Oil Pressure Solutions Mi16

[findlay 0]

Now there is an interesting point... what if its not so much an oil-surge issue but a lack of oil draining back quick enough to fill the sump properly.

 

Had a couple of Mi16 lads look at the car this weekend and as far as they can tell me the engine is sitting at a slightly odd angle so as to clear the master cylinder. I'll be looking at my gearbox mount when the car is stripped down over the winter time and making some modifications to bring my engine back into alignment.

 

The additional angle to the dangle could mean some of the galleries for draining out of the head might not even have any oil sitting near them to drain!

[C_W 3 1 Cars]

Having a tilted engine doesn't really affect it that much; I was hoping it did because i ran minetilted for a short time but it seemed the same when i "untilted" it.

[findlay 0]

Arse biscuits... back to the drawing board again.

 

[Rob Thomson 6]

Sorry, bit of a rant......

 

The 309's going tarmac rallying next year and the last thing I want is to be blatting around the stages with one eye permanently on the oil pressure gauge. It's bad enough on the road - I dread to think what it'd be like with sticky tyres and a driver in permenant 'maniac mode'.

 

The Accusump thing sounds tempting because of the relatively low cost, but it sounds a bit too crude for my liking....

 

1) The oil is essentially stored against a pneumatic spring which means that the oil isn't delievered at a constant pressure. When the accumilator is full it'll provide oil at normal engine oil pressure (say 60 psi), but the dregs will only be pumped out at the surcharge pressure (say 7psi as per their website). And in between the pressure will reduce linearly. What I'm saying is that when it's delivering its oil to the engine, an Accusump cannot provide the same pressure as the engine's pump for any longer than the briefest of moments.

 

2) If you've got a six pint Accusump and it discharges all of it's oil, where do those six pints go? I don't particuarly like the idea of that much excess oil floating around in the engine. This'll be self regulating to some degree - as more and more oil is added to the engine the level in the sump will rise and eventually the pump will start working again - which will then start to replensish the accumilator and reduce the quantity of oil in the engine, but it all seems a bit too hap-hazard for me.

 

3) And what happens to the engine when the Accusump's being replenished? Some oil is going to be diverted away from where it should be going to re-fill the Accusump. Obviously the pump has some excess capacity (which is normally discharged through the pressure relief valve) but I'd guess that partial oil starvation would continue for a few seconds as the oil chooses the easy path into a partially filled accumilator (as above - unless it's full the pressure resisting the inward flow of oil is less than 60psi) rather than through the engine's galleries to the engine's bearings.

 

4) I wouldn't want to use one without a valve between the oil pump and the point where the Accusump is tapped into the oil galleries. Oil from the Accusump may be pushed back through the pump to the sump without lubricating the bearings and whatever else en route. But putting a non-return valve into the system just adds loses and unreliability.

 

 

A proper dry-sump has it's own problems; cost, weight, the vulnerability of an external oil pump drive etc. But I don't think they're anywhere near as flawed as the Accusump - and to my mind, a dry sump would be worth the extra cash.

 

The thing is, if you spend two grand or more on a decent engine rebuild, spending another £1100 of Barlaycard's money on something that'll ensure it'll keep working seems like a reaonable investment.

[findlay 0]

spending another £1100 of Barlaycard's money on something that'll ensure it'll keep working seems like a reaonable investment

Hmmm... I'm thinkin that a grand goes an awful long way to buying a washing machine, bed, sofa TV etc

[Deadliest Pug 0]

To fix the Rover V8 high engine speed oil problems you..........

 

Polish the inside of the block around the followers to help the oil drain and fit a good breather.

 

Worth a try.

 

Dave!

[base-1 17]

Sorry, bit of a rant......

 

The 309's going tarmac rallying next year and the last thing I want is to be blatting around the stages with one eye permanently on the oil pressure gauge. It's bad enough on the road - I dread to think what it'd be like with sticky tyres and a driver in permenant 'maniac mode'.

 

The Accusump thing sounds tempting because of the relatively low cost, but it sounds a bit too crude for my liking....

 

1) The oil is essentially stored against a pneumatic spring which means that the oil isn't delievered at a constant pressure. When the accumilator is full it'll provide oil at normal engine oil pressure (say 60 psi), but the dregs will only be pumped out at the surcharge pressure (say 7psi as per their website). And in between the pressure will reduce linearly. What I'm saying is that when it's delivering its oil to the engine, an Accusump cannot provide the same pressure as the engine's pump for any longer than the briefest of moments.

 

2) If you've got a six pint Accusump and it discharges all of it's oil, where do those six pints go? I don't particuarly like the idea of that much excess oil floating around in the engine. This'll be self regulating to some degree - as more and more oil is added to the engine the level in the sump will rise and eventually the pump will start working again - which will then start to replensish the accumilator and reduce the quantity of oil in the engine, but it all seems a bit too hap-hazard for me.

