With the FirstLook sensor you now have a more comlete picture of an engine's performance, quickly and easily. Once you have learned to use the sensor combined with the timing chart you will be able to find burnt valves, bad injectors and other engine performance problems without major disassembly of the engine...and in a fraction of the time currently required. Consider how long it may take just to remove spark plugs to perform a compression test on today's engines.
FirstLook is unique because it looks at pulses in engine airflow, allowing you to display "the pulse of your engine" on standard scope equipment. While scanners interrupt the information they receive from engine sensors and engine analyzers tell us what the ignition system is doing, it is difficult to see what is actually happening in the engine without intrusive tests. With FirstLook in your diagnostic arsenal it will now be possible to see what is dynamically occurring in your engine. Although this user's guide will focus on automobile combustion engines, the FirstLook sensor may also be used with other gasoline and diesel four stroke engines.
Figure 1.0
Theory of Operation
The FirstLook sensor looks at the airflow pulses generated by the normal operation of internal combustion engine. The sensor detects these pulse waves through either the exhaust or vacuum sides of the engine. All engines produce a predictable pattern of these pulses that can easily be displayed on the scope when connected to FirstLook. This pulse wave is sensed and the voltage is output for display by the scope. Changes or irregularity in this predictable pattern may be traced back to problems in the engine. The pulse wave can also be affected by unburned fuel in the exhaust and this abnormality is also detected and displayed. The FirstLook sensor does not require any external source of power, so you never need to purchase or replace batteries.
It is important to note that changes in timing advance, pipe length, and the effects of tuned exhaust will have an impact on waveform outputs. Some waveforms will be almost perfect but others will show the effect of a tuned exhaust. Engine problems will always cause a fluctuation of the waveform that extends above or below the average of the other cylinders. This is where comparative analysis of cylinders becomes important. In general the more symmetrical the waveform and distribution above and below the zero reference line, the better the condition of the engine.
Conditions caused by lack of fuel or lean burn will cause a drop out in the waveform. Problems resulting in excess fuel (dirty injectors, poor combustion, dirty plugs, plug wire problems) will show up as a drop out in the waveform followed by an increase in waveform above zero as the engine works to compensate for the excess fuel that gets burned in the manifold. This is the work of the computer and oxygen sensor in today's engines.
Automotive Engine Timing Chart
The timing chart shown in Figure 1.1 is the key to the diagnostic power behind the FirstLook sensor by correlating the timing of engine events to the visual display. Data is shown for specific cylinder configuration.
The leftmost column in the chart shows engine speed in Revolutions per Minute (rpm).
The data in columns A to F is the time between valve opening events for a given engine with a 2 to 10 cylinders per 1 Cycle of a 4 stroke engine.
The next column, Time to Complete 1 Cycle is the total time in milliseconds to complete all firing events in a specific engine at a given rpm. Note that 2 revolutions equal 1 cycle in a 4 stroke engine. This is also the total time window that needs to be open to see the complete firing cycle of all cylinders. If it is necessary to look at multiple cyles, adjust your scope to a timebase that allows for viewing of multiple cycles of the engine.
Starting Time Base References are suggested for specific tests in the right most column.
