New oil control solution for Race/ORR/SC/Stroker/GTS/GT/CS/SE/S4/S3 928 Engines
05-10-2011, 12:45 PM
#151
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Not trying to be snarky so early in the morning, Kevin, but, uh, what??
I think it's a very good question and would be interested in your thoughts, as I know exactly zero about 16V 928 engines.
I think it's a very good question and would be interested in your thoughts, as I know exactly zero about 16V 928 engines.
05-10-2011, 01:12 PM
#152
I think greg mentioned the early motors in that the breathers in the 2V don't go near the cam boxes, so the oil packing happens but is not affecting the system in the same way. The 2V drinks oil like a drunk at St. Patty's day in its own way - through that huge hole at the front of the motor.
05-10-2011, 01:15 PM
#153
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Bearing failure at 2/6 has never been exclusive to 16V head engines. If it were we'd all be talking about NASA 928 Spec racing.
Last edited by Kevin Johnson; 05-10-2011 at 02:05 PM.
05-10-2011, 01:48 PM
#154
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I still dont see any unusual oil consumption on any of the 928s Ive owned and raced , nor scots engines that he has raced for many years. generally, my s4 would burn or lose 1 quart over a racing weekend and driving on the street, over the winter months, about 1 quart for about 1000 miles. that number seems to be the same for the stroker engine I have now.
I did put the vent hoses in a vertical extension postion, so if the oil is pumped up into it, it might not make it through the "loop" and then the oil would retreat back into the valve covers. Iwas thinking of making these tubes longer and making them into "coils". that way, there would be a much greater distance and vertical too for the oil to travel. (picture a coil of vent tube, as high as the intake plennum, for both breather lines). this way, you get a pretty high volume of oil to catch, but then it returns to the engine due to gravity and you dont have to emtpy a vent can.
you hear how I drive my car. very high rpm downshifts, redline upshifts, moderate RPM around high speed sweepers, street driving is 100mph , WOW every single weekend, a few times too.
I did put the vent hoses in a vertical extension postion, so if the oil is pumped up into it, it might not make it through the "loop" and then the oil would retreat back into the valve covers. Iwas thinking of making these tubes longer and making them into "coils". that way, there would be a much greater distance and vertical too for the oil to travel. (picture a coil of vent tube, as high as the intake plennum, for both breather lines). this way, you get a pretty high volume of oil to catch, but then it returns to the engine due to gravity and you dont have to emtpy a vent can.
you hear how I drive my car. very high rpm downshifts, redline upshifts, moderate RPM around high speed sweepers, street driving is 100mph , WOW every single weekend, a few times too.
05-10-2011, 01:58 PM
#155
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Lots of discussion!
Alex, while a logical next step might be a dry-sump package, there are some serious space considerations that make the dry sump pretty much a non-option for street cars. Like where to put the oil tank. Most serious race groups have restrictions on oil tank locations in the passenger compartment, so we are limited to what will fit in the rear of the front fender. On the driver's side (LHD cars...) there's a vacuum bottle and the cruise control servo. On Rob's car, the passenger side location was chosen for the oil separator, but he sacrificed the washer tank that normally lives there. Those that use the washer tank for an intercooler reservoir don't have that option. IIRC, Mark A's race car has the oil tank in the rear of the driver's fender area, but the fender area there is enlarged a few inches in width. Continuing, the oil pickups in the head need to be supplemented by oil pickups in the corners or at least the ends of the sump, so there are three or additional pump stages needed, beyond what Greg has now on the two GTS motors. This assumes that you are plumbing the oil tank to the stock oil pump for the pressure duty.
-----
One thing that jumped to mind after watching Rob's SITP demo is that we were seeing oil accumulation in the heads with cruise-level RPM's and no load on the engine. Any blowby that increases under load would choke the return drains even sooner than the 2500 or so RPM that we observed during the demo. Those of us with stock street-only pre-GTS engines are likely saved from some of the obvious effects of the head flooding carryover because we only have one, restricted, vapor return hose from the the passenger-side cam cover; the driver's side has plugs. The rest of the vapors are extracted from the oil filler area, above the louvered baffle. The GTS engines and those modified with the GTS breather system have a second vapor pickup on the driver's side cam cover. Still, the nozzle-elbows that the factory used have small openings inside, something like 4mm diameter, with the much larger ID hoses attached. Kind of deceptive.
