AOS modification.
#46
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Not sure if you realize it, but Silk is routing it to the air box, which is before the MAF. If you reroute after the MAF like you suggested, you're only a few inches away from the original location. Hope that brings some clarity why routing it after the MAF like you suggested is a wasted effort.
Yes, I got that. My brainstorming obviously went without much thought...Fouling the MAF has been on the back of my mind with this set up, but maybe it's a non issue?
I like your idea and look forward to seeing if it works.
#47
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Then the only possibility after MAF will be just before the TB. Otherwise you have the original situation. You will dirty your MAF with ‘unfiltered’ cranckcase fumes in that case.
#48
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It very well could be a non issue. The previous owner ran a k&n intake, and in his service history had to change the MAF two times after the "upgrade." I've since had to replace it once during my ownership, and then I swapped in the 997 3.8 intake. No MAF issues since. That being said, an oily k&n filter is completely different than this application, but it still leaves a bad taste in my mouth when it comes to putting something oily upstream from the MAF. A new MAF is heck of a lot cheaper than a hydrolocked engine, so I will move it there if there are no other viable alternatives.
#49
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This has too small all diameter to keep the airflow going
#50
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That being said, an oily k&n filter is completely different than this application, but it still leaves a bad taste in my mouth when it comes to putting something oily upstream from the MAF. A new MAF is heck of a lot cheaper than a hydrolocked engine, so I will move it there if there are no other viable alternatives.
Cleaning MAF is just temporary effect. They all eventually degrade. You should be surprised how much stronger all of your cars wil pull with a new MAF (given it was a long time ago replaced).
A new MAF is sometimes one of the cheapest ‘performance upgrades’ you can do.
#51
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The real issue with the AOS is the ‘massive’ vacuum it gets exposed to when going of the throttle and the throttle body closes. To prevent this vacuum sucking out the oil fumes without the cyclonal separation doing its work it has this diaphragm. The diaphragm is not perfect, to some extent in extreme situations some oil gets past, furthermore it wears out and eventually fails gradually decreasing the AOS filtration capacity.
The clue of the mod is to move the AOS exit to a less high vacuum position. The most suitable is somewhere before the throttle body. During driving there will be light vacuum to evacuate the cranckcase fumes via the AOS out. As the fumes are still dirty it is best that they do not directly come into contact with the MAF.
It is very important that the AOS vent line is unobstructed by small diameter bottlenecks. By rerouting the vent line you move it to a lower vacuum position. You will need a big enough diameter for compensating for that. Otherwise you risk to have higher crank case pressure. I saw some pictures above of converter pieces. The diameter is way too small to allow proper venting. I would say the min diameter is half an inch or so.
The clue of the mod is to move the AOS exit to a less high vacuum position. The most suitable is somewhere before the throttle body. During driving there will be light vacuum to evacuate the cranckcase fumes via the AOS out. As the fumes are still dirty it is best that they do not directly come into contact with the MAF.
It is very important that the AOS vent line is unobstructed by small diameter bottlenecks. By rerouting the vent line you move it to a lower vacuum position. You will need a big enough diameter for compensating for that. Otherwise you risk to have higher crank case pressure. I saw some pictures above of converter pieces. The diameter is way too small to allow proper venting. I would say the min diameter is half an inch or so.
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Related to the picture posted above. A line is still going from the catch tank to the airbox under the filter to create enough under pressure during driving. Furthermore a catch tank is not necessary. You can leave it out to simplify the mod. It is just a more clean solution as without it eventually some oily fumes end up in the airbox and could dirty a bit the airbox inside. Eventually in extreme cases a bit the engine bay.
The air filter keeps most greasy dirt out. But you are right. Eventually it could dirty the MAF. I noticed some degradation on mine after 30.000 miles. So I just replaced it. As it is one of the most crucial sensors in the whole system, nothing beats the performance kick, back to original, as a new MAF. I see it anyway as a wear item.
A new MAF is sometimes one of the cheapest ‘performance upgrades’ you can do.
A new MAF is sometimes one of the cheapest ‘performance upgrades’ you can do.
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#53
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you really need a free flow without bottlenecks to prevent pressure build up by the naturally blow by of the engine.
In the originaliteit situation with the butterfly valve in the TB open the AOS in full operation gets a higher vacuum/suction (also due to the venturi effect of the incoming airco’s at the vent line location at the plenum) for the cyclonal
separation to do its job then at the relocated place in the airbox. That is why the diameter of the tube should be not too small and also not too big. As the air flow will need to bridge a longer distance to a somewhat lower average vacuum position. You will want the air to be moving freely and but still fast enough.
Here lies the inventive part of the modification. To get the airflow right there to keep the AOS in its operating window. I did not design the modification so I am not aware what the special requirements are.
The extra venting on the oil cap is just a safety in case something gets blocked. At least it will prevent for some too high pressure built-up in the cranckcase.
#54
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You will need the overpressure of the cranckcase out and the AOS keeps functioning. It will separate the oil from the outgoing airflow. In fact you need to look at the AOS as a smart catch tank with a built-in shut of valve to close it when subjected to too high suction force from the engine intake.
With this modification you will take this excessive vacuum situations away. The AOS wil stay open all time. No more problem with a failing diaphragm.
I am not saying that the modification is the ideal solution. But for me it saved my engine at least already once from massive hydrolock. The previous owner of my car needed to do a rebuilt due to a cilinder scraper and a small twist in the cranckshaft. Probably also a hydrolock issue...
Besides oil the AOS could spit out a lot of dirt up till solid pieces which collect in the plenum. So there is more to it then hydro-locking alone.
With this modification you will take this excessive vacuum situations away. The AOS wil stay open all time. No more problem with a failing diaphragm.
I am not saying that the modification is the ideal solution. But for me it saved my engine at least already once from massive hydrolock. The previous owner of my car needed to do a rebuilt due to a cilinder scraper and a small twist in the cranckshaft. Probably also a hydrolock issue...
Besides oil the AOS could spit out a lot of dirt up till solid pieces which collect in the plenum. So there is more to it then hydro-locking alone.
#55
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Silk, Sorry if this is mentioned already but what is used to block the intake port in your setup?
#56
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Leave a piece of tube connected to the plenum and cap it off.
Used once a screw which fitted neatly in the tube and used a clamp to secure it properly. But feel free to use your imagination.
Used once a screw which fitted neatly in the tube and used a clamp to secure it properly. But feel free to use your imagination.
#57
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This is very similar to what I did with mine. Will now change mine slightly, to get the AOS out directly to the air box.
#59
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The diameters of the catch can connections is of utmost importance. Those shown on the pictures are too small. No free flow secured. You probably will need to modify an existentiële catch tank, drill wider entries and fit custom imkers and outlet with appropriate diameter.
All my catch tank catches is condensation.
All my catch tank catches is condensation.
#60
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thought this would be appropriate to post...
https://www.youtube.com/watch?v=T-B4VRxAtbw
I will probably add a catch can on my new engine build if I can fit it in there.
https://www.youtube.com/watch?v=T-B4VRxAtbw
I will probably add a catch can on my new engine build if I can fit it in there.