Louis Ott's full valve cover video now on youtube
05-25-2010, 07:38 PM
#46
Nordschleife Master
Tuomo,
I will be running a Kevin J scraper setup on the motor, in conjunction with the drysump.
The venting through the passenger side cam cover might not do much, but it cannot hurt either.
My pickups are 2 in the front of the engine, and 1 in the rear. They are all on the side so that all oil coming off the crank will be shot at them, and sucked up right away.
If I were to build the pan again there are some things that I would change, but I do feel that this pan will work more than well enough.
As to louie's comment about the oil pump not pumping 20GPM. I think that most of that flow is probably recirculated via the pressure valve. But it is difficult to say and noone has any raw data on it, just what the manual states.
The supply of oil to my pickup is from an external hose, the tanks oil level will be slightly above the oil pump itself, so it will have zero lift to actually have oil.
I will be running a Kevin J scraper setup on the motor, in conjunction with the drysump.
The venting through the passenger side cam cover might not do much, but it cannot hurt either.
My pickups are 2 in the front of the engine, and 1 in the rear. They are all on the side so that all oil coming off the crank will be shot at them, and sucked up right away.
If I were to build the pan again there are some things that I would change, but I do feel that this pan will work more than well enough.
As to louie's comment about the oil pump not pumping 20GPM. I think that most of that flow is probably recirculated via the pressure valve. But it is difficult to say and noone has any raw data on it, just what the manual states.
The supply of oil to my pickup is from an external hose, the tanks oil level will be slightly above the oil pump itself, so it will have zero lift to actually have oil.
05-25-2010, 07:55 PM
#47
Three Wheelin'
No, I haven't. I saw an oil pressure drop in sustained left turn on the stroker GT and I knew my sump baffle wasn't working as I thought it would. I was tired of working on it by then and didn't re-work the sump baffle. At least I now know what doesn't work. By using the oil filler cap breather on several cars, I did verify that no oil goes into the intake anymore. I felt that extra vent showed that intake oil really comes from crankcase pressure. Beyond that I didn't pursue another holy cam cover test. On my stroker motor, the crankshaft scrapers extend under the drain back holes to keep thrown oil from going directly up the drain backs. I didn't extend the drain backs further down which would be a better way to protect them.
05-25-2010, 08:05 PM
#48
Race Director
Great thread
Heres my thinking & I am NOT an engineer...just a guy who wants my stock 928 motor to last a long time on track! I think a stock-ish engine with OB pan setup and 3/8th spacer works pretty well to provide a reliable setup IF & its a BIG IF you keep the rpm's say 6000 or under.... I think the windage & drainback issues get substantially worse as RPM climbs.....928 motors are rock solid reliable on track at 6000rpm or less...they still can be reliable above 6000rpm, BUT you must design the oil system for it with proper breathers, windage and drainback controls.....it can be done...especially with drysumps...it just takes more effort & expense to get it right....
Heres my thinking & I am NOT an engineer...just a guy who wants my stock 928 motor to last a long time on track! I think a stock-ish engine with OB pan setup and 3/8th spacer works pretty well to provide a reliable setup IF & its a BIG IF you keep the rpm's say 6000 or under.... I think the windage & drainback issues get substantially worse as RPM climbs.....928 motors are rock solid reliable on track at 6000rpm or less...they still can be reliable above 6000rpm, BUT you must design the oil system for it with proper breathers, windage and drainback controls.....it can be done...especially with drysumps...it just takes more effort & expense to get it right....
05-25-2010, 09:59 PM
#49
Nordschleife Master
Thread Starter
pump displacement
Here's a quick measurement of the pump displacement. I did this with a caliper and third-grade geometry in the garage, so there's some margin of error. It shouldn't be too far, though.
dimension, inner gear, outer gear
depth, 2.1, 2.1
width , 0.7, 0.7
inner, 0, 1.1
outer, 1.1, 0.7
displacement cc, 0.8085, 1.323
#teeth, 9, 11
cc per pump revolution
21.83
pump sprocket teeth
35
crank sprocket teeth
24
Drive ratio
0.686
cc per crank revolution
14.97
gallons per 1000 crank revolutions
3.95
dimension, inner gear, outer gear
depth, 2.1, 2.1
width , 0.7, 0.7
inner, 0, 1.1
outer, 1.1, 0.7
displacement cc, 0.8085, 1.323
#teeth, 9, 11
cc per pump revolution
21.83
pump sprocket teeth
35
crank sprocket teeth
24
Drive ratio
0.686
cc per crank revolution
14.97
gallons per 1000 crank revolutions
3.95
Last edited by ptuomov; 05-25-2010 at 10:23 PM.
