I've had some minor blips of low oil pressure with my K24 under hard braking. Very short drops that basically last only long enough to trip a warning pop-up on my IC-7 dash. To be fair, these are really low pressure events, under 15psi. Hot idle with the OE-recommended 0W20 oil is right around that pressure, so I was hoping I could get away with it. I already moved away from 0w20 and will be running a thicker oil thanks to new bearings and increased oil clearances, but I still expect to have some dips when I put this motor back together.

Having gone through all the effort of replacing the rod and main bearings, I really want to try to maintain good oil pressure going forward.

I'm not sure I'll address the oil pressure issue in time for the September event, but I've got thoughts rattling around in my head and I'd like the hive-mind's input.

(Image borrowed from did-it-myself.com and edited by me)


The circled opening leads directly into the post-oil-filter galleries and is sealed by an o-ring to a blank spot on the timing cover. The place it lands on the cover isn't perfect and I'd have to "adjust" the little sheet metal cover over the timing chain tensioner, but this picture shows approximately where it dead-ends.



First question - The reason for me to not just use a sandwich plate adapter or the like is that this seems to me like a much better solution. I'm not running an oil cooler right now so I could easily add a sandwich plate, but if/when I go to add the cooler, that's going to be a mess of hoses, I may need a check valve, and so forth. My proposed location is upstream of the oil filter and feeds right to the main oil gallery, so I'm less concerned about the Accusump oil going "backwards" towards the pump (or cooler). It seems like a no-brainer. Am I wrong?

Second question - I think that an ORB fitting would technically be the correct fitting to put here, but for the -10AN size that Accusump recommends, that's going to be way too big. I think I can get away with a ~0.75" counterbore for a weld-on male fitting here, but it's going to have to be shallow. The through-hole for oil flow can certainly be 5/8" diameter without any interference. I don't think there's enough material for a 1/2" NPT and I really don't like that solution anyhow. Would I be asking for trouble by putting a male -10AN fitting here on the front of the engine?

Third question - Modern Accusump control. Canton only offers a few different pressure switches for their electronically-controlled valves and the switches themselves are poorly reviewed. I already have a high-quality oil pressure sensor that is feeding into my ECU. Canton and Moroso both sell oil-control solenoids without pressure sensors. Is there any reason I shouldn't let my ECU control such a solenoid based on pressure, RPM, throttle position, etc? I'd feel a lot better being able to set the point at which the solenoid opens based on my actual needs, rather than whatever switch these companies buy from who-knows-where. Allowing the ECU to control the valve could conceivably keep me from dumping the Accusump oil into the sump at idle.

Fourth question - Thinking logistically, I don't want the Accusump inside the cockpit and I'd like to keep the hose run as short as possible. The open space I'm eyeing is basically in the headlight area of my NA. I don't plan to hit anything with my car, but this does seem like a place that might take some damage. Is this location a bad idea, a really bad idea, or acceptable?

Thank you for your input!

 

Exactly the scenario that prompted my fitting an Accusump in my BP engined racecar. In the boot for me, pressure switch activated initially until advised of reliability issues, changed to manual valve within reach on the side of the tunnel. Left on while engine running, turned off prior to engine shutting down.

Total success, low OP warning never happened again. Can't say how it will work in your application, I can't see any dealbreaker but then I don't really understand the Honda oiling system.

 

I don't have experience with K24's, but I'll answer based on my turbo BP.

If you're plumbing the Accusump into the oil cooler return flow, you'll want a check-valve in the system to keep it from pressuring the oil coming from the motor to the cooler. Its even noted in Accusumps plumbing installatio notes. I used a high-flow flapper check valve from Improved Racing. The flapper doesn't impeed oil flow when fully open.

This is really going to depend on how thick the casting is. A weld on bung (NPT or ORB) would probably be the best option if there is enough real-estate.

Based on recommendations from fellow racers, I just left the valve open when on the track. Electric valves aren't of that size aren't quick to react. So by the time the motor sees low oil pressure, sensor registers it, tells the ECU, which then starts to open the valve, the event may have passed. I had an electric valve (because the Accusump was installed in the trunk). I opened it for prelube, started the motor, refilled the Accusump while oil pressure was high, and closed the valve. Then once I was on track for my warm-up lap, I would open the valve for the session. On my cool down lap, I would close the valve while on a straight where oil pressure was up. Then when I pulled into the pits, I would open the valve again, hold the RPM to get max pressure, then close it again.

I put mine in the trunk and ran the line down the transmission tunnel. Technically, its only supplying reserve pressure (not oil volume) so there is equal pressure from the Accusump to the motor. When the pressure in the motor is lower than the pressure in the Accusump, the Accsump pushes a little oil into the motor until the low pressure event passes.

