Does anything actually solve the oil pressure drop in corners?
09-18-2020, 02:40 PM
#61
Former Vendor
I also notice bigger pressure drops, and issues with 3 chain engines. This is due to the difference in the cam adjuster on the 5 chain, and the vane cell adjuster on the 3 chain engine. Others have yet to connect those dots. I did when working with Lake at Driven Racing Oil on the development of oil for the Ford Coyote engines. The primary oil system didn't change enough between the 5 and 3 chain engines, despite a huge difference in the way the engine uses volumes of oil, and pressure to actuate VV and Variocam+.
Adding a 25% larger oil pump will open your eyes, if you know what to look for.
Adding a 25% larger oil pump will open your eyes, if you know what to look for.
09-18-2020, 03:44 PM
#62
Originally Posted by Flat6 Innovations
I break every rule. This engine ran 14:1 CR, among other things. It revved like a motorcycle. It's my job to break things before anyone else does, and to experience the things that others never get the opportunity to.
The engine that I used as a "core" for this 4.0 that failed due to the drive snapping was a brand new, Porsche factory crate engine with zero miles on it. Back when these engines were cheap, and cores were not plentiful, I used to buy brand new ones, and take them apart, to make them my way..
That said, I've had two people in my hands- on classes experience this, and have assisted at least 2-3 other people who have had this occur. The other engines were stock, where mine was insanely modified.
I'll find the pics of the failed drive over the weekend. They are stored online in an archive, and they are pretty deep in there.
Also, you never answered my questions about your direct experience with building these engines. I guess I'll keep waiting for that.
The engine that I used as a "core" for this 4.0 that failed due to the drive snapping was a brand new, Porsche factory crate engine with zero miles on it. Back when these engines were cheap, and cores were not plentiful, I used to buy brand new ones, and take them apart, to make them my way..
That said, I've had two people in my hands- on classes experience this, and have assisted at least 2-3 other people who have had this occur. The other engines were stock, where mine was insanely modified.
I'll find the pics of the failed drive over the weekend. They are stored online in an archive, and they are pretty deep in there.
Also, you never answered my questions about your direct experience with building these engines. I guess I'll keep waiting for that.
09-18-2020, 04:40 PM
#63
Racer
As a data point, the 996's were used at the Porsche Sport Driving School in that period when they were new at Barber Motorsport park. I was lead Porsche Technician at the Porsche Birmingham Dealership 5 miles away and was in charge of repairs to the fleet of 996's at that time (later changed out for 997's, 991's ect as new models were released.) These cars were tracked daily 7 days week by Instructors and Students of the Driving School and none had oil pressure drops on turns using Mobil 1 0w-40 and running on "N" spec tires of Pirelli, Michelin, Continental.
You wrote
..The oil pump is large enough to handle the extra flow without any pressure loss, but the extra flow..
I had a discussion with my wife over lunch today, she is an hydraulic engineers. Completely un-interested in engines until I brought up baffling in a tank, hydraulic stuff. She told me the main reason for using baffles is to lower the highest level in the tank....that would mean in our case they are there to prevent oil pushing up in to the crank/cylinder area. After looking at the dimensions on the X51 baffles inlet ports, it is most likely design for this purpose. It's not design for keeping more oil at the pick up, it's just a short lived side effect (1-2 seconds).
Also, you never answered my questions about your direct experience with building these engines. I guess I'll keep waiting for that.
09-18-2020, 04:44 PM
#64
Racer
As Jake pointed out “keep the oil cool”. This makes sense to me and seems to be supported by anecdotal evidence: I never loose oil pressure in turns (on ramps as an example) when the oil is cooler. Once it gets up to operating temp, I see drops.
I am going to install an oil temp gage to document at what temps I notice this. If oil temps are high, then I can investigate as to why.
I am going to install an oil temp gage to document at what temps I notice this. If oil temps are high, then I can investigate as to why.
09-18-2020, 05:20 PM
#66
Rennlist Member
I tried to explain the correlation of oil temp and lubrication problems to Nick in a different thread.
I was a miserable failure on that objective.
Now the real experts have weighed in, but there’s still disagreement.
