early dyno results
02-17-2011, 02:16 PM
#286
Former Sponsor
I've given the 944S2 pressure reduction pieces more than just a few minutes of consideration, not just in this engine, but in many engines.
For many reasons, I do not consider this to be a viable option. Not every piece created for another application is useful for all vehicles.
1. The 944S2 engine is installed in a vehicle that is lighter than a 928 and has significantly shorter gears. This engine is going to turn more rpms, much quicker than a 928.
2. I don't think I've ever seen a 944S2 with an automatic. The 928 automatic transmission, when driven around town, will seek out high gear, before the car can get to the opposite cross walk. I further see this as an issue with oiling, at lower rpms....especially for the particular application that I'm working on.
3. I've seen the results of the 944S2 "snatching" the tensioner off of the cylinder head. It is a disaster! I've never seen this happen on a 928, nor a 968. I can not see that the design of the 944S2 system is different in any way...other than cam timing and the reduction of oil. The chain tensioner "spits" any oil that it doesn't need, out of the top of the tensioner and sprays this on the chain. I'm guessing that the 944S2 check valve limits this oil flow and the resulting lack of oil, on the chain, is what causes the problem.
For many reasons, I do not consider this to be a viable option. Not every piece created for another application is useful for all vehicles.
1. The 944S2 engine is installed in a vehicle that is lighter than a 928 and has significantly shorter gears. This engine is going to turn more rpms, much quicker than a 928.
2. I don't think I've ever seen a 944S2 with an automatic. The 928 automatic transmission, when driven around town, will seek out high gear, before the car can get to the opposite cross walk. I further see this as an issue with oiling, at lower rpms....especially for the particular application that I'm working on.
3. I've seen the results of the 944S2 "snatching" the tensioner off of the cylinder head. It is a disaster! I've never seen this happen on a 928, nor a 968. I can not see that the design of the 944S2 system is different in any way...other than cam timing and the reduction of oil. The chain tensioner "spits" any oil that it doesn't need, out of the top of the tensioner and sprays this on the chain. I'm guessing that the 944S2 check valve limits this oil flow and the resulting lack of oil, on the chain, is what causes the problem.
02-17-2011, 02:25 PM
#287
Former Sponsor
Thanks for the clarification!
I have a few german publications about the max moritz 928 racer and a few other.Maybe I scan the pages and mail it to you.
The other interresting point is a lot of GT engines grenade on fast autobahn trips.
My shop has every year one or two to fix with 2/6 main bearing.
His meaning was low oil level in engine and than Vmax for 10-15 min on the autobahn.
But after Gregs description of the problem we have here more than one problem.
Here in north germany you can drive at the right time on a few autobahn tracks very fast with long curves at high speed.
My 86.5 needs one litre and more oil after 100 km high speed.Driving fast on second grade streets around my town and you have the typical 1-2 litre oil per 1000 km.
A friend of me has a 928 s track car and the only modifications to the oiling system are a modified oilchannel to bearing 2/6 and very huge engineoilcooler and airinlets in the body.
The engine has ~300 rwhp.
This car is every weekend in the summer on the track and this for 4-5 years.Maybe this extreme oiling problem is a 32 v related problem?
Over the weekend I check my magazines for articles about 928 racers.After a quick read in one article they say the 928 gts racer use 968 oil valves with in the heads because the stock engines grenade in fast corners on the track.
The oil was in the heads and the oil pan was empty.
I have a few german publications about the max moritz 928 racer and a few other.Maybe I scan the pages and mail it to you.
The other interresting point is a lot of GT engines grenade on fast autobahn trips.
My shop has every year one or two to fix with 2/6 main bearing.
His meaning was low oil level in engine and than Vmax for 10-15 min on the autobahn.
But after Gregs description of the problem we have here more than one problem.
Here in north germany you can drive at the right time on a few autobahn tracks very fast with long curves at high speed.
My 86.5 needs one litre and more oil after 100 km high speed.Driving fast on second grade streets around my town and you have the typical 1-2 litre oil per 1000 km.
A friend of me has a 928 s track car and the only modifications to the oiling system are a modified oilchannel to bearing 2/6 and very huge engineoilcooler and airinlets in the body.
The engine has ~300 rwhp.
This car is every weekend in the summer on the track and this for 4-5 years.Maybe this extreme oiling problem is a 32 v related problem?
Over the weekend I check my magazines for articles about 928 racers.After a quick read in one article they say the 928 gts racer use 968 oil valves with in the heads because the stock engines grenade in fast corners on the track.
The oil was in the heads and the oil pan was empty.
