Stroker Scraper Kit
10-27-2009, 08:29 PM
#31
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I have a question about the scraper. There's a scraping blade on both sides of the crank. When the crank turns and whips oil with it, one of the blades will scrape oil below the blade and into the sump. That's good. However, the other blade will scrape oil above the blade. How will the system guide this oil that is scraped onto the upper side of the blade into the sump?
Scraping adhering surface oil off is a low to medium rpm function. At higher rpms you are disrupting the pressure differential and allowing a lower equilibrium of suspended oil in the cloud. The released oil droplets have quite a velocity.
10-27-2009, 08:35 PM
#32
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I hope i am using the word "unidirectional" correctly. I mean a one-way screen. It is designed so that the oil passes thru quickly in one way, but not quickly in the other.
Yes, if a crank scraper system is designed poorly, it can do more harm than good. Just like if a dry sump oil pan and system is designed poorly it will also do more harm than good.
Yes, if designed correctly, both wet sump and dry sump systems can be successful. Crank scrapers are common to both. Windage trays are usually found only in wet sump applications.
Crank scrapers and windage trays have a lot of documentation available all over the internet on many many engines spanning many many years. I dont want to debate it here. Personally, I dont think there is any question that they work.
They are known to: increase HP by reducing the oil cloud that the bottom of the crankshaft must power through; reduce the amount of entrained air in the oil which provides two benefits: better lubrication of the bearings and lowered oil temps.
Again - consult Google for all the info you need about crank scrapers. I just wanted to share that a scraper for the stroker crank is in progress and will be commercially available shortly.
Yes, if a crank scraper system is designed poorly, it can do more harm than good. Just like if a dry sump oil pan and system is designed poorly it will also do more harm than good.
Yes, if designed correctly, both wet sump and dry sump systems can be successful. Crank scrapers are common to both. Windage trays are usually found only in wet sump applications.
Crank scrapers and windage trays have a lot of documentation available all over the internet on many many engines spanning many many years. I dont want to debate it here. Personally, I dont think there is any question that they work.
They are known to: increase HP by reducing the oil cloud that the bottom of the crankshaft must power through; reduce the amount of entrained air in the oil which provides two benefits: better lubrication of the bearings and lowered oil temps.
Again - consult Google for all the info you need about crank scrapers. I just wanted to share that a scraper for the stroker crank is in progress and will be commercially available shortly.
10-27-2009, 08:43 PM
#33
Race Director
just to clarify my neither of the 928 engines I destroyed had a scraper.....the 1st was 100% stock and let go at 94k miles......the 2nd version of that engine failed due to a component failure....I DO NOT think Doc Browns windage trays or spacer had anything to do with it.....there is no evidence that would indicate a problem with that product....
10-27-2009, 08:46 PM
#34
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Based on what I've read on the internet, I would have assumed that the best way to install two scrapers would be as follows:
Attachment 395239
This way, the scraped oil from both scrapers will shoot to the sump.
Attachment 395239
This way, the scraped oil from both scrapers will shoot to the sump.
Now, I understand that scraping is not the only concern with 928. It may be that what that second horizontal scraper is really doing is stopping the oil from surging from that side when the car corners. I don't know. I assume Kevin Johnson had his reasons. However, I am wondering about how the oil accumulating on top of the second horizontal scraper is supposed to find its way to the sump.
10-27-2009, 09:03 PM
#35
Nordschleife Master
Originally Posted by ptuomov: "I have a question about the scraper. There's a scraping blade on both sides of the crank. When the crank turns and whips oil with it, one of the blades will scrape oil below the blade and into the sump. That's good. However, the other blade will scrape oil above the blade. How will the system guide this oil that is scraped onto the upper side of the blade into the sump?"
You mean besides the blasting air pushing it at around 120 mph?
So if I am following you, the spinning crank, oil, and air causes a low pressure area. I guess you'd call that a windage cloud. This low pressure area sucks in more oil in it and the windage cloud grows. The system has some equilibrium size of windage cloud, the amount of oil that is suspended in the whole mess. If you introduce an obstruction, such as a scraper, it slows down the cloud and therefore reduces the sucking low pressure area, making the equilibrium cloud size smaller. Did I misunderstand you?
