Heavy braking and my engine sucks air??? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 10-01-2009, 01:20 PM   #21
Senior Member
iTrader: (9)
 
Join Date: Oct 2006
Location: Lexington SC
Posts: 1,003
Total Cats: 14
Default

The pump flows just as much oil with normal or slightly higher oil levels. More oil will actually result in a larger positive suction head due to higher oil level in the pan since. The rest of the oiling system only holds so much oil and will not work any different with more oil in the sump. Thats why adding the oil helps with startvation since the oil level overall will be higher even with shloshing in the pan.
Rallas is offline   Reply With Quote
Old 10-01-2009, 01:24 PM   #22
Elite Member
iTrader: (6)
 
Join Date: Nov 2007
Location: Southlake,Texas
Posts: 3,251
Total Cats: 17
Default

My car used to hit 0 psi under heavy braking, but since the turbo install it doesn't do it anymore. Adding more oil will give you more oil pressure, until you burn it up lol.
Bond is offline   Reply With Quote
Old 10-01-2009, 01:54 PM   #23
Junior Member
 
Join Date: Aug 2008
Location: MD/DE/PA
Posts: 337
Total Cats: 0
Default

Quote:
Originally Posted by Dparks7 View Post
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.
O rly?

the_man is offline   Reply With Quote
Old 10-01-2009, 03:51 PM   #24
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,357
Total Cats: 1,322
Default

Quote:
Originally Posted by Dparks7 View Post
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
No, it won't.
Savington is offline   Reply With Quote
Old 10-01-2009, 03:54 PM   #25
Junior Member
iTrader: (11)
 
Join Date: Oct 2006
Location: Petaluma, California
Posts: 166
Total Cats: -3
Default Some other options

Thicker oil - try Mobil1 15w50. Sure, it will reduce power a tad, but it's better than a nuked engine.

Crank scraper and windage tray - requires dropping the subframe(or pulling the motor) to get to the oil pan, but crank scrapers are proven to increase power and reduce oil starvation by minimizing oil movement in the pan.

I had a crank scraper, windage tray and a modified oil pickup(1.8L pickup modified to fit my 1.6L pan) as the 1.6L pickup was not very low in the pan. I never saw low oil pressure on high speed sweepers(yes, on R compounds). I plan to rebuild the motor again(I nuked the #4 rings last year) and knife edge the crank and get a teflon scraper.

Probably the first thing I would do is as TheMan mentioned - make sure the electrical connections @ the sender are clean, but IMO if this is ONLY happening on high G sustained turns it most likely is oil starvation.

If dropping the pan is not your cup of tea I would first try some thicker oil and adding 1/2 to 1 quart additional oil. If that is no workie then an accusump would be the least painful option.
minime is offline   Reply With Quote
Old 10-01-2009, 04:15 PM   #26
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,653
Total Cats: 1,559
Default

At high sustained RPMs more oil is being pumped everywhere in your engine. The oil that is pumped out under pressure relies on gravity and passages to allow it to return to the pan. The oil that is pumped into your valve covers is designed to return primarily through the rearmost section of the head. With sustained high RPMs, prolonged extreme braking enhanced by upgraded brakes and tires, oil that is pumped into the cam and valve cover area could conceivably exceed two or three quarts in volume. Think of your engine sanding on it's nose with the valve cover area half full of oil. At 1+ g-forces the oil won't make it to the drain holes as quickly as it is pumped, and held, up there.

And for those who are not familiar, racers often run an extra quart (or two) if they are limited to a stock oil pan by rules. As long as you are not interfering with the rotational mass of the crank assembly, you are just fine.

