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Old 09-30-2009, 06:26 PM   #1
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Default Heavy braking and my engine sucks air???

Anyone else see this? Repeatably? Oil is at full mark on dip stick (if not a little higher). This is one of the next items on my list of 'to dos' this year. Want the car to be sound for some track use next year. Running Amsoil 0w-30 signature series oil and my engine details are in link below. Thoughts on causes, possible fixes?
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Old 09-30-2009, 06:58 PM   #2
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wtf are you smoking?
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Old 09-30-2009, 07:27 PM   #3
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i think he's saying he's getting oil starvation when braking. i don't know the answer, maybe better baffling or a dry sump
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Old 09-30-2009, 07:29 PM   #4
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i think he's saying he's getting oil starvation when braking. i don't know the answer, maybe better baffling or a dry sump
Yes, perhaps not clear in my post. Oil pressure gauge drops to zero. Looking to see if it is common and what solutions there may be.

Accusump is one but looks like a major under taking? Anyone installed similar? What would it involve?
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Old 09-30-2009, 09:18 PM   #5
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I get pretty low oil pressure after a full track session ~10PSI or so. Never seen 0 PSI, never want too either..
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Old 09-30-2009, 11:15 PM   #6
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Corvette people run a quart over full to prevent starvation. Any reason not to do this in our engines?
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Old 09-30-2009, 11:28 PM   #7
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Just fill it up until it wont take anymore, problem solved
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Old 10-01-2009, 12:06 AM   #8
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Do you have an oil cooler? If the fittings are facing down, you'll read full when you check it, but while it's running it'll actually run [insert oil cooler capacity here] quarts low.
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Old 10-01-2009, 12:08 AM   #9
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Corvette people run a quart over full to prevent starvation. Any reason not to do this in our engines?
So do turbo Subaru guys.
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Old 10-01-2009, 12:30 AM   #10
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Quote:
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Corvette people run a quart over full to prevent starvation. Any reason not to do this in our engines?
Excellent way to lose a ton of power from additional drag.
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Old 10-01-2009, 12:56 AM   #11
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just fill some oil, then fill the rest of it with water till it start flowing out the cap. That will make sure your oil system still stays pressurised :P haha

love that dumbass that ran water through the engine to get rid of the dirty oil
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Old 10-01-2009, 02:33 AM   #12
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Excellent way to lose a ton of power from additional drag.
But save your motor. I'd rather drive the car onto the trailer at the end of the day and make 5hp less throughout the day.
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Old 10-01-2009, 02:52 AM   #13
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I don't think a quart over would be enough to cause problems. When the engine is running, most of it is in circulation, which is why it is so easy to suck air in some engines. An extra quart would be fine I would think.
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Old 10-01-2009, 06:14 AM   #14
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Do you have an oil cooler? If the fittings are facing down, you'll read full when you check it, but while it's running it'll actually run [insert oil cooler capacity here] quarts low.
This may be the problem. I have an FM twincooler though - both in and out fittings are at the top (see here about 3/4 of the way down).

I suspect that the cooler itself wouldn't drain - but the lines might? The fittings and line are -8AN, ID 12.7mm and about 0.85m long in all, I make that about 340cc? I'll go 0.5L over the full mark on the dip stick and see what happens.
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Old 10-01-2009, 11:08 AM   #15
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I keep my oil level just over the top of the "F" on the dipstick, run r-comps with lots of sustained corners and never see oil starvation. If I did, accusump is the way. Its probably not a bad idea right now, but I know several peeps who've been tracking miatas hard, for a long time, that don't have this issue.
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Old 10-01-2009, 11:19 AM   #16
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however if you add oil the pressure will drop, so by adding oil it will show that your pressure is lower with regular driving/street driving, but will prob get rid of you sucking air in hard braking and cornering
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Old 10-01-2009, 11:41 AM   #17
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But save your motor. I'd rather drive the car onto the trailer at the end of the day and make 5hp less throughout the day.
And possibly, with a high enough level, see all sorts of frothing due to crankshaft/oil interaction. I don't know how high oil would have to be in a Miata to lead to this, and I'd rather not find out.

If it's the stock gauge dropping to 0, it's worth checking the connection on the sender. If it's actually dropping to 0, an Accusump is the cheap/effective solution.
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Old 10-01-2009, 01:00 PM   #18
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however if you add oil the pressure will drop
Wat?
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Old 10-01-2009, 01:05 PM   #19
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How will adding the oil (reasonable amount) reduce the oil pressure?
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Old 10-01-2009, 01:16 PM   #20
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adding oil maybe 2 qt or even 1 qt will cause the pump to work harder to push the same amount of oil through the system.
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