Sensor/Sending units?

[Smidge204]

I'm developing an embedded computer module to retrofit into my car (1964 AMC Rambler) to monitor and record various things such as temperatures, pressures and so forth. So far I've had good results finding ways to measure these things and interface the sensors with the microcontroller I plan to use, but I'd like to ask if anyone has ideas for the following:

1) Fuel use metering. I know they make devices that can be installed in the fuel line to measure flow rate, but I'm having trouble finding something that would be suitable for my situation. Any recommendations?

2) Oil pressure. Separate from the simple on/off switch sensor that drives the dashboard "Oil" light, something that outputs an analog or digital signal that can tell me actual PSI. The engine has a remote mounted oil filter and exposed oil lines (I believe only a portion of the oil pumped is diverted through the filter) so installing something would not be an issue.

3) Vacuum pressure. Same as above, something that I can electronically monitor. I plan to mount this sensor in the bottom of the air cleaner after the filter.

=Smidge=

[mazdatech177]

auto meter makes electric oil pressure gauges, i had one on my old chevelle, though all the sending unit was was a pressure transducer. go to a parts strore and buy a manifold absolute pressure sensor (MAP). take a vacuum line from your intake and run it to your sensor, youll need a 5 volt reference, a ground and the third wire is the signal wire that carries the varying voltage to the computer, or whatever you choose to run it to. generally the higher the vacuum reading, the lower the voltage out of the MAP sensor

[Smidge204]

That's seems like a good start. Thanks!

Still looking for some sort of fuel flow device, though.
=Smidge=

[curtis73]

You can use MAP and throttle position to estimate fuel usage, but the MAP must be in the manifold and you'll have to calibrate it based on actual numbers.

Some cars had MPG gauges which were vacuum gauges that had MPG numbers calibrated on it instead of inches of mercury. They worked pretty well as an instant economy meter. If you basically used a MAP sensor and a TPS, you could instruct the computer to extrapolate MPG estimates.

[Smidge204]

Well, what I'm really interested in is actual rate of fuel use, with the ability to calculate MPG as a side benefit. Also, how would the state of the engine effect the meaning of measuring fuel economy that way? (eg: just before vs. just after a much needed tuneup)

I've been searching around, and it looks like they make just the thing for marine and aircraft applications. Of course... that makes them expensive (~US$100), especially considering the rest of the project right now is figured to be about $60 worth of parts! But now that I have an idea of what to look for I might try to find a used one.

Thanks for the info, though. It may be interesting to try both methods and compare the results!
=Smidge=