early dyno results
02-12-2011, 02:06 AM
#121
Former Sponsor
Yes, I agree this engine will easily make 650 HP. If it is making 530HP at 5500 RPM, another 120 HP is very achievable with another 2000 RPM. Start dancing Greg.
Without spilling the beans, can you enlighten us to what the problems were on the dyno. Some here have suggested the Oiling problem causes Rod bearing failures. But reading your posts, you say the engine is still on the dyno cart. So whatever the problem is is did not hurt the engine. If this is the case, loss or lack of presuure cannot be the problem as this is still wet sump nor can it be sealing issue. The only thing I can think of left must be a breathing problem. Looking at your photos it shows the Valve covers with breathers going to the Intake box. Just guessing, but did the engine stop breathing and push all the oil out the breathers? This is an old time issue with wet sump engines. The stock pumps cannot keep up with the excavation of the sump gases and they are really liquid movers not air movers, the sump pressurizes and the oil pumped up into the Heads cannot return to the sump. The heads fill up and is pushed out the breathers.
Tell me how I know this. I been there before. It was solved by doing several things. The sumps (2 engines in my boat) were sucked dry with a scavenge pump and the stock pumps were left to provide the Oil to the engine. The oil sent up to the valve train was restricted and the heads were scavenged with their own pumps. This was used for sometime until I spent the money and the engine dry sumped properely. This was the cleaner way, but the other way did work. The engine was disassemebled after sometime with the first fix and the Piston pins showed some scoring due to the scavenge pumps working alittle too good. This was fixed by limiting the vacuum, but it had to be tested and adjusted.
Hope this is not the case as it cost me a small fortune and the time to do and recheck was costly. I suppose this is the cost of breaking new ground. At least you are doing it on 1 Porsche 928 engine. I was doing it 2 Lambo marine V12 engines.
Good luck. I love the work and the engine looks great. Maybe I need to look into these engines for the boat. At least the cost would be lower. Love to hear from you via PM on what it would cost to build 2 of these for marine use.
Without spilling the beans, can you enlighten us to what the problems were on the dyno. Some here have suggested the Oiling problem causes Rod bearing failures. But reading your posts, you say the engine is still on the dyno cart. So whatever the problem is is did not hurt the engine. If this is the case, loss or lack of presuure cannot be the problem as this is still wet sump nor can it be sealing issue. The only thing I can think of left must be a breathing problem. Looking at your photos it shows the Valve covers with breathers going to the Intake box. Just guessing, but did the engine stop breathing and push all the oil out the breathers? This is an old time issue with wet sump engines. The stock pumps cannot keep up with the excavation of the sump gases and they are really liquid movers not air movers, the sump pressurizes and the oil pumped up into the Heads cannot return to the sump. The heads fill up and is pushed out the breathers.
Tell me how I know this. I been there before. It was solved by doing several things. The sumps (2 engines in my boat) were sucked dry with a scavenge pump and the stock pumps were left to provide the Oil to the engine. The oil sent up to the valve train was restricted and the heads were scavenged with their own pumps. This was used for sometime until I spent the money and the engine dry sumped properely. This was the cleaner way, but the other way did work. The engine was disassemebled after sometime with the first fix and the Piston pins showed some scoring due to the scavenge pumps working alittle too good. This was fixed by limiting the vacuum, but it had to be tested and adjusted.
Hope this is not the case as it cost me a small fortune and the time to do and recheck was costly. I suppose this is the cost of breaking new ground. At least you are doing it on 1 Porsche 928 engine. I was doing it 2 Lambo marine V12 engines.
Good luck. I love the work and the engine looks great. Maybe I need to look into these engines for the boat. At least the cost would be lower. Love to hear from you via PM on what it would cost to build 2 of these for marine use.
Community gain outweighs the problem with people stealing information/ideas.
Go back and watch the video that Rob Edwards posted. We edited the end of the video, but left enough of it, so that the very clever could figure it out.
The far left hand bar graph is oil pressure. Watch it very carefully.
The engine had been running at 6,000 rpms for considerable time, as we programmed it at different loads...but since this engine is going to be run in the open road events, in Nevada, it needs to run for extended time at higher RPMs.
