I spent my birthday tearing down my 3.4 and found what failed

Some of you may recall last summer my engine failed on the track and Dundon Motorsports has been rebuilding and transforming my 996 in virtually every possible way including a 3.8 (that will be a separate post sometime in the future). Well, I got a great birthday present from Charles Dundon, when he invited me and a friend in yesterday on my birthday to tear apart my failed 3.4. Charles gave me a corner of his shop to do this with some guidance along the way. It was my first time taking an engine apart and it was a blast. In addition, we did find what failed (pic below)...the rod had broken, which looks like a result of oil starvation on the crank which is what we had diagnosed this summer. I was amazed about how simple the engine really is and really how few tools are actually needed to take it apart. While it is a messy job, I also found that the parts washer is my best friend really keeping the mess to a minimum. Finally, now I have a whole bunch of clean parts that I will likely sell on ebay but it you guys are interested in any of it let me know. The engine has 54K miles on it with a LN IMS with only 6k miles. I threw away anything that remotely could have been effected by the failure other than the case which Charles told me some folks would resleeve especially my case which has no porosity and low miles.

Nice, thanks for sharing. It's always fun to look at pix of the m96, as my knowledge base in that arena is limited. Normally, this would be a bittersweet experience, but given the sourness has had time to wear off I'm sure you had a blast. Funny, i got a completely different (but similar) bday gift on my big day Friday: i had dropped my car off for a new clutch/ims/rms a couple weeks ago and my mechanic called out of the blue late Friday afternoon to let me know it was ready -- little did he know he was making my bday better than i could have hoped for. Needless to say I'm having a memorable bday weekend, hope your doing the same.

Thanks, I did it for a learning experience, and finally now I understand how all this works. It was a bummer when it happened, but I am now building a totally custom 996. Two years ago, I parted out GT3 and that was also a great experience in that I learned all of the non-engine parts of the car worked so I am not afraid to do myself. In the end....its all surprisingly simple to take both a car and an engine apart. The hard part is putting it back together...now that is the art!

any idea why the oil starvation happened?

Lots of Track time for the car without a deep oil pan and baffles. My new 3.8 will have all of this corrected plus an additional 120HP :-)

Is the starvation a guess or is there a way to definitively know?

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Crank shaft bearings were heavily worn... and that was the opinion of Charles Dundon, and I don't question anything he says

I have heard some experts say that starvation is an issue and some say it is not. I wish I knew the answer.

Looks like cylinders #4,5,6 are heavily scored too. Do you have any photos of the failed bearing? Just curious.

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Here is a picture of the crank shaft at the failed cylinder location. You can see the excessive wear....I would love to here Jake's opinion on this. You can also see that there is discoloration which I think was due to excessive temperature.

Scoring shows this engine was slowly eating away at itself.

What an interesting way to spend your bday. Glad there is light at the end of the tunnel regarding your 3.8 rebuild/upgrade.

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There�s no question in my mind that a stock 996 suffers from oil starvation at the track. The evidence I�m basing this on is countless track videos that show oil pressure gauge readings that clearly show oil pressure drop on sweeping right handed turns. It�s either that all these cars have oil pressure sensor/gauge malfunctions, or that pressure drops are actually occurring. There is a saying in aviation that says something to the effect that - if an instrument tells a story, unless you have real evidence that the instrument is clearly wrong (an altimeter showing 80,000 feet while the aircraft is parked on the runway), you should trust the instrument and assume that it�s right. Some folks think that oil pressure drops on these cars isn�t an issue because it doesn�t go to zero, so at least some pressure is better than no pressure. WRONG. Oil starvation due to air getting in or pressure being low results in one of two scenarios: either there isn�t going to be enough fluid moving and carrying away heat, which will lead to overheating or viscosity breakdown of the oil film, resulting in metal to metal contact, or, the air/oil mixture will be compressible in the bearing and lead to metal to metal contact. It�s metal to metal contact either way and will ultimately result in failed bearings. If anyone is worried about this, simply position a camera to record your track event to read the oil pressure gauge. If there�s any oil pressures drops at all that aren�t in sync with RPMs, then it�s oil starvation or oil aeration. Temperature fluctuations and related viscosity changes won�t cause this problem.

