steveP911

Back to the engine rebuild, any thoughts from 997 track drivers on whether or not the upgrade to a "motorsports" AOS is worth it? Kinda pricey and it looks like a little creative engineering might be required to get it and the plumbing to all fit and work. LN Engineering has a couple versions.

The 996/997 Ultimate AOS UAOS-AL Complete Kit (lnengineering.com)
Porsche Motorsports AOS Air Oil Separator 98710792600 (lnengineering.com)

Thoughts? Worth it or risky, given the tricky installation? Thanks!

38D

Motorsport AOS is much less likely to fail. Was a common upgrade in Spec Cayman

De Jeeper

Eh, the uaos (with oil return) is a great product. Do your research if it fits your car u can run over full on oil and midigate a lot of oil starve issues. The 996 guys r amassing a ton a data on this.

steveP911

Thanks. Why did you upgrade yours? Did you have a problem or were you just being proactive? How positive are you (and others) that this is a significant improvement over the OEM AOS and particularly important for track use? I'm not challenging you, just trying to decide if it makes sense for my 997.1.

Thanks.

De Jeeper

I replaced mine with the uaos because my factory aos failed. At the time the track drain option was not available. The major advantage is, it will allow any excess oil to go back into the crank case and not the head. It also moves the diaphram to the rear if the motor so its easy to replace. The diaphram is the only part that fails and uaos uses a bmw part so its still a well made part.

The motorsport porsche unit still uses the factory aos and a resivior can. The aos part is expensive, fails often and its hard to replace. Although its effective its more of a band aid then a fix. I am 100% sure this is a very effective part and its how it should have been designed from the start.

full discloser...i now have a mezger motor in my car as the 3.4l nuked itsself. Mostly because it has 200k miles and had no business being in the track.

GC996

Steve, I have run all three on the track since 2004 on my 2002 996C2.

Along the way i had two factory aos failures on the track back to back in 2005/6 and then went to the motorsports aos thru last year of which i then replaced with the UAOS with the track drain. At the time, the motorsports aos was the only solution available. Today we have the UAOS.

My recomendation is to go with the UAOS track version. It's just an all around better designed product than the Porsche factory aos and Porsche Motorsports aos for many reasons.

1. It has a more robust diaphragm than the factory AOS and Motorsports AOS.
2. The diaphragm can be easily replaced in 5 min since it's been relocated to an accessible location that doesn't require lowering the engine.
3. With the track drain, the UAOS can handle and process an extra 1 quart of oil over full. Add in another 2 qts of oil with a deep sump and your engine now has 3 qts of extra oil which helps mitigate oil pressure instability and starvation to a greater degree.

As an example, Porsche recommends running 1/2 quart less oil under full for the factory aos. So if you run a 2 qt deep sump and the factory aos you are actually running 1.5 qts of extra oil (2 - 0.5 = 1.5) versus 3 qts (2 + 1 = 3) for the UAOS track version with a 2qt deep sump. With the motorsports AOS you are running the oil at full and 2 qts deep sump giving you 2 qts (2 + 0 = 2) total in extra oil.

Bottom line for the M96/97, the more oil the better.

4. Due to its design, the uaos can handle and process alot more oil during heavy Gs sending the oil back to the sump instead of the cylinders which creates the excessive smoke and catastrophic hydrolock.

Many other reasons for the UAOS, but its a no brainer for both the track and street if you have a M96/97 engine.

steveP911

Many thanks, GC. That was a really nice review of actual experience. After that, it's hard for me not to go with the UAOS from LNE. I will forward your comments to Brandon at Slakker and see what he thinks.

Appreciate you taking the time to write that up so well.

GC996

Good luck with Brandon. He will tell you that there is nothing wrong with the factory AOS and you don't need the motorsports AOS nor the UAOS. Hope his opinion changes. It will save alot of hartech rebuilt engines from hydrolock.

SlakkerRacingDev

The race shops I work with use oem AOSs. It isn’t even a yearly PM item for them. These are people supporting 10-20 m96/m97 engines on a given PCA race weekend for a living. My own experience is 150+ track days without an AOS failure and Hartech has been winning races for years with the stock AOS.

The motorsports AOS is a proven solution and adding a catch can to the AOS, which essentially is what the UAOS is, seems reasonable as well.

So the bottom line is we will support using any of these three solutions on our engines for track use.

steveP911

AOS - I have decided to go with the UAOS, having talked it over with Brandon (who was very fair about his totally legitimate perspective). I think I will buy that myself and have it shipped to Slakker.

Tires - Settled on the Yokohama A052's because (a) I haven't tried them yet, and (b) I have heard/read enough good things about them to give it a go. I have this feeling that purple crack is next, once the motor is rebuilt with better oil management upgrades.

Cheers.

steveP911

This was correct for me, especially coming out of tighter/slower corners. I read your advice, but it took a couple rear slides to get it through my head. Thanks.

