Some power steering flow rate information in gallons per minute and...
03-12-2009, 11:16 AM
#1
AudiWorld Super User
Thread Starter
Some power steering flow rate information in gallons per minute and...
resrvoir per minute. Based on my system draining my 48oz reservoir in 8.5 seconds at 800 RPM.
This would translate to 2.68 "GPM" (gallons per minute) at 800 RPM. Then "guessing" an OEM reservoir is +/- .5 qt capacity I can mathematically know how many times the reservoir cycles thru its entire reservoir volume per minute shown as "RVM." While GPM is a speed-related constant RVM is volume-based. I can figure my personal "RVM" on my 48oz reservoir by dividing all RVM numbers below by 3 which I have on my personal spread-sheet but no need to include them here. If someone wants to provide me exact reservoir volume for a specific chassis/model I'll be happy to do a custom spreadsheet with that model's RVM numbers.
I did this because I need a spread-sheet I can reference when/if this comes up again. And as with all things Audi, it's not a matter of "if" it will come up again, but simply "when." And you cannot find this info ANYWHERE! And while this spreadsheet isn't "empirically exact" due to ambient temps, component temps, M1 vs 11S viscosity differences etc it should easily be within +/- 2-3%.
800RPM 2.68GPM/20RVM
1k 3.35GPM/26.8RVM
1.5k 5.025GPM/40.2RVM
2k 6.7GPM/53.6RVM
3k 10.05GPM/84RVM
3.5k 11.725GPM/93.8RVM
4k 13.4GPM/107.2RVM
4.5k 15.075GPM/120.6RVM
5k 16.75GPM/134RVM
6k 20.1GPM/160.8RVM
6.5k 21.775GPM/174.2RVM
7k 23.45GPM/187.6RVM
7.5k 25.15GPM/201RVM
8k 26.8GPM/214.4RVM
8.5k 28.475GPM/227.8RVM
And while there is a "pressure relief" consisting of a ball/spring/seat system designed into the 12V series PS pumps there is no "volume relief" system in the pump. The vaned rotor impeller attached to the pulley MUST turn the EXACT same 1:1 RPMs as the pulley at any/EVERY RPM! There is no viscous clutch, no centrifugal clutch, no gear-reduction facility, no way whatsoever for the vaned impeller to turn off or slow down as that relates to pulley RPM. The vaned rotor MUST match RPMs with the PS at ALL engine speeds with a corresponding linear increase in oil volume displacement at higher RPMs than idle. If the pulley is turning the vaned rotor is turning the EXACT same RPM. If the vaned rotor is turnng the pump is pumping oil... simple as that! Pressure is released at xxx pre-set but oil volume being displaced is NOT reduced! In fact it's just the opposite... volume is INCREASED with higher RPMs!
As the vaned rotor within the pump housing spins, it pulls hydraulic fluid from the reservoir at low pressure and forces it into the high pressure/rack side. The amount of flow provided by the pump depends on the car's engine speed. The pump must be designed to displace adequate oil flow when the engine is idling. As a result, the pump moves MUCH more fluid than necessary when the engine is running at faster speeds.
The pump contains a pressure-relief valve to make sure that the pressure does not get too high, especially at high RPMs when so much fluid is being displaced. But the amount of oil "volume" thru-the-pump is unaffected by pressure-relief. Because the vaned impeller is again "fixed" to the pulley. If at high RPM the oil volume being displaced were to be limited/reduced or shut off the vaned rotor risks becoming welded/seized in a VERY short time.
That's a L-O-T of pumped fluid if you consider this pump would drain a 55 gallon drum of oil at 3k RPMs in under 5.5 minutes! Especially when you consider it would take me 25 minutes to fill one with the garden hose on full-blast. And just for the "trivia factor" the pump would drain a 55 gallon drum of oil in 1.93 minutes at 8,500RPM!! That's moving a TON of oil and robbing a LOT of engine HP to do it! It's also a LOT of reservoir cycles for such a S-M-A-L-L volume of oil. It's a testimony to ANY oil we can circultae thru this system that doesn't turn to lather! Surely it struggles cooling given its volume is SO low while its circulation rate is so friggin fast! And given all that heat, trapped debris, decades of service, millions and millions of circulative cycles and Audi pro
This would translate to 2.68 "GPM" (gallons per minute) at 800 RPM. Then "guessing" an OEM reservoir is +/- .5 qt capacity I can mathematically know how many times the reservoir cycles thru its entire reservoir volume per minute shown as "RVM." While GPM is a speed-related constant RVM is volume-based. I can figure my personal "RVM" on my 48oz reservoir by dividing all RVM numbers below by 3 which I have on my personal spread-sheet but no need to include them here. If someone wants to provide me exact reservoir volume for a specific chassis/model I'll be happy to do a custom spreadsheet with that model's RVM numbers.
I did this because I need a spread-sheet I can reference when/if this comes up again. And as with all things Audi, it's not a matter of "if" it will come up again, but simply "when." And you cannot find this info ANYWHERE! And while this spreadsheet isn't "empirically exact" due to ambient temps, component temps, M1 vs 11S viscosity differences etc it should easily be within +/- 2-3%.
