12-15-2020, 07:15 AM | #1 |
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Potential N20/N26 RWD Oil Sump Upgrade
Hey all, if you have read my Build guide on the N20 (https://f30.bimmerpost.com/forums/sh....php?t=1566013)
You would have seen I tackled the issue with the RWD sump being inadequate for doing track days or aggressive corning under speed due to oil starvation issues. Fortunately today, I have come across a place that sells Aluminium N20 RWD oil sumps that can be more easily modified to implement my baffle set-up (since the plastic ones required using silicone to hold the baffle plate in place). If you're interested, I might see if I can have a few sumps made up with my baffle kit. If you're interested in such an upgrade/preventative maintenance item. Send me a DM and I'll give you more details. I have provided a Mock-Up photo for what the aluminium pan would look like with my baffle plates, which from testing on my motor, have helped oil pressure. I might just add some info here.... The oil system in the N20/N26 is MAP based, Meaning Oil pressure is based on Engine Load and RPM. When you aren't at 100% throttle the car is in partial load/low load scenario, meaning oil pressure target is going to be low. This was intentionally done by BMW to help make the motor efficient, as the load on the main bearings of the crank is lower during low load situations it doesn't need the oil pump, sending more oil to the galleries and robbing power from the crankshaft. We know this forum post provided some good data, especially for cornering (https://f30.bimmerpost.com/forums/sh....php?t=1023545) However. The post doesn't detail the MAP based Oil Setup and how that also affects the motor. Yes the sump needs baffles for LEFT OR RIGHT HAND Cornering. During braking or cornering, you aren't on the throttle demanding maximum load from the motor, so Oil pressure is going to be naturally lower. From spending alot of time looking at this sump, until someone really sticks an accurate oil level sensor right next to the oil pickup to measure oil level during braking and acceleration (since we know from the above post and known documented cases of engine damage that cornering is an issue without baffles). Braking and Accelerating isn't an issue for oil pressure, the sump already incorporates a small baffle in around the pickup for forwards and backwards motion, furthermore, If hard braking was causing oil starvation issues, then oil would have to move so far forwards under braking it would end up in the crankcase and that causes its own issues with the crankshaft. All it takes is for a fraction of air to be sucked up and you get rod/crankshaft knocking. One other plausible way of measuring oil pressure issues is to log Oil Pressure Target and Oil Pressure actual (PSI) and see if under braking, cornering etc, if actual Pressure deviates from target pressure by more than 3-5%, that'll indicate pickup issues. The Oil system is capable of 5.5BAR, however at 5.5BAR the emergency relief valve opens up and pours oil back into the sump. The Oil Pump operates in MAP mode between 1.5-4.5BAR, and can drop out of MAP mode oiling if the oil temp exceeds 150 or below -20 deg C (plus other specific operating scenarios). A potential solution, for those Who Track or want to drift/hill-climb etc. Is get the baffle setup, and have your tuner adjust the oil pressure tables in the tune during Low load/partial load operation, so pressure is always consistent throughout RPM range/Driving operation, you might "lose efficiency" during low load/partial load but I mean who really cares, if you're pushing your car. These tables are available to edit in the tuning suites out there, if your tuner doesn't have them, then get them to add them. Correction note: I'm referring to hard breaking or acceleration in a straight line. As a result that doesn't cover all braking and there very well could be issues with oil starvation under braking. However the more data we have on this the better chance i have at improving this design and trying to accommodate all the necessary changes required to fix the n20 oiling issues. I encourage the community to send any available date so I can more accurately look at making the necessary adjustments we need. Thank you! Last edited by navardi; 12-18-2020 at 04:58 AM.. Reason: UPDATE RE: OIL PRESSURE |
12-15-2020, 11:13 AM | #2 |
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This is great! From my earlier thread on my my motor woes, the shop I found to replace the engine in my car has done this exact thing in another N20 and said it worked out really well. For sure this will be a welcome mod!
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12-16-2020, 06:46 PM | #5 |
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12-16-2020, 06:47 PM | #6 | |
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We don't have XDRIVE N20's here in AUS, so I can't test/warrant such an upgrade personally. |
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12-17-2020, 04:11 PM | #8 |
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Is there any chance that this could be a contributing factor to timing chain issues? If the pressure fluctuates under aggressive driving or hard braking, what about accumulated effects over 100k miles. Could there be numerous micro instances of pressure dropping?
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12-17-2020, 06:53 PM | #9 |
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I'm curious if you have any data to back these changes up? Esp why baffles are required for right hand turns?