Sometimes when everyone else is wrong, it means that you are either:
1.) Jesus
2.) Wrong
Either way, I’m sorry.
I was a miserable failure on that objective.
Now the real experts have weighed in, but there’s still disagreement.
Sometimes when everyone else is wrong, it means that you are either:
1.) Jesus
2.) Wrong
Either way, I’m sorry.
The following users liked this post:
Zuffwerks (10-05-2022)
09-18-2020, 05:36 PM
#67
Rennlist Member
Thicker oil does not cause a pressure drop, it does cause less flow though. Simple physics.
An increase in clearance (smallish) will lower the pressure at certain RPM's , but the volume of the oil pump is still over designed enough to reach full pressure of 5bar when the relief/by-pass valve opens. Of course if the clearance/leak is too severe , it cannot reach full pressure of 5 bar.
There was an issue with the 986 m96 engines with a vibration/rattle noise. The cause was too much clearance between the crank carrier and the cases (machined fit). Test procedure was to connect a manual oil pressure gauge to the port on the head, engine at operating temperature, rev engine to 4k, engine should have above 4 bar pressure oil pressure, if not replace engine..
I had a discussion with my wife over lunch today, she is an hydraulic engineers. Completely un-interested in engines until I brought up baffling in a tank, hydraulic stuff. She told me the main reason for using baffles is to lower the highest level in the tank....that would mean in our case they are there to prevent oil pushing up in to the crank/cylinder area. After looking at the dimensions on the X51 baffles inlet ports, it is most likely design for this purpose. It's not design for keeping more oil at the pick up, it's just a short lived side effect (1-2 seconds).
The following users liked this post:
Nick_L (09-18-2020)
09-18-2020, 06:35 PM
#69
Rennlist Member
The aerated oil is always lighter and the bubbles take at least 10 seconds to reach the surface and burst. These bubbles are less than 1mm in size.
Last edited by Porschetech3; 09-18-2020 at 06:40 PM.
09-18-2020, 06:52 PM
#70
Racer
Your incorrect, Yes I know the oil pump is a positive displacement pump, but it does displace more volume than the engine actually needs as a wear/safety/longevity factor, and hence one of the reasons for the pressure relief/by-pass valve of the oil pump, to limit the upper pressure to 5 bar and by-pass unneeded volume. Again simple physics.
Your just saying the same thing in a different way, ( and your wife)..lowering the highest level in the sump also keeps more oil at the pickup tube like every one says.(with same oil volume) Think about it, simple..
Everywhere on the internet when you read about baffles they show a nice picture where the doors/flaps are closed on one side. Initially it makes sense and is easy to understand. But, in an engine your pick-up will empty that 'high oil level' space in probably less than 2 seconds and new oil have to flow in.
Imagine the oil level decreasing in that chamber, where does the new oil flow in from? and what do the levels look like in an equilibrium state? You really don't get a higher level more than just momentarily 1-2 seconds (depending on RPM). If these trap doors also introduce flow restriction there might even be lower oil in the chamber at high RPM. Remember, the flow can be roughly 1 liter per second, that's quite a lot. If you look at the inner chamber where the pick-up sits on our engines, it's very small. The engine case is marked by the black "V" in the cross section picture, taking up a large part of the inner chamber space.
Last edited by Nick_L; 09-18-2020 at 06:58 PM.
09-18-2020, 07:57 PM
#71
Rennlist Member
Yes, most cars utilise this effect, just bypassing unneeded flow(check page 23 in the MIT document for example, fig 1-7....already at 3k rpm ). I think the 996 is not meant to be run like this, it's in the owners manual that you should have approx. 3.5 bar at 5k rpm....thus never really run in to constant bypass. Bypasses are known to cause aeration.
I
don't think it's that simple. You are blocking oil volume in pockets at each baffle step, that's where the lowering comes from. These pockets are made bigger on the X51 by moving the inlet ports up by circa 5mm.
Everywhere on the internet when you read about baffles they show a nice picture where the doors/flaps are closed on one side. Initially it makes sense and is easy to understand. But, in an engine your pick-up will empty that 'high oil level' space in probably less than 2 seconds and new oil have to flow in.
