Oil starvation problem at high rpm
10-30-2003, 12:45 PM
#76
Burning Brakes
Falco, The low oil level sensor is in the left front corner of the oil pan. I would agree that as the oil moves up the right side of the pan in a hard sustained left hand turn that we should see a warning light. I have never seen on on the track but, I know it is working because it comes on if I pause to long on the ramp while loading the car on to the trailer.
Glen, There are a couple things I have done on my car. I run the 3qt accusump, I installed the GTS oil pan baffle, and I run amsoil exclusively.
I have heard that the GTS baffle doesn't do much, after seeing it, I would believe that assertion. I do think that it does help keep oil from moving to the back, shallow part of the oil pan though.
I did a ton of reading on this before tracking my car and I am pretty confident the accusump is a good solution for those of us not ready to do a rebuild. If I were to ever need a rebuild I would definately move to a "drilled" crank. I would also continue to run the accusmp.
I like amsoil, Mark K has had very good success with it. It is supposedly formulated with anti-foaming additives, that is a plus.
I think that there are "plugs" you can fit to the heads to limit oil pooling. I believe they are a 944/968 factory part. I plan to add these this winter. I think this change would also help the oil ingestion problem some by keeping so much oil from reaching the top of the engine.
It is pretty obvious that there is a problem. I think you made a good list of the problems and some possible solutions. I think that anybody tracking their car, or running the bahn, should make as many of these changes as possible. My theory is, the more potential problem areas I address, the less likely I am to have a failure.
Glen, There are a couple things I have done on my car. I run the 3qt accusump, I installed the GTS oil pan baffle, and I run amsoil exclusively.
I have heard that the GTS baffle doesn't do much, after seeing it, I would believe that assertion. I do think that it does help keep oil from moving to the back, shallow part of the oil pan though.
I did a ton of reading on this before tracking my car and I am pretty confident the accusump is a good solution for those of us not ready to do a rebuild. If I were to ever need a rebuild I would definately move to a "drilled" crank. I would also continue to run the accusmp.
I like amsoil, Mark K has had very good success with it. It is supposedly formulated with anti-foaming additives, that is a plus.
I think that there are "plugs" you can fit to the heads to limit oil pooling. I believe they are a 944/968 factory part. I plan to add these this winter. I think this change would also help the oil ingestion problem some by keeping so much oil from reaching the top of the engine.
It is pretty obvious that there is a problem. I think you made a good list of the problems and some possible solutions. I think that anybody tracking their car, or running the bahn, should make as many of these changes as possible. My theory is, the more potential problem areas I address, the less likely I am to have a failure.
10-30-2003, 03:46 PM
#79
Rennlist Member
ther is no way this GTS had better mechanical grip than the holbert track car. think about it. my 928 racer is 2700lbs empty. I can run, 315x30 rear and sometimes 335 rears x 18s in speed GT. I have lowered my car to under 112mm and have a pretty decent suspension. (with a mildly effective wing and spitter ) So, just those factors alone, weight, ride hight and larger slicks would YIELD a much higher G force capability. Just plug in these variables into generally known handling equasions and you can see what Im talking about.
Anyway, 2 full seasons of beating the 928S4 in pro and top club races, and no signes of wear or oil issues. (again, knocking on wood) Not that i dont think it is needed, but oil quality is important, shifting style and limits are the other factor.)
Interesting that you have confirmed about the oil pressure with the use of redline vs Mobil one. I bet this is the real issue !!! I didnt notice any cooler running of my old dyno oil (very good Kendall 20-50) vs redline or amzoil. I did notice a difference in temp in my old 2 valve race car, when I plumbed up the euro oil cooler that is integral to the radiator, and not stock for US versions. that helped a bit. After seeing 260f race oil temps (sometimes 270 on real hot days and long races), I stopped monitoring the temps as my sensor was in the dip stick and it was leaking under high rpm loads. (street driving was fine)
Mark
30 race days on the holbert car, 6 of them in professional races, and the rest club. no trans cooler, no accusump, no problems. All run on Amzoil.