I attached data from a lap at Sonoma Raceway, turns 4-6. Track map available at https://www.sonomaraceway.com/docume...map-8-5x11.pdf or any other google search. Basically, T4 is downhill, requires braking, and is a right hand turn. T5 is more flat, right hand, no lift/brake required. The track then crests before descending into a banked left hand T6 - I'm sure better drivers are braking after the crest but lets just assume I was braking before the crest. I included lateral acceleration (cornering), longitudinal acceleration (braking/accel), accusump air pressure (yes I removed the gauge and replaced it with a sensor), oil pressure (as measured in the stock location using the stock sensor), and accelerator pedal position. Just a note that my car is not using MAP control of the oil pressure. I didn't like the nearly 10 bar spikes I was seeing both in my own control and in the Z4's data (link here: https://f30.bimmerpost.com/forums/sh...hp?t=1023545); the oil pressure relief doesn't kick in when under MAP control (read p80-p81 of the N20 doc for reference). This probably means my car is pumping more oil than a "managed pressure" motor, and thus I might be more likely to have starvation as it takes time for the oil to return to the sump. But given the data I saw from the Z4, I don't think that's necessarily the case. You can see for T4 (@3000 ft - see scale at bottom), when braking exceeds 1G the oil pressure drops like a rock to 3 bar. Still adequate, and not enough to trigger the accusump (note that T7 and T11 were enough to trigger the accusump on braking alone). Once off the brakes and back onto throttle (around 3250') the oil pressure has built back up, even in the middle of a 1g right hand turn. It stays up through T5 (3500'-4200'), again through a 1g right hand turn. It doesn't drop again until braking in the window of 4400'-4600'. Now enter T6, long left hand sweeper. This time oil pressure stays low for the duration of the corner, even with the accusump dumping down to 2.3 bar. You can see oil pressure build rebound a little at 5400' (when cornering g force reduces to "only" 1g) and then climb more at 5600' (when cornering g force reduces even more). I don't recall what my accusump pressure is when empty; I just tried dumping it and got down to 1 bar relative pressure, and it seemed to still have more to dump. Let's say I did what Canton recommended and used 11 psi relative pressure (0.6-0.7 bar?). That means that when the accusump is down to 2.3 bar-gauge, I dumped about an extra quart into the engine. Math is: Full accusump: 3 quart * (1 - 1.6 bar absolute / 7.6 bar absolute) = 2.4 quarts Accusump mid corner: 3 quart * (1 - 1.6 bar absolute / 3.3 bar absolute) = 1.5 quarts Compare that to the size of the winglets that we can cover with baffles - I measured right angle triangles of 6cm and 7cm that are in aggregate 10.5cm in length. That's only 0.22L of volume... I am thinking of increasing my base accusump air pressure to be more like 2 bar relative pressure. I will have less margin if there's a catastrophic failure, but I'll have more volume to supply at 2 bar and above: Full accusump: 3 quart * (1 - 3 bar absolute / 7.6 bar absolute) = 1.8 quarts Accusump drained to 2.3 bar relative: 3 quart * (1 - 3 bar absolute / 3.3 bar absolute) = 0.3 quarts So that'd be 1.5 quarts to supply, instead of 0.9 quarts.... |
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12-18-2020, 04:01 AM | #10 | |
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12-18-2020, 04:48 AM | #11 | |
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Good write up. So how did you go about disabling the MAP oil pressure control? Hardware wise or via the tune? Based on the bmw technical doco, when the correct situation is set car will always default to map mode, but "according" to the documentation map mode only operates between 1.5 and 4.5 bar, anything outside of that is supposedly just operates in volume control mode. Its suprising in that Z4 that there were spikes above 5.5 bar as thats supposed to be the pressure the emergency relief valve activates, again that's what the technical documentation states. I assume being you have your N20 setup in the E46 you're using an aftermarket ECU? Which probably explains the "easier" way to delete the MAP oil pressure control. Looking at your data. Whilst under breaking, it appears you're also turning? If so that makes sense why you're losing oil pressure, my analysis from the data I have regarding braking is, hard braking in a straight line which doesn't seem to cause any issues. Ill attach that data when I get home. The oil baffles to cover right hand turns, comes from experience of doing drifting to the right on my built motor and suffering rod knock immediately after it (costly repair exercise) on top of that where i place the baffle to fix this issue (the baffle next to the oil level sensor) it appears that naturally in the sump there is no moulded step to help stop oil from rushing all the way to the left up onto the side of the pan with the level sensor that's why I focused more so on baffling that section as well as i could before worrying about baffling those little small storage areas in the right side of the pan that seem to contribute to left hand cornering pressure loss. Naturally the sump factory is a week design anyone can tell that from looking at it. I might look at modifying the aluminium sump to a greater extent and create a recessed setup to baffle the oil specifically around the pickup from all angles it'll be more work and more cutting but probably more worth while. |
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Mollyran72.00 |
12-18-2020, 11:14 AM | #12 | ||||
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Also of interest - apparently the pump has a built in cold start relief valve that bleeds off at 12-13 bar, sort of a secondary emergency relief valve. Because, you know, why have a simple system when you can have a complex one. Quote:
I could show you T12, a whopping 0.6g left turn, where oil pressure drops to 3 bar. Contrast that to T5 above. Quote:
