Crank scrapers, pan spacers, Accusumps ?
06-04-2010, 01:32 AM
#16
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The oil I was using at the time was 5w40 Castrol Syntec. The scenario that day was 1st practice on a partly dry track scrubbed in the new Toyo's about 5-6 laps no problems. 2nd practice dry track new Hoosier R6's on the Kodiaks, lap times started coming down but did notice on the back straight the oil pressure on the autometer guage showing 20 psi! Did only 4 laps to heat cycle the new tires. By the end of the session was back up to 50 psi. Next session on my junk Toyo's lap times were falling more and was starting to carry good speed through turn 2, thought I heard a ticking and by the next corner was sure I heard a ticking, rolled through the turn, ticking turned into Knocking and then smoke came out from the edges of the hood, pulled off and the engine was locked tight. I didn't look at my pressure while in the fast turn as it was kind of using up all my attention.
The only thing different from my last time at PR was I was using synthetic instead of 20/50 dino oil and the track was repaved and way faster through turn 2.
All engines I have ran have had 100 psi cold, 50-60 on the track and around 20 when idling back to the pits.
The point about the Accusump pulling in aerated oil is valid but aerated oil is better than no oil no?
This was a strong used engine that I had raced at Mission only once on and don't really know it's history.
That's turn 2 in the distance, I go into it flat top of 4 th gear.
The only thing different from my last time at PR was I was using synthetic instead of 20/50 dino oil and the track was repaved and way faster through turn 2.
All engines I have ran have had 100 psi cold, 50-60 on the track and around 20 when idling back to the pits.
The point about the Accusump pulling in aerated oil is valid but aerated oil is better than no oil no?
This was a strong used engine that I had raced at Mission only once on and don't really know it's history.
That's turn 2 in the distance, I go into it flat top of 4 th gear.
06-04-2010, 01:52 AM
#17
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One key "feature" (that is one of the oldest tricks in the book to save connecting rods) is the side clearance. I'm very, very surprised this gets so little attention in these discussions.
I know it has been mentioned in other rod bearing threads (this isn't the first time I've brought it up either), just doesn't seam to get much attention.
This "mod" just happens to come along with most (if not all) strokers which most of are also dry sumped.
The concern is always getting oil to the bearings, just as important is getting the now heated up oil back out of the bearing.
06-04-2010, 08:53 AM
#18
Nordschleife Master
That's not the only difference between the design of the lower end in Mark's stroker and a stock 928. One key "feature" (that is one of the oldest tricks in the book to save connecting rods) is the side clearance. I'm very, very surprised this gets so little attention in these discussions. I know it has been mentioned in other rod bearing threads (this isn't the first time I've brought it up either), just doesn't seam to get much attention.
This "mod" just happens to come along with most (if not all) strokers which most of are also dry sumped. The concern is always getting oil to the bearings, just as important is getting the now heated up oil back out of the bearing.
This "mod" just happens to come along with most (if not all) strokers which most of are also dry sumped. The concern is always getting oil to the bearings, just as important is getting the now heated up oil back out of the bearing.
On speedtalk.com, some people switching to piston guided rods (and associated very large rod side clearances) were expecting an impact oil flow before doing the math, but couldn't detect any impact. With hindsight, this is not surprising given that the rod bearing clearance is so much smaller than the rod side clearance.
06-04-2010, 12:36 PM
#19
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Yep, the stroker has the one mod that my holbert 928 stock 5 liter didnt have.... the cross drilled crank. the Holbert 5 liter didnt even have the squirters either. by the way, it lasted 8 years of all out, never miss an event, racing! 
mk
mk
That's not the only difference between the design of the lower end in Mark's stroker and a stock 928.
One key "feature" (that is one of the oldest tricks in the book to save connecting rods) is the side clearance. I'm very, very surprised this gets so little attention in these discussions.
I know it has been mentioned in other rod bearing threads (this isn't the first time I've brought it up either), just doesn't seam to get much attention.
This "mod" just happens to come along with most (if not all) strokers which most of are also dry sumped.
The concern is always getting oil to the bearings, just as important is getting the now heated up oil back out of the bearing.
One key "feature" (that is one of the oldest tricks in the book to save connecting rods) is the side clearance. I'm very, very surprised this gets so little attention in these discussions.
I know it has been mentioned in other rod bearing threads (this isn't the first time I've brought it up either), just doesn't seam to get much attention.
This "mod" just happens to come along with most (if not all) strokers which most of are also dry sumped.
The concern is always getting oil to the bearings, just as important is getting the now heated up oil back out of the bearing.