I think the 928 people, over here, have always assumed that these cars worked flawlessly while screaming down the autobaun and the 2/6 rod bearing failures were only happening over here, in race situations. Obviously, not true.
Yes, If my theory about this problem is true, the 4 valve engines would have a much worse problem than the 2 valve engines...due to the increased area in the cylinder heads where oil can collect. The "extra" room for oil to be stored, in the 2 valve engines is minimal.
It is very interesting that the magazine article you read confirmed the problem...I think we are finally on the right path to fixing this problem!
02-17-2011, 02:55 PM
#288
Under the Lift
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Over the weekend I check my magazines for articles about 928 racers.After a quick read in one article they say the 928 gts racer use 968 oil valves with in the heads because the stock engines grenade in fast corners on the track.
The oil was in the heads and the oil pan was empty.
The oil was in the heads and the oil pan was empty.
02-17-2011, 03:09 PM
#289
For those looking for a proven solution you can simply buy my race car. You'll get a 2600 lb 928 with 500 RWHP . The Greg Brown built engine is dry sumped with hundreds of proven track miles and a GTS transmission with the PSD removed and a standard diff installed complete with the factory oil pump.
http://www.928intl.com/race/index.htm
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http://www.928intl.com/race/index.htm
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What is different here?
(fingers crossed)
02-17-2011, 05:39 PM
#291
Former Sponsor
As I mentioned, Mark's engine will "suck" the dry sump tank down, an inch or more, when it is run on the dyno above 5,000 rpms. I always thought that this was an "oil pan design problem", but now I realize that the oil is simply "packing" intot he heads. The crankcase vacuum, from the existing dry sump, is enough that Mark's heads do not completely fill and thus overflow the valve cover vents.
The solution, for this engine, would be to add a couple more stages to the dry sump pump and simply suck the oil out of the heads. However, since it doesn't really cause any problems that shorten the life of the engine (the cams and lifters are just "slugging" their way through extra oil), this is not likely to ever happen.
02-17-2011, 05:50 PM
#292
Former Sponsor
So, here's an interesting thought:
I've always assumed that in the GTS models, Porsche/Mahle screwed up and the oil return holes in the pistons were not drilled, by mistake. The problem, with this assumption, is that I've always thought it very strange that no one at the Porsche factory caught this "mistake" and they made all the '93, 94, and '95 models with this same defect.
Now looking closely, at the crankcase breather system and seeing that Porsche essentially "gave up" trying to vent the crankcase, I'm wondering if they intentionally deleated the oil "drain holes " in the pistons. If they knew the crankcase was going to get pressurized, they might also have assumed that this would force oil back through the pistons and put oil onto the cylinder walls, instead of removing the oil.
All these years, I thought it was a huge mistake.....now I'm thinking it might have been intentional.
I've always assumed that in the GTS models, Porsche/Mahle screwed up and the oil return holes in the pistons were not drilled, by mistake. The problem, with this assumption, is that I've always thought it very strange that no one at the Porsche factory caught this "mistake" and they made all the '93, 94, and '95 models with this same defect.
Now looking closely, at the crankcase breather system and seeing that Porsche essentially "gave up" trying to vent the crankcase, I'm wondering if they intentionally deleated the oil "drain holes " in the pistons. If they knew the crankcase was going to get pressurized, they might also have assumed that this would force oil back through the pistons and put oil onto the cylinder walls, instead of removing the oil.
All these years, I thought it was a huge mistake.....now I'm thinking it might have been intentional.
02-17-2011, 07:07 PM
#295
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if your thoughts about the oil holes in pistons are correct, and the holes were intentionally left blind, what are your thoughts of the consequences or longevity of the pistons and or cylinder bores if the holes have been drilled completely thru?
if your thoughts about the oil holes in pistons are correct, and the holes were intentionally left blind, what are your thoughts of the consequences or longevity of the pistons and or cylinder bores if the holes have been drilled completely thru?
02-17-2011, 07:13 PM
#296
Former Sponsor
All of the cars that got the holes drilled had significantly reduced oil consumption and did not "ping" from the oil mixing in the combustion chamber and reducing the effective octane of the fuel.
I've not seen any downside and will continue to do this, on these models.
02-17-2011, 07:26 PM
#297
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Yes, the dry sumped engine has enough oil, in the tank, that it can "pack" the heads full of oil and still have enough oil to feed the bearings....which only causes a loss in performance, a reduction of effective octane when the oil mixes in the combustion chambers, and perhaps a bit more smoke.