Alex, while a logical next step might be a dry-sump package, there are some serious space considerations that make the dry sump pretty much a non-option for street cars. Like where to put the oil tank. Most serious race groups have restrictions on oil tank locations in the passenger compartment, so we are limited to what will fit in the rear of the front fender. On the driver's side (LHD cars...) there's a vacuum bottle and the cruise control servo. On Rob's car, the passenger side location was chosen for the oil separator, but he sacrificed the washer tank that normally lives there. Those that use the washer tank for an intercooler reservoir don't have that option. IIRC, Mark A's race car has the oil tank in the rear of the driver's fender area, but the fender area there is enlarged a few inches in width. Continuing, the oil pickups in the head need to be supplemented by oil pickups in the corners or at least the ends of the sump, so there are three or additional pump stages needed, beyond what Greg has now on the two GTS motors. This assumes that you are plumbing the oil tank to the stock oil pump for the pressure duty.
-----
One thing that jumped to mind after watching Rob's SITP demo is that we were seeing oil accumulation in the heads with cruise-level RPM's and no load on the engine. Any blowby that increases under load would choke the return drains even sooner than the 2500 or so RPM that we observed during the demo. Those of us with stock street-only pre-GTS engines are likely saved from some of the obvious effects of the head flooding carryover because we only have one, restricted, vapor return hose from the the passenger-side cam cover; the driver's side has plugs. The rest of the vapors are extracted from the oil filler area, above the louvered baffle. The GTS engines and those modified with the GTS breather system have a second vapor pickup on the driver's side cam cover. Still, the nozzle-elbows that the factory used have small openings inside, something like 4mm diameter, with the much larger ID hoses attached. Kind of deceptive.
05-10-2011, 02:08 PM
#156
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Yes, no doubt about the location being a problem. We put Rob's there, because he wanted his engine bay to look as stock as possible. That Provent hanging out front doesn't look very stock, but it sure is easy to get to, when it is there. We're doing something a bit different on the "oil return hose" off of the bottom, but that could be plumbed.
I don't see any problem of putting it where DR did. I'd need to think about the plumbing, but initially I'd think all that would be required is....less hose. Perhaps I could get DR to make a "modified Provent" kit for my pumping system and he could handle that part of the kit/pieces. I certainly would not want to make any pieces that he could/should provide....Lord knows there is enough of that happening, in this small 928 world, already.
I don't see any problem of putting it where DR did. I'd need to think about the plumbing, but initially I'd think all that would be required is....less hose. Perhaps I could get DR to make a "modified Provent" kit for my pumping system and he could handle that part of the kit/pieces. I certainly would not want to make any pieces that he could/should provide....Lord knows there is enough of that happening, in this small 928 world, already.
Great Job on tackling those oiling issues in the heads!!
I had starting seeing some of the issues you came across a little over a year ago. Ironically it was the 16V engines that made it more obvious to me at first.
But yeah, for those that haven't seen how much oil will pump out of the heads under the right conditions...it is quite surprising.
Due to that I redesigned the entire SharkVent product line in March of last year (which reminds me, all the SV diagrams etc on the website are still the older version and I need to update them). As a side bonus these changes also simplified the system and made it easier to install (even more "less hose" :-).
Back to the subject of the location for the ProVent for your new system. I would be happy to send you one of my Provent mounting bracket/hardware setups if you want to work out the plumbing of your system to the front of the engine. Just give me or Jeannie a yell and we will send you one out to try, no charge.
Just as a guess from what I see of your system so far I don't think you (or your customers) would need much more than the ProVent mount to make it all work together. But I will gladly send you anything you may need to help give everyone options for the ProVent location with your system.
Keep up the great work as always!!
Cheers,
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05-10-2011, 02:20 PM
#157
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I still dont see any unusual oil consumption on any of the 928s Ive owned and raced , nor scots engines that he has raced for many years. generally, my s4 would burn or lose 1 quart over a racing weekend and driving on the street, over the winter months, about 1 quart for about 1000 miles. that number seems to be the same for the stroker engine I have now.
05-10-2011, 06:27 PM
#158
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Here I disagree (unless I'm misunderstanding what you're saying), I think that the ejection was certainly unmasked by the long extensions, but even if you put no breather extensions on the elbows to minimize oil ejection into the intake, you're still running around at sustained high rpm with quarts of oil in the heads. Add in some aeration from the windage cloud, some lateral g-forces and these damned 1978-1995 factory pans that are 20 mm too shallow 
, and some combination of all of these factors have to be killing all the engines that are indeed getting killed.