Lots of 6200rpm shifts!!
Anyway, 2 full seasons of beating the 928S4 in pro and top club races, and no signes of wear or oil issues. (again, knocking on wood) Not that i dont think it is needed, but oil quality is important, shifting style and limits are the other factor.)
Interesting that you have confirmed about the oil pressure with the use of redline vs Mobil one. I bet this is the real issue !!! I didnt notice any cooler running of my old dyno oil (very good Kendall 20-50) vs redline or amzoil. I did notice a difference in temp in my old 2 valve race car, when I plumbed up the euro oil cooler that is integral to the radiator, and not stock for US versions. that helped a bit. After seeing 260f race oil temps (sometimes 270 on real hot days and long races), I stopped monitoring the temps as my sensor was in the dip stick and it was leaking under high rpm loads. (street driving was fine)
Mark
30 race days on the holbert car, 6 of them in professional races, and the rest club. no trans cooler, no accusump, no problems. All run on Amzoil.
Lots of 6200rpm shifts!!
Originally posted by Mike Buck
I just saw this thread as well. Sparked my interest because I know a 928 GTS owner who had this #2/6 failure. Anybody here know Gary Grigsby? He used to race his GTS, but now runs a white 968. He told me when he was running big 18" Hooisers on his GTS it was just too much mechanical grip and the bearings spun. Replacement crank was a ridiculous amount of $$
I agree with Mark about Mobil 1. The "on track" oil pressure difference in my 944 turbo between 15/50 M1 and 20/50 Redline is amazing. A local shop here also told me Redline happens to run many degrees cooler. I haven't had any problems on track to speak of, all I do is overfill the tank with 20/50 Redline and shift just after 6k. 139k miles on my bottom end right now
I just saw this thread as well. Sparked my interest because I know a 928 GTS owner who had this #2/6 failure. Anybody here know Gary Grigsby? He used to race his GTS, but now runs a white 968. He told me when he was running big 18" Hooisers on his GTS it was just too much mechanical grip and the bearings spun. Replacement crank was a ridiculous amount of $$
I agree with Mark about Mobil 1. The "on track" oil pressure difference in my 944 turbo between 15/50 M1 and 20/50 Redline is amazing. A local shop here also told me Redline happens to run many degrees cooler. I haven't had any problems on track to speak of, all I do is overfill the tank with 20/50 Redline and shift just after 6k. 139k miles on my bottom end right now
10-30-2003, 06:41 PM
#80
Drifting
mark,
congrats on your self restraint as regards shift points and im sure you must be correct regarding the different qualities of oils available.
glen,
i like your roundup of the points raised so far and perhaps like me your motivation is to know which path to follow when the inevitable time for an engine rebuild/upgrade comes..
my take on the acusump is that it is a partial solution to the combination of oil ingestion, pooling and sloshing. oil pooling in the heads can be addressed by restricting the flow up that way, as mentioned. and a dry sump system may be a cure for all of the problems... but not quite, it seems!
what id like to know is the oil flow paths in a stroker crank, apparently they are drilled 'like a chevy' and dont suffer with bearing failures. perhaps scat who manufacture these will have this info? also, if one were to retro drill the crank (like a chevy), what would you do to the old oilways, leave them open?
did i read somewhere that the redrilled cranks supply oil from a different main bearing?
martin,
really informative pics, good work!
congrats on your self restraint as regards shift points and im sure you must be correct regarding the different qualities of oils available.
glen,
i like your roundup of the points raised so far and perhaps like me your motivation is to know which path to follow when the inevitable time for an engine rebuild/upgrade comes..
my take on the acusump is that it is a partial solution to the combination of oil ingestion, pooling and sloshing. oil pooling in the heads can be addressed by restricting the flow up that way, as mentioned. and a dry sump system may be a cure for all of the problems... but not quite, it seems!
what id like to know is the oil flow paths in a stroker crank, apparently they are drilled 'like a chevy' and dont suffer with bearing failures. perhaps scat who manufacture these will have this info? also, if one were to retro drill the crank (like a chevy), what would you do to the old oilways, leave them open?
did i read somewhere that the redrilled cranks supply oil from a different main bearing?
martin,
really informative pics, good work!
