I had one of the Zemco fuel mileage computers installed in my 73 pontiac back in the late 70's. i currently have one in my garage. I'm planning to put it into my dodge pickup which has FI. they didn't use a flow meter on diesels or DI engines on them. they had an adapter that measured injector pulse. this item was made buy floscan. i have contacted them about the details of this item. here is the link to the patent.. Google has a great patent search.
Method and apparatus for calculating ... - Google Patents
Here is a quote from the patent about fuel measurement
the fuel system 20 of the engine and incremental distance sensor 16 is on the vehicle where it can measure the vehicle's wheels It is distance sensor 16 to an axle output shaft of the vehicle Fuel system 20 is schematically tion system of a six cylinder diesel use in heavy duty trucks Such an Caterpillar Co The fuel system circuit 22 that receives fuel under pump not shown that is connected tank not shown The fuel supply to fuel injectors 24 and returns the system The directions of fuel circuit are shown by arrows Fuel consumption sensors 12 and into fuel supply circuit 22 in order to which fuel is supplied to and supply circuit respectively The fuel can be FloScan fuel sensors signal in accordance with the through the sensor The frequency by the fuel consumption to the rate at which the fuel is sensors For the application shown consumption sensors are chosen to mately 48,000 pulses per gallon of Approximately one fourth to passing through fuel consumption return to pass through fuel amount of fuel being supplied to Fuel consumption sensors 12 into fuel supply circuit 22 in order which fuel is supplied to and supply circuit respectively The can be FloScan fuel sensors signal in accordance with the through the sensor The by the fuel consumption to the rate at which the fuel is sensors For the application shown consumption sensors are chosen mately 48,000 pulses per gallon of Approximately one fourth to passing through fuel consumption return to pass through fuel amount of fuel being supplied to passing through fuel consumption sensor 12 does not
return to pass through fuel consumption sensor 14. The Circuitry 18 contains signal processing circuitry, a circuit for counting the pulses produced by the fuel consumption and incremental distance sensors, a microprocessor for performing the required calculations, and memory and a clock to serve the microprocessor. Signal conditioning circuits 32-36 receive the pulsed signals produced by sensors 12-16, respectively, and produce pulsed signals at the same respective frequencies. These pulsed signals are sent to a programmable timer/counter 38 which, under the control of microprocessor 40, accumulates pulse counts. The programmable timer/counter can, for example, be an Intel 8254, which contains three identical 16-bit timer/counters 42-46. Each counter can count, independently of the others, from 0 to 65535. Counters 42-46 are operated to accumulate the count of pulses respectively received from signal consitioning circuits 32-36. When microprocessor 40, which can be an Intel 8031, attempts to read the contents of one of the counters, the signal on the chip select line 48 is set to a logic "0" and an appropriate address is sent over address lines 50 to read/write logic 52. When it desires to read the designated counter, the microprocessor sets read line 54 to a logic "0" state, thereby sending a signal to control word register 56. Signals from the control word register cause the counter designated by address lines 56 to load its current count into a special register. This count data is then transferred via internal bus 58 to data bus buffer 60, and then to the microprocessor over 8-bit data bus 62. The 16-bit count read from the designated counter must be transferred to the microprocessor in two 8-bit bytes. Microprocessor 40 is also connected to a read-only memory (ROM) 64, a clock 66, and a random access memory (RAM) 68. ROM 64 can be, for example, an electrically programmable ROM (EPROM). The ROM contains the program for controlling the microprocessor and the RAM is used to store data generated and required by the program. Microprocessor 40 and ROM 64 can be replaced by a microcontroller, which can be
amount of fuel being supplied to the engine is proper- 40 programmed to serve the same function. Accordingly,
tional to the difference between the frequencies of the microcontroller can be regarded as an equivalent of
pulses produced by the two fuel consumption sensors. the combination of microprocessor 40 and ROM 64.
In another diesel engine application, such as a Cum- Finally, the microprocessor drives display device 70
mins engine, where a more nearly constant fraction of which displays the corrected fuel economy calculated
the fuel supplied to the fuel supply circuit is injected, an 45 by the microprocessor. The corrected value displayed
accurate measure of the fuel consumed by the engine
can be obtained by monitoring the frequency produced
by fuel consumption sensor 12. Accordingly, fuel consumption
sensor 14 can be dispensed with in such applications,
and the fuel returning from the fuel supply 50
circuit can be returned to the fuel supply system along by display device 70 can be the average of the corrected fuel economy over a period of time, for example, 5 seconds. Other averaging schemes to prevent erratic readings will be apparent to those skilled in the art. The calculations performed by microprocessor 40 on the data provided by sensors 12-16 correct the fuel
consumed by the engine to account for that fraction of
the "fuel" consumed which is converted to or from
kinetic energy. The fuel consumed by the engine when the "return " line. If only fuel consumption sensor 12 is to be used, the flow sensor can be chosen to produce fewer (e.g., 19200) pulses per gallon of fuel