800RPM 2.68GPM/20RVM
1k 3.35GPM/26.8RVM
1.5k 5.025GPM/40.2RVM
2k 6.7GPM/53.6RVM
3k 10.05GPM/84RVM
3.5k 11.725GPM/93.8RVM
4k 13.4GPM/107.2RVM
4.5k 15.075GPM/120.6RVM
5k 16.75GPM/134RVM
6k 20.1GPM/160.8RVM
6.5k 21.775GPM/174.2RVM
7k 23.45GPM/187.6RVM
7.5k 25.15GPM/201RVM
8k 26.8GPM/214.4RVM
8.5k 28.475GPM/227.8RVM
And while there is a "pressure relief" consisting of a ball/spring/seat system designed into the 12V series PS pumps there is no "volume relief" system in the pump. The vaned rotor impeller attached to the pulley MUST turn the EXACT same 1:1 RPMs as the pulley at any/EVERY RPM! There is no viscous clutch, no centrifugal clutch, no gear-reduction facility, no way whatsoever for the vaned impeller to turn off or slow down as that relates to pulley RPM. The vaned rotor MUST match RPMs with the PS at ALL engine speeds with a corresponding linear increase in oil volume displacement at higher RPMs than idle. If the pulley is turning the vaned rotor is turning the EXACT same RPM. If the vaned rotor is turnng the pump is pumping oil... simple as that! Pressure is released at xxx pre-set but oil volume being displaced is NOT reduced! In fact it's just the opposite... volume is INCREASED with higher RPMs!
As the vaned rotor within the pump housing spins, it pulls hydraulic fluid from the reservoir at low pressure and forces it into the high pressure/rack side. The amount of flow provided by the pump depends on the car's engine speed. The pump must be designed to displace adequate oil flow when the engine is idling. As a result, the pump moves MUCH more fluid than necessary when the engine is running at faster speeds.
The pump contains a pressure-relief valve to make sure that the pressure does not get too high, especially at high RPMs when so much fluid is being displaced. But the amount of oil "volume" thru-the-pump is unaffected by pressure-relief. Because the vaned impeller is again "fixed" to the pulley. If at high RPM the oil volume being displaced were to be limited/reduced or shut off the vaned rotor risks becoming welded/seized in a VERY short time.
That's a L-O-T of pumped fluid if you consider this pump would drain a 55 gallon drum of oil at 3k RPMs in under 5.5 minutes! Especially when you consider it would take me 25 minutes to fill one with the garden hose on full-blast. And just for the "trivia factor" the pump would drain a 55 gallon drum of oil in 1.93 minutes at 8,500RPM!! That's moving a TON of oil and robbing a LOT of engine HP to do it! It's also a LOT of reservoir cycles for such a S-M-A-L-L volume of oil. It's a testimony to ANY oil we can circultae thru this system that doesn't turn to lather! Surely it struggles cooling given its volume is SO low while its circulation rate is so friggin fast! And given all that heat, trapped debris, decades of service, millions and millions of circulative cycles and Audi pro
03-12-2009, 11:59 AM
#3
AudiWorld Super User
Thread Starter
I'm more disappointed in myself than Audi. I should've considered this in...
1984 when I purchased a shiney new pearl white 4k from Prestige Audi. Or on any of many Audis since. But necessity being the mother of invention I never looked twice at the PS system til I encountered a problem with one. Now I'm BURIED in PS research!
This isn't Audi's fault or problem least as far as my cars are concerned. This falls squarely on me.
But sure, I know how warrantees and planned obselescence works ;-)
This isn't Audi's fault or problem least as far as my cars are concerned. This falls squarely on me.
But sure, I know how warrantees and planned obselescence works ;-)
03-12-2009, 02:01 PM
#5
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You either never kept your cars long or had one with high mileage...if it took
25 years for you to encounter PS problem;-)
But I didn't know pearl white was an option as early as 1984??
But I didn't know pearl white was an option as early as 1984??
03-12-2009, 02:32 PM
#6
AudiWorld Super User
Ah come on, pluck that wild hair and get real! If you have a 20V, was your leak PS or PB?
Further, the pump has an over pressure relief valve which short circuits the pump, the PB accumulator also has an over pressure relief valve which recirculates fluid back to the reservoir, the rack also recirculates fluid back to the reservoir when little or no assist is needed.
The system has all the filtration needed with the suction screen in the reservoir, designed to protect the pump. Ever cleaned it?
The rack is capable of handling small rocks with no problem.
The system has all the filtration needed with the suction screen in the reservoir, designed to protect the pump. Ever cleaned it?
The rack is capable of handling small rocks with no problem.
03-12-2009, 02:36 PM
#7
AudiWorld Super User
Thread Starter
In my career I got a new car every 2-4 years and never had a steering issue until now...
my son had a steering rack leak on his 94 90 5 years ago but a one-time stop-leak additive cured it and it's been dry ever since. He later sold it to his best friend that still drives it daily.
I have no recollection about the pearl white 4kQ being standard, optional or special order. It was brand new, on the showroom floor. I drove it, loved it and bought it. Was my first quattro!
I have no recollection about the pearl white 4kQ being standard, optional or special order. It was brand new, on the showroom floor. I drove it, loved it and bought it. Was my first quattro!
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03-12-2009, 02:46 PM
#8
AudiWorld Super User
Thread Starter
Ummm not a 20V, no accumulator and not servotronic with rack over-pressure relief...
and if you think the strainer is a full-flow filtration system you're dead wrong and if you believe the rack or pump handles small rocks in its oil with no problem then we are at the end of our communicative road!
03-12-2009, 03:57 PM
#10
AudiWorld Super User
Racks, servotronic or not, do not have over-pressure relief valves. The torque sensing valve just...
bypasses the unneeded flow to the reservoir building up only the needed pressure to balance the input torque. The suction filter screen, it is indeed full pump flow, is only needed to protect the pump, the rack's filter requirements are an order of magnitude less. So, you've never cleaned your screen, nor knew where it was?