11-07-2003, 06:44 PM
#81
Nordschleife Master
Martin,
Lookng for some more discussion of that diagram. Also, does the feed to #5 in the photograph move toward the inside, against centripital force?
Thanks!
Lookng for some more discussion of that diagram. Also, does the feed to #5 in the photograph move toward the inside, against centripital force?
Thanks!
11-07-2003, 07:11 PM
#82
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Sorry Glenn, forgot to add the details, you should have PM ed me, I'll add some more info to the pic.
Yes on the #5 the last bit does go against centrifugal force till it gets to the cross drilling.
Yes on the #5 the last bit does go against centrifugal force till it gets to the cross drilling.
11-07-2003, 08:31 PM
#83
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I hope this pic. makes some more sense
Oil from main bearing enters cross-drilled main M1 ,then into major oilway (RED ARROW ) & then into the cross-drilled rod journals R1 &R2 in BLUE
I have just shipped a new S4 crank in for a friend from the USA (brought off of ebay for $200 with a S4 block, when I say new I mean BRAND new , you guys missed a bargain !) Apparently its drilled differently to the other stock S4 cranks, maybe Porsche tried a solution ? I hope to see it tomorrow & get pics.
Oil from main bearing enters cross-drilled main M1 ,then into major oilway (RED ARROW ) & then into the cross-drilled rod journals R1 &R2 in BLUE
I have just shipped a new S4 crank in for a friend from the USA (brought off of ebay for $200 with a S4 block, when I say new I mean BRAND new , you guys missed a bargain !) Apparently its drilled differently to the other stock S4 cranks, maybe Porsche tried a solution ? I hope to see it tomorrow & get pics.
11-07-2003, 09:30 PM
#84
Nordschleife Master
Martin,
Now that's crystal clear! I'm still wondering about this one. As you might guess, I'm thinking about having mine drilled and want to understand the issues.
Now that's crystal clear! I'm still wondering about this one. As you might guess, I'm thinking about having mine drilled and want to understand the issues.
11-08-2003, 04:47 AM
#85
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Originally posted by drnick
what id like to know is the oil flow paths in a stroker crank, apparently they are drilled 'like a chevy' and dont suffer with bearing failures.
what id like to know is the oil flow paths in a stroker crank, apparently they are drilled 'like a chevy' and dont suffer with bearing failures.
11-09-2003, 10:31 AM
#86
Nordschleife Master
Martin and all,
What do you think about "perp drilling" the crank? The Racing and DE Forum ans a thread about this. It shows a pic of what Huntley racing does to a 944 crank. That's described at the Huntley site.
The idea is to drill in from the outside straight towards the centerline of the crank. Then there's a boost to oil flow from the centripital acceleration. In Martins pic, I thinking that two holes would be bored from the top down in R1 and R2 passages.
Anyone with a drilled 928 crank care to say what it's like?
What do you think about "perp drilling" the crank? The Racing and DE Forum ans a thread about this. It shows a pic of what Huntley racing does to a 944 crank. That's described at the Huntley site.
The idea is to drill in from the outside straight towards the centerline of the crank. Then there's a boost to oil flow from the centripital acceleration. In Martins pic, I thinking that two holes would be bored from the top down in R1 and R2 passages.
Anyone with a drilled 928 crank care to say what it's like?
