Hokie

THANK YOU in advance for the advice. I'm pulling this out of the "oil pressure" and other threads for more specific feedback. Let me know if any other details would be helpful.

Context...

• Currently three track days (two at NJMP Thunderbolt on shot Summer tires and one Dominion Raceway with new 200TW tires) running in Advanced groups.
• I am seeing smoking out of the exhaust when starting the car up for the next track session.
• In my last event, I started seeing smoking while on track, including a 20' plume after a 3-4 upshift. Seemed worse in this last event when I was on new 200TW tires.
• After two cycles on the street, no more smoking from the exhaust and everything seems normal.
• Car is new to me, but have seen minimal oil usage normal on street (~0.5L per 3k miles). Using 1L of oil through a 2-day track weekend.
• Thanks to a local RL'er I check the crankcase pressure by testing though the oil fill cap, and read 3.5 inches/water, which seems lower than the tell-tale AOS failure reading over 5 inches/water.
• We plugged in a Durametric and seeing no codes, overrevs, or timing issues.
• I have my next event for a 3-day session at Summit Point starting July 9, but don't want to head out with trying something to remedy the situation.

The car...

• 2003 C2, 116k miles
• 1.2L Mantis pan, LN IMSB, high flow cats, sport clutch, lightweight flywheel
• Driven DT40 oil filled half-way up the dip-stick
• Bridgestone RE71Rs, Ohlins coilovers

The questions...

• Other than a failed AOS, could it be anything else?
• Any other tests I'm not thinking of to determine root cause?

hbdunn

Probably not the problem but I don't believe DT40 is recommended for track duty.

zbomb

My opinion:

You're overwhelming the AOS. If you're running at the track with stock AOS, I would run oil no more than 1/4 up the dip stick. even then, you may still have issues.

I would put a UAOS on with the oil drain back tube.

I have found the severity of this issue to be somewhat track dependent with little to no issue at one track and a little under a QT over 3 20 min sessions at another.

Take a look in your plenum sometime... Before the UAOS, mine looked like this after one track day. There is a bunch of my progression on this issue in my thread on here if you want to read up on it.

barbancourt

That is one mean looking 996.

Tom Loder

I just had an almost identical experience. First track day with the car at NJMP lightning. I'm an instructor with my PCA club, but this was my first time driving a 911 on track and I arrived for the last session of the day in the beginner group. I did one lap at slow pace, then moved to intermediate pace for lap 2 and when downshifting into Turn 7, I thought I noticed a white plume outback. Then after rolling out of the bowl (long, banked right hand) and upshifting 3-4 the car unleashed a mushroom cloud of oil laden smoke. Many people came to find me after the session to comment on the size and ask if I realized it happened. I spent the next morning mopping out the intake as it was pretty covered in oil. After that, I packed up and just rode in the right seat for the rest of the weekend.

I had measured the AOS prior and after with a manometer, and it read 5-5.5 which is high but still within the acceptable range. The oil was halfway up the dipstick, so probably too much in hindsight.

99 C2
Stock AOS
Stock Sump
Ohlins R&T
Yokohama Advan A052s
Hawk track/street pads

I'm familiar with the woes of the AOS and oil pressure issues of the platform, yet still, it was surprising to have this happen given the pace, duration, and that I've driven it much harder on the street with no issues. I've got the UAOS sitting on the shelf waiting to go in, but a friend has one installed and is still experiencing excessive amounts of oil being caught in the catch can.

This was not how I envisioned kicking off my 996 track experience, and so I've realized that I'll probably be going a different route for a track car. Nothing worse than working on your car at the track instead of driving.

zbomb

Tom - I would not hesitate to put the UAOS on as a result of your friends issues, in fact - I would argue they should be a motivation not a deterrent. The car having a lot of blow by, oil run too high and track layout all will contribute, among other factors. The UAOS will catch what would otherwise end up in the intake, add in the drain and it will cycle the oil from the res to the sump, this has allowed me to start experimenting with increasing the oil level with minimal concern of flooding the intake… again - it’s really a no brainer.

jobyt

I'm interested in the outcome/data with that higher oil level now that you have the UAOS with return drain...seems to reason that if you can run a higher oil level without worry of overwhelming the AOS, there may be direct correlation to fewer pressure drops as the pick up will (probably?) not see as many low oil level events.

Tom Loder

@zbomb I bought the UAOS with the plan to put it into a different 996 that was to be the track-only car along with seats, rollbar, 2 qt sump, etc. Then I bought another 996 aero which had Ohlins installed and thought I'll do a dual-purpose car instead. I put off installing the UAOS until after my first planned track weekend in the track-only car to see how it did on the track, in case it ended up on the dual-purpose car. I was set to go to NJMP but a last-minute alignment issue made me take the dual-purpose car instead. After I purchased the UAOS, Skip added the return line so I don't have that option yet. If I stick with the project I will definitely add it.

As much as I love the 996.1 platform (I have at least 3 of them), it was not designed to be a track car, and as you are well aware, the solutions to it's problems don't seem to exist yet. I'm really encouraged by the progress and interest your thread has produced though.

zbomb

JOYBT - I ran half oil capacity per dip stick and electronic gauge at last event. Consumed no oil and no smoke to speak of.

Previous time out same track, caught just under a QT of oil in my secondary reservoir with fill only at 1/4 capacity.

Car is consistently over 1G braking and cornering G kissing 1.5 at times.

Check the oil pressure thread for data.

I hear you Tom - the chassis performance is exceptional though - so I push on.