, and some combination of all of these factors have to be killing all the engines that are indeed getting killed.So, Greg observed huge oil ejection and an oil pressure drop. Why did the pressure drop? Was it due simply to oil packing in the heads or was the oil ejection, brought about by installing the 4 shrouds, a major contributor? Anyway, I still don't know whether scavenging is essential or whether the oil in un-modded head will drain adequately to prevent oil starvation. Once Greg observed huge oil ejection and pressure drop he went down the path of sucking out the oil and returning it to the pan, unless I missed some other parts of the experiment. I'm saying as far as I know it could be an artifact of installing the shrouds.
You might have noticed I normally don't get involved in these complex areas or comment directly on vendor products (although Greg is technically not a vendor I guess and there is no kit yet, but I gather it is planned), and I had just casually observed all the discussion of this system without saying anything, period. However, I started to get concerned when I saw some of the comments that implied that you and Dr. Bob, whom I regard among the most level-headed and truly sincere and most admired people on this board, were starting to believe this system would benefit your street cars. It seemed that the real meaning of the "demo" oil suckage might be getting smeared in our minds and you and Dr. Bob started to associate oil levels in your pans after driving around the state with whether you had this system installed or not. I really don't think there is any reason yet to expect this system to reduce oil consumption notably or affect oil pressure no matter how hard you drive on the street. Take out the cam breather shrouds or oil suction tubes and then tell me what happens.
05-10-2011, 06:38 PM
#159
I don't think Greg put any sort of scraping or shrouding on the engines in question. Only spacers and splash grills under the crank.
05-10-2011, 06:41 PM
#160
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put it this way. I buy a case of amsoil when i do the oil change. I put 9 quarts in and then save the 3 quart for top off. after 3 racing weekends and a 1000street miles, i finallly run out of oil.
05-10-2011, 06:55 PM
#161
@ Bill Ball -
I think it can be acceded that oil anywhere other than the pan in large quantities is not a good thing, right?
So if oil is in the heads, that's bad, using that logic.
A couple reasons are that if enough oil goes into the heads and does not return to the sump because of the difference in pressure (crank area is pressurized, head area is NOT as pressurized) then eventually, you are "pumping" oil into the heads and not getting it back until you return to lower RPMs.
Having oil just SIT there in the heads causes the valve seals to possibly be overworked, and can POSSIBLY or DOES cause all sorts of issues with the lifters and cams. Is not the idea of a lubricated system to have ENOUGH oil but not TOO MUCH?
Reading some of the responses more recently in this thread is confusing to me. In any 928 I have driven (maybe 20 all together) and owned and drive (I think 9 now), I have burned oil that has entered the intake. In every single 928 I have seen the throttle body on, there is oil sitting in a puddle in there.
So the 928 system, in its stock form, is consistently sucking oil into the combustion chamber.
The only issue is how much, and this is determined by the rpms and the cornering forces applied.
Catch cans put a kink in this process, but as some have said - certain people have required catch cans for their catch cans - which to me means that the oil ejection from the heads (which is where the oil is coming from if its not in the sump being pulled into the bearings) is a constant process.
I drive in the higher rpm ranges on a regular basis because its...fun. So I may use more oil than most. But I use alot of it, no matter the mileage of the engine. So its being sucked into the intake. Which means its in the heads. Alot of it.
I think that keeping the oil level lower in the heads, and keeping the oil out of the intake is Number 2 and 1 in the level of over-all importance. Ancillary but still important is that as you raise the power and compression and tuning levels, the disasterousness of burning oil instead of gas at high RPM increases in orders of magnitude.
It is one man's contention (many of us know) that the pressure in the crankcase on any of these engines is directly correlated to the constant small amounts of detonation. Even stock engines - too much blow by because when you attempt to blow the fuel when the piston is still going up, baring the head gasket blowing, the pressure has to go somewhere, and its going past the rings. Into the crank case. Which is where the pressure is going to be higher, thereby causing pressure to push up into the heads - making the heads fill with UNdrainable oil.
Which then makes the breathers suck in oil into the intake. Which then makes the combustion chamber blow off early because oil is what, 25 octane?
And that causes detonation. And the cycle starts over again.
It would be interesting to fit this system to a STOCK blocked and stock oil panned 928 32V motor and run it for a good hard track season. Maybe add in a drilled crank because we know that's pretty important as well.
