The next test that I have chosen is to look at an actuator
And were are going to measure control duty and current
The focus is purely on the electronic performance of the component
The actuator I have chosen is the turbo control actuator
Located there
This is a very old fashioned actuator because it allows a flow of vacuum
To be applied across the solenoid delivering it to the turbo
So duty and current are the electronic functions so what is the real purpose of the actuator
It is controlling the amount of vacuum or suction applied to the variable vain actuator on the turbo
To accompany this test and this is the real focus to show how to use the scope intuitively
proving pneumatic functionality not just mechanical functionality and movement of the solenoid
controlled by electronics and current also the use of a vacuum gauge
So that is the test and as always
Speed follows accuracy
So the accuracy of this test is a control duty against the amount of suction applied
to the turbo
I have also chosen for speed to apply a 100m/V range
Volts not current to the current clamp
Because this particular current clamp
The sensitivity or attenuation of the clamp for every 100m/V is 1 amp of current consumption
I am only expecting one or two Amps at the most
We will see when we run this device just how much current we have
I need to work out if this is a ground on or power on device
To do that we need to go to both sides of the actuator
The actuator is a coil
Its an inductor so we need to know which side of that coil is being switched
At the moment lets talk about time
I mentioned three time ranges
1m/s 100m/s and 50s
This is an event so I have initially chosen 1 m/s of timebase
And you can see that in free run we can clearly see that the device has been switched
But has it been switching power or ground we dont really know yet
You can see some current consumption in red is it the right way around
We dont really know that yet so lets establish which way it is being switched
First I am going to move my probe to the other side of the actuators
At the moment we appear to have an event
So if I move the probe across to the other side
You can see that we have a static power line
So if the power line is static at nominal battery voltage
And we have an event on the other side of the circuit
Then it must be a ground on device
In which case that current clamp is the right way around
Ground is on current will only flow when the circuit is on
And yo can see a rising current when the device is on
And the range is about right at 100m/V 1 Amp each
Increment 20m/V is .2 Amp .4 .6 .8
1 Amp of range
So you can see there is a very small duty a very small consumption of current
Lets run the engine because we need to look at the amount of control vacuum suction
That is being applied first of all to the actuator and then through the actuator
Because the relationship here with an actuator is that the on time duty
Which is a percentage calculation
So we could pull up a measurement to measure duty which I think we should do
So lets do that now
So measurements add on the blue Channel A
That is my priority the channel I am focusing most of my decision making on
Channel A
type of measurement we are selecting is duty
I play the whole trace and apply the measurements
And we then have the date we require in this bottom left column
We are not running this live yet
But I want to compare the amount of duty
This is the positive duty cycle so we have to do a little simple mathematics
To subtract one from the other
We need to know what the active negative duty event is
And then we able to decide if the amount of suction from the vacuum pump on the engine
Is being applied correctly to the turbo
Lets run the engine and have a look at the results
And work out if this device is not just being controlled electronically correctly
But is actually controlling the right amount of of suction from the vacuum pump to the turbo
Which is the end purpose of this device
Always focus on the end purpose of the device
ENGINE STARTS
Run the scope
Now you can see that the device duty has increased somewhat
Increasing duty increasing current
So we need to rescale our current to a higher value
So lets go to 2 Volts 2 Amps
200 m/V 2 Amps of current
Do I need any more timebase
I dont think so I am fairly happy with that
We could trigger it lets decide if we are going to trigger this or not
Do we have a stable reading
No so we need more events
I cant calculate duty so we need more time
I am going to increase this just by a little
We now have a stable reading
15% which is a positive duty
This is the off cycle at the top on the power line
The on duty is at the bottom
So 15 from 100 equals 85 even I can manage that
85% on
And you can see while it is ground on current increases
It increases in an inductor slowly and you can see the increase is progressive
The device is then turned off
Current drops and the begins to ramp up again when the device is on
So we have 85% on
That is something we need to focus on for the next part of the test which is over here
Control of suction
So if this vehicle came into me for repair and the customer said
I am not getting full performance I think my turbo is faulty
Before I start to worry about the turbo I want to worry about control
I love gauges
These gauge are designed and built for us by us and we have chosen this particular gauge
As there is no fluttering damping so it gives a very accurate reading
I am measuring the amount of suction created by the vacuum pump
All good vacuum pumps on diesel should create about 30 inches of Mercury
Or minus 1 atmosphere
This is gauge pressure of course
So we do have 30inches so there is nothing wrong with that pump
Nothing wrong with the pump right up to the actuator
We have an 85% duty cycle so I now need to move this across to the control side of the actuator
So moving the gauge from the supply
To the control side
And we should have 85%
There is a small drop in suction across the device
So in theory what we should have across that device is around 85% of the suction
From the pump delivered to the actuator
And we do have a slight drop in the amount of suction
So the device is working electrically
The duty is correct the current is correct
What about mechanical or physical blockage
Here that is not the case because we have a good suction
Now if I go and operate the turbo the throttle
Under dynamic drive cycle which is on the road
We will the be able to compare the control duty with the current
Against the actual suction applied to the turbo
The purpose of that test is to prove that the control side of the turbo
is working correctly
Therefore if we are not getting the right performance from the turbo
We can then concentrate on leaks on the charged air pressure system
Or the actual performance of the turbo itself mechanically
And that is the way actuators controlling mechanical performance or in our case pneumatic performance
Should be used in conjunction with the scope
Now this is a very old fashioned method of controlling turbos
Modern systems now use PWM Pulse Width Modulation
A complex arrangement of frequency and duty and for those types of simulation
You cannot just rely on simple vacuum
We would rely on devices like this so we can simulate and stimulate
The control of devices such as intake willow flaps turbo EGR valves all those types of components
Simulate them very accurately
Measuring current flow and the control duty cycle
There is always an argument that the best use of the scope
Quite often is in conjunction with other tools as well to provide a complete picture
Remember accuracy speed efficiency always