Another 2nd-gen engine failure at track...

[ZDan]

Originally Posted by RZNT4R

Moroso has a different idea with their accumulator

I don't think they have a different idea, in fact he said their recommended pressure was 7-10psi. It would have been good to see him dump pressure on the engines side with 20psi initial charge though, to see how much sooner the accumulator is emptied of oil.

I would be going with the 2-quart version for ease of fitment, so a lot less oil volume and hence reduced time of covering up for oil pressure drops. My thought is I'd rather have more oil being fed in for a longer time, which is what you get with lower initial air pressure.

It is encouraging to see that with the 3-quart unit, with 10psi initial air charge, that there's 14 seconds of oil supplied if there's pressure lost on the engine side, that would seem like plenty of time. With the 2-quart unit, it would be more like 9 seconds, still probably plenty of time to deal with temporary oil pressure drops.

I guess I'm not too worried running the recommended 7-10psi, but I wouldn't even consider 20psi due to reduced capacity and even greater reduction in time until accumulator is emptied...

[blsfrs]

The tradeoff for more precharge is less oil volume in the Accumulator (P1V1=P2V2) but it would also "react" more quickly.

[RZNT4R]

Originally Posted by ZDan

I don't think they have a different idea, in fact he said their recommended pressure was 7-10psi.

I meant he mentions (at 10:50) that on an engine with tighter clearances the higher precharge is recommended. I would suspect an FA to fall on the "tighter" side of things.

But the beauty of the system seems to be that you can find the right setup, initial capacity vs precharge, to suit your needs. Different engines with different clearances and a different number of journals, oil squirters, timing belts or chains with hydraulic tensioners, VVT, turbos and whatnot, likely all have different volume requirements so the times shown in the video probably don't apply to everything. Ideally you could probably charge it, close the valve, shut down your engine and then key on engine off, open it back up and watch the oil pressure to fine tune the pre-charge for how long/how high you want it.

[Ultramaroon]

Originally Posted by ZDan

There's this:

I have mixed feelings about the effectiveness of a simple accumulator. If I were to design a backup system, I'd build in a wide band of hysteresis so the accumulator retains maximum charge until the downstream pressure drops below a set threshold. This would keep the system to operate in positive displacement mode (as designed) and preserve the maximum effect of the accumulator for when it's needed during an actual starvation event.


I've mentioned before my opinion that the Accusump is an unfinished product.

[ZDan]

Originally Posted by RZNT4R

I meant he mentions (at 10:50) that on an engine with tighter clearances the higher precharge is recommended. I would suspect an FA to fall on the "tighter" side of things.

I still think I'd rather have something over a quart stored in a 2qt version at 7psi, than quite a bit less than a quart at 20psi. They don't see to actually be recommending 20psi, I don't think so anyway. For a long sustained right-hander, with oil up to temp (i.e. a LOT thinner), I'd be worried about very short discharge time to empty with 20psi air charge and starting with less than 1 quart in the 2qt accusump.

[ZDan]

Originally Posted by Ultramaroon

I have mixed feelings about the effectiveness of a simple accumulator. If I were to design a backup system, I'd build in a wide band of hysteresis so the accumulator retains maximum charge until the downstream pressure drops below a set threshold. This would keep the system to operate in positive displacement mode (as designed) and preserve the maximum effect of the accumulator for when it's needed during an actual starvation event.

You can get a pressure-triggered solenoid that only opens when engine oil pressure drops to 20-25psi. Also can get ones that open for different pressure thresholds.

I've mentioned before my opinion that the Accusump is an unfinished product.

A friend just installed one and had issues until he installed a diode to prevent back-EMF issues from blowing out fuses or some such.
I had one in my LS3 FD years ago, the 20-25psi oil pressure triggered solenoid quit working on it early on so I just wired it to open with ignition on and close with ignition off, with an inline switch as well.

[Ultramaroon]

Dump diode is a critical part of the system. Surprised that it isn't part of the kit.

[ZDan]

Originally Posted by blsfrs

The tradeoff for more precharge is less oil volume in the Accumulator (P1V1=P2V2) but it would also "react" more quickly.

Initial reaction should be identical, as in both cases you're starting with the same pressure on the air side of the piston. But with the 20psi "initial" case the air pressure will not drop off as quickly. Kinda good because that means the oil pressure being fed into the engine won't drop off as quickly either. But also means that it will run out of oil to feed into the engine more quickly, and it started with a lot less oil to begin with.

While durations look nice and long in this video, I'm guessing that's room-temperature oil. Under operational conditions at the track, it's likely to be a lot hotter than that, and hence much shorter time for the accumulator to be feeding oil back into the engine when oil pressure drops.

Anyway, they recommend 7-10psi, I would be OK running anywhere in that range and wouldn't try 5psi or 20psi.

I'm going to send out oil for analysis, if I'm seeing worrying levels of bearing metals in the oil after two track events, I'm getting the 2qt Accusump.

[NoHaveMSG]

Originally Posted by ZDan

There's this:

I have one, just haven't installed yet.

[blsfrs]

Originally Posted by NoHaveMSG

I have one, just haven't installed yet.

Well, what are you waiting for???(LOL)

I really want to see some datalogging. I know in my head accumulators should work but there's no hard data.

[blsfrs]

Originally Posted by ZDan

Initial reaction should be identical, as in both cases you're starting with the same pressure on the air side of the piston. But with the 20psi "initial" case the air pressure will not drop off as quickly. Kinda good because that means the oil pressure being fed into the engine won't drop off as quickly either. But also means that it will run out of oil to feed into the engine more quickly, and it started with a lot less oil to begin with.

While durations look nice and long in this video, I'm guessing that's room-temperature oil. Under operational conditions at the track, it's likely to be a lot hotter than that, and hence much shorter time for the accumulator to be feeding oil back into the engine when oil pressure drops.

Anyway, they recommend 7-10psi, I would be OK running anywhere in that range and wouldn't try 5psi or 20psi.

I'm going to send out oil for analysis, if I'm seeing worrying levels of bearing metals in the oil after two track events, I'm getting the 2qt Accusump.

Have you seen dips in your op on the tracks you run?

[ZDan]

Originally Posted by blsfrs

Have you seen dips in your op on the tracks you run?

I haven't been monitoring it. I have a non-CANbus Aim SoloII to record lap times and that's all I have for data collection...

[NoHaveMSG]

Originally Posted by blsfrs

Well, what are you waiting for???(LOL)

I really want to see some datalogging. I know in my head accumulators should work but there's no hard data.

Don't have the time.

[befepo6]

Same


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