I think it can be acceded that oil anywhere other than the pan in large quantities is not a good thing, right?
So if oil is in the heads, that's bad, using that logic.
A couple reasons are that if enough oil goes into the heads and does not return to the sump because of the difference in pressure (crank area is pressurized, head area is NOT as pressurized) then eventually, you are "pumping" oil into the heads and not getting it back until you return to lower RPMs.
Having oil just SIT there in the heads causes the valve seals to possibly be overworked, and can POSSIBLY or DOES cause all sorts of issues with the lifters and cams. Is not the idea of a lubricated system to have ENOUGH oil but not TOO MUCH?
Reading some of the responses more recently in this thread is confusing to me. In any 928 I have driven (maybe 20 all together) and owned and drive (I think 9 now), I have burned oil that has entered the intake. In every single 928 I have seen the throttle body on, there is oil sitting in a puddle in there.
So the 928 system, in its stock form, is consistently sucking oil into the combustion chamber.
The only issue is how much, and this is determined by the rpms and the cornering forces applied.
Catch cans put a kink in this process, but as some have said - certain people have required catch cans for their catch cans - which to me means that the oil ejection from the heads (which is where the oil is coming from if its not in the sump being pulled into the bearings) is a constant process.
I drive in the higher rpm ranges on a regular basis because its...fun. So I may use more oil than most. But I use alot of it, no matter the mileage of the engine. So its being sucked into the intake. Which means its in the heads. Alot of it.
I think that keeping the oil level lower in the heads, and keeping the oil out of the intake is Number 2 and 1 in the level of over-all importance. Ancillary but still important is that as you raise the power and compression and tuning levels, the disasterousness of burning oil instead of gas at high RPM increases in orders of magnitude.
It is one man's contention (many of us know) that the pressure in the crankcase on any of these engines is directly correlated to the constant small amounts of detonation. Even stock engines - too much blow by because when you attempt to blow the fuel when the piston is still going up, baring the head gasket blowing, the pressure has to go somewhere, and its going past the rings. Into the crank case. Which is where the pressure is going to be higher, thereby causing pressure to push up into the heads - making the heads fill with UNdrainable oil.
Which then makes the breathers suck in oil into the intake. Which then makes the combustion chamber blow off early because oil is what, 25 octane?
And that causes detonation. And the cycle starts over again.
It would be interesting to fit this system to a STOCK blocked and stock oil panned 928 32V motor and run it for a good hard track season. Maybe add in a drilled crank because we know that's pretty important as well.
05-10-2011, 07:01 PM
#162
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Hi Rob:
I'm more like a lay person when it comes to this stuff. Heck, I am a lay person! The oil ejection at even 4500 RPM was very impressive, like you said, but it's important that the lay public not think that is representative of what comes out of a stock cam cover breather at that speed or any speed. The stock breather shrouds (extensions) inside the cam cover only occupy 2 of the 4 breathers. Since in a stock system there is nothing below the level of the cam cover roof on two of the breathers, nothing like this ejection happens at 4500 RPM, and only a small fraction of this ejection occurs at even sustained 6000+ RPM. It's only when you install tubes extending down into the oil pool on all 4 breather openings, sealing off the breathers from breathing any air, that you see massive ejection, powered by positive crankcase pressure. Contrary to what you are assuming, there are not 4 breather extentions in Rob's engine, so what you are seeing/saw is representative of how much oil is actually piling up inside the cam cover, at 4,500. We did try breather extentions on all four cam cover breathers, on Andys' engine...for one test. All that ended up showing us was how full the heads were actually getting. We got lucky here. If we hadn't had those extentions in place, more oil would have been "pushed" into the heads and we would have possibly not learned what the problem was...but just thought we had high rpm oil pressure problems, like everyone else has assumed, for the past 20 years.
