New shiny parts
05-22-2019, 08:41 PM
#17
Former Vendor
Thread Starter
I'd call this a "token nod", by Carrillo, to my request to make the pin end of the rod stronger.
They do not remotely feel that the design or construction of the old connecting rod was an issue, nor did it need to be changed.
"New design" connecting rod on the left.
05-23-2019, 04:19 PM
#19
Former Vendor
Thread Starter
05-23-2019, 05:13 PM
#20
Rennlist Member
Just need the ST software to be taught:
1) An persistent option on startup to immediately start logging
2) The ability to have default LH & EZK logged parameters so that the data is never missing "Oh I forgot that one..." making it all useless (this happens..you forget that -1- checkbox)
3) Persistent log options between hard resets of the ST software if you select more than the logged basic parameters
Then yes, this would be absolutely possible.
A MS Surface 3 (Not Pro, this is what I use) for example in my use doesn't get hot from just being on, unlike my Surface Pro 1 did, and it if was secured in a case in soft foam with the ST unit, no reason that either wouldn't sustain operational vibration..both being solid state and of -very- low mass.
05-23-2019, 06:51 PM
#21
Race Director
"Pretty amazing, to me, for the incredible forces the pistons and rods were subjected to, the rod bearings (not Porsche bearings) looked like the day they were installed. No dimensional changes. No sign of pounding. No loss of crush. The rod bearings and oil definitely did their job, very well."
As a near expert in blowing up 928 engines on track it almost always was from knock causing rod bearing failure. Only one time it wasn't when it was excessive rpm (7000) on a stock S4 engine that caused a valve to drop. Given the amount of destruction this engine suffered, the fact that the rod bearings are not damaged or even worn is EXTREMELY impressive...... I do think a dry sump is required for a fully built race 928 engine, the seeming large expense (maybe $5k) is still excellent insurance on a much more pricey engine......same for race fuel....$10 per gallon ain't cheap and I would imagine the stroker race engines burn at least 15 gallons per hour, possibly 20. My 265whp engine under race conditions burned 10 gallons per hour.
The ONLY other proven way for a 928 engine under race conditions to survive is an OB pan with 3/8th spacer and proper oil cooling plus open crankcase breather (accusump isn't a bad idea) and under 6000rpm. The $300 junk 83 USA 4.7L engine I ran in the Krankenwagen lasted 176 hours on track for me when I sold her.
As a near expert in blowing up 928 engines on track it almost always was from knock causing rod bearing failure. Only one time it wasn't when it was excessive rpm (7000) on a stock S4 engine that caused a valve to drop. Given the amount of destruction this engine suffered, the fact that the rod bearings are not damaged or even worn is EXTREMELY impressive...... I do think a dry sump is required for a fully built race 928 engine, the seeming large expense (maybe $5k) is still excellent insurance on a much more pricey engine......same for race fuel....$10 per gallon ain't cheap and I would imagine the stroker race engines burn at least 15 gallons per hour, possibly 20. My 265whp engine under race conditions burned 10 gallons per hour.
The ONLY other proven way for a 928 engine under race conditions to survive is an OB pan with 3/8th spacer and proper oil cooling plus open crankcase breather (accusump isn't a bad idea) and under 6000rpm. The $300 junk 83 USA 4.7L engine I ran in the Krankenwagen lasted 176 hours on track for me when I sold her.
05-24-2019, 03:58 AM
#23
Rennlist Member
Join Date: Feb 2011
Location: Mostly in my workshop located in Sweden.
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"Pretty amazing, to me, for the incredible forces the pistons and rods were subjected to, the rod bearings (not Porsche bearings) looked like the day they were installed. No dimensional changes. No sign of pounding. No loss of crush. The rod bearings and oil definitely did their job, very well."
The not Porsche bearings are made by Clevite. The Clevite CB-1628HX high performance rod bearing can be installed using the existing cut in the stock con rod (the width of the bearing tab has to be filed down at one side) the bearing will sit 0,35mm offset the middle of the rod beam which should not be an issue. The alternative is to machine new cutouts in the rod which of course will add to the costs if you do not have your own mill.
The CB-1628HX bearing for the OEM con rod and a new GTS crank I have measured an oil clearance of 0,07mm which is perfect.
Åke
The not Porsche bearings are made by Clevite. The Clevite CB-1628HX high performance rod bearing can be installed using the existing cut in the stock con rod (the width of the bearing tab has to be filed down at one side) the bearing will sit 0,35mm offset the middle of the rod beam which should not be an issue. The alternative is to machine new cutouts in the rod which of course will add to the costs if you do not have your own mill.
The CB-1628HX bearing for the OEM con rod and a new GTS crank I have measured an oil clearance of 0,07mm which is perfect.
Åke
05-24-2019, 02:41 PM
#24
Nordschleife Master
Unfortunately, "I don't know" is the best responce I can make.
Looking at the amount of "cooked" oil that was deposited on the bottom of the pistons, in the latest failed engine, there can be little doubt that the pistons were extremely hot. And if just the pistons had failed, perhaps taking away more heat would have helped, some. The fact that rods failed makes me think that no amount of heat removal would have "saved" this engine.
