Crank Scraper/Windage Tray at Road America
05-23-2006, 03:40 PM
#31
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Originally Posted by Kevin Johnson
Originally Posted by BrendanC
Kevin -
...................................
If the sump was up to an inch from the motor, would this help even more?
...................................
If the sump was up to an inch from the motor, would this help even more?
05-23-2006, 04:01 PM
#32
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Originally Posted by Kevin Johnson
............................ One of the related areas to breather systems is piston bay to piston bay pumping losses -- pumping losses can also occur with breather systems because work is being performed as air is actively pushed in and out of the port(s).
Did you know that the 5.4 GTS blocks have bay to bay breathing holes in the main webs which the 4.7/5.0 engines don't have , obviously Porsche thought it necessary to put them in for a reason, just for the extra stroke ?
Heres some info I found on the Chevy LS6 engine on bay to bay breathing problems
Chevy LS6 redesign
05-23-2006, 04:27 PM
#33
Developer
Thread Starter
C.F. - That may be a good point. However - the GTS has higher oil consumption than other 928 models.... usually attributed to the piston oil scraper ring groove not being bored thru all the way, so the oil can not be removed and depositied inside the skirt like most normal pistons.
Still - bay to bay breathing is an interesting point you are making...
Still - bay to bay breathing is an interesting point you are making...
05-23-2006, 04:35 PM
#34
Nordschleife Master
I've got a few facts, factoids, suggestions and theories to add to this:
Sterling: Don't do that. You need a catch can before the lowered octane cracks your rings. Trust me on this.
Mark: If you've got them, post some pics of you special car's (special?) oil pan.
I've had oil consumption problems since track day 1 with my car. Like most people tracking 16v cars I've found that if filled to the dipstick line about 1/2 quart gets puked out in the first two or three laps. At the track I never fill to more than a half quart low. Some guys run it a full 1qt low.
I do tend to rev the engine up. The Euro S power peak is high with dyno runs on my car showing a power peak right about at 6K rpm. The rev limiter cuts in about 6400 rpm. Not terribly high by some standards and I make sure to keep it down in corners. Certainly no hard left-handers at high rpms. I use the Amsoil racing oil and never see the oil pressure bobble or go below 4bar when on the track.
I installed the crank scraper (both sides but no sump cover) along with a GTS baffle this Winter. At the first track session of the year the oil consumption (ejection) went from 1qt/hr to over 2qt/hr of running time. This is what was missing from the sump. My catch can was overflowing so not a good measure. A huge problem and setback to be sure.
Thinking about the design of the scraper I got some performance stats and a calculator out. What I found was really disturbing both for the scraper and the 928 in general. The first point of interest was the drain channels on the scraper. The original versions were just slightly sloped, maybe 2 or 3 degrees. Looking at the performance numbers for the car, the full-throttle acceleration of the vehicle in any gear is greater than the gravitational force pulling the oil down the channels. What this means is that whenever I've got the pedal down (often!) the oil is being fed into the rear of the pan. That are is very shallow. My theory is that so much oil was being delivered there that it was pooling up and coming into direct contact with the whirring connecting rods. Poof! Amsoil frappe!
Let me say that Kevin has been great about this all and I'm expecting a new set of channels this week for a trial run at Heartland Park June 3rd. The new design has more slope and includes a wire mesh to resist backwards flow of the oil.
Having run the numbers on the scraper channels, it made me think about the pan itself. The pan is just slightly sloped descending about 1/2" over 13". At that slope the oil is being force backwards at full throttle in all gears except 5th. That'd be 95% of the time the pedal is down. So for those fun 2-3-4 runs NO oil is running down into the sump. It's running to the back of the pan and, once again, creating an Amsoil mousse.
A further analysis that I've yet to perform is on the oil being forced out of the sump and into the shallow part of the pan. Under forwards, or lateral, acceleration the oil in the pan will move to an angle of repose of atan( lat g's / 1 ). For example, if you're cornering at 1g (we'll get close to that) the oil is canted at 45 degrees. If you're accelerating at 1/4g the oil is canted at 15 degrees from horizontal. If the sump is full then a whole bunch of oil is going to leave the sump and run to the back of the pan. That'll hit the rotating parts and get turned into an aerosol quick enough.
