addressing oil heat for track work

[ausrex]

Hi all

I come from a pretty hot part of the world (Australia) and frequently track my subaru Sti.

Now the effects of heat and viscosity appear to be an issue with Subaru suggesting at least a 15w-50 for any extended track work. Now I've read with interest how a lot of Bitog guys are running 5w30 in North American Subaru's however there are heaps of Australian Sti's that have spun bearings with quality 10w-40's doing track work even after having used fresh oil before and after an event.

This has me thinking that rather than run a 50 weight oil as subaru recommends, I might be better off adressing the oil heat issue properly by employing a well contructed cooler that will keep oil temps well down thus allowing me to use an lighter viscosity oil in the 10 cSt/100c range (rather than the recommended 18-20Cst range).

Am I on the right track??

 

[TR3-2001SE]

Yes. But I think you would still need at least a 40 weight for a road racing track. Someone must have done this on a Sabaru and could give you the real scoop on this issue.

 

[Steve S]

Has something to do with being upside down.

 

[RI_RS4]

ausrex, what you need is a shear-stable oil that will not change viscosity at high operating temperature, and has an additive package that will withstand the increased stress. I hate to be a broken record here, but I'd contact Terry Dyson and pay him to provide a recommendation to you for your track needs. It will be the best money that you've spent on your STI.

 

[glenncof]

two things come to mind;

First is the formulations of oils can change around the world. So here in U.S. can be completely different even for the same brand, name , and viscosity. As example, Valvoline SynPower 5W40 in US and Europe looks very different. So US experience may have little to do with your oil.

The STI looks like a hot package Find race oriented forums specific to this vehicle. It's better to consult with those that have specifc experience on this vehicle, in your application, and locality.

BTW, you may have an oil cooler already. If not, good idea.

 

[Leo]

Keeping the oil temps under control is worlds better than using thicker oil as a bandaid. The oil cooler is definitely the best way to address your problem. With controlled oil temps, I'd be inclined to use a 30 or 40 weight.

 

[ausrex]

Quote:

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Has something to do with being upside down.

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Thats why we run oil pumps in all our engines down here

 

[ausrex]

Quote:

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The STI looks like a hot package Find race oriented forums specific to this vehicle. It's better to consult with those that have specifc experience on this vehicle, in your application, and locality.

BTW, you may have an oil cooler already. If not, good idea.

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Plenty down here have spun bearings running 40 weight oils even with the assistance of an oil cooler. A

bout the only 40 weight oil that tends to allow these engines to live in a track environment is Redline so shear stability at elevated temps appears to be an issue.

 

[ausrex]

Quote:

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ausrex, what you need is a shear-stable oil that will not change viscosity at high operating temperature, and has an additive package that will withstand the increased stress. I hate to be a broken record here, but I'd contact Terry Dyson and pay him to provide a recommendation to you for your track needs. It will be the best money that you've spent on your STI.

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do you have his contact details?

 

[Lonnie]

I'd like to replay the broken record. Send a sample to Terry and let him give you some specific information about your situation. It's money well spent considering what you're up against and besides the results you might learn something. It might be better information than an off-hand remark that leads to making a problem a big problem. Learning is usually cheaper than fixing.

 

[ausrex]

Quote:

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I'd like to replay the broken record. Send a sample to Terry and let him give you some specific information about your situation. It's money well spent considering what you're up against and besides the results you might learn something. It might be better information than an off-hand remark that leads to making a problem a big problem. Learning is usually cheaper than fixing.

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^^^ please refer to post above

 

[simple_gifts]

http://dysonanalysis.com/

 

[bluemax1]

Not terribly familiar with the STi's, but do you guys log oil pressure on the roadcourses?

I have a 3000GT VR4 (GTO down under). We've had some problems with spun bearings on road courses. Partly to do with oil that can't resist shearing at high temps but also to do with the design of the sump.

In high G lefthanders, the oil flows away from the sump and if it's high enough G (R-compound tires) and of long enough duration it starves the oil pickup and sucks air (there was one particular track nicknamed a roval for roadcourse + oval that killed about 5-6 cars). sudden loss of oil pressure = instant death.

There are pressure gauges (like the Defi system) that allow logging of oil pressure to see if there's ever a drop in pressure like this. Another good backup is a device called an Accusump. It holds a certain amount of oil (dependant on the size of the reservoir you purchase, usually 2-3 quarts) pressurized and it has a pressure valve in the system. You select the pressure valve based on your car's lowest oil pressure (hot pressure at idle) and if the pressure ever drops below this, the pressurized reservoir immediately pumps this oil into the system, ensuring some oil pressure is maintained.

Send your oil to Dyson and have it analyzed to see if it's shearing. Look into maintaining stable oil temps and make sure oil sloshing in the sump never starves the engine of oil.


Max

 

[ausrex]

Others have logged oil pressures in rally and tarmac environments and based on their advice it doesn't appear to be an issue.

Shearing at temps on the other hand seems to be the main culprit if their experience is anything to go by. This is no doubt what Subaru specify a 15W -50 for motorsport competition.

 

[bulwnkl]

How does one experience detrimental shearing without simultaneously experiencing reduced oil pressure?

 

[ausrex]

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How does one experience detrimental shearing without simultaneously experiencing reduced oil pressure?

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I'm far from an expert, thats why I'm here to learn however I believe a reduction of oil pressure is a completely different scenario to a sudden loss of oil pressure due to oil starvation.

 

[bulwnkl]

What I meant was: If the data loggers are not showing declining oil pressure, then it seems as though one would be able to infer an absence of permanent, harmful, shear.

Perhaps I'm reading too much into the statement "Others have logged oil pressures in rally and tarmac environments and based on their advice it doesn't appear to be an issue." ??

 

[ausrex]

Quote:

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What I meant was: If the data loggers are not showing declining oil pressure, then it seems as though one would be able to infer an absence of permanent, harmful, shear.

Perhaps I'm reading too much into the statement "Others have logged oil pressures in rally and tarmac environments and based on their advice it doesn't appear to be an issue." ??

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sorry I'll just clarify my statement.

The consensus amongst most subaru racers in this part of the world who have logged the peformance of the standard sump set up on various road race tracks both employing "R spec" and full slick tyres is that they haven't seen momentary oil pressure drops around a race track consistent with what would occur in the event g force induced oil surge and subsequent starvation were present.

in other words


as opposed to

a permanent DECLINE or lower oil pressure over a given period which may be consistent with shear.