[dave968]

Had my PCA E stock 968 engine rebuilt. Now with 12 hrs track time on engine, after running on track after 4 laps at full throttle down the front straight at Roebling Road ~132 mph 6000 RPM my oil pressure is 40, sometimes 38 on my gauge. It will remain 38-42 for 20 min on track. Maximum oil temp is 180-200. At end of track session in pits when motor revved to 5000 RPM oil pressure increases to 50-60 psi. Using Joe Gibbs XP6 15W-50 oil.

Could an oil pump problem cause oil pressure to be low at max speeds on the track? OIl pump was rebuilt at time of engine rebuild.

Or is oil pressure on track 38-40 normal???

The oil sending unit and OilPressureReliefValve have been replaced and there is no change.

Thinking of changing to Millers performance racing oil, 10W60. Has anyone used a 60W oil on a track/race 968?

thanks



Dave

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[hk968]

I run Mobil 1 15W-50. At 3000 rpm or more, my oil pressure never drops below 4 bar (58 psi), even after 30min track sessions at the Glen in hot weather. Idle is around 2 bar after fully warmed up.



So to you question, 38-40 psi is not normal for the track, not in my car anyways.

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[quick968]

Your temps are just fine, spot on perfect actually.



Per the Porsche Factory Technical Specification book, Pg 16, minimum oil pressure at idle is .6 to .8 bar, which is 8.7 to 11.6 psi so you are well above that spec. Minimum oil pressure at 3000 rpm is 3 bar, which is 43.5 psi, so you are at the low end of normal but still normal given typical pressure gauge inaccuracy variations. What Porsche is saying there, reading between the lines, is that at or above 3000rpm's, 3 bar is sufficient oil pressure under all conditions. I'm not sure anyone would recommend going with a 15W-60W oil, at cold startup you risk seal leaks. Just my opinion there based on lots of years tracking these cars. Have you done any oil analysis since the rebuild? It would give some indication of whether your engine is "making metal" after the rebuild, particularly in the oil pump area. Depending on the amounts in ppm and the type of metal, Al, Fe, Cu, etc, they can tell you what, if anything, are wearing abnormally, be it rings, pistons, main/rod bearings, cams etc since each has a particular alloy signature. Not unheard of to have a rebuild go bad if not done properly, a remote possibility but it's there. But it's always a wise practice to do an oil analysis check at each oil change during break in to see how things are settling in. You should also check the oil filter element for particles. If you have pieces in the filter with serial numbers you have a problem. You HAVE changed the oil at some point since the rebuild right? <img src="/forum/images/smilies/968/whine.gif" class="smilie" alt="" /> Did your re-builder have break-in oil brand/type recommendations? How about change intervals?



Others will chime in on the 60W issue. Have you spoken to the guys who did the rebuild about the perceived issue and what was their response? Do they stand behind their rebuild? Track use or not is irrelevant, the engine is designed to be run hard with no ill effects.



Keep us posted.



Cheers

MIkey

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[94SilverCab]

A known point of weakness is the oil pickup tube, which has been know to crack under race conditions. Just a thought.



Jay

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[dave968]

Used Joe Gibbs XP6 15W-50 oil, changed oil at 6 hrs to Royal Purple 20W50, then at 12 hrs back to Joe Gibbs XP6 15W-50 oil. Planning to do oil analysis this week.

Yes my engine rebuilder has been concerned about low oil pressures, added larger oil cooler, changed oil pressure sending unit, tried shimming oil pressure relief valve (saw no difference), replaced oil pressure relief valve, added digital oil pressure gauge.

In asking others, Karl Poeltl Racers Edge showed me his Aim data oil pressures ran 30-40 at 6000 RPM at Daytona in Oct. Others say pressures should be >50 on track at all times.



Dave

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[flash]

aaccck! i wouldn't put royal purple in anything. i've seen an independent test that showed what it is made of, and i know way too many engines that blew due to the lack of protection from that oil. looks great on paper for a 1/4 mile run or two, and even can show a tad more power, but they don't show extended performance figures.



as for the low pressure, there are so many things that can contribute to low pressure that it is very hard to diagnose online. it could be anything from an improperly sized bearing to blowby at the oil pump. it's easy to mess this one up. i know of an engine that was assembled by the accepted expert that put out low oil pressure from day 1, even after trying to correct the problem. while it got better, it never got full pressure.



you may find that you either have to tear it down to find the problem, or run it until it blows.