 

Thanks for the replies!

@Midtenn I like the idea of a manual/electronic valve and I think that's the way to go. Before reading all the Accusump manuals, I had assumed that you pressurized the cylinder with air at the PSI you wanted the oil to come out, ie your minimum desired oil pressure. After some thinking, I understand their "pressurize to 60psi and then bleed down to 7psi" because that's how you get the piston to fully expand, but the 7psi number seems arbitrary to me, I guess that ends up controlling how quickly the oil is pushed out of the accumulator when the engine pressure dips.

In thinking about it, the Accusump with the valve open is just extra pressurized oil volume that will get fed into the system as the oil feed pressure changes. So as the oil sloshes away from my pickup and the oil pressure drops precipitously, the engine will be fed with the extra quart of pressurized oil from the Accusump. When I write it out like that, it makes more sense to me, especially when considering pressure-based control of the solenoid. Definitely makes sense to simply leave the valve open during hot laps and manually control it for pre-lube, etc.

 

The 7psi isn’t arbitrary. The accusump is literally just a tube with a floating piston. Oil on one side, air on the other.

The 60psi is just to make sure the tube is completely free of oil when setting the base pressure.

The significance of the 7psi is to put a known volume/pressure of air in the tube. As the air squishes down with oil pressure, the air pressure increases. At ~30 psi, the air volume is cut roughly to 1/4 of the cylinder, with oil filling 75% of it. At ~60psi, the air occupies about 1/8 of the cylinder, meaning close to 90% of the tube fills with oil.

If you get too much pressure, the tube won’t hold as much oil, and too little and the dead space in the air piston side will not be enough to maintain useful oil volume at pressure for the engine.

Its worth noting that when engine oil pressure drops and the accusump starts pushing oil back into the engine, the pressure it’s delivering drops rapidly, so to keep 15psi in the engine, less than 1/2 of the oil in the accusump is actually usable for oil volume.

That’s also why it’s good to have a solenoid valve to close the accusump, at least when the engine is off, because if you don’t and leave it open, all the extra oil that goes into the 1/2/3 quart cylinder needs to be stored in the oil pan when the engine is off resulting in a severely overfilled oil pan on engine startup. (And your dipstick will be useless)

If you do try to control the solenoid from the ECU, you’ll have to be clever about it. If you wait to open the 60psi accusump until oil pressure drops to 15psi, you can’t just close it again when it goes above 15psi, you have to wait till oil pressure is back up to 60 to charge the cylinder again.

What you gain by active control is more oil volume dispensed when the cylinder opens, vs letting the pressure (and fill %) float with engine pressure. Whether it’s worth the control headache is up to you.

If you were so inclined, you could accomplish the same thing with a pair of Hobbs switches at the two set pressures and a two-input latching relay (or a double coil solenoid valve)

 

Holy ****, what a great contribution Epssus! That is an Accusump education. Cat awarded!

I especially need to think about:

I was going to go with the smallest model for packaging reasons, but I'm going to rethink that.

Way to go from zero to hero on your second post!

 

Very good info indeed. Good to note that you can do all this with a manual valve too. Before shutting the engine off, rev it until the gauge on the back of the cylinder stops going up. Usually I would it at ~4000rpm for 10-15 seconds then close the valve while still holding higher RPM. Now you're ready to check the oil level with the dipstick. Read between the lines, and it's important to mount the accusump in a place where you can see the gauge from the driver seat.

Also good to note, oil changes are a little different. Not only do you want to open the valve so the oil is dumped into the engine, but you want to increase air pressure to ~40-60psi to ensure all oil is pushed into the engine to drain out the pan. Once oil change is finished, return air pressure to 7psi, add extra oil (roughly the capacity of your accusump), start the engine, and rev it up until the air gauge stops moving, shut the valve while still holding the high RPM, and again now you're ready to check oil level.

When starting the engine, key the car on and look at your oil pressure gauge, open the valve, wait for 5-15psi of oil pressure, then start the engine.

Its a lot of steps to remember, but once you're used to it, it becomes 2nd nature. Now if you have an enduro car you're renting out a bunch of random people, and electric valve is the way to go. I've used the Canton electric valve/sensor a number of times, the sensor seems to die frequently. If you have a PDM and a ECU reading oil pressure, it's fairly easy to program some logic to trigger the valve correctly.

 

Glad the info is useful, though not my second post - just a number of years of inactivity and my account got wiped.

It’s possible but slightly annoying to use a manual valve but the electric valve wired to “run” generally is the simplest and makes the most sense.

