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Oil pressure issue....turbo road race application


2eighTZ4me

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I have had a recurring pressure drop issue while on track. I will try not to be too 'wordy'. Some random information;

 

 - 3.1L stroker turbo. Remote Oberg oil filter system. Routing goes Block > Oberg > Mocal oil thermostat > oil cooler > return to block. All -10AN lines.

 

 - I have opened up the oil passages in the block that feeds the head per the "How to Modify" book. Internally oiled cam BTW.

 

 - When cold - I start the car and run up to 2k rpm's - oil pressure pegs the gauge at 100psi. 

 

 - As motor gets to operating temp, pressure averages about 10psi per 1000 rpm's - which is average from my experience.

 

 - When I get on track, however, pressure goes into the toilet once the oil temps start creeping up past 230. I have seen as little as 20psi at 4000rpm. 

 

 - Running a turbo automatic oil pump with the Wolf Creek Racing external oil pressure adjuster cranked in as far as it will go. 

 

 - Motor ate a bearing yesterday at the dyno. Was running Rotella straight 30wt. 

 

 - I have tried many other oils of varying viscosities and manufacturers - all with the same result. 

 

 - In speaking with my machinist yesterday - he asked if I had a deep sump oil pan. I am indeed running the Arizona Z Car aluminum baffled pan. His next question got me thinking....'do you have a deeper pickup tube as well'?? Well....no.  His thought is that - once the oil gets hot and thins out, it's flooding the head because of the enlarged oil passages, and the oil can't drain back to the pan quick enough. Even though there is an extra quart capacity - the pickup tube is still stock and does not get all the way down in the pan to get at that extra oil.

 

I have not cracked open the motor yet to measure the actual depth of the pickup tube and pan, but that was a good hunch. Will know that info this evening. 

 

Regardless, this problem has plagued me since day 1 with this motor. All bearing clearances are well within spec. I plastigage each motor I build, and am very particular about the clearances.  

 

As a note - when I drained the oil cooler yesterday - the oil was all black, whereas the engine oil was nice and gold (and full of engine bearing pieces). I'm thinking that thermostat might be causing some issues as well, and am thinking of removing it altogether so it's a straight shot from the filter to the cooler. 

 

I would like to hear ideas and comments from folks that actually get their cars out on track - as you cannot punish your car on the street like you do on track.

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The AZC oil pan does have a drain back issue.  I drill three  3/4" holes on the windage side of the tray.

 

Call Don Oldenberg at DP Racing and order one of his competition oil pans.

 

And yes, you might have thermostat and/or oil cooler could have issues.  Test the thermostat in a pot of boiling water with a meat thermometer.  Send the oil cooler out to be sonically cleaned and tested.

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Dare I ask how much the DP racing pan costs? The AZC pan was bad enough. I don't suppose you have any pics of where you drill those holes John? I'd like to avoid spending any MORE money on this thing if I can avoid it. I know it was you John, that recommended I go with the oil thermostat - what would be the disadvantage of removing it altogether? I don't have a problem with oil getting up to temp quickly with the turbo. Thank you for confirming a suspicion....

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Dare I ask how much the DP racing pan costs? The AZC pan was bad enough. I don't suppose you have any pics of where you drill those holes John? I'd like to avoid spending any MORE money on this thing if I can avoid it. I know it was you John, that recommended I go with the oil thermostat - what would be the disadvantage of removing it altogether? I don't have a problem with oil getting up to temp quickly with the turbo. Thank you for confirming a suspicion....

I would posit that the problem sounds more like the oil cooler itself than the thermostat, although it certainly wouldn't hurt to check both.

 

The t-stat bypasses the cooler when the oil is cold, which is where you are _not_ seeing a problem, and progressively routes more oil through the cooler as the oil gets hotter.  This to me sounds consistent with a clogged/restrictive oil cooler - the hotter the oil gets, the more of it gets routed through the restriction.  Oil t-stats are usually set to regulate around 170 or 180 degF, so by 230 degF you are probably routing pretty much all of the oil through the cooler.