I've never been able to run an engine for this period of time, on a chassis dyno. There simply isn't enough cooling to run something this hard, for this period of time. Even if we could keep the engine cool, the rear tires would overheat and start slinging off chunks of rubber....ask me how I know.
02-12-2011, 02:47 AM
#122
Yes, the engines are very expensive, but believe it, they are not the most expensive part of owning one of these.
Great thread and I'm very interested in this engine. I am interested to see how this ends as the newer P V8 engines are been considered as replacements. We need Torque and the weight is as important.
Great thread and I'm very interested in this engine. I am interested to see how this ends as the newer P V8 engines are been considered as replacements. We need Torque and the weight is as important.
02-12-2011, 02:15 PM
#123
Rennlist Member
Awesome engine build Greg, absolutely stunning results. As to the oiling issue, my eyes can see what's happening, my brain is too small to know anything other than hazard a guess...
Oil pressure starts out at 113 psi, in the first 30 seconds it slowly drops 13 psi to 100 psi.
Takes another 20 seconds to steadily drop 10 more psi to 90 psi. Is all this a result of aeration and/or viscosity thinning as the oil heats up?
In the last 2 seconds it appears the bottom is falling out of the oil pressure and I assume the engine is cut off. Is this a result of the oil being trapped in the heads or being pushed out the breathers? Very interesting, obviously no sweeping turns involved. I'd love to hear everyones theory. Thanks for sharing this Greg.
Oil pressure starts out at 113 psi, in the first 30 seconds it slowly drops 13 psi to 100 psi.
Takes another 20 seconds to steadily drop 10 more psi to 90 psi. Is all this a result of aeration and/or viscosity thinning as the oil heats up?
In the last 2 seconds it appears the bottom is falling out of the oil pressure and I assume the engine is cut off. Is this a result of the oil being trapped in the heads or being pushed out the breathers? Very interesting, obviously no sweeping turns involved. I'd love to hear everyones theory. Thanks for sharing this Greg.
02-12-2011, 02:31 PM
#124
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I think I prefer to know Greg's facts..."I'd love to hear everyones theory. " but agree that this is very interesting. Seems you can learn a LOT on an engine brake dyno too bad we all had to wait so long. Of course that is what Porsche used way back when.....
02-12-2011, 05:18 PM
#125
Supercharged
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OK.
Community gain outweighs the problem with people stealing information/ideas.
Go back and watch the video that Rob Edwards posted. We edited the end of the video, but left enough of it, so that the very clever could figure it out.
The far left hand bar graph is oil pressure. Watch it very carefully.
The engine had been running at 6,000 rpms for considerable time, as we programmed it at different loads...but since this engine is going to be run in the open road events, in Nevada, it needs to run for extended time at higher RPMs.
I've never been able to run an engine for this period of time, on a chassis dyno. There simply isn't enough cooling to run something this hard, for this period of time. Even if we could keep the engine cool, the rear tires would overheat and start slinging off chunks of rubber....ask me how I know.
Community gain outweighs the problem with people stealing information/ideas.
Go back and watch the video that Rob Edwards posted. We edited the end of the video, but left enough of it, so that the very clever could figure it out.
The far left hand bar graph is oil pressure. Watch it very carefully.
The engine had been running at 6,000 rpms for considerable time, as we programmed it at different loads...but since this engine is going to be run in the open road events, in Nevada, it needs to run for extended time at higher RPMs.
I've never been able to run an engine for this period of time, on a chassis dyno. There simply isn't enough cooling to run something this hard, for this period of time. Even if we could keep the engine cool, the rear tires would overheat and start slinging off chunks of rubber....ask me how I know.
As I watched the video again, it is clear that just as the oil pressure was dropping the AFR spiked lean. Went from 12.5 to 14.0. But fuel pressure remained contstant (65psi). So were you leaning things out on purpose?
But this is where I get stuck... How are these two linked together? I need to noodle on this a bit more.
02-12-2011, 05:43 PM
#126
Absolutely correct. We are all guessing as to the problem. If it is known and it is made public we will all then know. In the meantime we all can only summise what was happening.
As for the engine going lean at then end, that may be from just stopping the engine. It seems to be running in the mid to low 12's for most of time. I guess the other times is where the fuelis been adjusted for peak Torque.
Hope we all can learn from this. This is an amazing thread. kepp the info rolling
Thanks Greg for sharing.