Is your point that it doesn't much matter on which side the scraper is, as long as it slows down the air? If that's the point, then I guess you and Greg Brown disagree about this. (At least by my interpretation of his post, shouldn't be putting words into anybody's mouth.)
In any case, the screen in what Carl calls the 2008 version does block the fins in the bottom of the oil pan. Is there no cost to this? Or is there a cost, but a benefit that more than offsets the cost? What's the mechanism by which an engine that has your system installed pushes oil towards the front of the sump? Just gravity?
10-27-2009, 09:06 PM
#36
Nordschleife Master
This question came up on SpeedTalk or Engineering Tips some years back, I think. A tangential scraper will release oil with less hydrodynamic loss. A right angle scraper will intrude more deeply into the rotating assembly and disrupt the pressure differential better.
10-27-2009, 09:11 PM
#37
Nordschleife Master
10-27-2009, 09:13 PM
#38
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Yes, I seem to recall an engineer from Ford SVO questioning the idea behind the Teflon scraper. He related that they had a nice windage control system for the Cobra engine but accounting deemed it too expensive. They went with a Canton pan. Nice crew at Canton.
He related that they had a nice windage control system for the Cobra engine but accounting deemed it too expensive. They went with a Canton pan. Nice crew at Canton.
10-27-2009, 09:18 PM
#39
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Yes, I am curious too. The vertical ribs in the pan act as scrapers. Same design elements in the 944, 968 and 924 Audi based engine. Mercedes uses that general design as well. Ford as well. Oh yes, Dodge did too on the Neon 2.0. Better stop.
10-27-2009, 10:00 PM
#40
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Interesting.
So if I am following you, the spinning crank, oil, and air causes a low pressure area. I guess you'd call that a windage cloud. This low pressure area sucks in more oil in it and the windage cloud grows. The system has some equilibrium size of windage cloud, the amount of oil that is suspended in the whole mess. If you introduce an obstruction, such as a scraper, it slows down the cloud and therefore reduces the sucking low pressure area, making the equilibrium cloud size smaller. Did I misunderstand you?
So if I am following you, the spinning crank, oil, and air causes a low pressure area. I guess you'd call that a windage cloud. This low pressure area sucks in more oil in it and the windage cloud grows. The system has some equilibrium size of windage cloud, the amount of oil that is suspended in the whole mess. If you introduce an obstruction, such as a scraper, it slows down the cloud and therefore reduces the sucking low pressure area, making the equilibrium cloud size smaller. Did I misunderstand you?
Is your point that it doesn't much matter on which side the scraper is, as long as it slows down the air? If that's the point, then I guess you and Greg Brown disagree about this. (At least by my interpretation of his post, shouldn't be putting words into anybody's mouth.)
The Merlin V12 did have a scraper for its dry sump -- so about 70 years ago.
In any case, the screen in what Carl calls the 2008 version does block the fins in the bottom of the oil pan. Is there no cost to this? Or is there a cost, but a benefit that more than offsets the cost? What's the mechanism by which an engine that has your system installed pushes oil towards the front of the sump? Just gravity?
The situation with the GM LS V8 engine is similar in many ways to that of the Porsche V8. There are similar elements in the architecture and the failure modes.
10-27-2009, 10:19 PM
#41
Rennlist Member
Tuomo,
It sounds like you are assuming that the scraped oil that flows through the windage screen has to hit the pan fins with some sort of velocity? What's the difference if the oil hits the floor of the factory pan after passing through a windage screen? It seems that this would help the stock pan fins work better. Oil that passes through the windage screen will have a better chance of staying adhered to the floor of the pan and following the fins instead of getting sucked back up into the windage cloud before having a chance to make it to the sump.
