LS3 V8 RX-7 Accusump

Project V8 RX-7:  More Oiling Insurance From Improved Racing, Accusump and Earl's (Part 1 of 2)

by Jeff Naeyaert

It’s no secret the LS family of engines can have oil starvation issues particularly on the racetrack. In high-g turns oil is forced to once side of the pan leaving the oil pickup dry and thus starving the oil pump and the engine's components of oil. Catastrophic damage can result in as little as a few seconds depending on engine speed. Corvette and Camaro owners who track their cars regularly modify their oil pans with baffles, overfill their engine oil, add dry sump systems and oil accumulators. Chevrolet attempted to address the problem by equipping certain LS3 and LS7’s in their C6 Corvettes with a “sorta” dry sump system from the factory.

We’ve already installed an oil pan baffle from Improved Racing in Project V8 RX-7 but if big ole Camaros weighing as much 20% or more than our FD are pulling enough G’s to starve the oil pump it seems logical to conclude that risk would only be greater in our lightweight RX-7 with big sticky tires and wider track. A true dry sump system would be the ultimate in oiling insurance and quite fitting for our “nothing but the best” flagship project. Unfortunately, dry sump systems need big external oil tanks and we’re already out of real estate under the hood of our little Mazrolet. They also cost a lot of money and if we had to pay for one.. well we probably wouldn’t get one until we blew up a motor to prove we really needed it. Enter the next best thing—an oil accumulator.

Put simply, an oil accumulator is a pressurized tank of reserve oil. There’s a piston inside with pressurized air on the back side of the piston, oil on the top side and either a manual or electric valve that is then plumbed directly to the pressure side of the engine’s oiling system. When the engine is running, the engine oil pressure from the oil pump fills the accumulator and stores the oil. If engine oil pressure drops below a certain threshold while the engine is running the electric valve is opened and pressurized oil is immediately supplied to the oiling system. This oil is supplied until either the pressure rises above the threshold or all the oil in the accumulator is expelled—anywhere from 15-60 seconds depending on engine speed and the size of the engine. 


In this illustration you can see the oil in the pan is shifted to one
side leaving the sump dry--simulating a low-pressure scenario.
The valve of the accumulator opens and fresh oil is supplied to the engine.

Once the sump is submerged and oil pressure returns to normal the accumulator is again filled.

When the engine is shut off, the valve closes and engine oil pressure at the time of shut-off is maintained. Another neat feature of the accumulator is its engine start-up protection.  Opening the valve prior to starting the engine pre-oils engine components at whatever oil pressure the engine was at when last shut off and the accumulator valve closed.

We got our hands on the original and arguably the most well known and best selling oil accumulator, the Accusump, manufactured by Canton Racing Products.

Accusump Mazda RX-7 V8 LS3
Available in 1, 2 and 3-quart capacities we chose a 3-quart unit.  Bigger is better—the larger the accumulator's capacity the more pre-oiling and longer engine protection it can provide as long as you have the space to mount it.
Accusump Mazda RX-7 V8 LS3Our 3-quart Accusump unit measures 4.25 inches in diameter by 16 inches in length before adding the gauge on one end and valve and plumbing on the other.  There is no room for it to be mounted anywhere under the hood and we don't want to mount the accumulator inside the car because if a fitting or line fails that means hot oil spraying around.  It's a little far from the engine, but there is a gap between the rear subframe and the fuel tank on the FD RX-7 that looks like it may be just the place to stick our Accusump.
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Sunday, November 22, 2015 11:23 PM
Great to see you guys tackling the oiling on the car, it will be something that I will be doing over the winter on my car.

@Jeff Naeyaert - Did you guys ever get the Alpha-N tune on the AEM 30-1220 running?
Jeff Naeyaert
Jeff Naeyaertlink
Monday, November 23, 2015 1:04 AM
@Tai-Lun, yes we did... that was eons ago on the old LS1 though READ HERE
Monday, November 23, 2015 7:59 AM
They changed the design of the electric valve. Looks a lot more compact. I think the Accusump is great insurance.
Monday, November 23, 2015 4:11 PM
Great article, I went through this with my ls2 s13 last winter. I have a question though - what would you do on a drift car that spends a lot of time idling on hot grid? At idle the oil pressure is below psi of the switch, causing the valve to open and equalize pressure between the accumulator and oiling system. This would overfill the sump while waiting in line and would force the accumulator to refill during the run when rpm up and system pressure is higher than that of the switch. Once the run is over the system pressure falls back below the limit of the switch and you over-fill the sump again. Would you use a manual valve and turn it on/off between runs?

My solution (where I would like input) was to have the pressure switch ground through both a toggle switch and through an rpm switch. The toggle switch is so that I can flip it for pre-oiling and once the engine is running I can turn the switch off. The rpm switch is there so that the accusump pressure switch would only ground if the system pressure is less than 25 psi and rpm is over 3k. Only if these two conditions are met would the accumulator discharge oil into the system, which hopefully won't happen but it ensures that the valve stays shut during idle and opens if I need it to.

Sorry for the wall of text, everyone I asked for input didn't know how the system worked and shrugged their shoulders saying "sounds like it should work"
Jeff Naeyaert
Jeff Naeyaertlink
Monday, November 23, 2015 4:44 PM
@chcotrup which EPC valve are you using? I'm using the 20-25 psi valve. You shouldn't be seeing idle oil pressure lower than that on the LS2. Both your ideas sound logical but opening a mechanical valve is one more thing you probably don't want to be thinking about on the grid.. The RPM switch would work too but you could blow something, come in and not know about it till you're back in the pits--spending enough time below 3,000rpm to ruin something. Also it's one more thing to fail.. I'd invest in a lower psi switch if you don't already have it, check your oil pressure with a mechanical gauge and confirm it's really that low at idle and if that's the case maybe bump the idle speed enough to raise the oil pressure above the threshold. But yeah, "sounds like it should work" ;)
Monday, November 23, 2015 5:07 PM
I'm using the 20-25 psi valve. I just checked some in-car footage and you're right, pressure hangs out right around 28-30 psi at idle. I put everything together when I was still ka-t which idled below 20 psi and haven't really thought about it since, this article reminded me of my "fix" so I figured I'd see what MotoIQ thought. Oil pressure gauge has an audible warning if I drop below 10 psi so hopefully I'd hear it on the way back to the pits, but yes that thought had also crossed my mind :) Thanks for the response!
Tuesday, November 24, 2015 10:47 AM
I'd be really curious to see how you perform an oil change with this Accusump/oil cooler setup.
Tuesday, November 24, 2015 11:01 AM
Depends on how its wired, but flip the switch to open the valve. Fill up the pan and drain. There are other methods, but consider it all gets mixed together.
Jeff Naeyaert
Jeff Naeyaertlink
Tuesday, November 24, 2015 11:16 AM
i would add that i'll probably charge the Accusump canister with 100psi of pressure (via the schrader valve) to force out as much oil as possible before draining.
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