05-25-2010, 10:19 PM
#50
Nordschleife Master
Thread Starter
27.7 gallons per minute @ 7000 rpm displacement of the pump leads me to another point.
See the photo by Hacker:
So far there are no theories what caused this damage, other than the standard FOD. Here's one.
"Again I tell you, it is easier for a camel to go through the eye of a needle than 27.7 gallons of oil per minute to pass thru that 23mm ID pickup pipe."
So what happens when the pump demand exceeds the flow capacity of that pipe at 1 atmoshpere pressure differential? The pump cavitates. In English, the pump gear teeth pull a vacuum. Now suppose that the outer gear pulled a vacuum when passing the inlet and the inner gear pulled oil. It's all fine as long as the teeth are separated by the cresent. However, when the crescent ends, the vacuum collapses violently. Collapses such as these can kill propellers etc., so they can kill the 928 oil pump.
I am simplifying of course by ignoring the oil passed by relief valve, but still.
One more reason why we don't see everyone driving around with 10,000 rpm 928s.
See the photo by Hacker:
So far there are no theories what caused this damage, other than the standard FOD. Here's one.
"Again I tell you, it is easier for a camel to go through the eye of a needle than 27.7 gallons of oil per minute to pass thru that 23mm ID pickup pipe."
So what happens when the pump demand exceeds the flow capacity of that pipe at 1 atmoshpere pressure differential? The pump cavitates. In English, the pump gear teeth pull a vacuum. Now suppose that the outer gear pulled a vacuum when passing the inlet and the inner gear pulled oil. It's all fine as long as the teeth are separated by the cresent. However, when the crescent ends, the vacuum collapses violently. Collapses such as these can kill propellers etc., so they can kill the 928 oil pump.
I am simplifying of course by ignoring the oil passed by relief valve, but still.
One more reason why we don't see everyone driving around with 10,000 rpm 928s.
05-25-2010, 10:23 PM
#51
Brian thanks for posting that CarCraft link, I used to have a subscription and used to bang on here that people from this board should read that site for some decent mechanical insight. The info provided was especially relevant to myself. The reasons being I am looking to cut the various losses that occur in ICC engines as our engines are good candidates for that given 30 years ago that wasn't an issue to the designers.
A while back I was looking at either running a 15w-40 oil or lowering the oil pressure, I decided against the lower vis oil due to research surrounding longevity. Those lower vis oils are not any good for the older style (cam bucket arrangement) engines so lowering the oil pressure remained the goal.
How is this done, first there is no magic bullet, the increased clearances for higher RPM engines needs to be addressed. I don't know how strong the stock rods are but I do know that the piston and rods are heavy. So when the engine is above 6,000 rpm the forces are multiplying rapidly. (Can someone do the force on the conrod at 6,000 rpm versus 6.800 rpm please) as such the rods will have changing clearances and remember that the 928's clearance is tight from the factory so there is a chance to nip a bearing there especially if the oil supply is not pure.
So in my engines I have increased clearances, the 2V stroker (not built as yet) the mains are 3 thou and the rods 2.5 thou with the smaller rod journals of 48 mm. Lightening the parts makes a big difference to the loads, again if someone could do the maths, the pistons with rings and pin is about 550 grams and the rod with bearings is around 560 grams, also they will have less bearing speed due to reduced journal diameter, i.e 48 mm versus 52 mm.
Now the part that I don't know about the oil pressure is, how a large dry sump pump effects the pressure? Remember this is also a vacuum pump, so the crankcase will have a vacuum, as it has 5 vacuum stages the head that doesn't drain back into the cradle may get that stage with the other 4 stages attending to duties for the 4 individual bays. So the vacuum will actually be pulling the oil through the motor. Not just the pump pushing the oil. It will be great for flow, that is for sure. Does it lower the oil pressure? Yes it should due to the pressure differential, how much? That is the unknown. Will it help? It can't hurt.