06-04-2010, 12:45 PM
#20
Rennlist Member
Well, I think even the most severe doubters, would say that the oil you used could have certainly been the issues. not even 50weight???
40, 50psi, etc, is way way too low. If I ever saw those pressures, I would go home and yank the engine! 75psi, ALWAYS after 3000rpm, any place on the track, all the time, no exceptions. 20psi, 50psi, sounds like scot when he ran valvoline 20/50 racing oil. he had a day on that stuff and after seeing the oil pressures, we changed it out to redline and then later amsoil. I raced it for 3 races at laguna and it was 5 bar all the time. thats the engine I built for him.
(5 liter 2 valve euro)
your failure was probably due to oil quality based on your pressures. we never see near 1bar ilding back to the pits (near 20psi) thats close to the oil light going on . the only time ive seen that is with mobil one on a hot day.
you are not pushing the car to have any issues with extreme g loading to worry about that. that turn flat out in the picture in 4th is nothing that could cause such g loading to worry about. (based on your hp and wheel, tire sizes).
Really, that turn , flat out , top of 4th gear?? thats like 155mph for me, or do you have a 2.75 rear end? still, that would be 125mph or so, and that turn you are going that fast? if you are the top of that gear, why not go to 5th. the other thing that i believe that saves me is being in the right gear around sweepers. (not only for safety for the engine, but lap time).
BTW, Im running 108% of the top 2010 GT3 cup car times and scot is just over 110% of the stock cup car times for reference.
mk
40, 50psi, etc, is way way too low. If I ever saw those pressures, I would go home and yank the engine! 75psi, ALWAYS after 3000rpm, any place on the track, all the time, no exceptions. 20psi, 50psi, sounds like scot when he ran valvoline 20/50 racing oil. he had a day on that stuff and after seeing the oil pressures, we changed it out to redline and then later amsoil. I raced it for 3 races at laguna and it was 5 bar all the time. thats the engine I built for him.
(5 liter 2 valve euro)
your failure was probably due to oil quality based on your pressures. we never see near 1bar ilding back to the pits (near 20psi) thats close to the oil light going on . the only time ive seen that is with mobil one on a hot day.
you are not pushing the car to have any issues with extreme g loading to worry about that. that turn flat out in the picture in 4th is nothing that could cause such g loading to worry about. (based on your hp and wheel, tire sizes).
Really, that turn , flat out , top of 4th gear?? thats like 155mph for me, or do you have a 2.75 rear end? still, that would be 125mph or so, and that turn you are going that fast? if you are the top of that gear, why not go to 5th. the other thing that i believe that saves me is being in the right gear around sweepers. (not only for safety for the engine, but lap time).
BTW, Im running 108% of the top 2010 GT3 cup car times and scot is just over 110% of the stock cup car times for reference.
mk
The oil I was using at the time was 5w40 Castrol Syntec. The scenario that day was 1st practice on a partly dry track scrubbed in the new Toyo's about 5-6 laps no problems. 2nd practice dry track new Hoosier R6's on the Kodiaks, lap times started coming down but did notice on the back straight the oil pressure on the autometer guage showing 20 psi! Did only 4 laps to heat cycle the new tires. By the end of the session was back up to 50 psi. Next session on my junk Toyo's lap times were falling more and was starting to carry good speed through turn 2, thought I heard a ticking and by the next corner was sure I heard a ticking, rolled through the turn, ticking turned into Knocking and then smoke came out from the edges of the hood, pulled off and the engine was locked tight. I didn't look at my pressure while in the fast turn as it was kind of using up all my attention.
The only thing different from my last time at PR was I was using synthetic instead of 20/50 dino oil and the track was repaved and way faster through turn 2.
All engines I have ran have had 100 psi cold, 50-60 on the track and around 20 when idling back to the pits.
The point about the Accusump pulling in aerated oil is valid but aerated oil is better than no oil no?
This was a strong used engine that I had raced at Mission only once on and don't really know it's history.
That's turn 2 in the distance, I go into it flat top of 4 th gear.
The only thing different from my last time at PR was I was using synthetic instead of 20/50 dino oil and the track was repaved and way faster through turn 2.
All engines I have ran have had 100 psi cold, 50-60 on the track and around 20 when idling back to the pits.
The point about the Accusump pulling in aerated oil is valid but aerated oil is better than no oil no?
This was a strong used engine that I had raced at Mission only once on and don't really know it's history.
That's turn 2 in the distance, I go into it flat top of 4 th gear.
06-04-2010, 01:30 PM
#21
Nordschleife Master
I don't understand why the stroker crank would be cross-drilled though, but there's a lot of stuff that I don't understand.