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[quick968]

" aaccck! i wouldn't put royal purple in anything. i've seen an independent test that showed what it is made of, and i know way too many engines that blew due to the lack of protection from that oil. looks great on paper for a 1/4 mile run or two, and even can show a tad more power, but they don't show extended performance figures"





I do NOT want to start a Royal Purple/Joe Gibbs/(insert boutique oil brand here) flame war, gawd knows the "best oil" wars have been talked to death, so I kept my mouf shut. But since Flash start it, (grin) I can wholeheartedly agree with Flash on this one. Show me one pro GT team, or WRC team, ALMS team, F1 team, or Indy Team, who finishes races, be it a Porsche Motorsport team, or Ferrari, or Audi, or Mercedes, or BMW or whoever, anywhere in the US, or the world for that matter, who uses Royal Purple or Joe Gibbs or any of these AMSoil type boutique oils. With the exception of the Royal Purple NASCAR team, the answer is most likely near zero. And NASCAR may even force them to use some NASCAR approved oil common to all teams I don't know. All things being equal, two identical cars and drivers, no one podiums because one used Royal Purple and the loser used Mobil 1.



I'm always a bit curious when folks like us at our level of fiddling about the edges of motorsports, however seriously taken, feel the need to second guess the factories? The factories who have literally unlimited funds to research and work directly with the lubricant manufacturers to come up with the best oils. Porsche has been using Mobil 1 exclusively in all engines, including all Motorsport Cup cars since 1996. Nearly 20 yrs. Why do folks question that? Why do they think there's something "better" out there? "Better" in what way? The universe of variables under consideration include; does it make the engine last longer, run cooler, make more HP, run cleaner/have longer change intervals. That's kinda it for oils. So why second guess what the factory spent scrillions on to determine, and now has nearly 20 yrs and countless miles on and off track, all weather, temps, conditions to prove their choice? No Royal Purple or Joe Gibbs or AMSoil in sight unfortunately.



Joe Gibbs site states "Horsepower improvements will vary by engine type and application. In Joe Gibbs Racing Nextel Cup engines horsepower gains of 2 hp over other premium synthetic race oils are typical."



Um OK, I'll play along for the sake of conversation; on a roughly 775HP Nextel engine, a 2 hp improvement equates to a whopping .00258, or roughly 2/10's of 1% improvement. Wowsers!



So then, on our 230HP+/- 968 engines, that's an incredible .59 HP improvement. Maybe.



You couldn't see that on any dyno anywhere.



Please don't construe this to imply that using these oils ruined, or even affected, the oil pressure of the engine of the OP in question, they probably didn't harm it any at all. Probably. Just meant this as a general statement to just use what Porsche recommends in our very expensive engines. They recommend it for a reason. Use only Porsche approved oils and lubes. Or not; run what makes you happy. Maybe nothing will go wrong, maybe something will. But as far as gaining an edge on the track, it's the loose nut behind the steering wheel that is usually the area most in need of improvement, myself included.



Mobil 1 for me please.



Cheers

Mikey

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[flash]

my point was not so much about the lack of supporting evidence regarding power gains, but rather the damage i know of that royal purple results in. it's not pretty. that oil breaks down under extended heavy loads, and that kills engines.



but, back to the OP issue, and hopefully to avoid yet another oil thread, i agree that the oil type would have nothing to do with pressure.

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[netopyer]

i would prefer 10W60 oil for racing/trackday purposes.

anyway, do you have CST values of your oil?

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[dave968]

what are CST values? I am going to send an oil analysis this wk.

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[netopyer]

[quote name='dave968' timestamp='1391522278' post='154845']

what are CST values? I am going to send an oil analysis this wk.

[/quote]

www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.htm

i am asking because imho the 5w50 oil is "boiled" on hard track use ..

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[flash]

one thing to remember is that the wider the variance in viscosity, the shorter the lifespan of maximum protection. as an oil gets dirty, the polymers lose their ability to expand. this means you lose the upper number. the best selection would have a smaller variance. i.e. 5w40 is not as good as 10w40 in its ability to maintain maximum protection at temperature.

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[netopyer]

so the solution is maybe MOTUL Lemans 20W60?<img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />

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[333pg333]

With regards to Porsche recommending Mobil oils and therefore why use anything else...

Porsches relationship with Mobil has been largely based out of a commercial union. For many years they used a straight 60w Shell oil in their racecars even though they were covered in M1 livery.



If you contact Porsche US and ask them what oil to use in your 968/944 they will tell you something like a Synthetic 0w/40 which is not a great idea for our cars with flat tappet motors and especially on the track. They also lowered their ZDDP levels without telling anyone which resulted in a number of cars with excessive wear. They've now increased ZDDP in some more recent 'models' but I'd be checking before I used any oil in my car. Not wanting to enter the old oil war threads, just thought I'd mention this. For the record we use a Castrol 25w/60 for our track cars but I don't think this blend is available in the US. There is a rule of thumb that you should see approx. 10psi increase with each 1000rpm.

We ran a big 993 Oil cooler which also helped a lot.

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[netopyer]

i did first oil change yesterday, and switched from castrol 5w40 to Castrol TWS motorsport 10w60 , and the oil pressure is a bit higher on idle even when hot

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