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I am still not convinced about the oil pump and the oil level. But please consider me as not an expert. However I can be easily convinced by the right technical reasoning.
From what I understood from the earlier answers I derive that the oil pump is perfectly able to PROVIDE pressure. Given that there is enough oil to supply.
Supply is affected negatively by aeration. But is it sure that suction power on the supply side for the pump when the oil level is much lower compared to the pump.
For example it would be interested to compare output pressures in a test set-up when the pump position is 5 cm lower or higher.
Again I have no practical knowledge about these type of pumps. And I am unable to find some additional info about this. So I am
happy to believe that it makes no difference if someone can confirm this from his expert knowledge.
I am still not convinced about the oil pump and the oil level. But please consider me as not an expert. However I can be easily convinced by the right technical reasoning.
From what I understood from the earlier answers I derive that the oil pump is perfectly able to PROVIDE pressure. Given that there is enough oil to supply.
Supply is affected negatively by aeration. But is it sure that suction power on the supply side for the pump when the oil level is much lower compared to the pump.
For example it would be interested to compare output pressures in a test set-up when the pump position is 5 cm lower or higher.
Again I have no practical knowledge about these type of pumps. And I am unable to find some additional info about this. So I am
happy to believe that it makes no difference if someone can confirm this from his expert knowledge.
What you are playing with by moving the pump inlet up or down in the sump is net positive suction head (NPSH). Moving the pickup without lowering the pump does nothing to increase NPSH. Even moving the pump inlet down further does nothing for pump performance when discussing a positive displacement pump, until the point where the pump inlet pressure is below the vapor pressure of the liquid. Read up on NPSH for positive displacement pumps and you will better understand.
Gents, I solved this problem. I had a dry sump kit for sale for a couple years. I had about 10 sales and gave up on it. It is too expensive for this market, and not usable on a street car. I sold kits for $8500 and barely made money on it. The tech support alone made it not worth the trouble. This market wants an easy solution that can be installed in a day for under $3000.
IT IS NOT EVER GOING TO HAPPEN.
Most of the content of this thread is completely, 100% wrong. Just guys talking on the internet.
If you want your M96 to have oil pressure in all conditions, contact me. I have what's necessary to make that happen, but it costs as much as a decent used Boxster S. Also, even after you solve this problem, there are other technical issues standing in the way of GT3 type reliability.
Don't bother with the intermediate steps like sumps, auxiliary pumps, and Accusumps. They are a waste of time and money.
Good for you! You made your point.
But I think it is not because you solved it that we cannot talk anymore about alternatives or even just discuss the technicalities of the problem.
Good for you! You made your point.
But I think it is not because you solved it that we cannot talk anymore about alternatives or even just discuss the technicalities of the problem.
You guys are not actually doing that. You are just rehashing the same crap that's been on Rennlist for 20 years.
I am still not convinced about the oil pump and the oil level. But please consider me as not an expert. However I can be easily convinced by the right technical reasoning.
From what I understood from the earlier answers I derive that the oil pump is perfectly able to PROVIDE pressure. Given that there is enough oil to supply.
Supply is affected negatively by aeration. But is it sure that suction power on the supply side for the pump when the oil level is much lower compared to the pump.
For example it would be interested to compare output pressures in a test set-up when the pump position is 5 cm lower or higher.
Again I have no practical knowledge about these type of pumps. And I am unable to find some additional info about this. So I am
happy to believe that it makes no difference if someone can confirm this from his expert knowledge.
Originally Posted by rockhouse66
What you are playing with by moving the pump inlet up or down in the sump is net positive suction head (NPSH). Moving the pickup without lowering the pump does nothing to increase NPSH. Even moving the pump inlet down further does nothing for pump performance when discussing a positive displacement pump, until the point where the pump inlet pressure is below the vapor pressure of the liquid. Read up on NPSH for positive displacement pumps and you will better understand.
Rockhouse66 is right, moving the pump or inlet up or down a small amount will not have much effect as long as its not extreme enough to cause a dramatic lose of inlet pressure or cavitation.
For a scientific look at forces/pressures, and for simplification assume water and oil weight the same instead of oil weighing less by 0.91..
Start with Atmospheric pressure of 14.7 at sea level
Then with engine running, subtract crankcase vacuum of about -4 inches of water ( if using the UAOS) which equals 0.15 psi..so 14.7-0.15 =down to 14.55 psi on the surface of the oil..
Then to see the pressure at the bottom of the sump/pick up tube, add the inches of water/oil column, say 4 inches depth , So 4 inches wc or oc = 0.15psi so 14.55+0.15-14.7 ,so back to 14.7 psi at the pickup tube/bottom sump.
Then if the pump rotates enough to remove trapped air from the pickup tube, the oil level will rise to surface level with no additional suction needed.
Then if the pump inlet center is located 1 inch above oil surface level, then the pump will only need to lift 1 In water column or oil column to reach the pump inlet,To lift 1 inch requires a suction or negative 0.037psi. So the absolute pressure at the pump inlet would = 14.663psi. at sea level.