ETA - VERY few cars designed to be track cars, and these cars are using tech from pre year 2K. For what it is, what it is capable of doing on track, with as little power as they make is downright remarkable. But - it takes a pretty constant upkeep and parts selection / adding to achieve it. Not something I think much different for any car of the era. The difference is the 20K rebuild. If these were 5 k engines, no one would care about oil pressure because you’d just throw a rebuild in when it failed but, they’re not, so we have to push to add as much reliability into the system as we can because the consequence is so high.

IMO - the UAOS is the most progressive and functional product to that end that has ever been marketed for these engines.

Hokie

Thanks for all the responses, and greatly appreciate the thorough documentation of your journey zbomb.

I'll likely end up cancelling my event registration until I can get a new AOS or UAOS installed. Hoping to report back more positive news in a month or so

Hokie

Thanks for sharing, very similar indeed.

I too am hoping the 996 could be my dual-duty platform. Crossing my fingers this AOS fix gets me over the hump.

GC996

You can do dual duty.

These cars can and in my opinion should be used on the track. Grand Am raced our engines. PCA races our engines with Cayman, Boxters and yes, the 996 in the spec class.

However, to take any Cayman, Boxter and 996 on the track that is running a non-mezger engine, you gotta do a few things or you will blow oil and run the risk of oil starvation.

Zbomb nailed it and has continually nailed it with his threads. Read them. The good news is that there are plenty of "bolt-on" preventative measures that you can make to prolong engine life and have an dual purpose car.

1. Replace your Oem aos with something that is better. UAOS or Motorsports AOS. Do NOT attempt to track your 996 with an Oem AOS. It's kinda like crossing the street in Manhattan without looking both ways. You may or may not experience a problem, but the odds are you will.

2. Get a deep sump kit. The more oil the better.

3. Make sure you have relatively new fuel injectors as well as ignition coils and spark plugs. Why tempt the bore score God's.

4. Make sure you change your oil before and after you track the car.

5. Check your bores with a scope and check your oil with a test to make sure something isn't happening inside the engine that you can't see.

6. Replace your IMSB with an IMS retrofit or Solution

​​​​​​If you are more advanced and faster, this is where you can replace your radiators with CSF radiators, go to a third radiator, as well as add a low temperature thermostat to replace the Oem thermostat.

LN Engineering is in the process of testing a more powerful oil cooler. If all goes as planned, we will be able to buy it.

Porschetech3 who developed the UAOS as well as additional components for it as referenced by Zbombs threads is developing a new oil sump kit that is about to be tested which will add a positive wrinkle on keeping oil in your pan when you need it most.

CTS has a dry sump kit for those that truly want to race their car for 24 hours straight.

Here is the point, there are plenty of "bolt-on" solutions that are available to apply the right preventative procedures to address the issues and prolong engine life, while enjoying the track as well as street. With more on the way.

How do I know? Because my 02 is a great example. Having owned it for 19 years and tracking it consistently from 2004-2018, it's survived beautifully on just a 2 Qt deep sump, motorsports aos, Ims retro kit and maniacal oil changes and service without any problems.

My next step is to replace the radiators, talk to LN about their new oil cooler and wait for Porschetech3's new oil sump to be tested.

The wild card for everyone is how well serviced the car was before you owned it. If the previous owner skimped on service, you may have developed more advanced bore scoring than you realized. Hence getting the tests done. This is where you can adjust the oil you use to prolong engine life.

But, remember, every engine will eventually need a rebuild. 993, 964, GT3, Carrera GT, etc. The goal is to prolong engine life so you can decide on what you want your rebuild to look like and who to do it with.

CTS

Is there a consensus on what conditions lead to smoking? On Boxsters it requires a long right turn followed by a throttle lift, either for a shift or to negotiate the next corner.

At first glance the reversed engine placement in a 996 would be better because the AOS is in the front of the engine (and thus not flooded by acceleration) but evidently this is not the case.

How does the UAOS prevent smoking?

Chris Cervelli
Cervelli Technical Service

GC996

​​​​​​Mine occurred with my original Oem aos after very heavy braking and tight cornering under heavy acceleration. Got it replaced quickly with Motorsports AOS before Road America event so don't know how it would have performed in the carousel, or high speed turns.

Add edit: clockwise direction track.

Porschetech3

The conditions on 996 that cause the smoking are hard braking/long right hand turns/ followed by full throttle.

The " Porsche Factory Fix" for this was lowered oil level (1/2 qt on 996.1 and on mid 2002 up, a shorter dipstick (by 1/2 qt) , the problem is increased when the blow-by increases.

The original intention of the UAOS was ease of replacement of the diaphragm ( done in 10 min) along with a warning system consisting of a Microprocessor Controlled Infra-red Sensor placed in the Accumulator ( a secondary air/oil separator) that will warn the driver of system failure. The Accumulator is schedualed to be drained at 3k miles during regular oil changes on cars driven normally in good health ..

The high mileage/Extreme Track Duty Auto Drain was recently added as I am always improving the product, On Track cars with more blow-by than normal (Zbomb) it allows more drains (2) to the accumulated oil that before only had one factory size drain to the sump. And the reason I am not fond of the Motorsport AOS, it holds/removes more oil from the sump((@ 1.5 liters), and can only drain so fast given on one factory sized drain.

The car Tom mentioned above I think is Kris's car, who has had issues for years . He replaced the AOS 3-4 times thinking it was the issue,before he put the UAOS on and he even fills up the UAOS Accumulator really quick and sets off the warning, He just got the high mileage/Extreme Track Duty Auto Drain last week.