 

3) And what happens to the engine when the Accusump's being replenished? Some oil is going to be diverted away from where it should be going to re-fill the Accusump. Obviously the pump has some excess capacity (which is normally discharged through the pressure relief valve) but I'd guess that partial oil starvation would continue for a few seconds as the oil chooses the easy path into a partially filled accumilator (as above - unless it's full the pressure resisting the inward flow of oil is less than 60psi) rather than through the engine's galleries to the engine's bearings.

 

4) I wouldn't want to use one without a valve between the oil pump and the point where the Accusump is tapped into the oil galleries. Oil from the Accusump may be pushed back through the pump to the sump without lubricating the bearings and whatever else en route. But putting a non-return valve into the system just adds loses and unreliability.

 

 

A proper dry-sump has it's own problems; cost, weight, the vulnerability of an external oil pump drive etc. But I don't think they're anywhere near as flawed as the Accusump - and to my mind, a dry sump would be worth the extra cash.

 

The thing is, if you spend two grand or more on a decent engine rebuild, spending another £1100 of Barlaycard's money on something that'll ensure it'll keep working seems like a reaonable investment.

thats a worrrying but well thought post, and i thought i'd be ok with one of the damn things....

 

i absolutely HATE driving everywhere watching the bloody oil gauge, its not easy either cos my steering wheel is small so i have to duck, i need some way of ignoring it safely but im damned if im spending over a grand with pace, i just dont have the money - it might be "worth it" but id rather not be in as much debt

[Rob Thomson 6]

thats a worrrying but well thought post, and i thought i'd be ok with one of the damn things....

That post was really just a lot of speculation. I'm an engineer, but I'm much more au-fait with concrete than I am with automotive lubrication systems. It all makes sense to me, but it's based upon a lot of assumptions that I can't easily support. What I was hoping was for a bit of a discussion to determine whether or not I was talking bollocks.

 

Since writing that post, I've spoken to a mate of mine who's an aeronautical engineer. I remember reading somewhere that oil pressure accumulators are used on planes, so asked him what he knows about them and whether he would share my concerns.

 

The first thing he said is that "some oil flow is better than none" which you really can't argue with! Sure, the engine may normally run at 60psi, but how much pressure does it actually need to avoid damage? I have no idea - maybe it would be ok at 30 psi for short periods, in which case a 6 pint Accusump would give you about three pints of protection.

 

That leads to another question I can't answer - what rate of oil flow do you get around an Mi16 engine, and therefore how long does that 3 pints of useful Accusup oil give you as protection against surge? I would imagine that in most engines the actual flow is quite low, but what about in the Mi16 with its piston cooling oil jets? Still, I'd guess that three pints would give you about 10 seconds of protection - but that really is just a vaguely educated guess.

 

He also reckons that over-filling the engine for short periods probably isn't going to do any harm, but that you might end up with oil being pumped out of the breathers etc. Not really the end of the world, but something else to ponder.

 

He also reckons that the oil pump has probably got enough capacity to recharge the Accusump relatively quickly, so oil starvation due to replenishment might not be an issue. The thing is, if the pump doesn't have the capacity (and who knows whether it does - we're just guessing again) then this would be an issue.

 

He also reckons a Non-Return Valve is a must if there's any chance of it working.

 

So, I didn't really mean to imply that an Accusump definitely wouldn't work - just that I felt it to be a bit crude and that certain aspects of its operation weren't ideal. A dry sump kit would be a much better solution - but perhaps an Accusump is a perfectly acceptable solution. If it reduces the Mi16's inherent surge problems by 50% then that's one hell of an improvement. If it reduces the problems by 90% then I think most of us would be more than happy.

[Allan W 0]

My thoughts on this,

The oil pump must have some spare capacity cos if you change the spring you can get an increase in oil pressure in the engine.

If the oil pump did not have any spare capacity there would be no increase in pressure as it would already be at max pressure?

Using the accumulator with the increased oil pressure spring would result in the accumulator being recharged quicker by the oil pump, maybe?

 

How long does the 6 pint accumulator take to fill from empty at engine running temp?

 

I guess the above depends on the oil flow from the pump!

 

8 pints in a gallon

4.54 litres to a gallon

 

So the accumulator holds about an engine worth of oil.

 

Does anybody know the flow rate in of the oil pump at say 4000 rpm?

[Antoni1.9 0]

Rob,

 

I have the 6 pint accusump on my Mi16.

 

I would like to reply properly to your post as I have some reservations too.

 

I can answer a lot of your queries following my track day at Anglesey last week - but if you really want to know, I'm only in Stratford upon avon - if you wanted to come over we could do some tests on refill times etc etc.

