Normy

Dammit I wish I had an oil temp gauge on this car!

The only place to mount such a gauge that would look decent is on the pillar in my opinion. Does anyone know of an A pillar gauge surround for the 928?

My second car ever was an '85 VW Scirocco. This car was turbocharged- there was a rare dealer-installed factory option in '85, and this car had it. When I bought it, I was told that it had Shell oil in the sump. I decided to change the oil and use Mobil 1 15W-50. After the change, oil temperatures increased 10 degrees....

I didn't have an oil pressure gauge, and I went back to dino [Castrol GTX] on advice of a mechanic. This air- cooled turbo served me for 113k miles, and 8 years without failure. The oil temperature did slowly increase 10 degrees in typical driving over the 8 years, though I have no idea if that was gauge/sensor error or accurate. The girl that bought it was happy to have it....

That car started out registering 100 degrees C oil temp in normal driving. After changing to Mobil 1, it ran at 110 for years...slowly moving up to 120 in traffic when I sold it. It had the factory oil-to-water cooler with no leaks. I've always wondered if the change to synthetic for one oil change caused crud to be blown into the oil cooler, reducing it's efficiency....

N!
'85 S2 5 Speed

Rich9928p

The shop that maintains my 928s serves a lot of 944 spec racers. One engine that spun rod bearings was using Motul. Another engine that spun rod bearings was using Redline. They have not had an engine that used Mobil 1 spin rod bearings.

So does this mean that only Mobil 1 is a good race oil? I don't think so ... but it shows that MK's observations that only cars using Mobil 1 have engine failures is also flawed reasoning.

There can be a million reasons for an engine failure that have nothing to do with oil. Or, a driver can ignor problems such as too high of oil temperature and spin bearings ... or be a quart or two low on oil .... do you classify this as an oil caused problem?

Fastest928

Most bearing failures in 928 appear to be from oil starvation - either from lack of oil at the bearing/journal interface due to localized no flow/pressure (8000 rpm) or, loss of effective sump pick up 1g cornering.

Either one is going to cause issues.....I think Mark K shifting points keeps the oil pump volume at a level that allows the sump to remain at a level whcih allows the pickup to function well enough.

He may be skating on ice.....maybe his cam teeth failure is due to the low oil pressure in the cam tensioner causing some chatter. Maybe he has a restrictor in the head, or a really good scraper and windage tray......right now, his engine is an unknown..

Or maybe Amsoil is really that good?

?????????????

Marc
DEVEK

Z

Also keep in mind that it might have been that the Mobil1 was more efficiently removing heat from things like the pistons and bearing surfaces, which is one of the things it's supposed to do. *If* the same amount of heat is being generated in those areas, lower oil temperatures might mean that the original oil wasn't as efficiently removing that heat. Of course it depends on where the oil temperature was being measured. It could also be possible that the Moibil1 wasn't giving up heat in the oil cooler as well as the other oil had.

M758

Rich, Intersting information about the spun bearings on non-Mobil 1 motors. As I figured the 944 problem cannot be solved by oil type alone. It may be a factor however.

For those of use racing the 928 and 944 we need to learn what 5 or 6 things we can do to minimize the potential for failure. I believe that doing all of the 5 or 6 things can bring longevity. Clearly some racers have experieced it so it is possible.

Doug, Great thread! Lots of good information here!

Z

After checking with the owners of those two cars, I have additional information to provide. The GT that was experiencing oil pressure drops in corners at the track was using Mobil1 5W30 that day. The other GT, the one that experienced the 2/6 rod bearing failure, was using Redline 20W50, and had a GTS baffle and a street Accusump in it.

mark kibort

I dont think most of the falures have the abilty to **** at 8k or even 6800 unless it is a GT. so , why the failures?? I not short shifting, but i do not hit the rev limiter, but generally, all intense racing shifts are done at 6300rpm.

my oil level is always at the top level, and the use of amzoil may be helping here.

the cam teeth chatter is a possibilty, and that would yet be another reason to accusump, but why is my oil pressure always pegged at 5 bar, even in high G turns?? granted, there are no constant radiused turnes that force me to be at 6000rpm around the turn. (nor would any turn if driving right) However, there is a 5500rpm turn in 3rd gear at Willow springs that is a few more seconds than anything up in nor cal. this is one of the reasons Ive stayed away from Willow springs. their turns are longer in duration at High G loading. However, turn 2 at Thunderhill is 5000rpm 3rd gear and its very very high g loading! and then turn 3 is off camber right and a kind of long high g right hander.

those broken teeth are puzzleing. expecially, since the intake came with one missing is still only missing one and the exhaust came now has a missing tooth after the last 3 hard races! One would think that the tooth missing would put a load on the adjacent teeth and they would have broke. does this mean as long as I only loose a tooth every once in a while and its random due to oil pressure, I should still race it??

debating on what I should do. any ideas????

Mk

Z

I've talked to one owner who had a failure with only doing 5,500RPM. Very sticky track tires and high G turns though.

There seems to be some evidence that it's more of a problem during left hand turns.

mark kibort

Sticky tracks??? I dont think there are too many owners that are pulling more gs consistantly than the racers group. especially, with the fast that I run 315s and 275 tire sizes all in DOT racing slick variation. (always)

Left turn, High G, is not what willow springs is. Thunderhill does have the 5000-6000rpm 3rd gear hairpin left. no issues so far (knocking on wood) but also , no dips in oil pressure.

what kind of oil was he running?? mobil 1?????????

Mk

QUOTE]Originally posted by Z
I've talked to one owner who had a failure with only doing 5,500RPM. Very sticky track tires and high G turns though.


There seems to be some evidence that it's more of a problem during left hand turns. [/QUOTE]

Z

I really don't know what kind of oil was in that one at the time. About all I can add to that one is that it had a GTS baffle in it, and also a drilled crank when the failure occured.

heinrich

Sticky is relative.

Again, Louie was running REDLINE when he coughed up a couple of quarts (sa the smoke, don't know really how much), chomping his bearings. And I was running MOBIL1 when I did, however I didn't eat my bearings. So ....... our cars have a flaw. Will a different brand of performance oil cure or mitigate the resultant failures? Maybe. Louie's case proves that not only REDLINE but also a simultaneous righteous crank case ventilation setup will sometimes not save you.

Personally I think if you let oil out via the valve covers you're at greater risk. And that is everyone with a stock setup.

Z

I'm thinking that the oil coming out through the breather system like that is another symptom of the inherent problem that's occurring.

John..

I recently switched the Bastard to Lubro Moly, but I am seriously considering switching back to Mobil 1. I don't want to have to wait to get a quart of Amsoil, Redline or Lubro Moly when I need it.

I have over 4000 miles on this Lubro Moly (well it is now mixed with M1 because of two scavenger pump drive failures resulting in over 4 quarts of oil in my intake system). I have been doing countless hours of injection tuning and am close....but this oil has to go, since I am sure it is somewhat washed out. My oil pressure hot is around 2 bar, perhaps a tad bit less if I run it hard.

I will stick with M1 15-50 and keep my boy racer image going.

George 911-V8

John give royal purple a shot


George

mark kibort

stick with that mobil 1 and your crank is going to "stick" to your bearings!!

2 bar???? you shouldnt see anything less than 5 bar, or higher when the revs are over 2k. (which they usually are)

Im telling you, spooky oil pressure on the Mobil 1. the light was coming on!!!! thats less than 1` bar at idle after a track session on a hot day. my Holbert 928 s4, never never gets below 4.5 bar at any time NEAR idle or the 2k range.

MK