hobbsy
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| posted on 20/11/07 at 11:44 AM |
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R1 5PW Oil Pressure figures at ~7krpm (any1 got datalogs?)
During a really boring drive back from an MOT on the motorway a week or so ago I was looking at the oil pressure figures more than usual.
Sitting at a steady 80mph ish (and so around 7k rpm) it seems to centre around 70odd psi as you'd expect but occasionally I was seeing it shoot
up to over 90 psi then back to 45 psi and then back to around 70psi.
This is using a SPA digital gauge and a pressure sender mounting in the oil cooler bolt (well remote mounted from that on a 8" or so braided
hose).
The higher and lower figures than I expect are only seen for a fraction of a second (as quick as the gauge updates if you know what I mean).
Is this anything to worry about? Am I getting a lazy oil pressure release valve.
I understand this should operate at around 75psi but is there any lag?
I guess I was probably driving at the RPM right around where it opens and closes to maintain no higher than max pressure.
Anything to worry about?
Anyone got a high frequency data log that shows this hysteresis (?) around the oil pressure relief valve opening / closing pressure?
I'm probably just getting overly paranoid but having killed an engine (albeit a Blackbird) before from oil pressure related issues I've
come to be that way.
As you can imagine I was watching the gauge like a hawk driving back.
Normally when caining it through the rev range (normal driving!) I've not noticed this.
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Bob C
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| posted on 20/11/07 at 12:30 PM |
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digital guage - probably not real, just the ADC sample coinciding with a noise spike, so you get a dodgy reading until the next sample. Maybe you
could try a capacitor (1uF to start with) where the oil gauge signal goes into the dash, to the dash chassis connection.
Bob
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Dusty
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| posted on 20/11/07 at 12:33 PM |
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Maybe also influenced momentarily by oil cooler stat movements. I mean closing may give spike in oil pressure lasting just long enough to be sampled
by the gauge before the relief valve lifts, overcompensating before settling, leading to momentary drop. Because the valve has inertia these movements
may take long enough compared to the sampling rate of the gauge to register without in practical terms being of any importance.
[Edited on 20/11/07 by Dusty]
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02GF74
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| posted on 20/11/07 at 02:00 PM |
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hmm, I wouldn't buy either of these hypotheses.
noise spike - well these should be more or less random so you shoul see the gauge reading jumping all the time not just at around 7k rpm. I would
expect the guage to have some sort of
input filtering, either electrical or via software.
Do you have a thermostat fitted?
I am not sure this would be due to a thermostat or the pressure relief valve
opening/closing - both of those are mechanical - spring and thimble or a wax cartridge which melts to open the valve. I'd be very surprised if
either of those opened so quickly that you would see this sort of effect but that is my guess rather than fact.
Some more questions.
Does it do this in other gears/rpm?
Does it do this when oil is cold?
Has it always done this?
Anything changed to start this happening?
Is this happening in the dark (i.e. you have lights on)?
Check alternator/battery wires/earth straps are good contacting and tight.
Check for any loose wires, check sender is working and earthed properly.
Then report back.
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ChrisGamlin
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| posted on 20/11/07 at 06:40 PM |
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A lot of senders do need to be seperately earthed, so Id vote either for that or a dodgy earth on the gauge loom.
Here's a log of a couple of laps of a Spa trackday in my R1 if its of any use:
[img][/img]
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tks
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| posted on 20/11/07 at 07:41 PM |
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quote:
Originally posted by Bob C
digital guage - probably not real, just the ADC sample coinciding with a noise spike, so you get a dodgy reading until the next sample. Maybe you
could try a capacitor (1uF to start with) where the oil gauge signal goes into the dash, to the dash chassis connection.
Bob
Yups my thoughts to...
they should have taken 3 samples and avaerage the results... etc.
Tks
The above comments are always meant to be from the above persons perspective.
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hobbsy
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| posted on 21/11/07 at 03:17 AM |
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Chris,
Where? I can't see anything 
Others - yeah thought about sampling and to answer the "has it always done it" I'm not sure as I don't think I've spent that
long looking at it while holding a constant speed like that.
I tend to notice it when starting etc and make sure its about a certain figure and check I'm getting at least 10psi / 1k rpm etc.
It had crossed my mind it would be something electrical, I did actually pull over and check if anything was working loose but not different to when
first installed, though it could have been doing this before, just didn't notice.
Much as I like the SPA gauge like any digital gauge they aren't as easy to read from a quick "the needle should be pointing at around 12
o'clock" type glance etc.
quote:
Originally posted by ChrisGamlin
A lot of senders do need to be seperately earthed, so Id vote either for that or a dodgy earth on the gauge loom.
Here's a log of a couple of laps of a Spa trackday in my R1 if its of any use:
[img][/img]
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ChrisGamlin
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| posted on 21/11/07 at 01:20 PM |
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The link works for me both at home and here at work, so I presume everyone else can see it too, so possibly an IE issue your end?
Have a look in my photo archive if you can't see it though, the screen grabs are in there.
Chris
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