As for the engine going lean at then end, that may be from just stopping the engine. It seems to be running in the mid to low 12's for most of time. I guess the other times is where the fuelis been adjusted for peak Torque.
Hope we all can learn from this. This is an amazing thread. kepp the info rolling
Thanks Greg for sharing.
02-13-2011, 04:00 PM
#127
Former Sponsor
Here's some more background of the dyno testing and some observations.
We ran a "928 International" oil deflector plate in the filler neck location. We did not have enough room to run the stock filler neck, so a 5/8" chunk of aluminum was machined down to fit. Into this, we installed an oil filler and vent fitting into the far right hand (1-4 cylinders are right) rear corner. We then attached a -10 hose to this vent fitting and ran it back and up, into the air filter box. Total rise of the vent hose was about 10 inches.
The engine was equiped with our windage trays and pan spacer. We use a GTS oil pan baffle with our windage trays, to further keep the oil from being "disturbed" by the crankshaft, when it is in the oil pan. Other than this, the oiling system was stock. Yes, there are some modifications made to the passages in the cradle, but you will have to buy one of our engines and take it apart, before you know what these are. These modifications are not important, for this discussion, regardless.
Problems with this vent occurred at 4,000 rpms and everything higher. After approximately 60 seconds of running, at these higher rpms, this vent turned into a pretty much steady stream of oil ejection.
After reflecting on this, and looking at the different ways that Porsche dealt with this vent, I'd guess that the crankshaft is pushing and "holding" a solid slug of of oil up into this area of the block....and it has always been a problem. If you have ever looked down at the crankshaft through this opening, you can see #2 and #6 connecting rods (sorry...pointed out to me that these rods are actually #1 and #5...brain fade), almost perfectly centered in this opening. Obviously, the oil spraying off of this "throw" is very significant and gets worse, as the rpms increase.
We have done a complete re-design of the "928 International" oil deflector and will try this new piece, in the next dyno test. I do not have high hopes for ventilation, from this area, since I think it is pretty much a solid mess of oil and air, but it is worth a try. Maintaining crankcase ventilation is a very important thing...but is almost certainly lost at higher rpms on all the Porsche 928 engines as delivered from the factory, and was certainly lost on this engine, when it was on the dyno.
Once you know how this crankcase vent performs at different rpms, what Porsche has done, over the years, begins to make more sense.
The early cars had the ventilation opening in the filler neck pretty much unprotected. Later ('85?) they added a deflector plate that was sandwiched between the filler neck and the block. With the introduction of the '87 models, the filler neck had two openings for ventilation and had a "build-in" oil deflector, with a divider wall built into the filler neck. One ventilation hose ran back to the intake, above the throttle plate and the other hose ran into the valve cover. There is a build in, spring loaded, oil check valve/restrictor in the opening that goes back to the intake. This valve opens and shuts, with changes in air flow. Presumably, this valve allow vapors to escape into the intake system and shuts when the oil "arrives", which directs all of the oil flow to the valve cover.
By the time the GTS engines engine arrived, Porsche had changed this area, again. The filler neck got completely redesigned, as well as the hoses to the valve covers and to the throttle plate area. They eliminated the hose to the valve cover and raised the vent opening as high as possible in the filler neck. They put a significant restriction into this opening. Rob Edwards pointed out that the "early '93" GTS models had an entirely different filler neck/hose arrangement, which I had forgotten. There is a hose that goes from the very top of the filler neck to the right cam cover. There is no restriction in that hose or neck. The left valve cover was still not vented.)
I once thought that this must have been a step forward. I'm now thinking that this might be more of a "we give up" type of thing. I need to look closer at all the iterations, but right now my thinking is that they essentially gave up on ventilation of the crankcase through this area and decided to try and do the majority of crankcase ventilation through the oil return holes in the cylinder heads, instead. This is probably why they attached the previously non-vented driver's valve cover to the passanger side valve cover on the GTS engine. This also might change my mind about why they didn't drill the oil return holes into the pistons. I'd always thought that this was an "oversight" in machining the pistons. I'm now thinking that this might have been an intentional thing.....
I'll let you guys digest this stuff and give it some thought and then move on to the "show stopper".
