How much oil is in your dry sump tank at high revs?? Dom??
Discussion
If you chech your hot oil level after idling for a couple of minutes the tank should be full.
Now check the oil level after running at 2000rpm and cut off quickly.Level now not showing on dipstick. Add more oil (now full on dipstick), run at 3500 rpm (1 minute) and cut. tank dipstick not even reading minimum.
So I surmise more and more oil is in the engine as a whole, as the revs rise(poor scavenging).
How much oil? Any? is left in the tank at say 7500 rpm? Assuming you set it at idle.
Could be why they go bang occasionally?
Simon.
It would be good to get Doms view on this!
Now check the oil level after running at 2000rpm and cut off quickly.Level now not showing on dipstick. Add more oil (now full on dipstick), run at 3500 rpm (1 minute) and cut. tank dipstick not even reading minimum.
So I surmise more and more oil is in the engine as a whole, as the revs rise(poor scavenging).
How much oil? Any? is left in the tank at say 7500 rpm? Assuming you set it at idle.
Could be why they go bang occasionally?
Simon.
It would be good to get Doms view on this!
It's not that simple. Any dry sump engine should (has to) scavenge more than it pumps, because otherwise the engine will fill up with oil, obviously.
I'm not sure, and don't have one in front of me, but I'd expect that the dipstick doesn't reach to the bottom of the oil tank. More like there is 2-3L in the bottom of the tank and the dipstick measures the top Litre, say from 3-4L in the tank. The level in the tank can fluctuate on load and conditions, that's why it's important to follow the procedure for any given engine, which is why it's printed in the handbook. Some dipsticks are calibrated to be used with the engine cold, some hot and running, some hot and stopped.
I'm not sure, and don't have one in front of me, but I'd expect that the dipstick doesn't reach to the bottom of the oil tank. More like there is 2-3L in the bottom of the tank and the dipstick measures the top Litre, say from 3-4L in the tank. The level in the tank can fluctuate on load and conditions, that's why it's important to follow the procedure for any given engine, which is why it's printed in the handbook. Some dipsticks are calibrated to be used with the engine cold, some hot and running, some hot and stopped.
Yes it should scavenge better than it pumps, and it does not.Therefore it is theoretically possible for the tank to empty at high revs, the pressure pump stops pumpimg oil the bearings, will momentarily seize.Then BANG, conrod failure, engine cut in half!
Yes I
know the dipstick doesnt go to the bottom, hence no idea how much oil is left in the tank at 7000rpm.
Yes I
know the dipstick doesnt go to the bottom, hence no idea how much oil is left in the tank at 7000rpm.astonman said:
Yes it should scavenge better than it pumps, and it does not.Therefore it is theoretically possible for the tank to empty at high revs, the pressure pump stops pumpimg oil the bearings, will momentarily seize.Then BANG, conrod failure, engine cut in half!
Yes I know the dipstick doesnt go to the bottom, hence no idea how much oil is left in the tank at 7000rpm.
Very good question, Come on Dom, help us all out Yes I
know the dipstick doesnt go to the bottom, hence no idea how much oil is left in the tank at 7000rpm.Don't know the answer, but the oil pressure is a top engine-critical issue that I like to be sure of myself too.
So I've often taken a moment on track to check oil pressure while holding briefly close to and at the rev limit of 7400 my 'soft cut' is set to.
The pressure doesn't drop noticeably, even after many laps. For info my oil tank & pump system is still standard on the 4.2.
However, if I've allowed the level to drop to minimum on the stick, pressure DOES drop quickly in corners. I have heard that that is one thing that has definitely killed a few S6 engines. Thankfully mine has an extra oil light set at 17psi so it told me off before it had dropped too low, and it wasn't high revs.
That taught me to check the level regularly 'by the book' especially before and after trackdays when some oil is used by the engine (as it's designed to).
So I've often taken a moment on track to check oil pressure while holding briefly close to and at the rev limit of 7400 my 'soft cut' is set to.
The pressure doesn't drop noticeably, even after many laps. For info my oil tank & pump system is still standard on the 4.2.
However, if I've allowed the level to drop to minimum on the stick, pressure DOES drop quickly in corners. I have heard that that is one thing that has definitely killed a few S6 engines. Thankfully mine has an extra oil light set at 17psi so it told me off before it had dropped too low, and it wasn't high revs.
