yue KANG (Daniel) 4843 Input/output Chart

Chart of inputs and outputs

Chart below shows measurements of sensors and actuators we have done in our lab with multimeter

Device	Measurement	Condition 1	Condition 2	Note
Coolant Temperature Sensor	DC Volts	Cold Engine     2.6V	Warm Engine     1.07V	NTC warm engine should have lower reading
TPS Key on	DC Volts	Fully Closed     0.691V	WOT     3.91V	Give a higher reading when open more
TPS Key off	DC Volts	Fully Closed     0.72V	WOT     4.2V	With key on the reading is a bit higher
Crank Sensor	DC Volts	Idle     4.07V	2500rpm     7.52V	As speed increase gives higher reading
Map Sensor	DC Volts	Idle Vacuum     0.54V	Key on engine off     1.79V	Higher pressure when stopped
Air Temp Sensor	DC Volts	Cold Engine     3.46V	Warmed Up     3.2V	V decrease as temp goes up
Cam Sensor	AC Volts Or Hz	Idle rpm     1.2V	2500rpm     4.02V	Higher speed indicate higher voltage
Fuel Injector	Duty Cycle	Idle     36.7%	2500rpm     44%	High rpm indicate more fuel
IAC	Duty Cycle	Idle     50%	2500rpm     41%	High rpm less air bypass

Sensors:

l  ECT

l  TPS

l  CRANKSHAFT SENSOR

l  MAP

l  AT sensor

l  CAM SENSOR

Actuator

l  FUEL INJECTOR

l  IAC

I have got some of the diagrams from the following web and books

Books

l  Understanding automotive electronics 6^th edition written by william B. Ribbens

l  Automotive mechanics fundamental published by Gregory’s Publication

l  Hand out from Unite

Internet Resources

http://ljet4826.blogspot.com/2010/09/coolant-temp-sensor-cts-thermistor.html

ECT 

ECT Sensor	Cold Engine	Warm Engine
Result	2.6V dc	1.07V dc

Note

ECT – normally uses a NTC sensor which means as sensed temperature increases the voltage drop across the sensor decreases. This is because NTC sensor’s resistance decreases as temperature increase as shown in Figure1. We had 2.6V when engine start cold and it drops to 1.07V after engine warmed up. Our ECT sensor seems giving out a reasonable result.

TPS

TPS Key on	Fully Closed	WOT
Result	0.72V dc	4.2V dc

TPS Key off	Fully Closed	WOT
	0.691V dc	3.91V dc

The measurement we got shows that as the throttle valve opens up to WOT from closed this is due to the fact in the sensor there is a variable resitor which increases it resistance as throttle valve opens and decreases as it closes. When key is on will give a higher reading than when it is off

 

Crank sensor

Crank Sensor	Idle	2500rpm
Result	4.07V ac	7.52V ac

As we can see that when engine is speeding up the voltage output of the sensor will be increased because the rate of change in the magnetic flux is increased therefore more voltage is developed.

MAP sensor

Map Sensor	Idle Vacuum	Key on engine off
Result	0.54V dc	1.79V dc

When the car is at idle the throttle valve is fully closed therefore there is a high vaccum which indicates low pressure. The sensor indicated this situation with a low voltage. Where as when engine is off, there will be no sucking action from the engine. Pressure inside is atmospheric pressure. That’s why map sensor indicated a higher voltage.

 

AT sensor

Air Temp Sensor	Cold Engine	Warmed Up
Result	3.46V  dc	3.2V  dc

This is also a type NTC sensor its resistance decrease as the temperature increase therefore it gives a higher reading when engine is cold and lower reading when engine is warm.

CAM sensor

Cam Sensor	Idle rpm	2500rpm
Result	1.2V ac	4.02V ac

Cam sensor is basically very similar to a crankshaft sensor. It monitors the rpm and position of the pistons. As we have already seen with crankshaft sensor. This particular sensor is a magnetic type. As the tab move a crossing pole piece an alternating current is created in the sensor coil. The faster the camshaft turn the higher reading it will produce. Somehow crankshaft sensor will normally produce a much more reliable monitoring result because it is positioned next to the crankshaft.

Fuel Injector

Fuel Injector	Idle	2500rpm
Result	36.7%  duty cycle	44% duty cycle

In modern EFI system emission control and fuel efficiency are two main considerations. Control system will always try to stick to 14.7:1 air fuel ratio whenever is possible. It does this be adjust fuel injector opening and closing time. Duty cycle indicate what’s the percentage of time fuel injector will open or close up in a certain time. When the engine is at idle fuel injector only open about 36.7%, however as rpm increases it increased to 44%. Its control system’s job to decide what is the best duty cycle of a particular time is.

IAC sensor

 

IAC	Idle	2500rpm
Result	50% duty cycle	41% duty cycle

IAC is measured in duty cycle similar to fuel injector. This measures how much bypassed air will be allowed into the intake manifold. When the engine is idling throttle valve is fully closed therefore IAC may need to bypass more air into the manifold to provide a smooth idling condition. As engine is out of the idling mode the throttle valve is opened up by driver bypassed air amount is reduced. Therefore its reduced from 50% to 41%.