Last month I installed an Accusump on my track car (Vette) and thought some of you might be interested in seeing and reading a little about it.

For those who don't know, an Accusump is essentially an aluminium cylinder with a plunger in it. One side of the plunger is filled with oil and is connected to an oil gallery plug on the block of your engine (or can be connected to a sandwich plate on your oil filter). The other side of the plunger is filled with air. There is a valve on the oil side that controls the entry and exit of oil into the cylinder. As oil from the engine fills the cylinder it compresses the air and thus the oil is maintained under pressure.

The main purpose of this is to provide a reservoir of oil that can be 'injected' into the engine in the event of a low oil pressure situation. I have an electronic valve that is set to 25 PSI. It allows oil to enter the cylinder when the engine is running but doesn't allow it to escape as long as the engine pressure is above 25. So the oil in the cylinder reaches the same max PSI as your engine. Say your engine is running 50 PSI...to equalize pressure the oil in the Accusump will be the same. Then, if the PSI in your engine drops the Accusump stays pressurized, all the way down to 25 PSI. If the engine pressure drops below that the valve instantly opens and injects high pressue oil into the engine, up to 3 quarts of it (you can also get 2 quart Accusumps).

The devices are commonly used in race and drag cars to protect the engines in a low pressure situation - any time the oil pickup in the pan sucks air, mechanical failure, leak, etc. It will provide a few extra moments for the engine to recover (like in a high G turn where oil is pooling in the heads and the pickup sucks dry) or for you to shut it down due to some failure.

Hopefully my motor never has to use it but just in case I now have this extra layer of protection.

So thats the main purpose but I'm actually more excited about its secondary purpose - to end 'dry start'. Its often said the most wear on your engine occurs during startup. The theory being, if the car has sat for an extended period, most of the oil has pooled in the pan. When you start the car, until pressure builds, you are running 'dry' (not really but close) and this is when most of your wear occurs. The Accusump prevents this. When I shut my engine down the Accusump maintains its pressure. Then, the next time I start the car, I turn the key to accessory for about 10 seconds without actually starting it and the Accump releases its oil and pre-lubes the engine. I can actually see the oil pressure guage come up to about 20 psi before I ever light off the engine. Pretty cool.

You can think of this as a poor mans version of a dry sump. If you have the money, a dry sump system is the best way to go, but they cost more than 10 times what an Accusump does. So for most of us, who are uber serious about tracking our cars and don't have a CEOs salary, this is the unit to have.

Here is a picture - its located under my drivers side front fender:

 

that's pretty cool, I've heard of these systems, it's gotta be better for the motor to start up with the oil pressure already built up.

 

$170 isn't too bad for this piece of mind. How much does this cost to install?

 

Between the tank, the electronic valve, the AN fittings and braided lines I have almost 500 in this. I installed it myself.

 

Thanks for the write-up Argo. I've known about these for some time, but it's really nice to see a first hand account. Your explanation of how the system works in relation to pressure was helpful.

Thanks again.
Best,
-j

 

Hey Argo,

Thanks for the write-up. I've seen a couple of these at track days and I've started doing some install research. I made the mistake of not ordering the zillion color dash and didn't get full gauges with my car (didn't know that was part of the deal) so I'm not sure if my pressure is dropping in long radius turns. Usually when/if the idiot light comes on, you're in trouble pressure wise.

Did you go with a remote oil filter or oil cooler as part of the installation? Do you have any pictures of the engine side of the install?

I'm thinking about adding gauges for oil pressure and temperature as well as water temperature given I don't have them now.

Cheers,

 

Red, there's a guy on another forum, SoundGuyDave, who has done an oil cooler on an S197. You can see pics here. Go to post #28

He's also done an Accusump, but I haven't found pics of it yet. I should just take my own, as he's a buddy of mine and lives in the area.

Best,
-j

 

Joe - I put the Accusump on an LS6 so it will be a little different. I do have an oil cooler - its lines go in and out of the block right at the oil filter (GM planned for this and has ports there already.) The accusump just goes into a an oil gallery plug on the block. Its on the drivers side, near the front of the block. I don't know if the Mod motor has an equivalent.

As for guages - I recommend them. Once we start running big R-Comps we are pulling some pretty serious Gs and pushing the engines very hard. On the LS6 I have a huge radiator w/built in oil cooler. It works great - my temps are in general under 240 for both oil and water. Guys who run the stock radiators are hitting temps in excess of 280 and occasionally 300 . Not so good for the internals, seals, hoses, etc. The viscosity and protection of oil starts to diminish in a hurry as temps rise. Its also interesting to see what the oil pressure is doing. As temps rise the pressure goes down. Last year I was seeing pressure in the lower 20s - this year I have a new motor so the pressures are very good thus far (only 1 track day).

Brad

 

I've said it before, but it's worth repeating. Look to the FR500S as a template for a build. Their engine is our engine, but with an upgraded radiator. Those cars are being raced hard and driven hard on the track much more than our cars and their engines are holding up fine.

They don't use an aftermarket oil cooler. They don't use an Accusump.

Our stock setup uses a baffled oil pan--maybe not as well baffled as a Canton road race pan, but baffled well enough to maintain oil pressure on the FR500S which runs on BFG-R1's.

Our stock setup also has an integrated oil-to-coolant heat exchanger. That's why those of us with coolant and oil temp gauges notice that the oil temps tend to track within ~ 10 deg. F of the coolant temps (with the oil temp sender in the pan).

The best modification you can do is to upgrade the radiator. This helps shed the excess heat that is pushed into the system from (1) running hard on the track; and (2) the integral oil cooler. It is simple, relatively inexpensive, and it works.

 

Just so there is no confusion - I agree with Slaya - I have not seen any evidence that an Accusump is needed on the 4.6 mod motor in a S197. These motors don't seem to have the oiling problems that the GM LS motors do. My application is an LS6 (as I pointed out in the opening post). All LS engines have oiling problems - especially the later ones: LS2 and LS3. The current C6 Z06 (LS7) even has a factory installed dry sump system to combat the problem. For me the accusump is a no brainer for its protective function alone. But I also like it for its ability to prime the engine before start up.

I posted the info here because I know that many folks enjoy reading and learning about all track related tech.

Whether or not an oil cooler (or oil cooler upgrade) is needed really depends on what oil temps you are seeing. If oil temps are consistently below 250 then I'd agree - no point in it. But if they are getting into the 250-300 range then personally I'd be seriously looking at a fix. (note there is considerable debate on this subject of oil temps - some claim with synthetics oil temps close to 300 are ok. Most however do not think that way - its not necessarily the breakdown of the oil but rather the high temps affecting other parts: seals, hoses, etc.). I'd also point out that any direct comparison between a street going HPDE car and a full race car should be approached with caution. Most of us, driving our street cars, want longevity. Race cars...not so. All parts in a race car are consumables, including engines. I have no idea with what frequency teams are replacing motors in the FR500S but I do know that its a yearly or less endeavor on most high level amateur and pro teams. Without the data (oil temps, coolant temps, oil pressures) what is or isn't needed in a seriously tracked S197 is all speculative anyway.

Slaya - It sounds like you have installed guages. What oil and water temps do you see (before big radiator, after)? What pressures? Also - can you give us (me) more info on the stock integrated oil-to-coolant heat exchanger? - educate me...I didn't know we had such a thing.

Update: see Philo's post below where he references an Oil Viscosity thread. Looking at that I see the answers to my above questions.