That taught me to check the level regularly 'by the book' especially before and after trackdays when some oil is used by the engine (as it's designed to).
Edited by tail slide on Monday 11th February 22:04
astonman said:
If you chech your hot oil level after idling for a couple of minutes the tank should be full.
Now check the oil level after running at 2000rpm and cut off quickly.Level now not showing on dipstick. Add more oil (now full on dipstick), run at 3500 rpm (1 minute) and cut. tank dipstick not even reading minimum.
So I surmise more and more oil is in the engine as a whole, as the revs rise(poor scavenging).
How much oil? Any? is left in the tank at say 7500 rpm? Assuming you set it at idle.
Could be why they go bang occasionally?
Simon.
It would be good to get Doms view on this!
Sorry missed this one Simon:Now check the oil level after running at 2000rpm and cut off quickly.Level now not showing on dipstick. Add more oil (now full on dipstick), run at 3500 rpm (1 minute) and cut. tank dipstick not even reading minimum.
So I surmise more and more oil is in the engine as a whole, as the revs rise(poor scavenging).
How much oil? Any? is left in the tank at say 7500 rpm? Assuming you set it at idle.
Could be why they go bang occasionally?
Simon.
It would be good to get Doms view on this!
Only way to check levels on Speed six oil tanks "are" Run the engine till the First coolant fan kicks in 88 Deg turn the engine off check the levels, run the engine again until the second coolant fan kicks in 92 Degs, switch off check your levels Job done...
Dom
At first glance this doesnt make sense. The scavenge pump is pumping oil depending on engine rpm, but the pressure pump isn't .. it dumps excess oil through the relief valve back to the inlet pipe to the pressure pump .. so in effect once the relief valve opens there shouldn't be any greater volume of oil entering the engine regardless of revs (ok it doesn't quite work like that, but increasing revs doesn't increase flow by the same degree, but increasing revs does increase the potential scavenging by the same degree so there should always be a net loss of oil from the engine to the tank as described already above).
So what's happening?
Your engine could be worn, so the bearings are dumping more oil into the crankcase than expected.
Your scavenge pump could be worn, one of the three stages could be not turning if built incorrectly and is only now showing a problem, or the scavenge cavitates at high rpm meaning it can't pump oil back to the tank, or excess blowby might be aerating the oil in the crankcase increasing it's effective volume and overloading the scavenge capability. or something else I've not thought of.
I've seen a couple of sp6 engines on engine dynos with oil tanks with oil sight level glasses and I can't remember the level dropping at high rpm in them.
If you work out what it is that's happening please let us know
So what's happening?
Your engine could be worn, so the bearings are dumping more oil into the crankcase than expected.
Your scavenge pump could be worn, one of the three stages could be not turning if built incorrectly and is only now showing a problem, or the scavenge cavitates at high rpm meaning it can't pump oil back to the tank, or excess blowby might be aerating the oil in the crankcase increasing it's effective volume and overloading the scavenge capability. or something else I've not thought of.
I've seen a couple of sp6 engines on engine dynos with oil tanks with oil sight level glasses and I can't remember the level dropping at high rpm in them.
If you work out what it is that's happening please let us know
What is the oil pressure after a few minutes running ? (The manual says it should not fall below 35 psi @ 2000rpm and should be checked immediately after stopping and should be within levels of the dipstick marks)
I think there are about 6 liters of oil in total. Check if the filter-mesh in the sump tank is blocked.
I think there are about 6 liters of oil in total. Check if the filter-mesh in the sump tank is blocked.
Hi
My name is Terry and I own a dry sumped Escort Cosworth which is why this thread interested me.
When the engine isn't running there is a leak from the crankcase seal. With the engine running the leak stops.
I understand that , in my car anyway, the dry sump tank is higher than the sump and that some equalisation of pressure
must occur.
These days oil is too expensive to store on the garage floor.
Anyone got a solution to this problem.
Many thanks
Terry
My name is Terry and I own a dry sumped Escort Cosworth which is why this thread interested me.
When the engine isn't running there is a leak from the crankcase seal. With the engine running the leak stops.
I understand that , in my car anyway, the dry sump tank is higher than the sump and that some equalisation of pressure
must occur.
These days oil is too expensive to store on the garage floor.
Anyone got a solution to this problem.
Many thanks
Terry
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