As I mentioned, Mark's engine will "suck" the dry sump tank down, an inch or more, when it is run on the dyno above 5,000 rpms. I always thought that this was an "oil pan design problem", but now I realize that the oil is simply "packing" intot he heads. The crankcase vacuum, from the existing dry sump, is enough that Mark's heads do not completely fill and thus overflow the valve cover vents.
The solution, for this engine, would be to add a couple more stages to the dry sump pump and simply suck the oil out of the heads. However, since it doesn't really cause any problems that shorten the life of the engine (the cams and lifters are just "slugging" their way through extra oil), this is not likely to ever happen.
As I mentioned, Mark's engine will "suck" the dry sump tank down, an inch or more, when it is run on the dyno above 5,000 rpms. I always thought that this was an "oil pan design problem", but now I realize that the oil is simply "packing" intot he heads. The crankcase vacuum, from the existing dry sump, is enough that Mark's heads do not completely fill and thus overflow the valve cover vents.
The solution, for this engine, would be to add a couple more stages to the dry sump pump and simply suck the oil out of the heads. However, since it doesn't really cause any problems that shorten the life of the engine (the cams and lifters are just "slugging" their way through extra oil), this is not likely to ever happen.
I know this has not been a problem, but if you all ready have a dry sump then it is just a couple of more stages on the pump and some plumbing.
02-17-2011, 07:56 PM
#298
Rennlist Member
So, here's an interesting thought:
I've always assumed that in the GTS models, Porsche/Mahle screwed up and the oil return holes in the pistons were not drilled, by mistake. The problem, with this assumption, is that I've always thought it very strange that no one at the Porsche factory caught this "mistake" and they made all the '93, 94, and '95 models with this same defect.
Now looking closely, at the crankcase breather system and seeing that Porsche essentially "gave up" trying to vent the crankcase, I'm wondering if they intentionally deleated the oil "drain holes " in the pistons. If they knew the crankcase was going to get pressurized, they might also have assumed that this would force oil back through the pistons and put oil onto the cylinder walls, instead of removing the oil.
All these years, I thought it was a huge mistake.....now I'm thinking it might have been intentional.
I've always assumed that in the GTS models, Porsche/Mahle screwed up and the oil return holes in the pistons were not drilled, by mistake. The problem, with this assumption, is that I've always thought it very strange that no one at the Porsche factory caught this "mistake" and they made all the '93, 94, and '95 models with this same defect.
Now looking closely, at the crankcase breather system and seeing that Porsche essentially "gave up" trying to vent the crankcase, I'm wondering if they intentionally deleated the oil "drain holes " in the pistons. If they knew the crankcase was going to get pressurized, they might also have assumed that this would force oil back through the pistons and put oil onto the cylinder walls, instead of removing the oil.
All these years, I thought it was a huge mistake.....now I'm thinking it might have been intentional.
Porsche drilled 4 out of 8 holes in my Kolbenschmidt pistons. There is another car in the UK with the same piston design, but made by Mahle. Both cars are within the last 20 odd engines ever made...
Alex
02-17-2011, 08:01 PM
#299
The Parts Whisperer
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Yes, the dry sumped engine has enough oil, in the tank, that it can "pack" the heads full of oil and still have enough oil to feed the bearings....which only causes a loss in performance, a reduction of effective octane when the oil mixes in the combustion chambers, and perhaps a bit more smoke.
As I mentioned, Mark's engine will "suck" the dry sump tank down, an inch or more, when it is run on the dyno above 5,000 rpms. I always thought that this was an "oil pan design problem", but now I realize that the oil is simply "packing" intot he heads. The crankcase vacuum, from the existing dry sump, is enough that Mark's heads do not completely fill and thus overflow the valve cover vents.
The solution, for this engine, would be to add a couple more stages to the dry sump pump and simply suck the oil out of the heads. However, since it doesn't really cause any problems that shorten the life of the engine (the cams and lifters are just "slugging" their way through extra oil), this is not likely to ever happen.
As I mentioned, Mark's engine will "suck" the dry sump tank down, an inch or more, when it is run on the dyno above 5,000 rpms. I always thought that this was an "oil pan design problem", but now I realize that the oil is simply "packing" intot he heads. The crankcase vacuum, from the existing dry sump, is enough that Mark's heads do not completely fill and thus overflow the valve cover vents.
The solution, for this engine, would be to add a couple more stages to the dry sump pump and simply suck the oil out of the heads. However, since it doesn't really cause any problems that shorten the life of the engine (the cams and lifters are just "slugging" their way through extra oil), this is not likely to ever happen.
