AOS delete?

[ike84]

So I just had a thought and am curious as to what everyone thinks. I recently read an article about dry sump system setups in nascar and an engineer had stated that they look to get a full 1Bar of vacuum on the crankcase with their system - not only to scavenge the oil but also to evacuate crankcase windage which they estimate increases hp by 3%.

I personally run an oil catch can between my aos and the intake, because I'm sure it will fail again. I think jaay runs the same setup. But now I'm thinking - should I remove the AOS all together and run lines straight into the catch can? That way we get the advantage of windage reduction. I'm not sure how quickly the catch can will fill up though.

Thoughts?

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[JFP in PA]

Extremely bad idea. Without the sump vacuum supplied by the AOS, you will suffer ring seal issues as the rings are low tension designs, the system will not flash off water and fuel that collects in the oil, and you run the risk of blowing out the cranks shaft end seals due to pressure build up (both seals are just pressed in and have no other retention devices, so very low pressure is enough to push them out).

[ike84]

Originally Posted by JFP in PA

Extremely bad idea. Without the sump vacuum supplied by the AOS, you will suffer ring seal issues as the rings are low tension designs, the system will not flash off water and fuel that collects in the oil, and you run the risk of blowing out the cranks shaft end seals due to pressure build up (both seals are just pressed in and have no other retention devices, so very low pressure is enough to push them out).

No, that's my point - delete the aos but keep an oil catch can it is place, thereby transmitting the entirety of the intake vacuum to the crankcase. No more obnoxious AOS to deal with, plus maybe a bit of extra power by increasing the vacuum and clearing crank case windage.

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[JFP in PA]

Originally Posted by ike84

No, that's my point - delete the aos but keep an oil catch can it is place, thereby transmitting the entirety of the intake vacuum to the crankcase. No more obnoxious AOS to deal with, plus maybe a bit of extra power by increasing the vacuum and clearing crank case windage.

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That will still cause issues. The intake is often running at 24-26 inches of mercury, while the AOS is running at 5 inches of water vacuum. With one inch of mercury running at about 14 inches of water, the intake vacuum is many, many times the vacuum the that the AOS supplies, and just as too much pressure can blow out oil seals, too much vacuum can suck them in.

[kartman]

I have a 2000 Boxster that is raced in the Lucky Dog endurance series, 6 and 8 hour races. The car is raced hard often on the Rev limiter. I plugged the intake and plumed the AOS to a catch can vented to atmosphere. This car has over 60 hours of race time in it. No issues, no oil consumption, no plug problems. The AOS is for emission purposes. The engines run fine with out the vacuum.