mark kibort

look, you had one engine that was junk, suspect , unknown past and it blew. you had that engine rebuilt incorrectly, and it blew. you then had another suspect engine, and ran it 3-4 quarts low and on wall mart oil to boot, and it blew. then, you got a good engine and ran amsoil and its lasting and working great for all the right reasons, and has 50 hours of racing on it.

all my engines, scots included have worked for 100s of hours with never an issue. (on known quantities). amsoil, moderate revs in high g loading turns, good warm ups, etc. remember the experiement Ive did at laguna. at 3000rpm around high g loading turns, i could get even my amsoil to trigger 3 BAR at 3krpm. (experienment on a cool down lap on a race weekend) dont do it! you should be cornering at 4,000rpm or higher, but lower than 5500rpm.

think about all those GTSs running 100+mph at 3500rpm, with mobil 1, that probably have the oil pressure light blinking.

I have a pretty good statistical sample of long life from racing a 928 motor in quite a few cars now. 5 different engines, from 2 valvers to 4 valvers to a stroker. all are running fine and pulling way more Gs than any one out there today, besides anderson and Fan. no coolers, breathers, spacers, scrapers, accusumps, etc. those set ups, especailly when you dont tun on the accusump, makes the engine blow. scrapers and baffles....well, I have my doubts if they allow the oil in the pan fast enough.

Ill be racing my car this season and many more with NO modifications and do you want to bet against me that my engine will be fine? do you believe in the tooth fairy?

IcemanG17

MK
Interesting theory about the RPM vs pressure drops.... I DO see pressure drops on turn in...but it recovers and gains pressure with RPM exiting the corner..as it should...

The pump flows directly correlated to RPM...3.95 gph per 1000rpm... If the pressure drops are purely related to uncovering the pump....then its only G related and not RPM sucking it out, so the only thing that matters is time at a given G level before it uncovers....

Yes I had two suspect engines die....but both made at least the magic 10 hour window for rod bearing death on track....the third was built incorrectly..& the current one was inspected, but otherwise stock 117k engine...with over 30 hours on track has no indication of bearing wear in the oil analysis...however most of that time was with the lower G street tires....so the next analysis should be interesting

There have been many other recently rebuilt 32V engines die on track due to oil starvation...and ones that WERE rebuilt properly....so why did those blow up.....

mark kibort

"properly" rebuilt? scrapers, baffles and other unproven technology, is not "properly" in my book. (or mobil 1). that baffle on Dennis' engine looks like the oil would NEVER be able to get back to the pan.

Not to mention the other theories I have on failure. too high rpm through turns, too low rpm through turns, improper warm up, or even too large of a bearing clearance.

-M

Kevin Johnson

This is why it is important to look at many different examples of the technology and note how and why it was successful.

At the time the 928 engine was designed, Mercedes Benz had just filed a patent on an oil pan design using floor mounted scrapers that impart a vector towards the sump. Mind you, Ford had been using that tech in the prior decade with the 427. The OEMs keep close track of each others technology. Porsche incorporated this technology into the 928 pan floor. Be careful about what you call unproven.

The Triumph 2000 Mark 1 sump used a fine mesh screening over it -- that was also in existence before the Porsche 928 engine was designed but it was certainly contemporary.

Kevin Johnson

Per the flow, this is why it is important to examine the design of the pump. The pump used communicates with the pressure that already is developed in the circuit. I think the pump flow is correlated with the rpm but it is part of a complex function with many variables that can have stronger influence under various operating conditions.

Understanding that the pressure drops are not purely related to the pump being uncovered -- and this means that they could have nothing to do with the pump being uncovered -- is important. Look back in the history of this pump design. Beware of being caught up in either-or arguments -- this is sometimes known as a false dilemma. This does not mean that either-or situations cannot or do not exist but rather that a given problem is not necessarily of this nature.


A clue to Mark's success as a driver across many examples of the 928 may be the attitude of the car (suspension loading, driving style) in turns. The turntable experiment that I suggested indicates that equivalent lateral G loads will have different effects on part of the underlying movement physics of the oil, depending on the attitude of the car. Might be worth looking into.

justaguy

Great thread and very timely. This is my experience . I nearly blew the motor in my street 928 but caught in at the onset of failure by checking my oil filter for signs of wear after every track session as advised by some pretty smart people on this board. 2/6 were begining to fail so I rebearinged added the IJ crank scraper and switched from Mobil 1 to Amsoil. Since that time I put about 40 track hours on the other wise stock engine at T-hill, Infineon , and here at Race City in Calgary with no ill effects.Thats right 40 track hours on a stock motor that nearly failed before switching to Amsoil and adding the I-J scraper kit so One or both of those changes made a huge difference to the durability of my stock motor. I often see a peak of 1.4gs on the trackmate in almost every corner and sustained 1.2-1.3g for over 5 seconds.