There is much misinformation in this thread from people who really don't understand their engine's oiling system and shouldn't be commenting.
sixshooter is offline   Reply With Quote
Old 10-01-2009, 04:18 PM   #27
Junior Member
Thread Starter
 
Join Date: Jul 2006
Location: UK
Posts: 157
Total Cats: 0
Default

Thanks all. The pressure drop is real, not only on the stock gauge (now installed in a sandwich plate port), but also on my SPA gauge whose sensor is in the stock position in the block. First thing to try is to see if I can stop it by adding 1/2 litre of oil above the full dip stick mark. As has been mentioned here it maybe that I am getting 1/3 litre drain into the pan from the cooler lines anyway. If not then it looks like an accusump - but goodness knows where I'd mount it!
slowmx5 is offline   Reply With Quote
Old 10-01-2009, 07:29 PM   #28
Junior Member
iTrader: (11)
 
Join Date: Oct 2006
Location: Petaluma, California
Posts: 166
Total Cats: -3
Default

****, my bad. It might help if I didn't read like a dyslexic. I misinterpreted his issue as oil sloshing in the pan in sustained high G turns. Six-shooter is SPOT on: since this is happening only during prolonged hard braking the problem is a lack of oil @ the pickup, which is @ the rear of the pan. Whatever oil is in the pan is pulled to the front, away from the pickup. Come to think of it I remember seeing my oil pressure drop to zero a few times under prolonged braking, but since this was PRE-engine build + turbo install I didn't care since my engine was beat to crap.

Prior to the engine rebuild I used to do an oil change before every event and always overfilled by 1 quart(was running 15w50 on a very tired 1.6(150K miles) at the time. I found that I would burn off the entire quart during the event so I then tried only adding 1/2 quart and found that I still burned off the excess, but I still had ~ the same amount of oil at the end of the day(@ the full mark). Why did I burn more oil when I added more?

My theory is that if you overfill the crankcase you will end up increasing the air pressure in the crankcase which leads to oil getting past the rings and seals. I am not sure if that is bad, but it sure seemed like a waste of oil to me and I never saw a huge oil pressure drop at any time when I only added 1/2 quart, even under hard braking such as entering turn-2 and turn-11 @ Laguna.

I still think a crank scraper would help and I never saw zero pressure after the new engine was installed(maybe the crank scraper and modified oil pickup was enough?), but an accusump is probably the best way to avoid oil pressure loss when flogging on the track.

good luck,
Mike
minime is offline   Reply With Quote
Old 10-01-2009, 08:19 PM   #29
Elite Member
iTrader: (2)
 
triple88a's Avatar
 
Join Date: Apr 2006
Location: Chicago, IL
Posts: 9,131
Total Cats: 598
Default

perhaps can you weld a piece horizontally that is open at the back to prevent the oil from sloshing too far forward

Do you see the red piece of steel? When you slow down, the oil will be stuck there creating a nice cup.

Name:  weld.gif
Views: 1
Size:  1.2 KB
triple88a is offline   Reply With Quote
Old 10-02-2009, 12:09 PM   #30
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,653
Total Cats: 1,559
Default

Quote:
Originally Posted by triple88a View Post
perhaps can you weld a piece horizontally that is open at the back to prevent the oil from sloshing too far forward

Do you see the red piece of steel? When you slow down, the oil will be stuck there creating a nice cup.

My Moroso eight quart pan is designed just like that.
sixshooter is offline   Reply With Quote
Old 10-07-2009, 05:30 AM   #31
Junior Member
 
Join Date: Apr 2008
Posts: 46
Total Cats: 0
Default

Tomei has a fix for this problem for RB Nissan engines by designing little "reducers" (so to speak), which go into the oil galleries to reduce the flow.
There are quite a few sump baffles out there that are bolt-in. Doesn't Racing Beat sell one?
OZMX-5 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Changing from 460cc to flow force 610cc in diypnp 90 Turbo MEGAsquirt 19 10-19-2015 04:23 PM
Moroso Air Oil Separator Catch Can Aroundcorner Miata parts for sale/trade 2 10-01-2015 04:20 PM
Leaky Wilwoods mx592 Suspension, Brakes, Drivetrain 1 10-01-2015 01:45 AM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 11:28 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 06:42 AM.