Accusump install

[Dieselboy]

What's the aversion from placing this in the trunk? A denser engine bay is a hotter engine bay, especially with a cylinder full of hot engine oil. Placing in the trunk would offer some cooling benefit especially if it's being activated often.

[AndyW]

Originally Posted by Dieselboy

What's the aversion from placing this in the trunk? A denser engine bay is a hotter engine bay, especially with a cylinder full of hot engine oil. Placing in the trunk would offer some cooling benefit especially if it's being activated often.

1. Laziness. There's no reason you can't and if I had a stripped out race car I probably would. But I don't, so I didn't.

2. Marginal benefit. My engine bay has great airflow and you can also view the Accusump as an additional finless oil cooler.

[Fickert]

So after testing, I have a question in regards to measuring oil pressure. Is oil pressure measurements accurate to the stock sensor if measured from the oil cooler feed line off of the OFH? For some reason my 37 psi sensor is behaving a lot like a 55-60 psi sensor when comparing pressures to MHD.

[AndyW]

Originally Posted by Fickert

So after testing, I have a question in regards to measuring oil pressure. Is oil pressure measurements accurate to the stock sensor if measured from the oil cooler feed line off of the OFH? For some reason my 37 psi sensor is behaving a lot like a 55-60 psi sensor when comparing pressures to MHD.

I can't imagine it would be that much off. Not sure what the accuracy range of the setpoint and/or the sensor is supposed to be.

[Fickert]

I found my answers just now and can confirm the adjustment is working.

So to spare time, I found the actual sensor Canton supplies with their kits. Canton claims them to not be adjustable. I found out they are. The pressure switches supplied can be set from 0-60PSI.

And to adjust them is easy. There is a small round rubber cap in between the two terminals. Remove this to reveal an adjustment screw. Using a Tamper-Proof Allen Key set, I was able to adjust my sensor to just trigger below 37 PSI (right below lowest Idle PSI). So if you have a desire to adjust or tune the PSI value, this is how.

Note, the range Canton gives is likely due to the adjustment accuracy and accuracy of the sensor.. The actual accuracy of the sensor is +/- 1.5 PSI or +/- 3% of set value, whichever is higher.

Hopefully this helps, it makes me feel a lot better, and now knowing I can quickly adjust the sensor if I do ever do any track days with the kit is pretty reassuring.

Also see attached the instructions from the manufacturer to adjust and set the pressure switch:

[carguy138]

Originally Posted by AndyW

Sure.

1. With the discharge valve not energized, the Accusump will always allow oil IN. So after an oil change, it will fill to 80-100# and hold about 2.7 qts. This is the default condition. As long as you don't power the valve, you can pretend it doesn't exist. So the switch mentioned below stays off day to day.

2. I have a two stage power setup like bbnks2 because the EPC setpoint is above idle oil pressure. He uses a switch in the cab, I use a remote fob for a solenoid valve. First, is a physical switch under the hood to supply 12V power to the solenoid from the battery connection in the engine bay. This ensures the valve doesn't stay on 100% at idle and vent the oil and more importantly, burn out the valve. That way I can power the system to a "ready" state for the track with the switch and then, right before going on track, activate the fob to enable the solenoid to power the EPC. You could probably forego the mechanical switch, but I wanted to avoid a parasitic electrical load when the system is not in use.

The fob and solenoid are this: https://smile.amazon.com/gp/product/...e?ie=UTF8&th=1

Thanks a bunch! Got the accusump in (fitment test) and looks like it will work on my E90.

By any chance could you take a pic of the installed diode and remote relay wiring?

EDIT: I think I'm going to use some additional line over the pressure relief valve and run it down to the bell pan in case it ever opens or leaks. Bad idea?

[AndyW]

Originally Posted by carguy138

Thanks a bunch! Got the accusump in (fitment test) and looks like it will work on my E90.

By any chance could you take a pic of the installed diode and remote relay wiring?

EDIT: I think I'm going to use some additional line over the pressure relief valve and run it down to the bell pan in case it ever opens or leaks. Bad idea?

I did not take a pic and the car is at the shop so I can't take one. But I will when I get the car back.

I think a drain for the relief is overkill but it isn't a "bad" idea.