I'm still planning to modify my benchracer.xls spreadsheet to calculate how much oil the pan can hold while accelerating and how high the ejected amount is piled at the rear of the sump. This won't include dynamics effects (sorry MEs!) but will be pretty instructive.
As the car can experience higher g's in corners it's clear that the real killer mode is powering out of those exit speed turns. The design of the pan is asymmetrical with the right side being lower. This explains why people report more problems in left-handers; more oil is leaving the sump.
Based on these observations and analysies, I believe that the combination of broad, shallow sump with a lightly sloped pan in close proximity to the rotating assemply is the main cause of oiling problems on the 928.
There are a few questions that come from this. One that's been hit on in this thread is why different cars perform differently. I believe that's a function of several factors including driving style, track specifics, blow-by rate and how much oil is draining from the heads. As to my own oiling problems, while the engine was recently rebuilt the car has 175k miles so the lifters and cam bearings are worn. My home track is Brainerd Intl which is 3miles long and includes a straight of almost exactly 1 mile. Combine extra leaking in the heads with a nice 3-4-5 run to 140+ gives time and the oil will get extra frothy.
The most important question is what to do about it. The most clear solution is to use a dry sump. Another solution I've considered is a dry rear sump with a pump to the front sump. Call it a half-dry sump.
What I'm going to try next is a more practical solution. This is to add a top to the sump that keeps the oil in under forwards and lateral acceleration. Some people have already done this but it's not been tracked to my knowledge. The cover will replace the stock screen cover. It will be roughly U-shaped and extend out about 3" from each side. This will prevent the oil from climbing out. To prevent the windage from blowing oil off the flat cover I'll be putting a GTS baffle over the flat cover.
Here are some pics of the scraper and the GTS baffle:
http://home.earthlink.net/~bigdadglen/carpics/id10.html
The cover will be in addition to the crank scraper with new channels. One knocks down the windage and the other keeps the liquid in the sump. Get the combination working and the catch can will be dry.
This is all about keeping the oil in a liquid form and keeping more in the sump. I believe that's the basic problem with the 2/6 bearing failure. Either the pick-up gets a gulp of foam or is exposed to directly to the air.
Sterling: Don't do that. You need a catch can before the lowered octane cracks your rings. Trust me on this.
Mark: If you've got them, post some pics of you special car's (special?) oil pan.
I've had oil consumption problems since track day 1 with my car. Like most people tracking 16v cars I've found that if filled to the dipstick line about 1/2 quart gets puked out in the first two or three laps. At the track I never fill to more than a half quart low. Some guys run it a full 1qt low.
I do tend to rev the engine up. The Euro S power peak is high with dyno runs on my car showing a power peak right about at 6K rpm. The rev limiter cuts in about 6400 rpm. Not terribly high by some standards and I make sure to keep it down in corners. Certainly no hard left-handers at high rpms. I use the Amsoil racing oil and never see the oil pressure bobble or go below 4bar when on the track.
I installed the crank scraper (both sides but no sump cover) along with a GTS baffle this Winter. At the first track session of the year the oil consumption (ejection) went from 1qt/hr to over 2qt/hr of running time. This is what was missing from the sump. My catch can was overflowing so not a good measure. A huge problem and setback to be sure.
Thinking about the design of the scraper I got some performance stats and a calculator out. What I found was really disturbing both for the scraper and the 928 in general. The first point of interest was the drain channels on the scraper. The original versions were just slightly sloped, maybe 2 or 3 degrees. Looking at the performance numbers for the car, the full-throttle acceleration of the vehicle in any gear is greater than the gravitational force pulling the oil down the channels. What this means is that whenever I've got the pedal down (often!) the oil is being fed into the rear of the pan. That are is very shallow. My theory is that so much oil was being delivered there that it was pooling up and coming into direct contact with the whirring connecting rods. Poof! Amsoil frappe!