Experience 2 not so good
I just blew a race engine after 10 hours that was assembled with the utmost care and attention by some very knowledgable 928 guys. The engine suffered a total catastropic failure due to poor oiling. I was runing the same Amsoil same crank scraper and a pan spacer and cross drilled crank which the street car does not have

Why the failure ? 1.5gs vs 1.4 6,800 rpm shifts vs 6,200 thats the only things I can think of and I am inclined to believe the higher shift point had far more sevre cosequnce than the marginally higher G loading. Same driver same track same conditions same oil.

So what to do now? It is my intention to install a used stock motor and drive as I always have but try to shift between 6000 and 6200 and see how long the thing lasts. I will drive it for the rest of the season or until it breaks. I have over 100 track hours on the stock street car motor so I think the chances are pretty good of lasting the season. I will post how it lasts

I also intend to rebuild the race engine but will lower the rev limiter and will do alot of tuning and R&D
during the winter while down in sunny CA.

justaguy

Back to the original question Where is the best place to plumb in the accusump?

hacker-pschorr

One option is to tap into the return line of the oil cooler with a check valve just before the "T".

Another option would be a sandwich plate on the oil filter. Considering the size of the lines most use with the accusump, I'm not sure any sandwich (that I've seen) is large enough / thick enough.

IcemanG17

I used the oil cooler return line with a check valve.....don't know if it worked since the engine only lasted 2 hours Still have the accusump + valves-etc

hacker-pschorr

Just curious, what size accusump, lines, check valve etc.. Did you also have the electronic or manual valve on the accusump?

Which motor was this?

Kevin Johnson

I think you have refined the borders of the limits of a passive wet sump system in the 928 engine. Thank you for sharing the information. Time to start working on a dry sump setup for the second vehicle.

kccampro

Wow... this post couldn't come at a better time for me. I have my 32v sitting on the stand with my finger on the trigger of an oil mod as we speak.

ptuomov

There's so much disinformation here about oiling that I recommend you think thru every single modification that you make to the oiling system. Don't put anything in there that's not 100% stock and that you don't understand or someone you really trust as an expert doesn't understand. On this particular topic the internet advice is worth what it costs you, and in some extreme cases it's much worse -- might cost you an engine.

As a general rule, people who _really_ understand the 928 oiling issue (not me) are not posting about it here, partly because they've paid a lot to accumulate the body of knowledge and partly because of the behavior of some on this forum that is best described as vandalism and/or snake oil sales.

Talking to someone who actually builds and tests these engines (not me) would be really valuable. Send a pm to, say, Jim Morton or Greg Brown who are not posting here much (at least not on this topic) but have relevant empirical data.

justaguy

Ptuomov
Good advise. Love the the Snake Oil comment. Hear that Mark ........Snake oil Maybe I will try some of that. Just kidding.
No doubt 928 engine oiling is a challenge but one I intend to conquer I only post my personal experience to share with the community. I belive communication is the key to progress.

I suggest reading every thing you can and talk to every one you can Then make your own decisions.

mark kibort

why does porsche do all the calculations, designs, research, comparisosns, and then actually go out and test.....THEN, goes out and races to see if what they have designed, works? because there are so many factors, NO ONE can keep track of them, as well as predict the interactions of their effects.

You have in me, more racing miles than anyone here with the stock system, and not with one engine, more than 5. So, if you dont believe in the tooth fairy, why dont you start studying what Im doing to run faster and pull more gs, yet have engines that do not fail under racing conditions.
The "experts" have tried to apply a lot of concepts, designs and methods that have worked and been deveolped for OTHER cars, but not the 928, and I think that is a huge flaw. hey, they have tested those designs and how many of them have failed? so many, I have lost count and they are not posting their failures here, trust me.

Im not against innovation, but I am skeptical of change from something that appears to work, providing limitations are respected. In fact, do to the experts advice, I have one of the ONLY mods that has really proven to help in the oiling fight, and that is the drilled crank. accusump is effective, but has its drawbacks too. look at all the breather systems that have failed and cost folks 1000s of dollars of valuable track time as well as just time! I have no breather system, no oil cooler, no scraper, no baffle, no spacers, no accusump, nothing modified from the stock set up, yet Im running a 928 in a racing environment and have done so for over 10 years, AND supported another 928 that has ran a proportion of my racing seasons with no problems.

no on here has answered my suspicions regarding the screens restricting flow. some of those designes have been done to help breather systems , gain HP and keep more oil in the sump, but Im very curious if anyone knows if the flow rate based on those screen designs can be preserved.

Now, go ahead and mock what I have done, but you see the videos, my redline shift points, my 110% of the best GT3 cup car time in the world, and you be the judge. Luck or following limitations of the original 928 design. If you were me, would you change anything? The gauge doesnt lie. 5 bar pressure, all the time. when using mobil 1, the oil warning light comes on. Why would I ever want to use Mobil 1 or the other oils that dont seem to keep their viscosity up. Also, what about the foaming characteristics. maybe Amsoil has the ability to not foam as much and keep a major problem from happening.

I dont know, but, i said this a long time ago. I usually find someone in a field that im interested in that is successful, and do what they do, rather than reinvent the wheel. (i.e. Mark anderson and Joe Fan).

you wont see me installing baffles or screens unless you can show me an 928 engine that has survived its install and is being raced for a couple of years.