Nicole

I came across an interesting discussion on the German PFF board about oil starvation. It started with someone wanting to install single throttle injection for each cylinder, and veered off into oiling issues and that these prevented Porsche to ever use the 928 for racing.

One guy reports oil pressure dropping in fast Autobahn curves - it requires to press the clutch and get off the throttle immediately, he says, then he has to wait a moment, before getting back on it.

Someone says that GTS crankshafts are getting rare becaue for the rod bearing 2 and 6 failures.

Another - Uli from Turbo Technik Piez - says that cross drilling and accusump would certainly help in turns, but does not completely cure the fundamental problem of oiling all bearings above 6,200 rpm. He does not specify his solution, as it is proprietary. But he offeres to install it in engines delivered to him, without specifying a price... (He supposedly was involved in this one: http://www.t-t-p.de/gallery/index.php?id_rub=4)



Jochen from www.lansharks.de claims that lowering the oli intake and machining the oil pan accordingly is a good start for everyday use, but for any extreme power increase or racing you must install a dry sump to make it reliable. (His preferred solution for additional power is an optimized high flow cat from Liphardt combined with careful customized chip tuning, which he claims can yield about 40hp total, while reducing both fuel consumption and emissions. In Germany, it also reduces the emissions based vehicle registration fee). Landsharks now works with Turbo Technik Piez to offer this solution to local 928 owners.

In essence, there seem to be a lot of 928 GTS engines breaking in Germany, due to oil starvation on rod bearing 2 and 6 during fast Autobahn drivng (not track). Apparently, the standard factory tires are sticky enough to bring the oil pickup and whatever else in the oiling system to the edge. Cross drilling helps, accusump helps, dry sump helps, but the combination of high rpm AND high g-forces, is still considered a problem.

This is exaggerated by the fact that on full throttle, a 928 engine burns quite a bit of oil (they speak of 1 quart per 60 miles/100km), so the oil level can decrease rapidly during a longer Autobahn run.

I'm sure the racers and engine gurus on this board have a few comments about this. Let them come...

Old & New

Nicole,

This is certainly not a testament to the greatness of Porsche design...

Has the factory ever commented on this issue, or taken any steps to resolve the problem?

GlenL

Interesting post. Looks like the 928 is the same all over.

It makes sense that in long, high-speed Autobahn corners that the engine would face oil starvation.

For those new to the issues, there are a number of problems that combine into the perfect oil storm. The crank isn't drilled right and cetrifugal force (centripital for you purists) works against oiling of the rod bearings. Oil falling into the pan gets whipped up be the crank as it is too close to the pan towards the rear. Oil pools in the heads or at least doesn't drain back fast enough. In corners, the oil sloshes away from the pick-up.

Which leads to two problems. The crankcase gets filled with oil mist and that is sucked out leading to smoke and high oil consumptions. In a corner, the oil pump pumps air into the system. Then the bearings lose pressure and run dry. The passages run from the left so bearing starvation is worse turning to the right.

I believe the best solution is to have the crank drilled differently and then run a dry sump. And a catch tank for the blow-by instead of PCV.

I have tried only the catch tank. Track days mean topping off the oil between sessions and watching the oil pressure in longer corners. The tank worked OK but was sometime overwhelmed by blow-by. At 150+K it needs rings, I believe.

"Real" racers will often have accusumps or dry sumps and always catch tanks.

The later engines got more bafles and scrapers and different PCV routings. The exact year-by-year improvements escape me.

Vilhuer

Thanks Nicole for the info, keep it coming. Strange that factory never got this sorted out. GTS baffle must be attempt to thake care of it. Obviously not very good one as there has been large number of 928's with exchange motor for sale on Mobile.de, espeacially GTS's. GTS pistons blocked oil return lines must direct more oil into combustion chamber and when level in pan drops, bearing damaging rpm drops also. I've been thinking solutions short of building dry sump system. Isn't there auxillary electric oil pump in BMW E39 M5 engine? Maybe it or similar pump could be run above say 5500 rpm to boost oil pressure and raise starvation limit high enough? How to hook it up, I have no idea.

