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Blackbird accusump
INDY BIRD - 13/3/06 at 10:47 PM

After fiting my accusump i tested it out on the road this evening and with it running the car shows oil pressure around 70-80 psi at 5000rpm.

once on the move when i go around a right hand bend the oil pressure drops to around 40, but does not seem to move around left hand bends.

Does anyone think this is correct as it is hard to know if the accusump is working as the gauge for the accusump is fitted directly to it.

Any info much appriciated.

Picuture of accusump attached.

cheers Sean Rescued attachment accusump.jpg
Rescued attachment accusump.jpg

kb58 - 14/3/06 at 02:26 AM

It's hard to tell based on this little data. Did you do these same turns with the valve off? What happened?

Assuming worst case, that when you go around a right-hand bend your oil pump sucks air, then the Accusump begins pushing oil into the engine, beginning with a pressure of what the oil pump was producing immediately before air was found.

So, if oil pressure was 70lbs when the air hit, oil pressure is now supplied solely by the Accusump, so the pressure will slowly decrease from 70lbs toward zero, the rate depending on how much oil your engine consumes.

From the picture it appears you have the manual valve under the hood of the car, correct? This means you open it before starting the car? The trouble with this is the Accusump pushes all of its oil into the engine, severely overfilling the sump. Once up to speed it shouldn't be a problem. You may consider the remotely activated valve so you can control it from inside.

Here's mine:
http://www.kimini.com/Diaries/2006Mar-/manual%20valve.JPG

http://www.kimini.com/Diaries/2006Mar-/manual%20valve,%20inside.JPG

Accusumps are far from perfect, but as they're about 10% the cost of a dry-sump we'll continue to use them. I have several ideas for how to make them MUCH better... I just have to get off my butt and develop it.

ChrisGamlin - 14/3/06 at 01:20 PM

If the oil pressure is dropping at all whilst engine revs stay constant then surely air must have been sucked up already? I dont know the exact workings of the Accusump but from what I have seen its designed to react to the pressure drop and bring the pressure back up to normal running pressure?

The way I see it though, the damage could already be done by the time the Accusump decides to react. It only ever reacts to a pressure drop, so although it may be better than nothing, it still closes the door after the horse has bolted (ie after air has been sucked up). At some point this slug of air causing the low pressure situation has to come back out of the system, the only way is either past the bearings or through the spraybars etc. If it comes out via the bearings then momentarily the bearing will have zero oil supply so no pressure, and on a sensitive engine that could be enough to start picking up a bearing even if it doesnt immediately cause a catastrophic problem.

Coose - 14/3/06 at 01:35 PM

Do you have it plumbed in correctly? I've never had anything to do with one, but I would have thought it should be plumbed in downstream of the pump and should maintain the pressure at all times (unless the pump is not pumping oil for a long period, allowing the oil supply in the Accusump to deplete)?

Yep, description here

[Edited on 14/3/06 by Coose]

kb58 - 14/3/06 at 03:15 PM

quote:
Originally posted by ChrisGamlin
At some point this slug of air causing the low pressure situation has to come back out of the system.


That's only true if the oil pump is also an air pump... I don't think it is. If it gets air on the inlet side it simply stops pumping.

Think of an Accusump as a ballon attached to your oil system. As pressure increases, the ballon inflates, and as pressure decreases, it empties, pushing oil back into the system. It's far from perfect, taking oil away from the engine when rpm is increasing, which is only acceptable if it's an amount the engine can live without. Who of us know the oil pump output volume, and how much oil our engines use at various rpm... not me.

My rant about their marketing:
They say only the manual valve version is suitable for racing, OR, if you buy their pressure sensing switch to switch the electric valve option. Yet if only the electric valve is used, they say it's only good for pre-oiling the engine. Well since most engines these days last 200,000 miles without pre-oiling its effectiveness is questionable. The real problem with the electric valve is it's restrictive, yet by adding a pressure switch they claim it's then suitable for racing. Nonsense.

But overall it's better then nothing, and does the job of covering brief oil pressure drop-outs.

[Edited on 3/14/06 by kb58]

Jon Ison - 14/3/06 at 03:20 PM

If you do a search on yahoo list you will find a thread on this,

You will also find two data logging printouts, (well a link too them) one a lap of donnington with it on, one with it off, look at them then you might just go out and buy one.

I ran one for 3 years on a blackbird covering hundreds of flat out track miles on the same engine, we all know the reputation of bird engines.

kb58 - 14/3/06 at 03:24 PM

Do you have a link to that particular thread? 100s come up...

Jon Ison - 14/3/06 at 03:56 PM

Not sure but i seem to remember Mike Field of MDS batterys been the guy been the one you need too talk too, if its not him he will defo remember who it was.

ChrisGamlin - 14/3/06 at 06:52 PM

quote:
Originally posted by kb58

That's only true if the oil pump is also an air pump... I don't think it is. If it gets air on the inlet side it simply stops pumping.

[Edited on 3/14/06 by kb58]


Assuming the oil system from pickup to bearing is a closed system, the air must go somewhere though, the only way is either out through the bearing surfaces or back out through the pickup? My bet is that it won't find its way back down the pickup very easily so must go through the pump and into the pressure stage?

I can see what you're saying with the balloon analogy but here we're dealing with two fluids (oil and air). Imagine it more as a swimmer in a swimming pool treading water. There's an oxygen tank on standby to use when the exhausted swimmer can no longer keep afloat and swallows some water. Because they only swallowed a bit of water they might not drown but its still not as good as having the oxygen cylinder from the off to stop them swallowing it in the first place! Silly analogy I know but hey ho

Having said all that I can see that an Accusump may improve things to a degree, but I still think that the best its ever going to do is minimise the damage done on each oil surge moment by restoring oil pressure sooner, compared to a dry sump (or good wet sump design) that wouldnt allow any air in to start with, so the engine would suffer no oil pressure reductions at all.

Chris

kb58 - 15/3/06 at 01:16 AM

quote:
Originally posted by ChrisGamlin

Assuming the oil system from pickup to bearing is a closed system, the air must go somewhere though, the only way is either out through the bearing surfaces or back out through the pickup? My bet is that it won't find its way back down the pickup very easily so must go through the pump and into the pressure stage?


Chris


I'm still not sure about that. The pumps are either gear-drives or the rotor-type, and I don't think either one pumps air well at all. As soon as the pickup is uncovered, I think all pumping will cease. This is where the Accusump fixes things. HOWEVER, I agree that once air fills the tube from the sump to the pump, then is recovered in oil, the pump will pressurize the air to 60-something psi and send it on its way to all the bearings. That can't be good for anyone and the Accusump can't help because it sees 60psi... of air, but it can't tell the difference.

Oh well, until I can get a CCW-rotation (Honda) drysump pump, tank, and hoses for a couple $$$, I'm stuck with the Accusump.

ChrisGamlin - 15/3/06 at 09:09 AM

Im not sure either, its just the way I envisage it working, its interesting discussing it all though and getting a better understanding of it all

My thoughts are that although the pump doesnt pump air very well, it will still pump it to a degree. Thinking about it if the pump never pumped air at all, you'd never get any oil pressure when first filling an engine with oil as you'd never be able to draw oil up the pickup to reach the pump. I guess it would be similar when you start the engine every day, I'd imagine there's oil in the pump, but the oil in the strainer / pickup would have drained back down into the sump leaving a section of air in the pickup that has to be pumped through in order to regain oil flow?

cheers

Chris