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Old 04-13-2017, 04:36 PM   #127
KillerBMotorsport
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Member#: 198281
Join Date: Dec 2008
Chapter/Region: MAIC
Location: Virginia
Vehicle:
2005 WRX/STi
WRB of course

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Quote:
Originally Posted by subydude View Post
I still think a lower G value would be better here, because otherwise the valve is going to only close briefly and then open right back up still allowing oil to be pushed.
You might be right, or wrong. At this point, without trying, it's speculation. I have no answer, besides that I auto-X on 295s and have a bone dry inlet. I'm also out there to have fun more than being competitive so take that as face value.

Quote:
Originally Posted by subydude View Post
You're missing the point here. Throttle time in seconds is not important. Throttle percentage over the course of turns is.
Lets debate this some more, because I think I'm right and so do you. We both need to better detail the arguments here and why I say it IS important is because oil flow changes with on/of throttle. Of course these cars have positive displacement pumps; flow out is dependent on crank RPM, but I think what you may not be considering is how the AVCS (on/off throttle) does effect oil flow.

The other thing to consider is that we may be trying to compare two means of oil making its way up to the head ports. Sloshing is what you'd see in auto-X vs pooling (often called surge) what you see on a road coarse. On a road coarse with sustained Gs the outside head is not flowing back into the pan. Instead it is filling up the head/valve cover. Under a high enough lateral load, even oil from the crank can join the party. Eventually, the head pools a decent amount of oil, reducing the oil available in the sump, and you have starvation.

So while the means of getting oil into the heads may be different, there is also the premise of oil being pumped into an outside facing head for 2 seconds or 6 seconds at full tilt. The longer you're at that load the more you run down the level in the pan. For a road coarse anyway. This is why long sweepers tend to define the oiling system's limitations.

Quote:
Originally Posted by subydude View Post
Since you're always turning in autox WHILE on the throttle we're not allowing the oil to settle or the AOS to drain while on course.
This is where my experience differs. That doesn't mean it's right, or you are, we just differ. I had always been a fan of Crawford's A/O separator. Under 96% of conditions it worked well. Truth be told, on all three of our shop cars we never had a single issue with oil coming into the inlet during ANY auto-X events. The ONLY time I experienced the limitations were under severe load at high power levels (+900 crank HP) for long periods of time (5th and 6th gear WOT). The drain on the Crawford, and out unit for that matter, drains fast. If you are off throttle or feathering the throttle, it's drained. Even for a split second it drains fast. Now if you have excessive blow-by, you're getting too much flow through the drain and it WILL blow oil everywhere inside that separator and make it's way out. I've seen that happen, and the assumption at the time was that the drain was not working properly.

Quote:
Originally Posted by subydude View Post
Thing is, throttle lifts in autox are incredibly short and there are no gear changes except at the beginning. We build oil up in the head(s) and it never goes away until the run is over.
understood, but if you go into any kind of straight line, or opposite direction (which is done a lot in auto-X) all that oil rushes right back out of the head. It doesn't build up. It might slosh back and forth, but unless you're running a crappy flat baffle it should not be all going directly from one head to the other. At least some, has to make it's way into the pan during each direction change. This is the point of our baffles, and even the factor pan baffles.

Quote:
Originally Posted by subydude View Post
I've ran on small lots where I have no issues, or courses where there weren't many slaloms, but all digs and still had no issue. But on courses with a good mix of elements and good speed (like most of my locals and all national courses) I'm pushing oil.
This is great information right here! By your own statement there is a defined set of circumstances that effects the pressure. You want to find out exactly why? Log it! All this takes is knowing the load, durations, pressure, and RPMs. The vid was nice to see something is happening, but it's extremely difficult to pull truly useful data from it. You get more information and I promise I'll work to find or create a solution.


Quote:
Originally Posted by subydude View Post
Can placement can have an effect for sure, and physics should always be reviewed.
Absolutely.


Quote:
Originally Posted by subydude View Post
You can't replace a positive displacement oil pump at 7,000 rpm with a reasonably sized pressure canister for very long at all, but you can augment a system that's dropping pressure for a short period of time to help a potential dip in pressure.
Yes, it will prevent the pressure from dropping as much, but is limited on the amount of time it will do that for so it could be the reason the engine blew at the turn's exit vs 3/4 of the way through. Maybe you bought enough time to complete the turn. It's not a solution to the problem is my point. The other downside, and I think it's often overlooked, is that these accusumps are dumb devices. Once pressure is restored they will recharge. Think about this for a second, when you have oil pressure restored, you're likely exiting a corner. When you are exiting a corner, you're very likely WOT. Bearing loads and oiling demands are at their highest. This is the absolutely worse time to reduce system pressure to 'recharge' the accusump. I can't recall who (I want to say OpticalNZ), but they datalogged using an accusump and you saw system pressure drop everything the unit recharged. It was tossed (along with most of his other current oiling system) after discovering that.

So does it have a place, absolutely, but IMO not as a saving grace for engine bearings. There are many more better reasons for owning an accusump.
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