[imported_mega]

ohhh great find on that adjustment screw! I've put this off because the two switch options were both too far away from our idle and running PSI

[joeo]

Recently made a change to my accumulator setup. I installed an electric ball valve that I can turn on off from the driver's seat.
The car is track only; so the procedure is:
1. Open valve.
2. Start car.
3. Drive.
4. When coming back into paddock, close valve.
Repeat.

[carguy138]

Originally Posted by AndyW

I did not take a pic and the car is at the shop so I can't take one. But I will when I get the car back.

I think a drain for the relief is overkill but it isn't a "bad" idea.

Hey by any chance could you take a pic of the diode placement and the remote relay setup?

I have everything ready to go and still trying to figure out how to get this remote relay wired.

+ DC input 1 -->
- DC input 2 -->

+ DC output 3 -->
- DC output 4 -->

Also on the pressure sensor, I see a third white wire. What is that for?

Sorry for all the questions and thanks again for everything you did to document the install.

[AndyW]

Originally Posted by carguy138

Hey by any chance could you take a pic of the diode placement and the remote relay setup?

I have everything ready to go and still trying to figure out how to get this remote relay wired.

+ DC input 1 -->
- DC input 2 -->

+ DC output 3 -->
- DC output 4 -->

Also on the pressure sensor, I see a third white wire. What is that for?

Sorry for all the questions and thanks again for everything you did to document the install.

No problem. A pic won't really help as I wrapped everything in tape. Here is a diagram that should help. The white wire is the line to the activation LED.

[fe1rx]

Something mystifies me about Canton's recommended 7-10 psi Accusump pre-charge pressure.

Boyles law says if you halve a fixed volume of a gas you double it pressure. So if a 3 gallon Accusump is pre-charged to 10 psi, at 20 psi oil pressure it will be holding 1.5 gallons. Extend that thinking out to 80 psi oil pressure, and look at pre-charge pressures of 10, 20, 30 and 40 psi gives us the following graph of stored volume as a function of oil pressure for each those precharge pressures.



Assuming your goal is to prevent your oil pressure from ever going below 30 psi, and you are successful in doing this, only the oil stored between maximum (80 psi) and minimum (30 psi) is actually usable. The rest never leaves the Accusump. As a function of pre-charge pressure, the usable volume is plotted below.



What seems self-apartent after considering this is that you should pre-charge the Accusump to the minimum oil pressure you are trying to allow. This will provide the greatest actually usable volume in the Accusump.

I have trouble seeing how Canton's recommendation of 7-10 psi can ever be a good choice, and certainly not in the case of our vehicles.

Edit: One thought that came to mind is that if precharge is set at room temperature (20°C = 293°K) and the Accusump operates at 100°C = 373°K then the absolute precharge pressure is effectively 25 x 373 / 293 = 32 psi. or 17 psi gauge at operating temperature. That does make a difference. Precharging to 20 psi cold would be about 30 psi hot.

[joeo]

I've thought the same, and have been experimenting with different initial values. Right now I'm at 12psi, but yeah - seems like it should be higher.
Thank you for this!

-Joe

[rac]

Vol. Useable = Bottle Vol * [pre-charge/min. operating pressure - pre-charge/max. operating pressure]

regarding the 40psi data point, how do you operate below pre-charge pressure?

as a general rule of thumb pre-charge pressures should be set just below minimum operating pressures such that the bottle is never fully vacated.

[bbnks2]

I think I pre-charged mine to 10-12psi which would be closer to 16psi at operating temps of 240-260f. A little higher than Canton's recommendation. This was based on discussion with them and the higher operating pressure of the typical bmw. They were surprised the car hit 60-80psi under load even at low rpms and idled at ~36psi. 2nd gear you can see 100psi under load... Much higher than they were used to working with. I think for sure their recommended settings are more oriented around oldscohol hot rods that run <10psi oil pressure at idle and maybe 40-60psi under load.

fe1rx You're charts are in gallons for some reason but I imagine the plot for 3gallons will look the same as 3 quarts?

From what we see in data charts, oil pressure in sweepers sees dips to ~30psi when we should be at 55psi+... a ~20psi precharge @70f might be more beneficial to shift the discharge to the region of oil pressure we are trying to address (staying above 30psi)... However, there is a trade-off there in that it will cut the total available accusump capacity from 2.6 quarts or so to 1.8quarts or so.