06-04-2010, 03:00 PM
#22
Rennlist Member
AFAIK, all 928 cranks are drilled the same. the "drilling" we talk about is like a chevy. its not done on any 928 cranks and is done on custom cranks to help with oiling of the #6 -2 bearings.
06-04-2010, 03:36 PM
#23
Nordschleife Master
When I say "cross drilled," I mean there's a straight passage drilled thru the main journal, from one side to the other, passing thru (or near by) the crank centerline.
When I say "straight shot" or "I" drilling, I mean a single straight passage from the main journal surface to the rod journal surface.
When I say "T cross drilled," I mean cross-drilled and then a passage to the rods intersecting the cross drilling near the crank centerline.
When I say "V cross-drilled," I mean straight-shot I drilling combined with cross drilling, such that the cross drilling and the straight shot drilling intersect at the main journal surface.
When I say "web drilled," I mean any drilling such that if you would block all surface holes in the journals except one hole in main #1 and one hole in main #5, and fed pressurized oil from the main #1, then it would squirt out of main #5.
06-21-2010, 05:48 AM
#24
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That's not the only difference between the design of the lower end in Mark's stroker and a stock 928.
One key "feature" (that is one of the oldest tricks in the book to save connecting rods) is the side clearance. I'm very, very surprised this gets so little attention in these discussions.
I know it has been mentioned in other rod bearing threads (this isn't the first time I've brought it up either), just doesn't seam to get much attention.
This "mod" just happens to come along with most (if not all) strokers which most of are also dry sumped.
The concern is always getting oil to the bearings, just as important is getting the now heated up oil back out of the bearing.
One key "feature" (that is one of the oldest tricks in the book to save connecting rods) is the side clearance. I'm very, very surprised this gets so little attention in these discussions.
I know it has been mentioned in other rod bearing threads (this isn't the first time I've brought it up either), just doesn't seam to get much attention.
This "mod" just happens to come along with most (if not all) strokers which most of are also dry sumped.
The concern is always getting oil to the bearings, just as important is getting the now heated up oil back out of the bearing.
The grooves do not increase the net amount of oil ejected from the bearings (unless you count blocked flow from stacking which is bad in itself) nor do they negatively impact the pressure gradient in the shell. They just increase the probability that the ejected oil will land someplace useful.
Are they sound engineering? Yes, and there are plenty of oem examples. The NA Honda B16 and B18 rods have a total of 20 oil squirters for a four cylinder engine. Four are tapped into the galley and 16 are these slots. BMW uses the technique as well.
http://www.crank-scrapers.com/HONDA_B16_ROD.jpg
Good luck.
06-21-2010, 06:46 AM
#25
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A very simple technique is to mill grooves on the side faces of the rods aimed at the pistons. Make the cross area of the groove on either side equal to or greater than the radial area on that side as defined by the clearance between the journal OD and the bearing ID. This way if the rods stack up hard against each other either way on the journal then the grooves act as a safety valve that is actually doing something useful at the same time.
The grooves do not increase the net amount of oil ejected from the bearings (unless you count blocked flow from stacking which is bad in itself) nor do they negatively impact the pressure gradient in the shell. They just increase the probability that the ejected oil will land someplace useful.
Are they sound engineering? Yes, and there are plenty of oem examples. The NA Honda B16 and B18 rods have a total of 20 oil squirters for a four cylinder engine. Four are tapped into the galley and 16 are these slots. BMW uses the technique as well.
http://www.crank-scrapers.com/HONDA_B16_ROD.jpg
Good luck.
The grooves do not increase the net amount of oil ejected from the bearings (unless you count blocked flow from stacking which is bad in itself) nor do they negatively impact the pressure gradient in the shell. They just increase the probability that the ejected oil will land someplace useful.
Are they sound engineering? Yes, and there are plenty of oem examples. The NA Honda B16 and B18 rods have a total of 20 oil squirters for a four cylinder engine. Four are tapped into the galley and 16 are these slots. BMW uses the technique as well.
http://www.crank-scrapers.com/HONDA_B16_ROD.jpg
Good luck.
Then thinking some more about it occured to me that the clearances in the bearing are such that the proper oil flow relies on the oil being able to escape from the centre to both sides of each rod bearing. Am I right ?
I guess the situation would get even worse if the rods stacked at one end of the journal thus reducing 4 escape paths down to one ?