If the pressure is lowered to an acceptable range job done, if you recall I posted a Nascar Chevy engine's oil pressure along with dyno sheet a while back, so I have something to compare it to. Otherwise there is other measures I can look at. I will also look at the changes suggested by Tuomo in relation to the girdle. So there is a lot of changes required to get this to work properly but essentially it is a different engine now.
Louie, great insight, I know what it is like to work on a tight budget, everytime I have had money to spend on the car, I couldn't bring myself to do it but this time I will. Time is ticking for me. The cracking of the block was one reason I looked at using much lighter components to address what is a mass force issue in my mind. Even the 8 counter weight stroker crank I have at 26.7 kgs is a bit too heavy. At least most of the weight is close to the centre line due to the small journal and it will have a beautiful balance with full counter weighting and ATI balancer so hopefully that will keep things alive in the bottom end.
Colin, the F1 oil tank is still in the UK, I am organizing a shipment back from there soon, until then I don't know. You would think it would be enough capacity if combined with appropriate cooling, that is where I hope to bring in the Laminova coolers I bought and place them in the front guards with the shark gills that I have to fit and have posted previously about. I let you know when I get it.
Greg
A while back I was looking at either running a 15w-40 oil or lowering the oil pressure, I decided against the lower vis oil due to research surrounding longevity. Those lower vis oils are not any good for the older style (cam bucket arrangement) engines so lowering the oil pressure remained the goal.
How is this done, first there is no magic bullet, the increased clearances for higher RPM engines needs to be addressed. I don't know how strong the stock rods are but I do know that the piston and rods are heavy. So when the engine is above 6,000 rpm the forces are multiplying rapidly. (Can someone do the force on the conrod at 6,000 rpm versus 6.800 rpm please) as such the rods will have changing clearances and remember that the 928's clearance is tight from the factory so there is a chance to nip a bearing there especially if the oil supply is not pure.
So in my engines I have increased clearances, the 2V stroker (not built as yet) the mains are 3 thou and the rods 2.5 thou with the smaller rod journals of 48 mm. Lightening the parts makes a big difference to the loads, again if someone could do the maths, the pistons with rings and pin is about 550 grams and the rod with bearings is around 560 grams, also they will have less bearing speed due to reduced journal diameter, i.e 48 mm versus 52 mm.
Now the part that I don't know about the oil pressure is, how a large dry sump pump effects the pressure? Remember this is also a vacuum pump, so the crankcase will have a vacuum, as it has 5 vacuum stages the head that doesn't drain back into the cradle may get that stage with the other 4 stages attending to duties for the 4 individual bays. So the vacuum will actually be pulling the oil through the motor. Not just the pump pushing the oil. It will be great for flow, that is for sure. Does it lower the oil pressure? Yes it should due to the pressure differential, how much? That is the unknown. Will it help? It can't hurt.
If the pressure is lowered to an acceptable range job done, if you recall I posted a Nascar Chevy engine's oil pressure along with dyno sheet a while back, so I have something to compare it to. Otherwise there is other measures I can look at. I will also look at the changes suggested by Tuomo in relation to the girdle. So there is a lot of changes required to get this to work properly but essentially it is a different engine now.
Louie, great insight, I know what it is like to work on a tight budget, everytime I have had money to spend on the car, I couldn't bring myself to do it but this time I will. Time is ticking for me. The cracking of the block was one reason I looked at using much lighter components to address what is a mass force issue in my mind. Even the 8 counter weight stroker crank I have at 26.7 kgs is a bit too heavy. At least most of the weight is close to the centre line due to the small journal and it will have a beautiful balance with full counter weighting and ATI balancer so hopefully that will keep things alive in the bottom end.
Colin, the F1 oil tank is still in the UK, I am organizing a shipment back from there soon, until then I don't know. You would think it would be enough capacity if combined with appropriate cooling, that is where I hope to bring in the Laminova coolers I bought and place them in the front guards with the shark gills that I have to fit and have posted previously about. I let you know when I get it.