We ran a "928 International" oil deflector plate in the filler neck location. We did not have enough room to run the stock filler neck, so a 5/8" chunk of aluminum was machined down to fit. Into this, we installed an oil filler and vent fitting into the far right hand (1-4 cylinders are right) rear corner. We then attached a -10 hose to this vent fitting and ran it back and up, into the air filter box. Total rise of the vent hose was about 10 inches.
The engine was equiped with our windage trays and pan spacer. We use a GTS oil pan baffle with our windage trays, to further keep the oil from being "disturbed" by the crankshaft, when it is in the oil pan. Other than this, the oiling system was stock. Yes, there are some modifications made to the passages in the cradle, but you will have to buy one of our engines and take it apart, before you know what these are. These modifications are not important, for this discussion, regardless.
Problems with this vent occurred at 4,000 rpms and everything higher. After approximately 60 seconds of running, at these higher rpms, this vent turned into a pretty much steady stream of oil ejection.
After reflecting on this, and looking at the different ways that Porsche dealt with this vent, I'd guess that the crankshaft is pushing and "holding" a solid slug of of oil up into this area of the block....and it has always been a problem. If you have ever looked down at the crankshaft through this opening, you can see #2 and #6 connecting rods (sorry...pointed out to me that these rods are actually #1 and #5...brain fade), almost perfectly centered in this opening. Obviously, the oil spraying off of this "throw" is very significant and gets worse, as the rpms increase.
We have done a complete re-design of the "928 International" oil deflector and will try this new piece, in the next dyno test. I do not have high hopes for ventilation, from this area, since I think it is pretty much a solid mess of oil and air, but it is worth a try. Maintaining crankcase ventilation is a very important thing...but is almost certainly lost at higher rpms on all the Porsche 928 engines as delivered from the factory, and was certainly lost on this engine, when it was on the dyno.
Once you know how this crankcase vent performs at different rpms, what Porsche has done, over the years, begins to make more sense.
The early cars had the ventilation opening in the filler neck pretty much unprotected. Later ('85?) they added a deflector plate that was sandwiched between the filler neck and the block. With the introduction of the '87 models, the filler neck had two openings for ventilation and had a "build-in" oil deflector, with a divider wall built into the filler neck. One ventilation hose ran back to the intake, above the throttle plate and the other hose ran into the valve cover. There is a build in, spring loaded, oil check valve/restrictor in the opening that goes back to the intake. This valve opens and shuts, with changes in air flow. Presumably, this valve allow vapors to escape into the intake system and shuts when the oil "arrives", which directs all of the oil flow to the valve cover.
By the time the GTS engines engine arrived, Porsche had changed this area, again. The filler neck got completely redesigned, as well as the hoses to the valve covers and to the throttle plate area. They eliminated the hose to the valve cover and raised the vent opening as high as possible in the filler neck. They put a significant restriction into this opening. Rob Edwards pointed out that the "early '93" GTS models had an entirely different filler neck/hose arrangement, which I had forgotten. There is a hose that goes from the very top of the filler neck to the right cam cover. There is no restriction in that hose or neck. The left valve cover was still not vented.)
I once thought that this must have been a step forward. I'm now thinking that this might be more of a "we give up" type of thing. I need to look closer at all the iterations, but right now my thinking is that they essentially gave up on ventilation of the crankcase through this area and decided to try and do the majority of crankcase ventilation through the oil return holes in the cylinder heads, instead. This is probably why they attached the previously non-vented driver's valve cover to the passanger side valve cover on the GTS engine. This also might change my mind about why they didn't drill the oil return holes into the pistons. I'd always thought that this was an "oversight" in machining the pistons. I'm now thinking that this might have been an intentional thing.....
I'll let you guys digest this stuff and give it some thought and then move on to the "show stopper".
Last edited by GregBBRD; 02-14-2011 at 02:21 PM.
02-13-2011, 05:07 PM
#129
Any time you re invent the wheel, there has to be some time spent developing the idea. It's obvious that this is new ground been covered and no one has been here before.
It sound like a simple fix, but there are never simple fixes with engines. However, the first part of solving a problem is knowing what the problem is, then understanding it and finally fixing it. I believe the firsd two are already completed by rerading Greg's last email.
I think many previuos engine failures can be attributed to this very fault and finally someone has found the cause.