Let me say that Kevin has been great about this all and I'm expecting a new set of channels this week for a trial run at Heartland Park June 3rd. The new design has more slope and includes a wire mesh to resist backwards flow of the oil.
Having run the numbers on the scraper channels, it made me think about the pan itself. The pan is just slightly sloped descending about 1/2" over 13". At that slope the oil is being force backwards at full throttle in all gears except 5th. That'd be 95% of the time the pedal is down. So for those fun 2-3-4 runs NO oil is running down into the sump. It's running to the back of the pan and, once again, creating an Amsoil mousse.
A further analysis that I've yet to perform is on the oil being forced out of the sump and into the shallow part of the pan. Under forwards, or lateral, acceleration the oil in the pan will move to an angle of repose of atan( lat g's / 1 ). For example, if you're cornering at 1g (we'll get close to that) the oil is canted at 45 degrees. If you're accelerating at 1/4g the oil is canted at 15 degrees from horizontal. If the sump is full then a whole bunch of oil is going to leave the sump and run to the back of the pan. That'll hit the rotating parts and get turned into an aerosol quick enough.
I'm still planning to modify my benchracer.xls spreadsheet to calculate how much oil the pan can hold while accelerating and how high the ejected amount is piled at the rear of the sump. This won't include dynamics effects (sorry MEs!) but will be pretty instructive.
As the car can experience higher g's in corners it's clear that the real killer mode is powering out of those exit speed turns. The design of the pan is asymmetrical with the right side being lower. This explains why people report more problems in left-handers; more oil is leaving the sump.
Based on these observations and analysies, I believe that the combination of broad, shallow sump with a lightly sloped pan in close proximity to the rotating assemply is the main cause of oiling problems on the 928.
There are a few questions that come from this. One that's been hit on in this thread is why different cars perform differently. I believe that's a function of several factors including driving style, track specifics, blow-by rate and how much oil is draining from the heads. As to my own oiling problems, while the engine was recently rebuilt the car has 175k miles so the lifters and cam bearings are worn. My home track is Brainerd Intl which is 3miles long and includes a straight of almost exactly 1 mile. Combine extra leaking in the heads with a nice 3-4-5 run to 140+ gives time and the oil will get extra frothy.
The most important question is what to do about it. The most clear solution is to use a dry sump. Another solution I've considered is a dry rear sump with a pump to the front sump. Call it a half-dry sump.
What I'm going to try next is a more practical solution. This is to add a top to the sump that keeps the oil in under forwards and lateral acceleration. Some people have already done this but it's not been tracked to my knowledge. The cover will replace the stock screen cover. It will be roughly U-shaped and extend out about 3" from each side. This will prevent the oil from climbing out. To prevent the windage from blowing oil off the flat cover I'll be putting a GTS baffle over the flat cover.
Here are some pics of the scraper and the GTS baffle:
http://home.earthlink.net/~bigdadglen/carpics/id10.html
The cover will be in addition to the crank scraper with new channels. One knocks down the windage and the other keeps the liquid in the sump. Get the combination working and the catch can will be dry.
This is all about keeping the oil in a liquid form and keeping more in the sump. I believe that's the basic problem with the 2/6 bearing failure. Either the pick-up gets a gulp of foam or is exposed to directly to the air.
05-23-2006, 04:42 PM
#35
Developer
Thread Starter
How easy it is to overfill...
Here's one to knock you back a bit:
The variables in dipsticks. See photos below - three 928 dipsticks, all lined up exactly the same on the handle end - all with different "add oil" and "full points" .
I took these to my motor last night and used them all one at a time. I had answers from "you are between the add and fill lines" to "add a pint" to "you are a pint below the ADD mark".
The dipstick with the yellow hose over the end is 78/79. The dipstick in the center with the longest handle is NOS part number 92810773711 . The dipstick at the top is the most common one I see.