I can drive for a year and 15,000 miles with a mixture of hard driving including many bursts of redline acceleration and sustained episodes at 4500 RPM (130 MPH) and not lose any measurable amount of oil and not have any oil pressure issues suggestive of pickup exposure. It takes me 100 miles at an average of 152 MPH (with long periods at 165+) to blow out 1-2 qts (and at least half of that appears to be valve stem seal related based on catch can collections compared to total loss - my intake was sealed from the breathers which went to catchcans). And despite whatever oil packing, I never see any evidence of oil pickup starvation. Nor do Tim and Cheryl despite exceeding 200 MPH regularly. Still, under those ORR conditions, this system would provide a good benefit if it prevents consuming 1-2 qts of oil. But that could be done much more simply. Under street driving conditions, it becomes rather useless. So, for you I think this system is performing an unnecessary task. I'm not sure it will do much for Andy other than prevent a couple of quarts of of oil from getting burned (that's still a very good thing) as the massive ejection the system has to handle is largely an artifact of the 4 long breather shrouds/pickups extending into the oil pool. Had only the two stock shrouds been installed, there never would have been massive liquid oil ejection. Yes, there would have been some oil packing in the heads, and I gather some think this is responsible for engine failures on the Autobahn. I'm not convinced from my ORR observations. My takeaway has been not to install shrouds on all 4 cam breathers. Yes, I still have a problem, but it's not massive. Please correct any misconception in the above. I'm not saying that anyone tried to say oil ejection was a real problem, but you can see how it might be misconstrued. (EDIT: In a subsequent message below, Dr, Bob seems to suggest his S4 might benefit from this oil control system. I think that's a bit too far of a stretch.) Tim and Cheryl's car will be no different than any other 928. It will "pack" the heads full and push oil into the intake. If you check with Tim, he will confirm that his engine uses almost 2 quarts of oil in one "pass" on the ORR events.The only salvation of that engine is the Accusump. It "replaces" the oil that is "packed" into the heads. I'd guess that the oil level, even with the Accusump, is getting very critical by the end of this event. I'd guess that engine failure would occur, if the event was even slightly longer.
In my car the vast majority of oil I collected in catchcans in ORR was not from the cam cover breathers but was from oil slung up by the crank into the oil filler neck and breathers. Greg's system addresses that largely by sealing off those breathers or routing them into the Provent. Completely incorrect. Not only is the breather in the filler neck enlarged and very active, but we have added an additonal breather into the top of the crankcase. Neither goes to the Provent. Keep in mind that one of the goals was to keep the crankcase from getting pressurized.. I think that area should be attacked more directly. I know there are a variety of "diverters", but the problem has been nobody has specifically looked at and dealt with this phenomenon in detail.
I'm more like a lay person when it comes to this stuff. Heck, I am a lay person! The oil ejection at even 4500 RPM was very impressive, like you said, but it's important that the lay public not think that is representative of what comes out of a stock cam cover breather at that speed or any speed. The stock breather shrouds (extensions) inside the cam cover only occupy 2 of the 4 breathers. Since in a stock system there is nothing below the level of the cam cover roof on two of the breathers, nothing like this ejection happens at 4500 RPM, and only a small fraction of this ejection occurs at even sustained 6000+ RPM. It's only when you install tubes extending down into the oil pool on all 4 breather openings, sealing off the breathers from breathing any air, that you see massive ejection, powered by positive crankcase pressure. Contrary to what you are assuming, there are not 4 breather extentions in Rob's engine, so what you are seeing/saw is representative of how much oil is actually piling up inside the cam cover, at 4,500. We did try breather extentions on all four cam cover breathers, on Andys' engine...for one test. All that ended up showing us was how full the heads were actually getting. We got lucky here. If we hadn't had those extentions in place, more oil would have been "pushed" into the heads and we would have possibly not learned what the problem was...but just thought we had high rpm oil pressure problems, like everyone else has assumed, for the past 20 years.
I can drive for a year and 15,000 miles with a mixture of hard driving including many bursts of redline acceleration and sustained episodes at 4500 RPM (130 MPH) and not lose any measurable amount of oil and not have any oil pressure issues suggestive of pickup exposure. It takes me 100 miles at an average of 152 MPH (with long periods at 165+) to blow out 1-2 qts (and at least half of that appears to be valve stem seal related based on catch can collections compared to total loss - my intake was sealed from the breathers which went to catchcans). And despite whatever oil packing, I never see any evidence of oil pickup starvation. Nor do Tim and Cheryl despite exceeding 200 MPH regularly. Still, under those ORR conditions, this system would provide a good benefit if it prevents consuming 1-2 qts of oil. But that could be done much more simply. Under street driving conditions, it becomes rather useless. So, for you I think this system is performing an unnecessary task. I'm not sure it will do much for Andy other than prevent a couple of quarts of of oil from getting burned (that's still a very good thing) as the massive ejection the system has to handle is largely an artifact of the 4 long breather shrouds/pickups extending into the oil pool. Had only the two stock shrouds been installed, there never would have been massive liquid oil ejection. Yes, there would have been some oil packing in the heads, and I gather some think this is responsible for engine failures on the Autobahn. I'm not convinced from my ORR observations. My takeaway has been not to install shrouds on all 4 cam breathers. Yes, I still have a problem, but it's not massive. Please correct any misconception in the above. I'm not saying that anyone tried to say oil ejection was a real problem, but you can see how it might be misconstrued. (EDIT: In a subsequent message below, Dr, Bob seems to suggest his S4 might benefit from this oil control system. I think that's a bit too far of a stretch.) Tim and Cheryl's car will be no different than any other 928. It will "pack" the heads full and push oil into the intake. If you check with Tim, he will confirm that his engine uses almost 2 quarts of oil in one "pass" on the ORR events.The only salvation of that engine is the Accusump. It "replaces" the oil that is "packed" into the heads. I'd guess that the oil level, even with the Accusump, is getting very critical by the end of this event. I'd guess that engine failure would occur, if the event was even slightly longer.