It sound like a simple fix, but there are never simple fixes with engines. However, the first part of solving a problem is knowing what the problem is, then understanding it and finally fixing it. I believe the firsd two are already completed by rerading Greg's last email.
I think many previuos engine failures can be attributed to this very fault and finally someone has found the cause.
02-13-2011, 07:52 PM
#131
Former Sponsor
I think that this is what they decided to do with the GTS engines, now that I look very carefully at them, armed with the new information that I learned from the dyno testing. We all know how much oil the GTS engines "push" up into the combustion chambers...and some of this is bound to be from the engine, building crankcase pressure.
I'm going to not only let this vent push out whatever it wants (remember I made a new oil deflector), I'm going to open up the "center" plugged threaded hole, in the valley of the block. Since I don't have a stock intake in the way, I have great access to this hole. It is directly in line with the center main bearing and is "protected" from direct oil spray by the crankcase casting.
I think it is uber important to make sure that the crankcase does not build pressure...and the only way to do that is to keep the vent paths open.
02-13-2011, 08:14 PM
#132
Race Director
I think that this is what they decided to do with the GTS engines, now that I look very carefully at them, armed with the new information that I learned from the dyno testing. We all know how much oil the GTS engines "push" up into the combustion chambers...and some of this is bound to be from the engine, building crankcase pressure.
I'm going to not only let this vent push out whatever it wants (remember I made a new oil deflector), I'm going to open up the "center" plugged threaded hole, in the valley of the block. Since I don't have a stock intake in the way, I have great access to this hole. It is directly in line with the center main bearing and is "protected" from direct oil spray by the crankcase casting.
I think it is uber important to make sure that the crankcase does not build pressure...and the only way to do that is to keep the vent paths open.
I'm going to not only let this vent push out whatever it wants (remember I made a new oil deflector), I'm going to open up the "center" plugged threaded hole, in the valley of the block. Since I don't have a stock intake in the way, I have great access to this hole. It is directly in line with the center main bearing and is "protected" from direct oil spray by the crankcase casting.
I think it is uber important to make sure that the crankcase does not build pressure...and the only way to do that is to keep the vent paths open.
Something like this
http://nutterracingengines.com/racin...uum_facts.html
Of course dry sump is ideal, since it accomplishes the same goal as the vacuum pump wet sump..but is way more $$$ too
02-13-2011, 08:36 PM
#133
Greg,
We measure the Crankcase pressure with the EFI and have limits sets so that if either the pressure gets too high or the oil pressure drops it shuts off the engine. From memory, 1 limit is set to engine speed and the other is set to throttle position. This way the engine cannot be throttled if the crankcase pressure gets too high and the other way the engine is limited to a certain speed if the oil pressure drops or is shut off completely if the pressure drops too low. From your first posts I seem to remember we use the same EFI system you are using. Would probably be a good thing to at least watch on the dyno. I see no reason you could not use a standard MAP sensor for that. As long as it reads negitive and positive pressure, it should work. Real differential type sensors cost $ so this may be a cheaper way to check the mods are working. For those who are racing or having any Oiling or bearing failures, this could be a great addition. You may have the problem, but at least you see it beofre it cost you an engine.
We measure the Crankcase pressure with the EFI and have limits sets so that if either the pressure gets too high or the oil pressure drops it shuts off the engine. From memory, 1 limit is set to engine speed and the other is set to throttle position. This way the engine cannot be throttled if the crankcase pressure gets too high and the other way the engine is limited to a certain speed if the oil pressure drops or is shut off completely if the pressure drops too low. From your first posts I seem to remember we use the same EFI system you are using. Would probably be a good thing to at least watch on the dyno. I see no reason you could not use a standard MAP sensor for that. As long as it reads negitive and positive pressure, it should work. Real differential type sensors cost $ so this may be a cheaper way to check the mods are working. For those who are racing or having any Oiling or bearing failures, this could be a great addition. You may have the problem, but at least you see it beofre it cost you an engine.
02-13-2011, 08:49 PM
#134
Nordschleife Master
I find your information very interesting Greg.
I have believed that the slung, and suspended oil has a great deal to do with the oil problems we always see in our motors.
On push rod motors, they normally take a pickup off the valve cover. However pushrods have significantly less oil in the top end of the motor. Which is why they normally have coked oil up there!