Point is, too many of us have reported that the "right" oil level seems to be 1 pint down on our 928's... and something as simple as this could be why.
The variables in dipsticks. See photos below - three 928 dipsticks, all lined up exactly the same on the handle end - all with different "add oil" and "full points" .
I took these to my motor last night and used them all one at a time. I had answers from "you are between the add and fill lines" to "add a pint" to "you are a pint below the ADD mark".
The dipstick with the yellow hose over the end is 78/79. The dipstick in the center with the longest handle is NOS part number 92810773711 . The dipstick at the top is the most common one I see.
Point is, too many of us have reported that the "right" oil level seems to be 1 pint down on our 928's... and something as simple as this could be why.
Last edited by Carl Fausett; 05-23-2006 at 05:10 PM.
05-23-2006, 05:04 PM
#36
So basically, whatever the hell is happening in the sump, as long as you have a good solid flow of un-aerated oil to the regular oil pump, you could drive upside down and sideways at 3gs. Sounds great. Thats a dry sump.
Can Mark Anderson give us some pics of the pan that he uses?
As Jim Bailey has always said - a very nice oil can could be put into the passenger side fender area where the windshield fluid reservior is - this is if you think haveing a tank in the passenger footwell is too much.
Can Mark Anderson give us some pics of the pan that he uses?
As Jim Bailey has always said - a very nice oil can could be put into the passenger side fender area where the windshield fluid reservior is - this is if you think haveing a tank in the passenger footwell is too much.
05-23-2006, 05:06 PM
#37
With a tiny starter, it seems that most of the pan could be redesigned, except for the dimentions needed to get over the k-member.
05-23-2006, 05:09 PM
#38
Developer
Thread Starter
More Fuel to the Oil-Level fire
Q: why does the capacities chart show 8 quarts w/o oil filter and 8.5 with, yet makes no allowances for the Euro and its remote oil cooler and oil lines? Surely the remote oil cooler and lines would suggest that a 928 thus equipped would neet a little more oil... wouldn't it?
Q: is the volume of all the oil pans the same? I think not (but I am not sure), so if you go swapping them around you may have to watch it.
Q: do you add another 3 Qts because you have a 3 Qt Accusump accumulator?
Actually, no, you don't. And how much do you add to fill the plumbing to/from your accumulator?
In my case, I have a M28/41 block (32v), fitted with 16v heads. The previous owner pulled the late-model dipstick tube and tapped the block for an early model dipstick tube. I hope the dipstick tube is the right height, but if it is too high, I am overfilling the engine. I am using a 78 oil pan because it has all my fittings and senders already in it. Do I use the 78 dipstick to match the pan/sump... or a 32v dipsrtcik to match the motor?
Swaybar - when you said "there are to many variables" you hadn't even seen it all.
Then add more oil because of the Accusump and hoses? And the electric valve for the Accusump - wired to the key or wired to separate switch? It wouldn't be the first time an engine has been "overfilled" by an Accusump that was not used correctly.
Then the Accusump electric valve.. Installed at the oil filter (lot of hose capacity behind it) or installed at the accumulator?
Yikes!
When I started the Frankensteinian package the first time, I added 8 qts and disconnected the coil wire. Cranked it over till I saw pressure. Added oil again till "full" on the stick. Started it up, after a minute, check oil level again now that oil cooler, lines, Accusump, heads and camtowers, etc, were full and purged.
I wish I had a site glass in the oil pan. Then I would mark the dipstick where I see it is just at top of sump and before it starts to overflow onto the long flat sloping plane to the rear.
Oh yes... one more variable... how much does motor oil expand when heated? Enough so that a cold motor will register down a pint while the same motor hot will show more? This one I don't know....
Q: is the volume of all the oil pans the same? I think not (but I am not sure), so if you go swapping them around you may have to watch it.
Q: do you add another 3 Qts because you have a 3 Qt Accusump accumulator?
Actually, no, you don't. And how much do you add to fill the plumbing to/from your accumulator?