Greg
05-25-2010, 10:35 PM
#52
Archive Gatekeeper
Rennlist Member
Rennlist Member
Tuomo:
Huh. Half way thru your post I thought you were going to conclude that at high rpm the super-high capacity oil pump exceeds the supply of oil to it and the it's the pump itself at sustained high rpm that is contributing to the generation of foam by exceeding the ability of the pickup tube to supply it. Coupled with g-force- induced sloshing around in the pan and windage of course.
Or are you saying that caviation is ruining oil pumps? From a purely non-tech-having gestalt, I would have guessed that oil pump failure is more uncommon than 2/6 failure in tracked engines.
Huh. Half way thru your post I thought you were going to conclude that at high rpm the super-high capacity oil pump exceeds the supply of oil to it and the it's the pump itself at sustained high rpm that is contributing to the generation of foam by exceeding the ability of the pickup tube to supply it. Coupled with g-force- induced sloshing around in the pan and windage of course.
Or are you saying that caviation is ruining oil pumps? From a purely non-tech-having gestalt, I would have guessed that oil pump failure is more uncommon than 2/6 failure in tracked engines.
Last edited by Rob Edwards; 05-25-2010 at 10:38 PM. Reason: Mis-read of Louies' post.
05-25-2010, 11:23 PM
#53
Nordschleife Master
Thread Starter
Tuomo: Huh. Half way thru your post I thought you were going to conclude that at high rpm the super-high capacity oil pump exceeds the supply of oil to it and the it's the pump itself at sustained high rpm that is contributing to the generation of foam by exceeding the ability of the pickup tube to supply it. Coupled with g-force- induced sloshing around in the pan and windage of course. Or are you saying that caviation is ruining oil pumps? From a purely non-tech-having gestalt, I would have guessed that oil pump failure is more uncommon than 2/6 failure in tracked engines.
05-26-2010, 12:15 AM
#54
Nordschleife Master
Tuomo,
Your theory on the cavitation destroying the pump is fairly sound actually.
However when cavitation occours, it may not do damage, depending on the severity of the cavitation. But once it occours, I have seen it cause serious removal of chromoly metal in gear pumps.
If cavitation gets extreme it can, and will cause the oil to aerate, or turn into a gas. But that I doubt is happening in these motors. I can say that as when the cavitation gets that bad, the oil turns into a 100% froth almost instantly! And then the pumps would have massive pits on the gear surfaces, of which I have never seen any pitting on them.
Your theory on the cavitation destroying the pump is fairly sound actually.
However when cavitation occours, it may not do damage, depending on the severity of the cavitation. But once it occours, I have seen it cause serious removal of chromoly metal in gear pumps.
If cavitation gets extreme it can, and will cause the oil to aerate, or turn into a gas. But that I doubt is happening in these motors. I can say that as when the cavitation gets that bad, the oil turns into a 100% froth almost instantly! And then the pumps would have massive pits on the gear surfaces, of which I have never seen any pitting on them.
05-26-2010, 12:29 AM
#55
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27.7 gallons per minute @ 7000 rpm displacement of the pump leads me to another point.
See the photo by Hacker:
So far there are no theories what caused this damage, other than the standard FOD. Here's one.
"Again I tell you, it is easier for a camel to go through the eye of a needle than 27.7 gallons of oil per minute to pass thru that 23mm ID pickup pipe."
So what happens when the pump demand exceeds the flow capacity of that pipe at 1 atmoshpere pressure differential? The pump cavitates. In English, the pump gear teeth pull a vacuum. Now suppose that the outer gear pulled a vacuum when passing the inlet and the inner gear pulled oil. It's all fine as long as the teeth are separated by the cresent. However, when the crescent ends, the vacuum collapses violently. Collapses such as these can kill propellers etc., so they can kill the 928 oil pump.
I am simplifying of course by ignoring the oil passed by relief valve, but still.
See the photo by Hacker:
So far there are no theories what caused this damage, other than the standard FOD. Here's one.
"Again I tell you, it is easier for a camel to go through the eye of a needle than 27.7 gallons of oil per minute to pass thru that 23mm ID pickup pipe."