Imagine the oil level decreasing in that chamber, where does the new oil flow in from? and what do the levels look like in an equilibrium state? You really don't get a higher level more than just momentarily 1-2 seconds (depending on RPM). If these trap doors also introduce flow restriction there might even be lower oil in the chamber at high RPM. Remember, the flow can be roughly 1 liter per second, that's quite a lot. If you look at the inner chamber where the pick-up sits on our engines, it's very small. The engine case is marked by the black "V" in the cross section picture, taking up a large part of the inner chamber space.
Everywhere on the internet when you read about baffles they show a nice picture where the doors/flaps are closed on one side. Initially it makes sense and is easy to understand. But, in an engine your pick-up will empty that 'high oil level' space in probably less than 2 seconds and new oil have to flow in.
Imagine the oil level decreasing in that chamber, where does the new oil flow in from? and what do the levels look like in an equilibrium state? You really don't get a higher level more than just momentarily 1-2 seconds (depending on RPM). If these trap doors also introduce flow restriction there might even be lower oil in the chamber at high RPM. Remember, the flow can be roughly 1 liter per second, that's quite a lot. If you look at the inner chamber where the pick-up sits on our engines, it's very small. The engine case is marked by the black "V" in the cross section picture, taking up a large part of the inner chamber space.
Except you are more educated and don't really understand the complexities of the dynamic forces and the trumping of some theories by simple laws of physics.
09-18-2020, 08:50 PM
#72
Rennlist Member
I wonder if modern tire technology (improvements in grip) could be partially responsible for an increase in pressure losses in the turns for street tires over the last 10 years or so? I was able to get pressure loss in turn 9-10 (Carousel) at Road America with just Michelin All Seasons (AS3+)!
Also like it or not there are just inherent design concerns with a horizontally opposed engine. Unlike a V engine, gravity doesn’t help oil get back to the sump as quickly. The horizontal design also exacerbates bore scoring issues.
These are the consequences of choosing Porsche for your fun car. Yes a flat design has better balance, a lower CG, but it has drawbacks too.
The following users liked this post:
Mike Murphy (09-19-2020)
09-20-2020, 04:17 PM
#74
Rennlist Member
The one I described above, for engine noise on the M96 engine in the 986.
Since I have retired I don't have access to TBS's anymore. But there was a service you could buy access for a year, month, day, or even by the hour for like $8 an hour. I don't know if the serivce is still available, I did a post on it a few years ago and gave the link to it. Be forewarned that the TSB's are Porsche property, and some have been lost/deleted if they feel they are no loner necessary or beneficial.
Since I have retired I don't have access to TBS's anymore. But there was a service you could buy access for a year, month, day, or even by the hour for like $8 an hour. I don't know if the serivce is still available, I did a post on it a few years ago and gave the link to it. Be forewarned that the TSB's are Porsche property, and some have been lost/deleted if they feel they are no loner necessary or beneficial.
09-20-2020, 05:23 PM
#75
Racer
There was an issue with the 986 m96 engines with a vibration/rattle noise. The cause was too much clearance between the crank carrier and the cases (machined fit). Test procedure was to connect a manual oil pressure gauge to the port on the head, engine at operating temperature, rev engine to 4k, engine should have above 4 bar pressure oil pressure, if not replace engine..
The M1 0w40 is a thin 40wt oil, it's 12.9cst when new. 12.5 to 16.3 cst is 40wt and 12.5 - 9.3 cst is 30wt. Reading UOAs the M1 0w40 in 996s, it is at 11.5-12 already around 3-4000mils, thus sheared to 30wt. If you follow the 15,000mil service, the actual oil weight in the engine would be mid to low 30wt at that time. When you change oil, there is some left in the engine. When doing a new fill of 0w40 after 15,000 mil you dilute your new oil with some old. Basically if following Porsche's oil and change interval recommendation, you run 30wt in you car.
To all contributors to this thread, I'm trying to find the solution to this. Some times I will push you a little to get more/correct information. Sorry Porschetech3(and others) if you find it offensive, I'm not here to put anyone in a corner.