27 replies to this topic

[Lplus]

 

 

in terms of hot readings, your likely to see @25 psi at idle, and i wouldnt be to concerned if its a bit lower as long as it picks up when you blip the throttle.

Ive been through the "ball bearing " thing before, and they can give erratic readings, as the oil flows around them causing them to bobble/oscilate ( like a malteaser in a stream of air) this can be remedyed with a " cup" behind them to stabilize them, but thats a lot of effort, in most cases you are probably just better off with the std shuttle.

Been using a the ball on various engines for years and never had that issue.

 

 

There is some damping in the gauge and usually, because of the way they are installed, also adds to that damping, so it most likely was occurring, you just weren't aware of it. For a road car, they are not a good idea.

 

https://www.theminif...huttle-vs-ball/

 

Minispares sell the ball and a stronger spring as Cooper S releif valves.  I'm not sure if the cooper S engines were fitted with them as standard though.  I tried that set up, but apart from blowing off at 90psi cold the hot blow off was peculair in blowing off at about 70psi indicated then settling back to a slightly lower figure.

[Spider]

 

 

 

in terms of hot readings, your likely to see @25 psi at idle, and i wouldnt be to concerned if its a bit lower as long as it picks up when you blip the throttle.

Ive been through the "ball bearing " thing before, and they can give erratic readings, as the oil flows around them causing them to bobble/oscilate ( like a malteaser in a stream of air) this can be remedyed with a " cup" behind them to stabilize them, but thats a lot of effort, in most cases you are probably just better off with the std shuttle.

Been using a the ball on various engines for years and never had that issue.

 

 

There is some damping in the gauge and usually, because of the way they are installed, also adds to that damping, so it most likely was occurring, you just weren't aware of it. For a road car, they are not a good idea.

 

https://www.theminif...huttle-vs-ball/

 

Minispares sell the ball and a stronger spring as Cooper S releif valves.  I'm not sure if the cooper S engines were fitted with them as standard though.  I tried that set up, but apart from blowing off at 90psi cold the hot blow off was peculair in blowing off at about 70psi indicated then settling back to a slightly lower figure.

 

 

No A Series (or A+) ever left the Factory or Special Tuning or the Works dept with a Ball Bearing fitted here.

[Lplus]

 

 

 

 

in terms of hot readings, your likely to see @25 psi at idle, and i wouldnt be to concerned if its a bit lower as long as it picks up when you blip the throttle.

Ive been through the "ball bearing " thing before, and they can give erratic readings, as the oil flows around them causing them to bobble/oscilate ( like a malteaser in a stream of air) this can be remedyed with a " cup" behind them to stabilize them, but thats a lot of effort, in most cases you are probably just better off with the std shuttle.

Been using a the ball on various engines for years and never had that issue.

 

 

There is some damping in the gauge and usually, because of the way they are installed, also adds to that damping, so it most likely was occurring, you just weren't aware of it. For a road car, they are not a good idea.

 

https://www.theminif...huttle-vs-ball/

 

Minispares sell the ball and a stronger spring as Cooper S releif valves.  I'm not sure if the cooper S engines were fitted with them as standard though.  I tried that set up, but apart from blowing off at 90psi cold the hot blow off was peculair in blowing off at about 70psi indicated then settling back to a slightly lower figure.

 

 

No A Series (or A+) ever left the Factory or Special Tuning or the Works dept with a Ball Bearing fitted here.

 

A touch of erroneous description by minspares then...

[Spider]

 

No A Series (or A+) ever left the Factory or Special Tuning or the Works dept with a Ball Bearing fitted here.

 

A touch of erroneous description by minspares then...

 

 

I haven't looked up what's on the Mini Spares webpage, however from one of the factory parts books - first up, the 850 engine;-

 

and the Cooper S Engines;-

 

Sorry these are not the clearest, but both use the same shuttle valve, 12H865.

 

[Lplus]

Minispares describes the ball and shorter spring the "Cooper S" relief valve.  Interestingly Keith Calver also use the phrase "Cooper S" for a ball and spring valve.  Your excerpts do show a different spring though.

[Spider]

Your excerpts do show a different spring though.

 

While all engines used the same Shuttle Valve, there was at least 3 springs as you have picked up on and it is the spring here that sets the Relief Pressure. With the Cooper and Cooper S Engines, that was set at 70 PSI, the MPI is 30 PSI and all others 60 PSI.
 

[Spherix]

in terms of hot readings, your likely to see @25 psi at idle, and i wouldnt be to concerned if its a bit lower as long as it picks up when you blip the throttle.

Ive been through the "ball bearing " thing before, and they can give erratic readings, as the oil flows around them causing them to bobble/oscilate ( like a malteaser in a stream of air) this can be remedyed with a " cup" behind them to stabilize them, but thats a lot of effort, in most cases you are probably just better off with the std shuttle.

I managed to warm up the car today to the point where the SPI's aux fan triggered, at that point the mechanical gauge was reading just shy of 40 PSI, and moved to the previous value of around 60-70 if I revved to 3000 rpm. Seems healthy to me! I did see the oil temp gauge that I have run hotter before in traffic, so chances are the oil does get a little hotter still under load.

The porsche gauge at that point was reading close to 0 Bar, so I'm pretty confident the issues lies in either that gauge or the sender at this point. Sure saves some effort in not having to change the pump!

Edited by Spherix, 12 June 2023 - 01:05 PM.

[Spider]

Good result !

I'd say you'd need a Gauge Matcher to use the Porsche Gauge or find the matching sender to use with it, but does this gauge have the range needed to use with an A Series Engine ?  I'd suggest you would want to reading up to at least 80 PSI / 5.5 Bar.

[Spherix]

Yeah the sender I have is matched, thats the odd thing. Its a 0-5 bar range gauge, and I matched it with this one: https://vdo-webshop....3590691088.html

That in theory should match the ohm ranges on the gauge as well, and trigger the warning light below 20 psi. It's brand new, so I'm a little bit confused why it wouldn't work as intended. Annoyingly, if I would get a sender with higher bar ranges, the gauge would read inaccurately.

The gauges on the other hand came out of a flood damaged car, very rusty. I did measure and check all the gauges before installing it, but perhaps one of my shakedown tests has actually shaken something loose. I'll be taking it out to test it on the bench for the next step of elimination.

[Spider]

Maybe get yourself a potentiometer say a 0 - 250 Ohm and use that to check the operation of the gauge.

[Spherix]

Using a multimeter and the mechanical gauge as reference I was able to plot the ohm values given by the sender, compared to the pressure on the mechanical gauge, and in turn comparing that to the spec sheet of the sender, which I can now confirm works perfectly. That leaves the gauge!

[Spherix]

I figured I could also isolate the wiring as the cause by drawing some direct + / - and sensor wires to relevant terminals. Positive directly from battery, negative from body, and sensor wire directly from the sensor. Slightly annoyingly, this gives a bit higher reading, but still half of what it should give. 

 

I've contacted the person I know that worked on these gauges at VDO, in the hopes that he can isolate the problem. I'll wait with continuing my search behind the dashboard wiring until I'm certain the gauge is not faulty, as all other instruments work as expected and measure the right values..

 

[Spherix]

Finally visited the person mentioned above, he explained these gauges work by having two spools in an X pattern underneath the needle that form an electromagnetic field to move the plate the needle is attached to.

As I had made a test setup on the bench with a potentiometer, I was able to see that I needed about twice the Ohm's as expected to reach the full range of the gauge. His quick assesment was that one of these spools has failed, so he will replace it for me as he still has a lot of the original tooling to open things and press them back together.

Mistery solved!