So what happens when the pump demand exceeds the flow capacity of that pipe at 1 atmoshpere pressure differential? The pump cavitates. In English, the pump gear teeth pull a vacuum. Now suppose that the outer gear pulled a vacuum when passing the inlet and the inner gear pulled oil. It's all fine as long as the teeth are separated by the cresent. However, when the crescent ends, the vacuum collapses violently. Collapses such as these can kill propellers etc., so they can kill the 928 oil pump.
I am simplifying of course by ignoring the oil passed by relief valve, but still.
05-26-2010, 08:14 AM
#56
Racer
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That's an interesting theory, but the reality of what happened isn't quite as elaborate. Kind of boring actually. A foreign object got sucked up and jammed in the pump, breaking it. Sometimes things really are a lot simpler than they get made out to be. It is kind of entertaining to hear some of the theories that come up in some online discussions though.
It was surely interesting to read about cavitation, but in this picture you can actually see the foreign piece that jammed the pump.
05-26-2010, 08:20 AM
#57
Nordschleife Master
Thread Starter
I was naively thinking that this part was knocked out of the crescent. Just eyeballing the crescent on my pump, it doesn't have as big of a corner cut as this pump. I was putting 2+2 together when I saw the right size piece jamming the pump gears. Did I jump to conclusions?
The pump's owner thinks that's what happenend:
https://rennlist.com/forums/3223373-post5.html
"The part stuck in the teeth is from the little thin piece that runs along the gear on the upper right side (in the last picture)"
My theory was about why the piece got knocked out of the crescent, not about why the pump seized when that piece got stuck between the gears.
The pump's owner thinks that's what happenend:
https://rennlist.com/forums/3223373-post5.html
"The part stuck in the teeth is from the little thin piece that runs along the gear on the upper right side (in the last picture)"
My theory was about why the piece got knocked out of the crescent, not about why the pump seized when that piece got stuck between the gears.
05-26-2010, 03:38 PM
#58
Nordschleife Master
Thread Starter
That's an interesting theory, but the reality of what happened isn't quite as elaborate. Kind of boring actually. A foreign object got sucked up and jammed in the pump, breaking it. Sometimes things really are a lot simpler than they get made out to be. It is kind of entertaining to hear some of the theories that come up in some online discussions though.
05-26-2010, 05:02 PM
#59
Administrator - "Tyson"
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I now have a co-worker that is banned from ever coming withing 50 feet of any of my vehicles, he's broken every one he's ridden in. Even if we didn't make it 2 feet that day.
Sure is a lot of rubber smoke when an oil pump stops spinning
It actually ran fine, cams never went out of time, even with 1/2 of every tooth sheered off.
Z was there for the disection / inspection / finger pointy "look what you did" portion of the FAIL........
05-26-2010, 05:48 PM
#60
Race Director
Here's a quick measurement of the pump displacement. I did this with a caliper and third-grade geometry in the garage, so there's some margin of error. It shouldn't be too far, though.
dimension, inner gear, outer gear
depth, 2.1, 2.1
width , 0.7, 0.7
inner, 0, 1.1
outer, 1.1, 0.7
displacement cc, 0.8085, 1.323
#teeth, 9, 11
cc per pump revolution
21.83
pump sprocket teeth
35
crank sprocket teeth
24
Drive ratio
0.686
cc per crank revolution
14.97
gallons per 1000 crank revolutions
3.95
dimension, inner gear, outer gear
depth, 2.1, 2.1
width , 0.7, 0.7
inner, 0, 1.1
outer, 1.1, 0.7
displacement cc, 0.8085, 1.323
#teeth, 9, 11
cc per pump revolution
21.83
pump sprocket teeth
35
crank sprocket teeth
24
Drive ratio
0.686
cc per crank revolution
14.97
gallons per 1000 crank revolutions
3.95
Great calculations!!!!!!!!!!!!!!!!!!!!!!! This is exactly what I was looking for.... not what some lost manual in german said, but an exact calculation of what is possible!!!
I gotta wonder though what the pumping losses are with oil...I would guess significant, but how much...I dunno....still nearly 4 gallon per 1k...thats HUGE....
It must take significant HP to drive this pump too.....especially at higher RPM...