On the outlet side of the pump the pressure is determined by the efficiency of the pump and the pump volume, and is developed by the resistance to flow using clearance and oil viscosity.
For the track, isn’t one solution to use racing oil at the track? Aren’t there oils that simply don’t aerate nearly as much as good ol’ Mobil 1 (Street) oil?
As Jake said, it doesn’t solve the temperature problem, but then again, racing oil can generally withstand higher temps anyway.
You guys are not actually doing that. You are just rehashing the same crap that's been on Rennlist for 20 years.
Not really, just because it hasn't been much improvement in 20 years doesn't make it impossible. The AOS hadn't received any technical advancement in 20 years until I designed and invented the UAOS, you can look here. https://ultimateaos.com/
I agree the factory concept of " Integrated Dry Sump" missed the mark, but with a little technical advancement it will work .
Last edited by Porschetech3; 09-24-2020 at 05:50 PM.
So, the investigation continues. I had one of the scavenge pumps out today for inspection/measurement. It's properly worn(177k km) so a new is on order. So, what would the effect be of a worn scavenge pump?
So, the investigation continues. I had one of the scavenge pumps out today for inspection/measurement. It's properly worn(177k km) so a new is on order. So, what would the effect be of a worn scavenge pump?
Why don't you ask the person that told you that Scavenge pump snout right there was designed to break off on purpose, or the one that told you the main oil pump drive was supposed to break to save the engine?
Or just go away, and stop spreading false stupid information, you're hurting the forum badly..
Porschetech3. How many years have you been here on this forum telling people to use thicker oil, baffles and deep sumps etc to stop the pressure drops? Like Cervelli said, rehashing the same crap over and over. Here we are in 2020, still people are having the same issues to this day. Makes you look quite stupid. DEAL WITH IT.
The red line here shows where the oil level is when doing a steady 1g turn with 10cm oil level in the sump. 10cm is 1cm lower than minimum(the dot) on the dip stick. So, i doubt that the oil pressure drops we are seeing is due to oil moving left/right in the sump and causing the pick up going dry. I suspect the baffled chamber goes dry because the flow in-to it is too slow...or fills with aerated oil due to the inlets is skimming the aerated top surface of the oil. I haven't found an exact number but the flow is roughly 1qt of oil per second close to redline, that is a lot of oil flow. Jake, maybe you have a more exact oil flow number I can use?
This is a cool diagram. Your basic assumption is wrong though. There isn't 100mm of oil level in the sump under track conditions. I don't know the exact number, but I expect it is closer to 2 cm, which is why modifying the sump or pickup is a waste of time.
Porschetech3. How many years have you been here on this forum telling people to use thicker oil, baffles and deep sumps etc to stop the pressure drops? Like Cervelli said, rehashing the same crap over and over. Here we are in 2020, still people are having the same issues to this day. Makes you look quite stupid. DEAL WITH IT.
Nick,I usually don't give out advice like that, unless I know it will help someone in need.
You on the other hand go out of your way to say things like" the oil pump drive is designed to break on purpose to save the engine" and "the Scavenge pump snout is designed to break on purpose" and " the sump baffles are not there to help keep oil around the pick-up".. I know your wife told you the last one, but who told you the other two? Oh and" the IMSB problem is made up, the factory bearing is best !!" Did you dream it up?
I know for sure Porsche hasn't written any thing of the such !!!
How long have you been interested in M96 engines?
If you would get off your "high horse", you might be usefull to the community, as it is you are just spouting stuff you read out of context, and making your self look ignorant..
Last edited by Porschetech3; 09-22-2020 at 06:29 PM.
Do you have inputs for improvement that don’t include putting a boxster S under the 996 hood ?
External oil cooler ?
As Mr Raby says, cooler oil is better. He does not say what temperature he prefers, but I would like to see a normal operating oil temp of 200 degrees.
This is not going to happen unless you are racing in 30 degree weather and the cooling system remains in the control range of the coolant thermostat. Maybe in Canada, but I doubt it.
It seems very unlikely that you could run oil lines to the front of the car, install an air-to-oil heat exchanger there, runs lines back and have that arrangement be an improvement over the stock oil-to-water heat exchanger, which works very well. With the stock cooler and with a 3.4 engine, expect to see an oil temp 40 degrees F higher than the coolant temp when you are racing, which means the oil is likely to be over 250 on a hot day. So the engine and everything else has to be able to withstand that temperature, and all you can do is try to drop the coolant temp and drag the oil down with it. It would be great if the stock cooler were more effective and could shrink that 40 degree delta, but it is what it is.
It is not going to happen. On a hot day, the coolant will be 210 and the oil 250. Plan accordingly. I have raced these engines many hours with the coolant temp at 235, and they will sustain that without damage. The resultant high oil temp is a much greater concern, even with a dry sump.
09-21-2020, 06:09 PM