11-09-2003, 05:25 PM
#87
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Cross drilling only provides 360 degrees of oil to the bearings
There are a lot of other factors to be considered, not only for the 2/6 bearing failure but for a bearing failure in general; poor crank case venting will pressurize the crank case forcing oil into the rotation assembly foaming and aerating the oil causing oil starvation and bearing failure. A windage tray with added crank case ventilation will help
Higher oil viscosity and lower oil tempeture will reduce the oil pumps ability to maintain a high rate of oil flow, yeah the oil gauge will read an ideal pressure but what counts is the flow and that will be low.
Running higher bearing clearances or worn bearings will throw off a lot of oil causing oil starvation. A lot of NASCAR engine builders run their bearing clearances at .0018 to .0022. “The tighter the better, so long as you don’t touch the bearings to the crank.” There is no one solution. I think fixing the problem is a total package.
There are a lot of other factors to be considered, not only for the 2/6 bearing failure but for a bearing failure in general; poor crank case venting will pressurize the crank case forcing oil into the rotation assembly foaming and aerating the oil causing oil starvation and bearing failure. A windage tray with added crank case ventilation will help
Higher oil viscosity and lower oil tempeture will reduce the oil pumps ability to maintain a high rate of oil flow, yeah the oil gauge will read an ideal pressure but what counts is the flow and that will be low.
Running higher bearing clearances or worn bearings will throw off a lot of oil causing oil starvation. A lot of NASCAR engine builders run their bearing clearances at .0018 to .0022. “The tighter the better, so long as you don’t touch the bearings to the crank.” There is no one solution. I think fixing the problem is a total package.
02-06-2004, 05:36 PM
#88
Instructor
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Interesting Toyota research article
I've been reading a lot about the bearing failures lately, including this thread.
I found an interesting Toyota research article about crankshaft oiling that I thought I'd add. It doesn't apply *exactly* to the 928/944 problems - but it's close. It does discuss the "Chevy style" V oil passages. I think the 928/944s are somewhere in between the "V" and "I" style discussed in the paper.
The most interesting thing to me was the graph in Fig. 10(a). The "hockey stick" in the graph is what I think happens when the #2 bearing gets damaged. A combination of low oil pressure and high RPM (6K) causes the flow to the bearing to drop like a rock - or stop all together.
It's an interesting read:
http://www.tytlabs.co.jp/office/libr..._044suzuki.pdf
--Brian Morris
89 951
I found an interesting Toyota research article about crankshaft oiling that I thought I'd add. It doesn't apply *exactly* to the 928/944 problems - but it's close. It does discuss the "Chevy style" V oil passages. I think the 928/944s are somewhere in between the "V" and "I" style discussed in the paper.
The most interesting thing to me was the graph in Fig. 10(a). The "hockey stick" in the graph is what I think happens when the #2 bearing gets damaged. A combination of low oil pressure and high RPM (6K) causes the flow to the bearing to drop like a rock - or stop all together.
It's an interesting read:
http://www.tytlabs.co.jp/office/libr..._044suzuki.pdf
--Brian Morris
89 951
02-06-2004, 07:05 PM
#89
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Brian
Thanks for that , its very interesting, The V type is as per. Chevy, not sure what they mean by I type though, but if it is similar to a 928 it would start to explain the oiling problems !
Thanks for that , its very interesting, The V type is as per. Chevy, not sure what they mean by I type though, but if it is similar to a 928 it would start to explain the oiling problems !
02-06-2004, 10:01 PM
#90
Nordschleife Master
That's good information.
Check out figure 2 for the V vs. I issue. The I has one hole bored from the crank journal to the rod. The V has that plus a passage that runs across the crank journal. It's like is the pic above where Martin (you) show the cross drilled main.
Eureka! Now I need to find a local shop that can do this.
Check out figure 2 for the V vs. I issue. The I has one hole bored from the crank journal to the rod. The V has that plus a passage that runs across the crank journal. It's like is the pic above where Martin (you) show the cross drilled main.
Eureka! Now I need to find a local shop that can do this.