 

 

FYI - my car has the PTS high pressure spring in the oil pump - with cold oil, the pressure in the accusump is nearly 100 psi. (minus the nominal 7 or 8 psi precharge)

 

On hot oil, this is about 65 psi.

 

 

I was a bit concerned at Anglesey because on hard acceleration, the oil pressure guage was dropping down - I've not had this on the road during the running in period - but duriing running in, the accusump was only midly wam - on the track, you couldnt touch it with your hands.

 

I need to go know, but I'm happy to pick this up if you're interested = just let me know.

 

Only problem is that the car comes off the road on thursday night - so if we need to drive it it will have to be wednesday night.

 

Cheers

 

Antoni

[Anthony 1,000]

I was a bit concerned at Anglesey because on hard acceleration, the oil pressure guage was dropping down - I've not had this on the road during the running in period - but duriing running in, the accusump was only midly wam - on the track, you couldnt touch it with your hands.

Interesting, as my bog standard Mi16 didn't have this problem - the only issue I was having was the oil pressure dropping through the Radar complex and the last chicane, basically the two sections on the track that have rapid left-rights in them. I reckon that a basic sump baffle will noticeably reduce that effect too, as it's clearly being caused by oil rapidly sloshing from side to side in the sump.

 

Can't say I've ever noticed any pressure loss on acceleration or braking, and generally not on single corners either (except long left handers, where the pressure will slowly drop due to the inadequate head drain the Mi suffers with). It's quick left-right's that kill the pressure on mine, because I think of the lack of baffles in the sump - I get this both on the road and on track.

 

Where you running your oil level at maximum Antoni?

[C_W 3 1 Cars]

I get surge at both chicanes, but also noticed a little loss under very hard braking at the end of the main straight.

[smckeown 1]

I got pressure loss (under 25lbs) at a few right handers

[Antoni1.9 0]

The oil level was OK I think, but I say I think because the oil is at a different level on one side of the dipstick to the other.

 

On one side its about 10mm above the top fill line, and on the other side it about 10mm below.

 

Wierd.

 

The only thing i can think now I'm thinking about it is that the pts baffle is for the 8v and the slot for the dipstick is in the wrong place because the dipstick certainly doesnt push in very easiy.

 

And thinking about it more, I couldnt get enough oil in it the car - the accusump should have nearly 3 litres and the engine about 5 - i only reckon I've got 6.5 litres in it - I'll check the remainder in the bottle.

 

Rob is coming over on wednesday so we'll have a look.

 

Cheers

 

Antoni

[base-1 17]

fantastic, some reports back on this would be well interesting!

[Rob Thomson 6]

I have a nasty feeling this may turn into a rant of similar length to my degree dissertation, so you might want to make a nice cup of tea before reading further....

 

Despite being horribly ill with some evil little flu thing, I braved the rush hour traffic in my smoky 309 and headed up to Antoni's on Wednesday evening.

 

It has to be said it was a very interesting evening. Not only is it always a pleasure to meet someone who's as knowledgeable and enthusiastic as Antoni, but thrashing around the countryside in fast Pugs is always a good laugh. And I think we managed to learn a lot about the behaviour of the Accusump fitted to Antoni's 205.

 

We were a little hampered by the instrumentation in Antoni's car. The on-dash oil pressure gauge isn't calibrated correctly and only shows pressure loss during extreme surge incidents. Also, the dip-stick appears to be fouling the PTS baffle kit which means that an accurate reading is currently impossible. Still, the gauge on the Accusump shows what is essentially engine oil pressure, and we were confident that there was enough oil in the car that at worse it could only be slightly under-filled.

 

The gauge on the Accusump (which shows the pressure in the air reservoir - which is equal to the engine's oil pressure) is hidden behind the driver's seat, so it was my job to watch the gauge as Antoni chucked the car around a few corners.

 

It is amazing how much and how frequently the gauge moves. It's also scary because this shows the scale of the inherent surge problem with this engine. The engine's oil pressure stabilises at about 90 psi when revving, and yet almost any corner taken vaguely enthusiastically would cause the pressure to drop to 45 psi where it would then stabilise. The pressure loss was worse going right than going left, and higher engine revs helped keep the pressure up - presumably because the pump was scavenging at least some oil.

 

What was really surprising was how fast the pressure would drop to 45 psi. The transition never took much longer than a second when entering a corner. This is indicative of how much oil an Mi16 engine needs, and thus how ineffective the (largest available) Accusump is through long corners.

 

What was reassuring was that the Accusump would re-fill very quickly once a supply from the pump was restored. We really couldn't see starvation in this mode being an issue at all.