Perhaps worth noting, the amount of "cooked" oil deposited on the bottom of the pistons varies quite a bit, indicating higher piston temperatures (which agrees with which pistons were damaged the most), from one cylinder to the next. The intake manifolds, on both of these engines, were never tested for individual air flow....so individual cylinder mixtures were/still are a complete unknown. (The manifolds were never more than a sales mock-up, as far as I can tell.) Therefore, It's not surprising that some cylinders would have been hotter than other cylinders. However, all 8 pistons have cracks in the tops...indicating severe pounding.
The damage to the connecting rods is not from heat....the wrist pins are not "blue", but a very light straw color. And the surviving rods have no oil residue "cooked" onto them.
Additionally, none of the pistons actually melted. There were signs of deformation from heat on a couple of the pistons and some "pitting" in the top surface of some of the pistions, but no "holes" from actual melting.
My conclusion was that the "pounding" from detonation was the direct cause of failure, not actual heat.
A couple of "real life" events made me question the "need" for piston oil squirters:
Once I directly observed the huge volume of oil that is present in the oil filler neck area of the block, when a 928 engine is running at 6,000+ rpms, I really questioned if piston oil squirters (adding more oil upwards) were necessary...or even desirable.
Additionally, whenever we ran Mark Anderson's dry dumped 928 engine over 6,000 rpms (under load for extended amounts of time), his dry sump tank volume would drop by several inches, indicating large amounts of oil being held in suspension inside the engine.
More study is necessary before I can draw any conclusions.
Looking at the amount of "cooked" oil that was deposited on the bottom of the pistons, in the latest failed engine, there can be little doubt that the pistons were extremely hot. And if just the pistons had failed, perhaps taking away more heat would have helped, some. The fact that rods failed makes me think that no amount of heat removal would have "saved" this engine.
Perhaps worth noting, the amount of "cooked" oil deposited on the bottom of the pistons varies quite a bit, indicating higher piston temperatures (which agrees with which pistons were damaged the most), from one cylinder to the next. The intake manifolds, on both of these engines, were never tested for individual air flow....so individual cylinder mixtures were/still are a complete unknown. (The manifolds were never more than a sales mock-up, as far as I can tell.) Therefore, It's not surprising that some cylinders would have been hotter than other cylinders. However, all 8 pistons have cracks in the tops...indicating severe pounding.
The damage to the connecting rods is not from heat....the wrist pins are not "blue", but a very light straw color. And the surviving rods have no oil residue "cooked" onto them.
Additionally, none of the pistons actually melted. There were signs of deformation from heat on a couple of the pistons and some "pitting" in the top surface of some of the pistions, but no "holes" from actual melting.
My conclusion was that the "pounding" from detonation was the direct cause of failure, not actual heat.
A couple of "real life" events made me question the "need" for piston oil squirters:
Once I directly observed the huge volume of oil that is present in the oil filler neck area of the block, when a 928 engine is running at 6,000+ rpms, I really questioned if piston oil squirters (adding more oil upwards) were necessary...or even desirable.
Additionally, whenever we ran Mark Anderson's dry dumped 928 engine over 6,000 rpms (under load for extended amounts of time), his dry sump tank volume would drop by several inches, indicating large amounts of oil being held in suspension inside the engine.
More study is necessary before I can draw any conclusions.
I agree that with stock pistons, the engine doesn't need piston oil squirters. They have enough mass to live without oil cooling.
I also agree that the 928 has more than enough, really too much, oil on the bore walls. One wouldn't want to add any more oil there. The second ring in the stock pistons has it's work cut out for it in trying to scrape the excess oil off the walls.
I think the piston oil squirter nozzles are designed to be straight jet nozzles such that the spray doesn't have any cone to it. Therefore, ideally, the oil would just hit the piston and then the piston would throw the oil down to the sump at the deceleration stage.
My guess is that many of the 928 oiling problems at high rpms are caused by gas flows due to piston pumping pulses. Whether dry sump or wet sump, I believe that crankcase vacuum would alleviate those. This is a guess, haven't tried it.
With super light pistons and high rpms, I'd go with oil squirters and depressed atmosphere in the crankcase.
05-24-2019, 05:31 PM
#27
Archive Gatekeeper
Rennlist Member
Rennlist Member
O
05-24-2019, 06:40 PM
#28
05-24-2019, 06:48 PM
#29
Archive Gatekeeper
Rennlist Member
Rennlist Member
I know, it's just that poor Greg is sitting at his keyboard right now, reading glasses shaking in his left hand at the thought of venting to the atmosphere. It needs a trigger warning.
05-24-2019, 07:03 PM
#30
Nordschleife Master
Yes, I believe there would be. Lowering the density of the crankcase gasses will lower the energy that the piston pumping pulses transfer to the crank case gases. Think of an extreme case where the crankcase has a perfect vacuum. Now, the piston moves in empty space and can’t push oil up the drains.