How to possibly prevent cylinder scoring

[hartech]

Hi Gary, the only part of the system that the oil pressure effects (in terms of cylinder scoring) would be the oil spray jet effect on the under piston temperature and cylinder lubrication - but I don't think 100 rpm would make enough difference to that. But of course just pulling away more gently before ragging the car (or even just revving it up a few times before setting off) achieves a lot more with fresh oil everywhere and time for the coolant to circulate and the thermostat to re-set and keep the engine at the right temperatures.

Baz

[static2010]

gtphile said:

The turbo and GT3 engines do run an intermediate shaft, but it uses white bearings, running in oil, I beleive that was what the guy above you was suggesting converting too.

That was my point yes.

I know it has the IMS too, only direct driven with gears instead of a duplex chain.

But as I see, Baz has answered it for me. It would require a pressurised feed instead of splash lubrication.

[Dan911]

Does the X51 suffer the same problem? 996.2 3.6

[churny]

"Does the X51 suffer the same problem? 996.2 3.6"

From personal experience yes, when i bought mine i thought the extra cooling would help but still ended up with scored bores.
The mileage was 58k.

[hartech]

Yes the problem being that regardless of the additional radiator the engine will still run at all the same temperatures controlled by the thermostat - without lowering the temperature of the thermostat the only advantage of the third radiator is in instances when the thermostat is fully open yet the system cannot cool the engine enough with two radiators.

The assumption is that someone buying an X51 will be likely to drive it faster than a std car - hence the need for extra cooling capacity in hot conditions.

Withough lowering the coolant temperature below that of the std thermostat - all the same conditions at the piston and cylinder face remain just the same.


Baz

[KipIngram]

"So – put simply – I think that if the owner of one of these models – on a spirited drive - could not then resist the temptation to floor the car away from standstill (at say lights or junctions) - then I think we could have the worst possible scenario for piston/cylinder scoring at that precise moment."

I have to admit - this sounds right to me. I am, unfortunately, someone who's recently experienced this in my 2011 Cayman S. I had the TPS high pressure turbo kit installed, and the car is just a wonderful thing of beauty. One day on the way home from work I got into just such a situation as described above, right down to the punch-launch from a red light. The car "gave up" on that acceleration, and I limped home, humiliated at having been dusted. The next morning on the way to work it failed altogether and I had to pull over and have it towed to my shop.

I'm hoping it will be ready to pick up tomorrow - they replaced my 84k mile engine with a 36k mile one, so I'm trying to tell myself that this wicked expense is tantamount to buying a large chunk of the car's life back. Needless to say, I will be much more circumspect about playing with the turbo in the future - I'll probably completely give up my "from standstill" launches and push the edges only when I'm in a thoroughly warmed up condition. It was an absolutely heartbreaking experience that I never want to endure again (nor can afford to, for a few years at least).

Thanks for the superb write-up, Hartec.

[KipIngram]

So, in hopes of avoiding this problem in the future I do want to consider that lower-temp thermostat, and also am interested in making the best "oil decision." I've simply followed manufacturer's recommendation on the oil in the past. But I live in Houston, Texas, so it never gets "up north cold" here - I'd be very happy to hear any advice on how that should affect my oil choice.

Thanks,
Kip

PS: Love the deep technical talk here. I'm not a car expert myself, but I am an engineer and PhD, so I'm able to follow along pretty well.

[ooid]

Are you saying your 6 years old gen2 engine just gave up on 87k mile?

[KipIngram]

Well, it had a failure. This particular failure, based on the shop diagnosis, and my driving behavior just prior fits the OP's suggested "scenario" about as closely as it possibly could. Bore scoring, etc.

[G-996]

I've just read this old thread start to finish - some very useful information for a 996 owner - many thanks to Baz @ Hartech for taking the time to pass on his findings and advice.

One other point to add, I recently changed the engine oil on my 2003 996 C4 from 10w-40 grade to the slightly thicker Millers 10w-50 which Hartech recommend. I did see a noticeable increase in engine oil pressure when the revs dropped to idle with a hot engine, which is I would think a very good thing considering the failure mode/root causes discussed by Baz.

[EGTE]

Especially good of Baz to disseminate such good info, when it is effectively doing himself out of business.

I value his advice very highly and am extremely grateful for it.

I use an LTT and Millers Nanodrive10W-60 changed annually at most, for peace of mind, based on his advice posted online.