MoTeC Global Forum

Hi,

I use a M800 pnp, CDI4, E888 in my modified Impreza STi v8 and yesterday the belt to my dry sump pump snapped but lukly I was in the car and at idle speed when it happend so I managed to shut the engine down before something really bad happend.

So I wondered is there anyway I could make the MoTec system to shut down the engine if it loose oil or fuel pressure automaticly?

regards

Bjørnar

Hi,

Yes you can setup the m800 to do this, but it is not an actual function.

There may be a different method but this way should work well.
Use the RPM limit table and set the X axis to 'oil pressure' and the Y axis to 'Run Time'.

In the table, fill it out so that if Run Time is over say 10 seconds and the oil pressure is 0 to 5 psi then set the RPM limit to 1 (setting to 0 reverts back to the overall RPM limit).

You could go further and say if the oil pressure is lower than in should be for a given RPM then limit it then also.
So your table will look something like this, for example -

Code: Select all

                Oil Pres [PSI]
Run Time [s]    0       5       10      20      40      60      80      100
1000            1       1       2000    2000    5000    8000    8000    8000
11              1       1       2000    2000    5000    8000    8000    8000
10              2000    2000    2000    2000    5000    8000    8000    8000
0               2000    2000    2000    2000    5000    8000    8000    8000


The Run Time value starts counting up when the Engine RPM reaches the Run RPM set in the Miscellaneous Setup and resets to 0 when the engine stops. By setting the 0 to 10 seconds range to 2000 RPM, this gives the oil pump 10 seconds to prime before stopping the engine due to lack of oil pressure.

The second part of the functionality says that if the oil pressure is lower than it should be then limit the RPM, so if you do still have some oil pressure, like if pressure drops to 20psi when reving at 4000 then the RPM will be limited, indicating there is a problem but enabling you to 'limp home'.

You will need to set the table to suit your needs/pressures.
Adding Fuel Preessure into this as well is possible but becomes more complicated.

I've tried to implement this but "Run time" does not appear on the list of items in the list under axis setup. Do I set up this table under Adjust > General Setup > RPM limit or somewhere else please?

Lorcan wrote:I've tried to implement this but "Run time" does not appear on the list of items in the list under axis setup. Do I set up this table under Adjust > General Setup > RPM limit or somewhere else please?

Under axis setup, when you hit 'select' button for axis channel a box pops up, near the bottom is a tick box that says 'show non-sensor channels' which allows nearly anything to be set as an axis.

Got it, thanks

I like it.

I have also heard of people using a mag or hall pick up to monitor the pump's pulley speed.
This makes sense as most of the issues I have heard about usually involved a stone of other object (FOD) causing the belt to leave the scene.

Using that approach how would the code appear to shut down below a minimum pump speed after X-seconds of start up?

Can you apply more than one table? i.e. could I also shut the engine down if fuel pressure dropped?

Lorcan wrote:Can you apply more than one table? i.e. could I also shut the engine down if fuel pressure dropped?

If you are monitoring fuel pressure then you maybe can apply a compensation for it using a lookup table that is something like:
FuelPrs: 0 20 30 35 40 45 50 55 60
xFactor: 0 0 0 sqrt(45/35) ... etc

Where you either measure the flow versus pressure or just assume flow = base-flow * (press/base-pressure)^0.5
The zeros on the left would take care of shut off if the pressure dropped too low.

Excellent, thanks. But in general terms I guess you can't apply more than one table to something?

Not sure if the m800 etc can do it, but best is to monitor relative fuel pressure.

ie FP relative to MAP. If it strays too far out of expected, then there is a problem that warrants a limp or shutdown.

that keeps a tight control over it for safety.