In my car the vast majority of oil I collected in catchcans in ORR was not from the cam cover breathers but was from oil slung up by the crank into the oil filler neck and breathers. Greg's system addresses that largely by sealing off those breathers or routing them into the Provent. Completely incorrect. Not only is the breather in the filler neck enlarged and very active, but we have added an additonal breather into the top of the crankcase. Neither goes to the Provent. Keep in mind that one of the goals was to keep the crankcase from getting pressurized.. I think that area should be attacked more directly. I know there are a variety of "diverters", but the problem has been nobody has specifically looked at and dealt with this phenomenon in detail.
I just spent two solid months of my life looking at all the little details of this problem...Rob isn't telling people everything. No need to go into all the little details that we discovered...especially not here.
However, we are not guessing here....this stuff is fact. I've done it. I've watched it. I've measured it.
The heads fill up with oil. This gets worse as the rpm's increase. Eventually, the crankcase gets completely separated from the heads, due to blockage. Crankcase "pressure rises, significantly. Significant amounts of oil get "pushed" into the intake system. Eventually, so much oil will collect in the heads that the pan will not have enough oil in it that the pick-up will be uncovered and suck oil. Engine failure follows shortly, after that.
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
05-10-2011, 07:14 PM
#163
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Bill--
I wasn't at all promoting the system as something needed on street-only cars. For the miles I drive and the oil consumed, it would only take me, uh, carry the six, uh, 48 brazillian years to save back the cost of the oil. And that calculation assumes 30% annual increases in oil costs. I just wanted to relate the oil consumption numbers that Rob posted to what I saw with the stock breathers, under almost the same road conditions and driven distance. I don't have a horse in this race except as an interested observer.
But for you go-fast ORR guys, Greg's method might save your engine a lot, and in more ways than the obvious oil-consumption improvement. Just looking at George's supercharged car, there's a bit of sdditional oil venting going on with the extra hoses and connectors over the valve covers, and what looks like a couple separators including a ProVent. Seems like the supercharged car would be even more sensitive to oil vapor carryover and related detonation. You guys are Sharktuning to get performance nailed and also to limit detonation, so you know what's at stake as far as power with the timing retarded a bit on knocks. Is the GB scavenging and venting system capable of letting you run faster/harder/longer? I suspect so, but it's only a suspicion. You guys with the Sharktuner are in a much better position to look at timing and knocks and spark retard events, and how much oil ends up in the bottom of the intake manifold to be drawn through the engine.
I wasn't at all promoting the system as something needed on street-only cars. For the miles I drive and the oil consumed, it would only take me, uh, carry the six, uh, 48 brazillian years to save back the cost of the oil. And that calculation assumes 30% annual increases in oil costs. I just wanted to relate the oil consumption numbers that Rob posted to what I saw with the stock breathers, under almost the same road conditions and driven distance. I don't have a horse in this race except as an interested observer.
But for you go-fast ORR guys, Greg's method might save your engine a lot, and in more ways than the obvious oil-consumption improvement. Just looking at George's supercharged car, there's a bit of sdditional oil venting going on with the extra hoses and connectors over the valve covers, and what looks like a couple separators including a ProVent. Seems like the supercharged car would be even more sensitive to oil vapor carryover and related detonation. You guys are Sharktuning to get performance nailed and also to limit detonation, so you know what's at stake as far as power with the timing retarded a bit on knocks. Is the GB scavenging and venting system capable of letting you run faster/harder/longer? I suspect so, but it's only a suspicion. You guys with the Sharktuner are in a much better position to look at timing and knocks and spark retard events, and how much oil ends up in the bottom of the intake manifold to be drawn through the engine.