 

Also, if the oil looks black in the cooler and clean everywhere else, that sounds like not much is getting through the cooler.  

 

What cooler are you using?  How big are its passages in the first place?

Edited by TimZ
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Here are my thoughts:

 

- Oil pressure is always higher when the engine is colder. I see this on my road race car, and my remote cooler adapter does not have a thermostat, so oil is going through the cooler all the time. I would by pass the cooler, and just run a filter on the block. Do a test and tune to see if the pressure is steady.

- When you set the Wolf Creek adjuster, did you set it so that you see max pressure on the gauge? I noticed that I had to play around with it a bit until I saw the max (85psi cold)

- I never drill out the oil restrictors. You are probably getting too much oil going to the head now, so flow and pressure of the overall system is now lower. The oil system cannot deliver enough flow with the restrictions you have in your setup to achieve a dceent pressure at temperature.If you were running a dry sump system with a lot more flow, then you can probably drill out the restrictors.

- 30wt oil is a little light for road racing (unless you're an ice racer). I would run 40 or 50wt. I don't know about Rotella (sounds like a chocolate spread) , but I run the Brad Penn stuff.

Edited by z-ya
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Haha!! You guys!! At the risk of not knowing you guys' familiarity with Rotella (and forgive me, if you're screwing with me!!) - it's a diesel oil made by Shell - comes in 15-40, and straight 30wt. Over the years, the EPA has been cutting zinc out of passenger car oil, as you know. Rotella was/is exempt, because it's a diesel motor oil, yet still retains 'some' of that zinc, and my turbo buddies swear by it too. I've been using it in every one of my vehicles for the past 10 years - don't even have to add a bottle of ZDDP. 

 

And yes - as I thought initially, it's probably way too much oil to the head. I have an internally oiled cam, that I ran with a spraybar setup too. Thought that was the issue. Blocked off the spraybar, and still the same problem. I believe the oil passage modification was meant to be used in conjunction with other mods - yet I have the automatic turbo oil pump...and as I stated, it is maxed out on the Wolf Creek adjuster setting. Probably just going to get a new oil pump for the turbo automatic - leave the Wolf Creek adjuster off - and roll with it. Maybe my machinist can weld up the oil passage holes back to stock size. Hate to lose this block....

 

Going out to tear it down now... :)

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Haha!! You guys!! At the risk of not knowing you guys' familiarity with Rotella (and forgive me, if you're screwing with me!!) - it's a diesel oil made by Shell - comes in 15-40, and straight 30wt. Over the years, the EPA has been cutting zinc out of passenger car oil, as you know. Rotella was/is exempt, because it's a diesel motor oil, yet still retains 'some' of that zinc, and my turbo buddies swear by it too. I've been using it in every one of my vehicles for the past 10 years - don't even have to add a bottle of ZDDP. 

 

And yes - as I thought initially, it's probably way too much oil to the head. I have an internally oiled cam, that I ran with a spraybar setup too. Thought that was the issue. Blocked off the spraybar, and still the same problem. I believe the oil passage modification was meant to be used in conjunction with other mods - yet I have the automatic turbo oil pump...and as I stated, it is maxed out on the Wolf Creek adjuster setting. Probably just going to get a new oil pump for the turbo automatic - leave the Wolf Creek adjuster off - and roll with it. Maybe my machinist can weld up the oil passage holes back to stock size. Hate to lose this block....

 

Going out to tear it down now... :)

 

 

Just kidding on the Rotella. It's just every time I see it in the store I think of the Nutella spread my Daughter loves... Brad Pen has ZDDP and all the good stuff too.

 

Order some new restrictors from Nissan and drive them into the block. If you drilled out too much material, you can tap for a small NTP plug, and drill the plug with the correct hole.

