New S2 Avant Nothelle N300 owner

[Error404]

Is the shim the dark grey washer between spring and brass part? Live and learn! I still don't think the shim will have any effect on the oil pressure but if it is meant to be there it should stay.

The spring in Alex's picture looks like a constant rate spring with evenly spaced coils and they need the same amount of force to compress 10% as they do 100%.

This is an interesting website re springs.

https://www.yostsuperior.com/variabl...ive-vs-linear/

All springs compress proportional to force - otherwise they wouldn't be springs they would be more like dampers - lean on them and they sag to the bottom of their travel under a constant load.
Linear spring rates compress at a rate linear to the force increase, hence the name. "Progressive" or non-linear springs follow a rate curve.
Normally in this century, the unit used is commonly n/mm. For example a 10n/mm linear rate spring, the spring will compress 1mm for each 10n of force applied. I.e. 20n = 2mm compression, 100n = 10mm and so on. Compression=Instant rate / force.
If you pre-load the spring, (by compressing it), you are increasing the force needed to compress it further, as your required force is always 0+preload. Thats why shimming the relief valve increases PEAK pressure as it increases the force needed to be applied to the piston (and spring) before the valve starts to open.

In the context of the oil pump though the relief valve is only open when the oil is cold and more viscous. I have an accurate & calibrated analog 0-5v oil pressure gauge on my car and cold start PEAK oil pressue is around 800kPa = 7 bar gauge pressure. During normal running, more like 500-600kPa = 4-5bar gauge pressure. I will say also that my OEM VDO oil pressure gauge misreads by at least 1 bar under all conditions! They are an indicator, nothing more so don't get too hung up on what they read as long as it's somewhere about right.

Dave you need to verify that the gauge is tell the truth - easiest way is to put a mechanical oil pressure gauge on the car and see what its actually doing

HTH
Alex

[twoqu]

It's unclear whether there is a direct connection between a fuse and the aux guages but no harm in checking. It looks as those its S14 a 5A fuse. Might just be for the illumination.

[twoqu]

Going back to the multimeter. You could test something convenient such as an injector. Remove the connector and touch the terminals. We know it should be in the high teens Ohms. I have measured one I had laying around so we can use that to illustrate the different scale readings:

16.5 @ 200 Ohms scale
0.016 @ 2K Ohms scale
0.01 @ 20K Ohms scale

As you can see you lose the fine detail from the measurement higher up the scale. For most automotive measurements we are only concerned with the lower end of the scale. So for the sender either the 200 or 2K would give us the answer. From the specs of your multimeter it still use those scales for resistance it just does it automatically !
The reading with the engine off is probably not as important as with it running. If you could find something with a resistance of @100 ohms you could feed that to the guage and see if it read mid scale.

[steve briance]

Is the shim the dark grey washer between spring and brass part? Live and learn! I still don't think the shim will have any effect on the oil pressure but if it is meant to be there it should stay.

The spring in Alex's picture looks like a constant rate spring with evenly spaced coils and they need the same amount of force to compress 10% as they do 100%.

This is an interesting website re springs.

https://www.yostsuperior.com/variabl...ive-vs-linear/

[twoqu]

Too be clear you need to remove the terminal to the guage to test the sender readings. So its just the sender to ground.

[Tractor Dave]

Error 404 kindly pointed out that the shim is fitted to the ABY/AAN engine. Pic from his re build thread. Its staying put.

[Tractor Dave]

Having hurt my neck and eyes, does it not say Auto Range on it?
If 0.6 is 6 ohms that would be within spec. If its 0.6 ohms then its a bit low.
Just try it when the engine is next started and see what it reads unless you have something with a known resistance to test the scale.

Guess its a matter of how many 0 are before the decimal point!

Yes it does. I never noticed that! I will have a play tomorrow. Thanks very much.

[twoqu]

Having hurt my neck and eyes, does it not say Auto Range on it?
If 0.6 is 6 ohms that would be within spec. If its 0.6 ohms then its a bit low.
Just try it when the engine is next started and see what it reads unless you have something with a known resistance to test the scale.

Guess its a matter of how many 0 are before the decimal point!

[Tractor Dave]

Are you sure the multimeter is not autoranging?

Could be. There is only one setting for Ohms on the dial. It's a cheap one from screwfix. Engine off it said 0.6. Do I just move the decimal point?

[twoqu]

Are you sure the multimeter is not autoranging?

[Tractor Dave]

That's excellent, thanks twoqu. I will need to buy a new multi meter as mines doesn't have an adjustable range on Ohms.

And I'm dumping the running in oil immediately. The bucket tappets don't like it at all!

[twoqu]

The only specs I have seen are from the AAN/3B for the pressure sensor. Doubt whether its different for the ABY.

5-10 Ohms - Engine off
70-120 Ohms - Idle
170-200 Ohms @3000 RPM

That is measuring from the G terminal to ground. So you can verify that the sensor is producing a signal that makes sense. You could also measure pre and after the connector to see if it varies. If it does then the issue might be the connector itself. If it passes through the connector ok then that leaves the wiring back to the guage.
It looks as though the higher the resistance the higher the reading!

Should say thats with engine oil at 80C!

More useless info. Found some VW1301 measurements that equate to oil pressure from the sender. You have to divide by 2 and add 10 to convert to resistance.

350 = 5.0 bar
150 = 2.0 bar
10 = 0 bar

So converted:

185 Ohms = 5.0 bar
85 Ohms = 2.0 bar
15 ohms = 0 bar.

Not as accurate as a guage but hopefully that should allow you to determine whether there is an issue.

[Tractor Dave]

I've seen shims being made by a Swedish company I think which claimed to increase oil pressure. Not entirely sure they do anything as the spring and plunger are a relief valve and the shim won't make the spring any harder to press. If it stopped the valve opening all the way then maybe it would increase oil pressure. Not a standard item as far as I know and with new shells and all the rebuild work, I can't see you being short of good pressure!

Yes, the shim would make the spring harder as it's on the collar of the temperature sender and therefore puts the spring closer to the valve needing a higher pressure to operate.

[steve briance]

I've seen shims being made by a Swedish company I think which claimed to increase oil pressure. Not entirely sure they do anything as the spring and plunger are a relief valve and the shim won't make the spring any harder to press. If it stopped the valve opening all the way then maybe it would increase oil pressure. Not a standard item as far as I know and with new shells and all the rebuild work, I can't see you being short of good pressure!

[Tractor Dave]

Just to add to the above, the reason it worked ok hot wired yesterday was due to me bridging the wrong blue/black wire. There is a thin on the left round plug ( which goes to the sender) and a thick on the right round plug (return?). So, in effect I was telling the auto check all was well (when actually it wasn't).