06-21-2010, 08:11 AM
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My first thought when I read about the rods stacking being a problem was "must be nonsense" the oil would just come out the other side of the bearing.(Assuming the rods stacked in the centre of the journal)
Then thinking some more about it occured to me that the clearances in the bearing are such that the proper oil flow relies on the oil being able to escape from the centre to both sides of each rod bearing. Am I right ?
I guess the situation would get even worse if the rods stacked at one end of the journal thus reducing 4 escape paths down to one ?
Then thinking some more about it occured to me that the clearances in the bearing are such that the proper oil flow relies on the oil being able to escape from the centre to both sides of each rod bearing. Am I right ?
I guess the situation would get even worse if the rods stacked at one end of the journal thus reducing 4 escape paths down to one ?
It also points out how important it is to have accurate machining of the journals. A taper or some such could make the rods have a tendency to migrate one way or another rather than be "free floating."
06-21-2010, 09:18 AM
#28
Nordschleife Master
A very simple technique is to mill grooves on the side faces of the rods aimed at the pistons. Make the cross area of the groove on either side equal to or greater than the radial area on that side as defined by the clearance between the journal OD and the bearing ID. This way if the rods stack up hard against each other either way on the journal then the grooves act as a safety valve that is actually doing something useful at the same time.
My first thought when I read about the rods stacking being a problem was "must be nonsense" the oil would just come out the other side of the bearing.(Assuming the rods stacked in the centre of the journal)Then thinking some more about it occured to me that the clearances in the bearing are such that the proper oil flow relies on the oil being able to escape from the centre to both sides of each rod bearing. Am I right ? I guess the situation would get even worse if the rods stacked at one end of the journal thus reducing 4 escape paths down to one ?
Yes, you're correct. It doesn't seem significant at first but it will have a big impact on how long oil will stay inside the shell and then how much heat that is not carried away promptly by the oil flow. It also points out how important it is to have accurate machining of the journals. A taper or some such could make the rods have a tendency to migrate one way or another rather than be "free floating."
For piston-guided rod setups, like in many of the modern imports or serious race engines, the rod is located by the piston-to-rod small end clearance. In those case the rods can't stack or bunch right next to each other.
For crankshaft-guided rod setups, it's my understanding that the oil pressure from the rod bearings will center the rods on the crankshaft journal. Suppose that the rods were about to "stack" in one end of the crank pin. Now, the oil temporarily can't escape freely and the oil pressure will push the rods away from each other and the crank fillet until it can. The oil pressure centers the rods.
For a piston-guided engines, one can slot any number of squirter slots to the rods. For crankshaft-guided engines, the slots reduce the effectiveness of one of the centering mechanisms.
When sending out random piston slotted rod pictures, it would be useful to note with each of them whether they are from a piston-guided or crankshaft-guided engine.
06-21-2010, 09:38 AM
#29
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Here's my understanding of what's going on:
For piston-guided rod setups, like in many of the modern imports or serious race engines, the rod is located by the piston-to-rod small end clearance. In those case the rods can't stack or bunch right next to each other.
For crankshaft-guided rod setups, it's my understanding that the oil pressure from the rod bearings will center the rods on the crankshaft journal. Suppose that the rods were about to "stack" in one end of the crank pin. Now, the oil temporarily can't escape freely and the oil pressure will push the rods away from each other and the crank fillet until it can. The oil pressure centers the rods.
For a piston-guided engines, one can slot any number of squirter slots to the rods. For crankshaft-guided engines, the slots reduce the effectiveness of one of the centering mechanisms.
When sending out random piston slotted rod pictures, it would be useful to note with each of them whether they are from a piston-guided or crankshaft-guided engine.
For piston-guided rod setups, like in many of the modern imports or serious race engines, the rod is located by the piston-to-rod small end clearance. In those case the rods can't stack or bunch right next to each other.
For crankshaft-guided rod setups, it's my understanding that the oil pressure from the rod bearings will center the rods on the crankshaft journal. Suppose that the rods were about to "stack" in one end of the crank pin. Now, the oil temporarily can't escape freely and the oil pressure will push the rods away from each other and the crank fillet until it can. The oil pressure centers the rods.
For a piston-guided engines, one can slot any number of squirter slots to the rods. For crankshaft-guided engines, the slots reduce the effectiveness of one of the centering mechanisms.
When sending out random piston slotted rod pictures, it would be useful to note with each of them whether they are from a piston-guided or crankshaft-guided engine.
So is a a 928 engine piston guided or crank guided ?
Just remembering my observations from dismantling a TBF 928 engine the crank had moved forwards by about 1.5mm (approx) but hadn't quite got to the point where the rods had used up all the sideways (fore and aft) play in the little end and big end bearings.