IMO, it was the torque curve change that made the biggest difference. The graph is in my Engine Rebuild thread (2005 3.8S Engine Rebuild - Page 12 - Rennlist - Porsche Discussion Forums post #170). This gave me more speed at my brake points and then more at my turn-in points. Progressively of course. I found that my top speeds in various sectors for the two tracks I have run this season (Summit Point and VIR) with the rebuilt motor are 5-15 mph faster. This may not be a big change for experienced racers to manage but it took a little time for me to adapt. So, the definition of "big change" is in the hands of the driver, and really nobody else. IMHO.

Thanks again for your sound advice. You were absolutely correct. There are many variables that can affect performance as much or more than engine torque or power, like temperature and rain, but my original basis for the discussion was for optimal conditions, where I knew things would be happening faster for me. Took me almost two of the three days to get myself where I was comfortable enough.

Another round of good advice. Much appreciated.

I would add a comment that certain tracks can have characteristics that can have a bigger effect on speed, such as the braking zone for T1 at VIR. This area has a slight (but very real) downhill section at the early markers (maybe 5-3) and then it flattens out at around marker 3. So, you have a condensed braking zone that already challenged me to figure out how to handle it, and this was made more challenging by the higher approach speed. Frankly, I never did carry full throttle up to the first marker (like I think I used to) because I just did not feel I could handle that in a shortened brake zone. Too much wiggle and ABS.

Lastly, it seems that many of the very experienced drivers (racers) have quite naturally forgotten when they were in the earlier parts of their progression. That is not a knock - very understandable. Boy, when I watched the Red (and Black) groups at certain areas of the VIR track, I was blown away by the skill and spine of the drivers. So, I appreciate it when guys like LV take the time and have the patience to offer sound advice for me at my level. Thanks!

ProCoach

Yes, approach speed does make a difference, but the fundamentals are still the same.

If you're tickling the ABS initially, then you're really too brutal with the initial application AND the car is unstable when you hit it too quickly and hard. Too binary with the middle pedal.

If you tickle the ABS at the end, close to and past initial steering at turn-in, you've left just about the right amount of speed left at the end of the straight line portion of the brake zone.

You are correct in that the initial slope down is significant and could see it up close, but still nothing like the approach to Turn 1 at the Glen. More like the steady downhill into Turn 1 at Summit.

What is hard to see from the car is that it goes UP from marker 2 to the arrow, THEN levels out, then goes down from crossing centerline to apex approach all the way to an area just before the second inside curb. It's why people that miss the apex or early pick up a big push and don't know why...

The downward slope starts after 6 (the initial mark) and stops at marker 2, allowing full throttle up to the marker you select. Then, execute an exponential, quick squeeze on the brake, followed by a harder push once the nose is down and loaded.

The squirrely behavior at the back of the car is a result of too quick a weight transfer FROM AN UNLADEN STATE.

So, what we've seen is that the drivers that DO keep their foot down to the brake point is that the car is actually progressing from a better damped state (thrust positive acceleration) to another well damped (hard braking) state. It's the in-between that feels funny!

It would be wonderful to see the differences in vMax between the pre-mod state and post-mod, but I can assure you that the physics doesn't know the difference. There are best executions of fundamental skills that can solve all (or most all) of these "comfort" issues. And allow you to go faster with less risk.

Thanks for posting your impressions!

winders

Well, let's be fair here...which you have not been! You said you were gaining about 30 HP. Basically going from 350HP to 380HP. That's not what happened here. You went from ~350HP at the crank to ~407 HP at the wheels. If we assume 15% drive train losses, you went from ~298 HP to ~407 HP. That's almost 110 HP. That is a a 36% increase in power. That is 4 times what you said it would be. Hell yes you will feel that. Hell yes that will change everything.

I would have answered the question completely differently given the actual facts. So don't give me a snippy "IMHO" here...

And, if the results are from a SuperFlow engine dyno, 57 HP is still noticeable....not as much as 110 HP...but it makes a difference.

sbelles

I don't think you will need to change much besides maybe shift points but if you want to be safe, start out a gear up on corner exits until you get used to it and make sure that you are tracking out as much as you can when you go a gear down to make sure you don't loose the back end until you get used to where it will break loose.

GC996

Yeah, changes create changes. Just the way it is.

Rebuilt engine with more overall power especially on the lower end of the band certainly means adjustments on how you use the throttle, brakes, brake capacity requirements, etc will result. I was impressed on one of your posts about shaving off 6 seconds a lap at VIR. Huge. Sounds like you are having a blast getting to know the capabilities of your new engine and the resulting characteristics of your car.

Sure seems to me that it would be a hell of alot of fun getting to know the new package. Looking forward to hearing more about your observations, adjustments and enhancements you make as the season progresses.