Regards,

Erkka
1992 928 GTS 5-speed without oiling problem at the moment
Oak Green Metallic 22L
Classic Gray MX

John Struthers

We don't see it often , but maybe Mark Anderson has been racing 928's for a loooooong time.
In the earlier 928 INTL catalogs there was a write up on the 2/6 crank bearing problems.
I believe he tried a 5 gallon dry sump system, the scraper and of course cross-drilling, a service which I think they still offer. While I believe the article stated that the cross-drilling was the best all around fix my feel for the article was that you needed to do all three.
You'd have to ask him for specifics and any increased reliability at racing events. He was running a 'streetable 88 MY' S4 with a stroker -104.mm overbore, Mahle 968 pistons- 6.4L.
Wasn't there a post or two last year from one of our Norse sHARk wranglers who toasted an engine on the Bahn. Same deal?
Nicole regarding that post on trashing engines on the Bahn...
These guy's - on post's that I've read - are stating they drove on the Bahn for 4, 5, and 6 hours... At high speed, right?
Do you see anything wrong with those statements?
I cruised the Autobahn beacoup, mogu, many lot's of times... and the longest run I can imagine is the Bremerhaven (Koln? or Kale?) run south to say Munchen (O.K., Munich..) On many, not all, of my North to South Deutchland runs I really hauled a** and burned fuel like a Saturn V booster with my built 750 and later 1100 Suzuki's. These were high speed runs - I'm talkin' "you start thinking about mortality speeds"- and the times are not reflecting what these folks are saying, re: road speed vs distance on the Bahn.
I think oil starvation could be the cause but some underlying factor - shoulda put in that extra half-quart or so before a high speed, or perhaps, should of checked the oil level in the first place- might be the cause of their demise.
Europeans' in general do a better job of pre-flighting their cars than we do but they were getting a little lazy towards the end of my last tour.

PorKen

Nicole - can you please post the link for the original discussion?

"single throttle injection" = individual throttle bodies

Hopefully Google language tools will BabelFish it for me.

Nicole

Here you go... It started with a guy named "Cubitus" havin rod bearing failures during a long fast Autobahn drive:
http://www.pff-online.de/wbb2/thread...d=2610672&sid=

Then Uli chimed in with a link to the older thread that started about a conversion to carburators (not sure, if I'm spelling this correctly, but who still writes about such old technology anwyay?) and veered off into more general discussion of 928 engine tuning and the limitations due to the oiling issues. Uli does not reveal much, as you will see - he says it took a lot of time and effort to develop this solution, and he wont' give it away other than selling it to someone who sends an engine to get it installed...
http://www.pff-online.de/wbb2/thread...&hilightuser=0

PS: At one time, one of the guys mentions that in Germany, none of the Kompressor or Turbo conversions lasted more than 20k km (about 12k miles). To me that's a sign that a stroker might be a lot more durable, if the simpler enhancements like the chip/cat upgrade or head work are not enough - no?

PorKen

Thanks,

Here's a better free translation service, it seems Google's only translates a certain number of words, whereas this one does the whole page.

www.FreeTranslations.com

Porsche Fan Forum | www.pff-online.de

GlenL

Porken, Thanks for the link.

Sounds very much like the post I made: crankcase oil fog at RPMs and failures of the 2 and 6 rod bearings.

Could someone (OK, someone who started the thread) translate that last post or paraphrase? There are a few words that don't work in the tool that are used when describing a solution. Thanks!

Yoakim Larson

It would be nice if someone had a scematic drawing of the flow of oil to the 2/6 bearing and how it compares to a chevy.

Nicole

Last post of the first thread, or last post of the second thread?

Second is easy: ds says "OK I found it"... ;-)

Nicole

Here is a summary of the other last post:

Bernd spoke to someone who participated in the 928 project at the time and writes:

>>The 928 oil pan does not have enough space inside, and the engine is more like a racing engine that wouldhave benefited from a dry sump. The solution implemented is a compromise with some disadvantagnes like insufficient oil supply under g-forces, ane not enough space for 'gas reactions' (not exactly sure what that would be) at high rpms.

Because the engine ventilation is routed over the valve cores into the intake system, oil fog is burned (resulting in oil consumption) at high rpm. A condensation recervoir for the oil would have prevented this, but was not put into production.

The problem appears when it comes to a certain anoount of blow-by, which increases with mileage and provides for ever increasing presures and gas movements inside the (too small) crank housing.

A kind of remedy would be in sealing the pistons, but is too expensive. Uli might have a solution that is certainly interesting, if it is coupled with a warranty.

At the moment I'm a little unsure because I have a hard time imagining a classic design flaw at Porsche.

Maybe some of you have an opportnity to get mor information from a direct source.<<

Lagavulin

Nicole, thank you for the translation. It sounds like they have an interesting conversation going!

GlenL

And thanks from me also!

So the oil fog solution is to seal the pistons better. And at a certain amount of blow-by it gets worse. Sounds like a description of the past Summer and the Winter coming up.

Fastest928

There are some facts and fiction about the 2/6 rod failures.

Here are some facts:

1