Timlin

Hi all

I have a 99 C2 and I'm using about 1 litre of oil for every 1200 km's. We did a compression test and these are those results:

CYL 1: 180 PSI/ 16%
CYL 2: 185 PSI/ 11%
CYL 3: 140PSI/ 18%
CYL 4: 175PSI/ 12%
CYL 5: 155 PSI/ 12%
CYL 6: 185 PSI/ 12%

My mechanic suggests it could be valve stem leakage, or worst case, rings etc, meaning total rebuild. The engine was rebuilt (IMS, Nikkasil liners, increased to 3.6L) at 80,000km's (now has 120,000km's) and its had 2 track days in its life... am I missing something? Should this be happening so soon?

Ahsai

Do you know what piston rings were used and what (if any) machine work or parts replacement were done to the heads?

Timlin

Sadly I do not know which brand of oil rings were used. But, the workshop are a very old established Porsche workshop and I'd suggest that they did everything properly, using the best parts etc...

As far as any details on what was done, no, I don't have any info on this. But I do know it was a complete rebuild.

Rgd's


Timlin

5CHN3LL

What oil are you running? My '99's oil consumption can vary significantly depending on the oil.

extanker

bore scope #3

Chris(MA)

Can you comment on how they finished the bores? nikasil is a tricky surface and the correct Ra is important plus the right bed in technique for the rings.

Also check your sump pressure, more vacuum in the sump will equate to lower oil consumption. How old is your AOS?

Schnell Gelb

Probably wise to do a Leakdown test to help us speculate. It is a tedious test to do because of the deeply recessed plugs.It helps to have a very comprehensive kit with angle adapters if you are doing the test solo.The fittings in this cheap kit helped in a pinch. Unfortunately the sizes/shape are oddball so it is difficult to integrate it with parts you may already have
https://www.ebay.com/itm/Engine-Cylinder-Compression-Tester-Kit-With-Extension-Bar-Auto-Engine-Diagnostic/121874241348?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
.

Timlin

All

Thanks for the suggestions! As I mentioned earlier, the workshop who did the 80,000km rebuild are fastidious and totally professional in their work. I have no doubt about the qualities of their workmanship with regard to the Nikiasil sleeves. What happened after the rebuild however I cannot offer any advice on that... The oil is a Caltex "EdgeSport" synthetic 0W/40.

Anyway, I'm told that a total engine rebuild with nothing fancy done to the internals will cost around AU$25k... I can't afford that, plus it'd be way over spending on a car thats worth AU$60k on a very good day...

The car goes very well and has no performance failings - yet! As far as mods go, it has CarGraphic headers and exhaust, the IPD plenum kit, a K&N Cold air intake and a flash tune.

Thoughts anyone?

Rgd's


Timlin

Flat6 Innovations

Replace the fuel injectors.

Macster

The oil consumption if you are accurately monitoring it is above the 1l/1000km Porsche gives. While the oil consumption is a bit high as long as the engine runs ok, doesn't smoke while running, that's not really any cause for concern.

Sure, it would have been nice to after a rebuild have the oil consumption less but there are a lot of factors that control oil consumption. The oil used; how long the oil is run; the type of driving (lots of idling or lots of high RPMs); selection of rings: low tension rings are favored by some to reduce engine friction but this can result in an increase in oil consumption; the quality of the cylinder wall finish; the efficiency or lack thereof, of the AOS. On this note the AOS must remove a lot of oil vapor from the crankcase fumes and if the AOS is less efficient at this this oil vapor gets routed to the intake and burned in the engine. Oil consumption is "high" but it is not due to the oil getting past the rings or past the valve stem seals.

I'd offer as long as the engine runs ok and doesn't manifest any real signs of needing internal engine work just continue to drive the car.

Ahsai

BTW, are the % numbers from leak down test??

5CHN3LL

If your builder doesn't have an issue with it, try TOTAL Quartz Energy 9000 5W40. In addition to being religiously recommended by my indie for years, it tends to stay in the sump instead of disappearing into the ether like the zero-weights I've tried.

Flat6 Innovations

Excess enrichment is the main cause of oil consumption, especially in new engines that don't have many miles on them. Watching fuel trim is the key, as well as employing a stand- alone gauge in the vehicle to monitor air/ fuel ratio during break in.

What was the issue that led to the engine being built, with the cylinders being addressed?

5CHN3LL

Do you install widebands with Flat6 rebuilds? Watching AFR makes sense, but - except street racers - JDM cars with massive turbros are the only ones I see with widebands...

Flat6 Innovations

During my break- in service period I install a wideband O2 as well as a compliment of other portable instruments that makes the car somewhat of a "rolling dyno". I do not trust calculated values generated by OBDII during break in at all.

The instruments are removed before the vehicle is shipped to the owner. I find a lot of underlying issues this way. Many times we see mechanical issues that were created by ancillary items, which would carry- over to our engine if they were not sought out, and found. These cars are aging, and things like fuel pumps, injectors, and etc are taking out engine mechanicals, and often they have no symptoms.

My mindset with every car we complete is that something is wrong with the car, and will take out my engine, and that this problem must be found. Its basically guilty until proven innocent.

I have a car here now that killed its engine due to an ECU issue that locked out fuel trim. It ran great, but would have killed my engine before break- in was even complete, had I not found it. The car runs great, unless it was being watched under my microscope it would have never been found.