It sounds like you are assuming that the scraped oil that flows through the windage screen has to hit the pan fins with some sort of velocity? What's the difference if the oil hits the floor of the factory pan after passing through a windage screen? It seems that this would help the stock pan fins work better. Oil that passes through the windage screen will have a better chance of staying adhered to the floor of the pan and following the fins instead of getting sucked back up into the windage cloud before having a chance to make it to the sump.
10-27-2009, 10:22 PM
#42
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BTW, I'm currently going through the effort of modifying a 5L I/J scraper to fit my stroker.
It is a Godsend that Carl is taking the time to make this a repeatable event. It is very tedious work, and my cuts into the scraper to clear the stroker are not going to be as well made as the machining and edge treatment that Kevin give the scrapers before they leave his shop.
Nice job Carl, thanks for taking the time to develop this.
It is a Godsend that Carl is taking the time to make this a repeatable event. It is very tedious work, and my cuts into the scraper to clear the stroker are not going to be as well made as the machining and edge treatment that Kevin give the scrapers before they leave his shop.
Nice job Carl, thanks for taking the time to develop this.
10-27-2009, 11:28 PM
#43
Nordschleife Master
The situation with the 928 sump floor is so severe. With the 944/968 they were able to drop the floor a further 4mm. In those systems I cut back the screening to allow the factory components to work. It is part of my design philosophy to try to retain factory components if at all possible. The windage systems for the Nissan KA24E and DE have the screening cut back to allow the louvers in the pan floor (another tray) to work.
If I install that pan spacer, the problem you refer to with the sump floor becomes less severe. Without understanding the issues completely and thinking out loud, would that extra clearance give room to make the factory angled vertical ribs (or scrapers or fins or whatever) to work? My instinct would be to extend those vertical ribs higher up to use the proverbial tornado to blow the oil into the deep end of the sump.
Last edited by ptuomov; 10-27-2009 at 11:53 PM.
10-27-2009, 11:49 PM
#44
Nordschleife Master
Tuomo, It sounds like you are assuming that the scraped oil that flows through the windage screen has to hit the pan fins with some sort of velocity? What's the difference if the oil hits the floor of the factory pan after passing through a windage screen? It seems that this would help the stock pan fins work better. Oil that passes through the windage screen will have a better chance of staying adhered to the floor of the pan and following the fins instead of getting sucked back up into the windage cloud before having a chance to make it to the sump.
What I was thinking is that if the oil rotates with the crankshaft and then hits the vertical pan fin at speed, it would get forcefully deflected forward towards the deep end of the sump. That's because the fins are angled at about 45 degrees.
The shallow section of oil pan is basically flat. You definitely don't want the oil staying in the flat section. The car will accelerate close to 1g (ok, wishful thinking), which means that the oil surface would naturally want to be at a 45-degree angle. That would not be pretty, imagine the rear end of the crankshaft is submerged and the oil pickup is sucking wind! ;-) Somehow, the oil has to be forced towards the front end of the sump against its will.
In my limited imagination, I can't see any other way how the oil is going to actually go and stay in the deep end of the sump other than something pumping it there. It seems to me that the factory engineers intended that something to be the crankshaft.
10-28-2009, 12:11 AM
#45
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I have a pan spacer made by Mike Simard. It will drop the pan 3/8" or about 9.5mm. That creates some room. It's similar to what Greg Brown and Louie Ott have on their web sites.
If I install that pan spacer, the problem you refer to with the sump floor becomes less severe. Without understanding the issues completely and thinking out loud, would that extra clearance give room to make the factory angled vertical ribs (or scrapers or fins or whatever) to work? My instinct would be to extend those vertical ribs higher up to use the proverbial tornado to blow the oil into the deep end of the sump.
If I install that pan spacer, the problem you refer to with the sump floor becomes less severe. Without understanding the issues completely and thinking out loud, would that extra clearance give room to make the factory angled vertical ribs (or scrapers or fins or whatever) to work? My instinct would be to extend those vertical ribs higher up to use the proverbial tornado to blow the oil into the deep end of the sump.
Sure, it is possible. $ and time.