Doing a fancier control algorithm might get you more useful oil volume in really low pressure situations by delaying metering, and give extra pre-oiling volume, but generally it’s just as good for the simple full-open valve to just start pushing out oil as soon as the pressure starts dropping rather than waiting until the situation is more dire.

 

I really appreciate all the input folks, I'm glad we're getting a chance to talk about electronic control of the Accusump.

I don't think I can come up with logic that would allow my ECU to fully control an electronic valve for both pre-oiling and low-pressure situations. I have a keypad and PDM with a couple extra outputs so I'm fine doing that as a manual operation.

As long as I don't have to rev the engine sky-high in the paddock to recharge the cylinder, it seems OK to me to have the shut-off be manual too. The K24 doesn't require too many RPM to fully peg the oil pressure sensor, so that's handy.

The over-engineering answer that I don't want to get caught up in would be to have the ECU open the valve when I turn on the "Accusump" button, and when I turn off the button, have it rev the engine up, hold it for a few seconds, and then close the valve.

Have I mentioned that I'm insane, with a tendency to over-engineer?

 

I totally hear the urge to over-engineer a solution. But realistically, you’ll gain very little over an ignition triggered solenoid, or if you want to get really fancy a dual-Hobbs solenoid, unless you’ve got a scheme to save a few pounds by using a smaller accusump than you would otherwise. You don’t need a huge volume for pre-oiling, just enough to get oil into the bearings, so idle pressure is plenty for that

There’s also something to be said for simplicity and reliability in something like your oil system…

 

I started out wanting fine control over the Accusump, pre-oiling, auto activation via a pressure switch, but manual valve to isolate it. After hearing of people here having problems with the pressure switch, it was removed.

I then reverted to manual opening prior to start-up, left it 'active' thereafter and closed the manual valve after a few seconds of full OP on the cooldown lap (if I remembered, which would have been <50%).

That worked, no more low OP warnings. And when the engine was stripped by the builder several years later for a refresh, it was basically as it had left his shop. bearings were fine, bores were fine, rings were fine, etc. It looked as if it could have lived for a many more years - and this was an 8000rpm screamer. I put it down to a good engine builder, frequent filter and oil changes, and the Accusump.

YMMV, but for me just letting it do its thing seemed to get the result I wanted, and the engine certainly showed no ill-effects of operating in that mode.

 

I debated having mine setup with a manual switch (electric full flow ball valve) for pre-lube and post fill. I was going to have 2nd input that was controlled by the ECU based on speed and time. Basically, so once speed got above X value it would open and stay open for the full session (maybe having it close if there was a FCY).

 

This was the valve recommended to me on my 3qt accusump.

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They offer a lot of options in that size. IIRC I found one that would take 3 different inputs. I was going to use one input for manual control and one for ECU (if I ever figured out a logic I like).

Motorized Ball Valves丨U.S. Solid

 

They arent fast enough if you think you will have your ECU commend it open if pressure drops...

Like everybody else has said put it on a 12v switch, open it to pre-oil, leave it open while running, close it before shut down...

 

I manually triggered mine in the past due to a lack of ECU inputs/outputs. I was thinking of using the ECU to trigger it to open the valve at certain speed so I wouldn't have to remember to manually flip the switch on my warm-up lap. Then use a time delay so it didn't try to close the valve in slow corners.

 

I was perusing valves last night because I am an over thinker, and I came across a manufacturer’s note that their solenoid-based valves are not intended for continuous use, which they define as more than ~8 hours in the “on” position. For continuous use, they recommended their motorized ball valves. I believe this was US Solid.

This seemed like something worth noting and sharing. If you look at both the Accusump and Moroso valves, they use solenoids and a diaphragm. The solenoid will be drawing full power the entire time it’s open, which is going to be several to tens of amps. It’s also going to be dissipating a lot of heat during that time. It makes sense why these are not good for continuous use, and why in the McMaster catalog, this design of valve is for pulsing, not on/off.

For the use we’ve all settled on here, it seems like the motorized ball valve is the correct solution. I’m a little concerned that the price point from US Solid is too low for a quality part (especially in stainless!), but that’s thinking for another post.

 

The solenoid valves from canton are ~1-2amps, monitored over 8 hours. So it’s possible, despite what they say, but you’ll probably risk burning out the solenoid.

 

My fat *** sits corrected. 1-2A, thanks!

 

One of the perks of having a PDM in the car. Engine eventually had the accusump removed, but we tried pressure sensor activated, then left it on constantly like a ball valve, then eventually removed it. Turns out S54s on 200 treadwear tires don't really need an accusump. We're blowing them up from vanos issues or over-temps WAY more than bearing issues.