You really shouldn't see below 30psi much if ever unless the engine dumps its oil but I have actually had oil lines break on me twice now and having a longer discharge time down to ~10psi definitely helped save the engine whereas if I had precharged at ~20psi the accusump would've been empty pretty much instantly given the almost instant total loss in oil pressure.

is there any way to calculate how long ~1.8qts of oil capacity (20psi pre-charge @70f --> 27psi @250f operating temp pre-charge) can help maintain 60psi when operating pressure has fallen to 30psi? That's the bigger picture of the functionality of the accusump... providing some oil over time not just how efficiently to use the capacity in a given range. If a 20psi @ 70f precharge only supplements oiling for <1second given a sudden dip from 60psi-->30psi operating pressure then it's kinda useless... a lower pre-charge would discharge at a slower rate like over 2-3 seconds providing SOME oil over a 3 second sweeper even if a at a lower pressure than desired.

Basically, I am getting at RATE of discharge and CAPACITY also being important. I recall this from conversations with Canton about the trade-off of higher pre-charge reducing capacity and increasing the rate of discharge shortening the window of available oiling in the event of a loss in oiling. It has been a few years since I discussed with Canton and researched this stuff so please any info you can provide to these aspects would be great for the discussion.

I remember calculating a very rough (not having any BMW specific data) figure around the oil pumps flow and it is likely pumping over a quart of oil per second at any decent RPM/ I based my figures off what I could find of the GPM at x-psi of some other vehicles all generally between 10-30gpm depending on engine and rpm.

[fe1rx]

Originally Posted by rac

Vol. Useable = Bottle Vol * [pre-charge/min. operating pressure - pre-charge/max. operating pressure]

regarding the 40psi data point, how do you operate below pre-charge pressure?

as a general rule of thumb pre-charge pressures should be set just below minimum operating pressures such that the bottle is never fully vacated.

Well said.

If your engine pressure goes below the pre-charge pressure, the accusump empties completely and in that instant does nothing further. It is a good argument for not setting the precharge too high.

[AndyW]

Originally Posted by bbnks2

... Good Stuff....

I think I summarize all that in my mind as the tradeoff between having at or above "normal" pressure for a short period of time or below "normal" pressure but still have oil flow for a longer period of time. In either case, when oil can no longer be taken in by the pickup tube, pressure will ultimately fall to zero and the Accusump with empty itself regardless. I fall on the side of reduced pressure with some flow for a longer period of time rather than a lot of pressure then zero in a shorter period of time. But I admit I have no data to prove why I think that is better. Nor do I have measurements to quantify the time difference. I just know long left sweepers and sharp braking tight lefts are the engine killers. Either solution solves the sharp short lefts. But the "more oil flow longer" solution also mitigates the long left sweeper problem.

Then again, when the Accusump is charged to 80-100# with a 10# precharge, and I energize and release it to zero to change the oil(sensed oil pressure 0#, it empties in like two seconds or so anyway, so maybe we are majoring in the minors here...lol.

Interesting discussion.

[fe1rx]

Originally Posted by bbnks2

fe1rx You're charts are in gallons for some reason but I imagine the plot for 3gallons will look the same as 3 quarts?

Thanks for seeing the forest for the trees there. I meant quarts ...

Originally Posted by bbnks2

is there any way to calculate how long ~1.8qts of oil capacity (20psi pre-charge @70f --> 27psi @250f operating temp pre-charge) can help maintain 60psi when operating pressure has fallen to 30psi?

Modeling the engine and accusump using electrical principles helps get a grasp of things. Ohm's law, and the equation for discharge of a capacitor can be repurposed to help.

To get things started though, we need to make some best guesses about the engine oil flow characteristics. In my N54, the oil pressure follows the blue line in the graph below.

Attachment 2868870

Oil pumps are positive displacement, meaning they produce a fixed flow rate of incompressible fluid at a fixed rpm. Confounding that, our pumps have variable displacement - high at low rpm to maximize pressure, low at high rpm to minimize parasitic power losses. Also, there is a pressure relief valve to set a maximum pressure. Cold oil messes all this further due to increased viscosity.

Dispensing with the unnecessary complications - between A and B the pump is at maximum displacement, there i no flow through the relief valve, and the pressure is a function of the flow rate and the engine's inherent resistance to oil flow.

