Chris,
That's just the point. Combined with the tiny inlet restrictor in the
gage line It does alter the high frequency pulses to much lower
frequency. This reduces flutter & the wear & tear on the rack & pinion
gage mechanism. It has the same effect as damping. The system time
constant is changed.
I thing you will find that the accumulator diaphram spring constant is
minimal, compared to the air.
Anyway, suit yourself. I'm sure that you are very knowledgeable on such
things.
Dave Russell
Chris Masucci wrote:
> Ahh, but air doesn't damp anything. In fact air is one of the most
> reliable springs that there is, since it loses very little energy
> under compression and returns almost 100% of that energy during
> expansion. The only thing that air in the line might do is alter the
> frequency of the pulses (depending on air volume), but not the
> overall energy in the system. The pulses will still be there, but at
> a lower frequency and greater amplitude in order to conserve energy.
> Those pesky Physics laws are a b!tch aren't they. A damper, on the
> other hand, must convert one form of energy into another, such as up
> and down motion into heat by way of fluid friction (think shock
> absorber).
>
> An accumulator is different since it not only has nitrogen (or air)
> to work against, but a rubber diaphragm that has it's own spring
> constant and internal friction to provide the damping. Most
> accumulators are not used for damping since that's not what they are
> designed for. They are mostly used for storing pressure that has
> been built up against that pre-pressurized diaphragm...like in the
> brake booster system of a late 80's or early 90's Jag or some Saab's.
>
>
>
> It's important to not confuse a single impulse force compression,
> like in those water system air chambers that prevent water hammer, to
> something that has a frequency dependent impulse input like an oil
> pressure gauge.
>
> Cheers, Chris BJ8
>
>
>> Hi Chris,
>>
>> After the car has been sitting for a while, try disconnecting the
>> gage line at the block. On my engine, the oil has drained out of
>> the oil gallery & also some out of the copper line & out of the
>> flex line. When the engine is started, some of the air is trapped
>> in the line. If you ever have a "buzzy" oil pressure gage, loosen
>> both ends of the line & let some air into it. Engine shut off of
>> course.
>>
>> I can't imagine why bleeding the line would give more accurate gage
>> readings. Whether you bleed the line or not has no effect on
>> actual oil pressure. Pressure is pressure, be it air or oil. The
>> fast oil pressure pulses are damped because air is compressible.
>> Think accumulator.
>>
>> Can't say if the loop traps more air or oil. It certainly could
>> help prevent vibration, but that's what the engine to oil pipe flex
>> line is for.
>>
>> Regards, Dave Russell BN2
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