 

Talking to Antoni about his engine rebuild, I learnt that the piston-cooling oil jets have valves to shut themselves off below a certain pressure. This makes obvious sense since because they're not needed at low engine speeds, and yet at low speeds the oil pump isn't delivering much oil so it's best to divert it to the bearings where it's needed most. Anyway, we wondered whether the consistent stabilisation of the oil pressure at about 45 psi was due to these valves closing and massively reducing the oil flow requirements of the engine - which in turn gives the sump a chance to refill and allows the pressure to stabilise around that point. The stabilisation at that point could also be due to the oil from the Accusump raising the level in the sump to a point where the pump begins to work again and the pressures and levels begin to self regulate.

 

But, it may be that by closing the piston jets the engine saves itself to some degree. When surge is experienced it shuts down some less critical parts of its oil system to give the more critical parts a break. That could be complete bulls*it, but it's something that could be read into the results of our tests.

 

Anyway, I think in summary it's fair to say that an Accusump is a cost-effective solution for a fast road car that might do a couple of track days a year - because it does offer at least some protection. But on the other hand, Antoni and I convinced ourselves that the only real way of solving the Mi16's oil surge problems sufficiently for a dedicated track or competition car is to fit a dry sump kit.

 

Scary. Very, very scary.

Edited October 1, 2004 by Rob Thomson

[findlay 0]

Dry sumping??? :cry: lol

 

Hmmmm well this has certainly given us an insight into the Mi. I just wish that there were some consistent results.

 

Some cars have no surge problems, other cars (like mine) really suffer.

 

Now Kev_G suggested his track cars running slicks and 15w-50 or 15w-60 suffered no surge problems. I'm assuming its knockhill he refers to which only has 2 surge inducing left-handers and 2 heavy braking zones.

 

My first plan is to try a baffled sump (will the Pug Sport 8v one fit? Can't imagine so)... if that fails... I really don't know where to go. Dry sumping seems expensive but it may yet prove the only way to go.

 

For the money the accusump seems to only solve part of the problem. So why not spend just a bit more to cure it?

 

First thing... where am I going to get a baffled sump from?

[base-1 17]

the 8v one does fit but you need to do a minor mod or something

 

what is it with this bloody engine - why is it so bad? there must be a reason!

[smckeown 1]

great! that means i'm f***ked! Coz on the track most corners give me surge issues

 

I might just shell out on a dry sump for my next spend. Anyone know a qualified person to fit one ?

 

Arse

Arse

Fick

and

Arse!

 

Sean

[Wurzel 16]

Just to add my worthless penny,

 

We use hydraulic accumulators on our helicopters for supplying the rotor controls with fluid under pressure in case the pumps cavitate or worse still, you have a major hydraulic leak.

 

Having spoken to Miles about the accusumps he can get hold of, it seems they can plumb in using a sandwich plate between the block and oil filter. As has already been stated, the engine oil pump will prime the accumulator, and boost the oil pressure supplied by the pump should it begin to reduce it's output (lack of oil to suck up).

 

Obviously the larger the accumulator, the longer the supply of oil. As the oil fills the sump, it feeds back to the accumulator as well as supplying the engine internals. In the case of our helicopter, if all the fluid went to the accumulator to recharge it and then to the systems needing it, the thing would fall out of the sky!

 

From the last PM I had from Miles, the four pint accusump was around £180 delivered so this is something to go on price wise.

[base-1 17]

g-g-g-gaybar

[C_W 3 1 Cars]

Robs report conflicts with the experience I have with mine; that is left handers are much worse than right handers. Mine will go round right handers all day, of any length. A good test is the first corner at Mallory Park (which is pretty much half the lap! ) and t here was no noticeable pressure loss. But lefthanders are differen't; anything remotely constant resutls in pressure loss. Also chicans can cause it too.

 

With right handers being OK, I would guiess it's something to do with the sump design; the left hand side of the sump has an indent near the flywheel; I wonder if this affects it?

[base-1 17]

mines the same, i can do right handers without fear unless its really sharp and long and the oil is pretty hot, but lefts even at normal running temp are a constant worry!

 

was the idea of oil drain from the head disproved? i think i noticed at the weekend that the galleries at each end of the head are different sizes?

 

also where abouts does the pickup sit, is is fairly central between cyls 2+3? maybe if so, with that indent in the sump it is kept submerged for longer? (clasping at straws here!)

[findlay 0]

i think i noticed at the weekend that the galleries at each end of the head are different sizes?

... I just told you that on MSN you twonk!!!

 

Yes you are right. The oil drain on the g/box end is slightly bigger than the gallery on the front of the engine.

 

From what I can see my engine sits slightly higher at the g/box end (not for long) which won't be helping matters much.

[base-1 17]

yeah but i was talking about when we were putting kates engine together on saturday i know we were talking about it a minute ago!

 

kates knackered engine had a brand new looking oil pump on it - how easy are they to strip and clean cos i might nab it, although the pickup is slightly dented and theres dust in it cos it has had to be stored outside although teh rest of it is scrap, and i mean all of it!