Ohms Law says V = I x R

In our analogy V = Oil Pressure (OP), I = Oil Flow (OF), R = Engine Resistance to Oil Flow (OR)

Assuming the pump was constant displacement with an 80 psi relief valve, at point C, all flow would be through the engine, none through the relief valve. If we assume a maximum oil flow through the engine of 10 gallons per minute (gpm), we can calculate the engines Oil Resistance, by rearranging Ohms Law

OP = OF x OR; or,

OR = OP / OF = 80 psi / 10 gpm = 8 psi/gpm

During low pressure transients the oil pump will always be in maximum displacement mode (but actual oil flow will be reduced because it is a mixture of air and oil). No oil will be bypassed by the pressure relief valve. That makes life simpler.

If we have an oil pressure of 30 psi or 20 psi, our oil flows must be:

OF(30 psi) = OP / OR = 30 psi / 8 psi/gpm = 3.75 gpm

OF(20 psi) = 20 psi / 8 psi/gpm = 2.5 gpm

So if we have an oil pressure transient to 20 psi, and we want the Accusump to hold the pressure at 30 psi, it must contribute an additional 1.25 gpm to the pump's 2.5 gpm flow.

The Accusump is not a constant dispacement device (electical analog being a current source), or a constant pressure device (electrical analog being a battery). It is analagous to a capacitor. A capacitor discharges through a resistor with an exponential decay. The associated electrical analogs are:

Charge "q" (Coulombs) is analgous to Oil Volume "Vol" (gallons)

The volume in question is the usable volume of the Accusump, which depends on precharge and carge pressure. For simplicity, assume a usable volume of 0.5 gal.

The Capacitance of a Capacitor: C = q / V

The Capacitance of an accusump of usable volume 0.5 gallons at charge pressure of 80 psi is:

Coil = 0.5 gal / 80 psi = 0.0083 gal/psi

For the discharge of a capacitor, the time constant "RC" is important. The accusump analog is:

OR x Coil = (8 psi/gpm) x (0.0083 gal/psi) x (60 sec/min) = 4 sec

Assuming the Accusump is fully charged at 80 psi, and at time zero the engine oil pressure drops to 20 psi due to reduce oil pump flow, and the Accusump instantly opens we can calculate the resulting oil pressure as a function of time from the Voltage decay equation for a capacitor:

Oil Pressure = 20 psi + 60 psi x e^-(t/TC)

where TC is the 4 second time constant previously calculated.

Attachment 2868871

Similarly we can calculate the oil flow rate from the Accusump as a function of time from the capacitor discharged equation:

Flow Rate at 60 psi = 60 psi / 8 psi/gpm = 7.5 gpm

Accumsump Flow Rate = 7.5 gpm x e^-(t/TC)

Total Flow Rate = 2.5 gpm + 7.5 gpm x e^-(t/TC)

Attachment 2868869

[fe1rx]

not sure what the problem with the image links is ...

[fe1rx]

A thought about how to increase the available oil from an Accusump, and also to reduce the intitial flow spike. Both features increase the protection time.

Basic idea: add a remote mounted air tank to increase the size of the gas spring.

This allows the full volume of the Accusump to be filled with oil.

[fe1rx]

The flow and pressure graphs for the above configuration follow:





Without the remote tank you get 7 seconds of protection, with it, 12 seconds.

My variables are completely arbitrary, and just intended to be food for thought. 12 seconds is a long time and maybe way too long to wory about. Bumping up the air pressure for a higher level of protection might be a better choice, In any case, virtually any size of remote air tank gets you an extra 1 quart of oil in the Accusump.

[rac]

My 2c's on general discussion;
- wet sump systems are never perfect,
- a lot of racing classes have wet sumps mandated and live with oil pressure dips for many racing seasons without failure.
- bearing failure is a function of both rpm and load
- the minimum requirement for oil pressure would be a function of rpm, load and bearing surface area.

these engines are capable of producing high loads at low rpm hence oem design of the oil pressure curve rapid ramp up.

my advice to anyone logging oil pressure would be to plot their track data against both rpm and load. if the dips are only at high lateral g's with low engine load but still > 10psi per 1000rpm i wouldn't waste your time resources solving it. if the dips persist as you load up the engine and go full throttle on corner exit then that might be something to specifically target. this is were electronic control of the accumulated oil with say both rpm and tps as inputs could be useful in making the best use of a limited volume of oil.

alternatively if you really wanted to re-create the oem pressure v rpm curve i guess you could program a solenoid with that curve minus a practical trigger margin and just keep adding accumulators until there are no more significant dips past the trigger margin....