05-10-2011, 07:24 PM
#164
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Greg:
Unfortuantely nothing you've said above changes my view. Whether Rob had 4 shrouds or not means very little. Whether Tim and Cheryl burn two quarts in ORR means little if you do not know where it is coming from. And two quarts in 100 miles, even if from the breathers, is not massive oil ejection and could be dealt with other ways. I burn it too and I have shown it's largely not from the breathers in my car when supercharged, and the part that is comes largely from the filler neck (and despite Mark's plate). Yes, there's oil in the heads and you say de facto that is bad. There's going to be oil in the heads no matter. Had you never created the oil ejection with the shrouds and observed the pressure drop you would never have gotten real concerned about that. As much time as you spent on this, I don't think we know some critical things. That didn't bother me at all until I saw the sideways drift into comments implying this might help a street car, and I finally felt I had to say something. I dare say I drive my street car harder than 99% of other drivers, and I've fussed a bit over oil issues, but I just don't think at this point there is any relevance of this system to street cars and not for my car in ORR and I think not for Tim and Cheryl's. They have the benefit of a 2.2 rear end and don't exceed 6K RPM. Anyway that's up to them. What I think only matters to me, and you can see I am on the highly skeptical end of the spectrum. Carry on. Jim Morton often is irked by me not immediately buying what he says despite his engineering degree and years of experience dealing with the issues at hand too.
Unfortuantely nothing you've said above changes my view. Whether Rob had 4 shrouds or not means very little. Whether Tim and Cheryl burn two quarts in ORR means little if you do not know where it is coming from. And two quarts in 100 miles, even if from the breathers, is not massive oil ejection and could be dealt with other ways. I burn it too and I have shown it's largely not from the breathers in my car when supercharged, and the part that is comes largely from the filler neck (and despite Mark's plate). Yes, there's oil in the heads and you say de facto that is bad. There's going to be oil in the heads no matter. Had you never created the oil ejection with the shrouds and observed the pressure drop you would never have gotten real concerned about that. As much time as you spent on this, I don't think we know some critical things. That didn't bother me at all until I saw the sideways drift into comments implying this might help a street car, and I finally felt I had to say something. I dare say I drive my street car harder than 99% of other drivers, and I've fussed a bit over oil issues, but I just don't think at this point there is any relevance of this system to street cars and not for my car in ORR and I think not for Tim and Cheryl's. They have the benefit of a 2.2 rear end and don't exceed 6K RPM. Anyway that's up to them. What I think only matters to me, and you can see I am on the highly skeptical end of the spectrum. Carry on. Jim Morton often is irked by me not immediately buying what he says despite his engineering degree and years of experience dealing with the issues at hand too.
05-10-2011, 07:35 PM
#165
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Dr. Bob: I think if you consumed that much oil in a short trip at mostly sub-Autobahn speeds, it's not likely the stock breather system. My car has recently started to show oily soot on it's white tail end. I clean it off and it's back in a few days/weeks of hard driving. I'm planning on installing some custom cams later this year. I thnk it's time for valve stem seals (general head refresh). When I had my supercharger installed, I started lately to get oily grunge inside the manifold over time. That manifold and throttle were not plumbed with any breather tubes, further evidence I have an oil source other than the breather system. You might too.
No rocket science needed, here. I'm using pretty much simple logic.
Not sure if you've noticed, but 928 intake systems always are absolutely "dripping" with oil, everytime they are opened/removed. Hell, most are so full that if you "tilt" the intake when you remove it, oil will run all over the fender covers.
Pretty sure this is a "universal" problem and there isn't some ghost running around my shop squirting oil into every intake that I have removed for the past 25 years....
Also, I've never found a "separate" little "oil filler" for the intake system...so I've had to assume that this oil comes from the oiling system for the engine.
Where do you think it comes from???....and why don't you think that enough of this oil gets pushed into the intake that it mixes with the air and burns? You think only enough to completely coat the inside of the intake gets pushed in there and it stops, once the intake is full?
If we went over to Dr. Bob's house and pulled the air flow meter, the bottom of his plenum would be dripping with oil, after this trip. Guaranteed.
That's exactly where his oil wemt. Heads got filled and oil got pushed into the intake.