almost bent valves in a DFI engine because the timing chain was stretched so much that the main tensioner was literally about to extend and fall out of the housing. That image of the tensioner is forever burned into my memory. There was zero indication of impending doom from a drivability standpoint or any way otherwise. The timing was running only slightly retarded under these conditions, call it 5 degrees, but when it gets to enough stretch it can skip teeth and brick a head while you are minding your own business before you have the first clue what just hit you. What is it specifically about the 9A1 head that makes it 3 times longer to work on? Trying to study up on this. Thanks again for the information and have a nice weekend.

jfischet

any improvements in your feelings about the 9a1 between the 997.2 gen and the 991.1 gen? or is it pretty much the same?

Flat6 Innovations

Everything about the DFI heads take more time. Especially port work. Just assembling the heads is tough, since the lifter carrier is incorporated into the head. It is not separate like an M9X. Performance valve springs and retainers were hard to make, since assembly has to be accomplished through the lifter bores. Lots of special tools have been made to make this easier.

Soot laced oil kills timing chains in any engine. My method of checking for chain condition offers baselines, as well as a safe operating range, and then a “red zone” where the engine should not be operated. Ironically the first engines we experienced chain issues with were Mezger turbos, and my method was first used to create health checks for those engines. Then I cross- applied it to all the other watercooled engines, and the DFI have proven to need it worse than the others. Not suprisingly, the Cayenne DFI engines have also had chain issues and need to be evaluated, too.

I have created the system for both M9X and 9a1 engines, as well as Mezger, Cayenne and 718. We’ve used it to save engines when OBDII data had proven inconclusive. I have been bitten by it, and I no longer trust it. At all.
As we move forward the soot induced issues will be a major concern for the 9a1 engines. This is especially true for the engines that follow the factory oil service directives. Soot laced oil must be purged with a focus on time, more than just mileage.

Flat6 Innovations

I don’t like either of them, but the 991 is even lesser favored.
All of us here fell the same way. We build them, and have been since they were first released. We make big power from them, and have since that first 4.2L in 2010.
It took a lot more time to develop them than any other engine. Other people have just started to learn what we did over a decade ago. I purposely didn’t share these things, wanting all those who decided to enter the playground to go through the same agony that we did back then.. We had no lifeline, and no help. We didn’t even have assembly tools, and had to make our own.
997.1 is the newest Porsche I’d consider owning.

groovzilla

997.1 Bore Scoring news has been quiet as of late.
Very slight/light scoring on engines over 100K I believe is normal. My engine has 106K and just Bore Scoped and all cylinders clean like baby's butt after diaper change.

*I was surprised to hear about the 2012 TT over on 997 Turbo Forum having bad scoring. I thought all of the Turbo engines were not prone to it.

I will however mention, 2 997S's I was interested in buying last year (1 w/78K miles,1 w/95K miles) that I had PPI'd & Bore Scope Inspected revealed some bad scoring & a cracked cylinder wall.
I see on the OP's initial post he had concerns about cracked cylinder so thought I'd mention it.

silver_tt

I never realized chain stretch was even a consideration on the port injected Mezger. I bought one to use as a track car (I do realize there is some irony in that statement) and it's my favorite car I have ever owned.........by a country mile.

Agree. With respect to soot, IMHO it's one of the least understood, most underestimated topics, and the single biggest drawback of DFI. Things like where the injector is placed in the cylinder and the spray pattern can influence how much soot is created. I personally find this completely fascinating and not intuitive that just moving the injector down from the intake into the cylinder and shooting at very high pressure has such a fundamental and profound impact. Ditch factory directives on oil, monitor crankcase vacuum routinely, and run a high ZDDP oil specifically for direct injection with short OCIs -- I know people go crazy about this topic but these concepts are all proven and widely published/understood in international tribological journals so there is nothing to fight about. Charles has done a good job of taking academic and industry information and breaking it down into layman speak in his white papers. Everything I have ever read from you and Charles about engines has been spot on with my own experience and readings. Really appreciate everything you have done for this platform.

silver_tt

Not surprised.

silver_tt

All the TTs after the Mezger, with Nikasil cylinders submerged in a water jacket, can have the problem. The Mezger was too expensive to produce and so they killed it and the new design isn't as good quite frankly. This is the reason some folks feel that the Mezger is the last great Porsche engine ever created and that nothing that has come since can come even close as far as being bulletproof.........

ATX_Native

Meh, if you have problems, get your intake valves cleaned and you’re golden.

The B7 RS4 needs a cleaning every 20k-30k miles.

It appears as if the 9a1 is pretty clean on the intake valves, I have yet to see a horrifying pics of gummed up valves.

silver_tt

The DFI soot formation we are discussing here has nothing to do with carbon build up on the intake valves -- totally separate topic and just proves my point about how little understood it is.

ekam

Charles Navarro

Exactly. Just like a diesel engine, a gasoline direct injected engine will generate soot as a combustion byproduct that gets into the oil. As fuel dilution increases, ring seal will decrease, and contamination will increase. That's also why manufacturers are adding GPFs (gasoline particulate filters) to these engines as the tail pipe emissions are higher than port injected vehicles when it comes to soot.

Soot in the oil is the #1 contributor to chain stretch. The simplest thing you can do to minimize this is to use a quality oil and change your oil every 5,000 miles or 6 months, whichever comes first.

_MWC_

I know this is the forbidden question but is there a specific oil that's preferable for the 9A1? The 5000 miles or 6 months whichever comes first is duly noted, just wondering if there's an oil that helps with the soot issue. I've been running liqui moly for what it's worth.