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Man, if that�s not evidence, I don�t know what is. Question: what oil viscosity has you been running and what were your observed coolant temps? I have concerns that my 996 runs too hot. I�ve seen 110-111C temps at the track and even 107C at idle on a hot summer day.

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Yeah....that is a great point. I did put in a center radiator a few couple of years ago to get my coolant temps lower because they tended to be on the high side. In fact, I am so concerned about temps that even with the new 997S engine (expecting between 400-420HP) I am putting in 996 Turbo radiators which are much larger +center radiator cause I want to make sure the engine stays cool. One thing I forgot to mention is the engine only had 54K miles on it but the car was tracked through its whole life....thus the starvation.

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What about a lower temp thermostat? After reading 74 pages of the Hartech white paper on M96 engine failures, I think all engines save from those only driven in cold temps could benefit from it.

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A low temp thermostat will certainly help along with larger radiators (and the upgraded center), but oil temperatures will still be over 240F easy on the track. Adding the 2 quart deep sump with baffling will help with oil control (the added volume doesn't hurt either), but if you use crappy oil, you can still suffer from engine failure. Aeration of the oil as well as loss of viscosity are still a possibility with a 2 quart deep sump and added engine cooling, so the key is to use a race oil on the track. We run Driven XP9 in all engines that will see track use - it's a must. Street oils aren't made for the track.

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That�s a good point. The larger oil volume can keep temps down only for shorter runs, but at some point, the heat has to be removed. And regarding street oil vs race oil, are there any aeration tests that compare street vs track oil? There seem to be quite a few tests for strength and temperature, but I don�t see much on aeration.

https://rennlist.com/forums/racing-a...mp-system.html

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Tests for foaming and aeration aren't something you see, nor is viscosity at higher oil temperatures approaching 300F. I'm a big fan of DT40, but it's no good for the track. But then again, all street oils are just for that - street use. You need a true race oil for the track, even if it's only a DE event. To be perfectly honest, most race cars are better maintained than mixed use street/track driven cars.

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One interesting thing about the broader discussion is that a true dry sump seems to work ok even with mobil1, which is flagged by many (even the guy that uses M1 in dry sump) as being inadequate for track when used in conjunction with the stock M96 wet sump. from the thread I linked above:

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Maybe someday we will. It used to be that video of inside an engine to view the actual flame burning was not possible.

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The main difference is the models with Mezger engine and its true dry sump, both aircooled and watercooled, are inherently stronger and more reliable than the M96 engine. Even with race oil, if you don't do the required oil system updates on an M96 engine, it will blow up. Likewise, using race oil won't prevent IMS or scoring issues. Some things are just design flaws and can't be overcome simply by using a certain fuel or oil. That said, there are better choices the M1 for Mezger engines, but that's a different topic.

So does the X51 baffle and deep sumo effect the oil pressure drop in sweeping rights? If so, by how much?

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I cannot give you a number as there are many things that will affect this. What I can tell you the race cars originally fitted with the 2 quart deep sump and campaigned professionally using racing oil suffered zero oil pressure drops after the addition of the 2 quart deep sump including 997 oil returns and the anti-slosh tray that is included in our kit.

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Can you comment on the addition of an accusump as a preventative measure for starvation? I know many of the Boxster spec cars run them. I believe you offer them on your website iirc.

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Yes, we do offer the Accusump as an option, but most choose the route of the 2 qt deep sump as it's fool proof and doesn't require driver input for proper operation. I have seen multiple times where the customer forgets to turn the system on or improperly fills the oil and causes an engine failure. The EPC valve must be tested regularly to ensure it is operating as well as there have been problems in the past where the solenoid does not excite properly and the system is non-functional. That said, I ran one for years in my Boxster before I came up with the 2 quart deep sump.

Thanks for the info! Sorry lowpue, don't mean to hijack thread. I would love to tear down a motor to learn more about M96.

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No worries....I am learning a lot from my own thread even though it has taken a tangent... btw, Charles Dundon has a GT3 motor he wants to tear down for parts and he asked my buddy and I if we want to tear that down too. Charles gets free labor and I get a free lesson....win..win.

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Isn't it also possible that air still gets delivered to the bearings even if Accusump is used? I thought that how Accusump worked is that it�s pressurized via the oil system and then it can release oil pressure when/if oil pressure drops. But if an oil pump sucks air, that air has to be delivered to the system.