In my case, I have a M28/41 block (32v), fitted with 16v heads. The previous owner pulled the late-model dipstick tube and tapped the block for an early model dipstick tube. I hope the dipstick tube is the right height, but if it is too high, I am overfilling the engine. I am using a 78 oil pan because it has all my fittings and senders already in it. Do I use the 78 dipstick to match the pan/sump... or a 32v dipsrtcik to match the motor?
Swaybar - when you said "there are to many variables" you hadn't even seen it all.
Then add more oil because of the Accusump and hoses? And the electric valve for the Accusump - wired to the key or wired to separate switch? It wouldn't be the first time an engine has been "overfilled" by an Accusump that was not used correctly.
Then the Accusump electric valve.. Installed at the oil filter (lot of hose capacity behind it) or installed at the accumulator?
Yikes!
When I started the Frankensteinian package the first time, I added 8 qts and disconnected the coil wire. Cranked it over till I saw pressure. Added oil again till "full" on the stick. Started it up, after a minute, check oil level again now that oil cooler, lines, Accusump, heads and camtowers, etc, were full and purged.
I wish I had a site glass in the oil pan. Then I would mark the dipstick where I see it is just at top of sump and before it starts to overflow onto the long flat sloping plane to the rear.
Oh yes... one more variable... how much does motor oil expand when heated? Enough so that a cold motor will register down a pint while the same motor hot will show more? This one I don't know....
05-23-2006, 05:35 PM
#39
I think the wider border is great idea (opinion) - Kevin - what can you tell is about the issue of the oil draining back, and any issues with making that pan cover very tight?
05-23-2006, 05:39 PM
#40
Originally Posted by Kevin Johnson
This tells me that Porsche did not fully understand what was going on either.
Porsche is a brand, and we cannot rely on that brand for anymore sound oil-control engineering principles in 1971 (when the engine was designed in basic form I believe) then we could rely on the Taliban for Childcare priniciples. When they designed this engine, they had dry sump engines, no? They had flat fours and flat sixes - with separate sumps.
If people want to continue racing with these, then it IS time to reinvent the wheel.
Thats my .02 ounces of aerated oil.
05-23-2006, 05:41 PM
#41
I have the baffle in the box still. I hope to implement any changes you guys find out are needed before i put it in.
05-23-2006, 05:45 PM
#42
Originally Posted by Sterling
the bummer for me is that if I want to make any changes to the sump baffle I have to pull the engine. I went with studs on the oil pan.....grrrr
But thats a great excuse to do the whole new list of things I know you have.
05-23-2006, 05:56 PM
#43
Developer
Thread Starter
I have Kevin's full-boat everything installed. crank scaper on both sides, oil drops, windage tray.
Glen has the L and R side scrapers and the drops.
Glen has the L and R side scrapers and the drops.
05-23-2006, 06:02 PM
#44
Nordschleife Master
Kevin,
Those look great.
I was originally going to go with only a flat plate. You mentioned not having the flowing oil exposed like that in an email. Then I thought about a sandwich of two plates, ~2cm apart, with possibly the top one being tighter around the sump. Then I realized that the GTS baffle was just about that.
Email me regarding those parts and shipping. Thanks so much.
Brendan, Venturing a guess on the crank, I think the extra drilling is most important for high RPM operation.
Those look great.
I was originally going to go with only a flat plate. You mentioned not having the flowing oil exposed like that in an email. Then I thought about a sandwich of two plates, ~2cm apart, with possibly the top one being tighter around the sump. Then I realized that the GTS baffle was just about that.
Email me regarding those parts and shipping. Thanks so much.
Brendan, Venturing a guess on the crank, I think the extra drilling is most important for high RPM operation.
05-23-2006, 06:15 PM
#45
Drifting
ive installed something like the flat plate in my GTS engine, over the open part of the sump with a hole for the oil pickup. where are any pics of mark andersons drysump? surely this isnt propritary info and it could be usefull for any of us who would like to take resolving the oiling issues a stage further!