As for pressure loss when braking - oil pressure dropped so much in a straight line that the accusump kicks in at 11425'. I don't start turning right until 11525'. Coincidentally, that's when oil pressure starts climbing, which is again why I feel like right hand turns are not an issue for oil pressure. Quote:
If you get the aluminum pan, can you weigh it for me? The X pan is 10 lbs vs 3 lbs for plastic. I posted somewhere else but I'll add it here too: https://bringatrailer.com/listing/20...a-st-race-car/ An F30 N20 professionally built race car. With a custom oil pan: https://bringatrailer.com/wp-content...it=2048%2C1365 And yet still running an accusump: https://bringatrailer.com/wp-content...it=2048%2C1365 After I saw that I decided to abandon any plans to build or design my own sump. |
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Mollyran72.00 |
12-27-2020, 06:18 AM | #13 | |
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I am taking this data onboard to help solve the issue ~hopefully~ for good. I can 3D print a new pickup if need be, but aiming to try and work with what we have first. Going to do any prototyping with 3D printing first. I have ordered an Aluminium Sump and should be here sometime in the new year to do the fab work on. Not going to bother posting my data, since its not as comprehensive as yours, and yours clearly shows there being an issue. I am thinking I can get away cutting the recessed "box" of the sump and reworking it to house a nice neat little baffled area around the pickup, and If need be print the new pickup to go with it. (I can get 3D printer filament stronger than the grade of plastic used in the current pickup which should help the life of the setup.) Shame the oil pump isn't a simple setup, I am surprised the Emerg Valve doesn't quite work the way its supposed to, but oh well, guess we're just going to have to live with that. I assume you're using the Link G4+ GDI? As for drift flicked left first but for a fraction of a second, once I completed the drift and a nice 4th gear pull I heard the beloved knock knock sounds we all hate to hear I wonder if that 328 Race car had the accusump as an added precaution? that or they didn't baffle the sump in the correct way? not quite sure why they couldn't solve the issue with a custom sump? Once the sump arrives, I will begin sharing progress pics |
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12-27-2020, 10:55 PM | #14 | ||||
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01-04-2021, 08:00 PM | #15 | |
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Okay weight wise its 3.75-4KG Amazing quality for a cast aluminium piece! Definitely recommend it, ill upload some photos, now its time to cut and modify it lol. Comes with a metal sump plug with a built in magnet! |
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01-05-2021, 05:50 PM | #17 |
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01-05-2021, 07:17 PM | #18 |
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I'm going to have to weigh it again. I thought it was closer to 10 lbs. But that's in addition to the stock plastic pan, whereas this is instead. But some quick math based on 3mm wall thickness implies more like 3 lbs. Maybe I'm not counting end caps, or fittings, or solenoid (1.5 lbs), or hoses, or extra oil (5-6 lbs). I did make sure to replace all the brass fittings with aluminum ones to save weight.
Are you thinking of adding an extension/box on the side of the pan, or just adding baffles? I was thinking a box on the left side would help store oil for using on left hand turns; baffles would keep it from then starving oil on right hand turns. Not sure what to do for braking, since the transmission is in the way of storing extra for braking. Maybe adding storage below and behind the oil pickup, so that under braking it floods up toward the pickup? |
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01-08-2021, 07:43 PM | #19 |
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Maybe you can find a way to put an oil dip stick in there. The M235iR has one, the N55 crowd can retrofit the M235iR solution, but we have nothing for the N20.
I know the diesels still have one, even on 2L engines, so maybe you can find inspiration there.
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01-12-2021, 06:37 PM | #20 |
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Weight of 3 qt Moroso accumulator, with stock pressure gauge, an electronic solenoid, a brass fitting with a pressure sensor, and an NPT to AN aluminum fitting is 8.8 lbs. Though I don't know how much oil it had in it (if any).
The nice thing about using an aftermarket ECU is I can drop the brass fitting with pressure sensor, and just use the stock pressure sensor to decide when to fire the solenoid. BTW I was looking again at the stock oil pump and I could see adding a shroud above the pickup. That might help for a short time under braking, but I don't know if it'd be enough for longer braking zones. |
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01-13-2021, 05:18 AM | #21 | |
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I have done some basic mockups using Plastic I 3D printed and just super glued in place. I am now waiting for my fabricator to fit me in so we can weld the aluminium equivalents or similar. I elected to go against cutting the bottom out and add a new larger redesigned bottom section with custom pickup, due to sub frame issues and ground clearance. Pretty confident the below setup will work as it surrounds entirely the pump/pickup and tries to keep oil where it should. Final product will use Rubber doors (the slits you can see in the plastic MOCKUP baffles is where the Rubber "doors" mount, then there will be a circular opening that the rubber will block in 1 direction, you can see an example of this in the photo in the first post in this thread). final design will ensure all gaps between baffles are sealed to ensure a solid enclosure around the pump/pickup. I did my best to have these baffles get as close and cuddly to the pump module as possible. Please view photo. |
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01-13-2021, 05:21 AM | #22 | |
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Baffles are super important first then other nice to have features will come |
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