However the 928 has a steady bath of oil in the top end of the motor. This makes air extraction here difficult.
Like you I had thought about removing the center, or all 3 of the plugs above the mains. I elected not to do this because a) they are small, this means that the air speed will be high. This then means that the oil will remain suspended in the air for longer. b) all the air surrounding those areas are in a constant froth, meaning they will be the same as the stock filler port directly above the #2/6.
On a 16V car I did, I used Ken's block off plate with an o-ring grove. I then cut a hole in it, and used a 2" or 1.5" pipe cut at a 45 through the plate. I had to pinch the pipe to fit inside the filler neck. I then put a 90 at the top and ran this along the V to the back of the motor. I cut up a stock 16V filler bottle and welded it to the pipe. I then put a few copper scrubbers in the filler neck.
The logic behind it is that with the pipe being such a large diameter will cause such a slow air speed that the oil will become unsuspended and will be returned to the crankcase. Even running this car right up to 7100RPM there was zero oil injection. This is also the only breather on the system.
I have found for a street car with mild abuse a 1" breather hose connected to a 3" air oil separator with a 1" exit hose will result in zero oil ejection/usage. However this is not nearly enough for track duty!
I do feel that a crank scraper could help to keep the oil cloud down to a minimum with no ill effects. But I do not feel it is enough.
Greg,
I would be interested in having you make a similar breather system for the crankcase with the pipe cut at a 45, and run to the back of the motor with a 3" canister at the back with a couple copper scrubbers in it. Try it with 2x 1" breather ports coming off it. I would be interested in hearing what you get for oil ejection on that motor.
I have believed that the slung, and suspended oil has a great deal to do with the oil problems we always see in our motors.
On push rod motors, they normally take a pickup off the valve cover. However pushrods have significantly less oil in the top end of the motor. Which is why they normally have coked oil up there!
However the 928 has a steady bath of oil in the top end of the motor. This makes air extraction here difficult.
Like you I had thought about removing the center, or all 3 of the plugs above the mains. I elected not to do this because a) they are small, this means that the air speed will be high. This then means that the oil will remain suspended in the air for longer. b) all the air surrounding those areas are in a constant froth, meaning they will be the same as the stock filler port directly above the #2/6.
On a 16V car I did, I used Ken's block off plate with an o-ring grove. I then cut a hole in it, and used a 2" or 1.5" pipe cut at a 45 through the plate. I had to pinch the pipe to fit inside the filler neck. I then put a 90 at the top and ran this along the V to the back of the motor. I cut up a stock 16V filler bottle and welded it to the pipe. I then put a few copper scrubbers in the filler neck.
The logic behind it is that with the pipe being such a large diameter will cause such a slow air speed that the oil will become unsuspended and will be returned to the crankcase. Even running this car right up to 7100RPM there was zero oil injection. This is also the only breather on the system.
I have found for a street car with mild abuse a 1" breather hose connected to a 3" air oil separator with a 1" exit hose will result in zero oil ejection/usage. However this is not nearly enough for track duty!
I do feel that a crank scraper could help to keep the oil cloud down to a minimum with no ill effects. But I do not feel it is enough.
Greg,
I would be interested in having you make a similar breather system for the crankcase with the pipe cut at a 45, and run to the back of the motor with a 3" canister at the back with a couple copper scrubbers in it. Try it with 2x 1" breather ports coming off it. I would be interested in hearing what you get for oil ejection on that motor.
02-13-2011, 09:16 PM
#135
Supercharged
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Interesting...
But I still don't understand the significance of why the 2/6 bearing is the one affected. I'll re-read Greg's explanation a few more time to internalize it a bit more.
Thanks to Tony, when I had my motor out, he suggested and built for me a simple baffle to keep the oil from plugging up the breather setup. Here a a number of shots from back when he did it for me. It's basically a couple of plates for the oil the hit and run back down into the sump.
Here's pics.
But I still don't understand the significance of why the 2/6 bearing is the one affected. I'll re-read Greg's explanation a few more time to internalize it a bit more.
Thanks to Tony, when I had my motor out, he suggested and built for me a simple baffle to keep the oil from plugging up the breather setup. Here a a number of shots from back when he did it for me. It's basically a couple of plates for the oil the hit and run back down into the sump.
Here's pics.