 

Takes John's advice and get your cooler cleaned and flushed. Also add the extra holes in the windage tray.

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It's been close to 20 years, but I thought I had checked the pickup depth in the AZC pan and found it OK. It's easy to check and pretty easy to fix too, so that's worth doing. You can add a metal shield around the sides of the pickup screen to make sure it sucks from the bottom and avoids air bubbles, and get the depth right that way too (1/4 to 3/8 is recommended IIRC). I would run a thinner oil too. Talked to a machinist a while back and was told that you essentially never see oil issues because of lack of viscosity, but you do see them as a result of having oil that is too thick (drainback to the pan is slower). Now that you lost a bearing flushing the cooler is a no brainer. I'd add an accusump on top of all the rest. Very easy to plumb into your existing setup since you already have the adapter/thermostat/cooler.

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  • 5 months later...

Sorry to dredge up this post from the past, but a nasty, expensive divorce kinda got in the way. I finally got all my stuff back from the machine shop, and have obtained a new stroker crank. 

 

So - here's the pan with the tray laying on top of where it's supposed to go.

 

AZCPan_1.jpg

 

Crank spins clockwise if you're looking at the front of the motor (counterclockwise if you're sitting in the driver seat) - so most of the oil is getting thrown at the driver's side of the pan. Is this where I'm supposed to drill the holes?

 

AZCPan_2.jpg

 

Looks like I have room for a fourth toward the back of the pan - and I would think that couldn't hurt at all either... I just don't want to hack this thing up - measure twice, cut once....

 

Thanks all!

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Well, to be a fellow necroposter, the only engines I run synthetic in are air cooled and turbos...

 

My Corvair lost a belt at the top of Willow Big Track and made it back to the pits (didn't  realize it was gone until the slight straight going into the turn for the front straight past the pits.)

 

Oil temp gauge was pegged well past 150C gauge limit.

 

Thought it would be 'bearing city' like when I threw a belt on the 405 and coasted  to the off ramp. The synthetic held together  and saved my bearings. Marc Natale recommended it to me, having the same sort of failure  going  uphill into the turn at the top of Big Willow and was well past the water barrel going back downhill before noticing himself. Like me, he had trashed an engine before when the oil went over 300F using dead dinosaurs...

 

After that, he used Synthetic, and convinced me to change my Straight 40 Wt inmy VW and Corvair to Synthetic as well.

 

FWIW...

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I just read this post. Low pressure could have been the oil pump. Make sure to change it out on rebuild. As far as oil, there is plenty of info on the web. Bobistheoilguy. How hard you push it on track and how much you spent on that engine should influence your decision. I stay away from additives and straight weight oils. Most damage happens on start up. For a severe duty L6 stick with a multi-grade at least 40w or more for higher temps and to allow margin for some degredation. 40W oil turns into 35W oil when contaminates are introduced.

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I have run several different oils in different cars. The Vair got Baker Neo in the engine and Amsoil in the trans. I use Redline in the trans and in the TurboZ.

The Bus has had Amsoil in it since 79 when I changed it due to it being the only damn oil I could get that would let me shift gears at -40 without holding all the gears against the balk rings to warm them up and soften the oil.... I briefly let it drain out, for about 30,000 miles when the tranny died. Once I replaced it with the new tranny, it lasted about a month before the reduction gears burned up the oil driving at 80 out to Phoneix one june... and Amsoil went back in and been in there ever since.

 

Amsoil

Baker Neo

Redline

Royal Purple

Mobil 1 (but only because that was all they had in Alabama)

 

Used all the above.

 

Synthetic does way different things when it gets hot and severe duty, something dead dinosaurs can never do: Get thicker with the heat! It's really neat to talk to a Petroleum Engineer. I suggest one day if you're around the area, at any Cafe in Houston or Dallas strike up a conversation. They get off describing how the molecules work. They may not even notice you didn't leave a tip on the check!

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