CAN node for pre-1996 Vehicles

[JRC903]

Well yes--that is generally true, However, the type of sensor I refer to costs less than $15--- but oftering +2/-2 gs in increments of about 0.003 gs/bit(10 bit a/d) In my exprience, to fully appreciate subtle changes in velocity influenced by other physical force (air pressure or rolling friction) tends to require data acquisition times at least 10-100 times faster then sampling the VSS.

[dcb]

Using both vss and accelerometer might be the most robust actually. Either one by themselves would have no way of knowing if you are climbing a hill or being affected by wind (though you need a wind sensor for that one).

The vss is a little chunky, but pretty accurate, since it is limited by your CPUs ability to measure time (i.e. within a few microseconds). If it is your typical 'murrican car with 5000 pulses per mile then @60mph, if you can measure 10us, then you will get 83 samples per second where each sample is accurate to 1 part in 1200, slower = more accuracy but lower sample rate.

[JRC903]

You are right about the VSS's utilty. I would not discount the VSS's usefulness at all. In the first version of the VID, I spent processor time measuring VSS pulse width etc--but only to within the nearest 250 microsecond. The new version, just counts pulses over a fixed period of time. Given the time interval i use, this naturally can result in slower response to non-average velocity conditions. But till now--this was good enough. The addition of a two or three axis accelerometers. would serve to augment the VSS--- not replace it.. And, it would be cpu time intensive-- to make multiple measurements and integrate fps/s to fps would take CPU resources. Because when you think about it, the VSS is doing most of the work.(most of the time--anyway)... it is more than adequate for simple fuel meter applications. My VSS gives about 4000 PPM. At 60 MPH that is about 66 counts per second (1.1 % error)--or about 15 millisecond period. My basic clock is current set to (a slow) 125 microseconds--so 15 ms resolves to an even 120 counts. So--yes i agree.. VSS is GOOD.

[alohaspirit]

I do understand why this would be good

Better diagnosis on older engines + some people want the simplicity of plug and play
(and lots of times, those are the people you need to persuade to get better mileage)


The downside of course would be money, time and effort

[JRC903]

Yes, this might be the closest to Plug-n-Play old cars can get.

[dcb]

It isn't plug and play if you have to hook up a bunch of wires. All my mpguinos have the same plug and I can move them from car to car easily, or even connect multiple with a simple 4 conductor Y adapter, but the matching plug had to be installed first.

[JRC903]

You are correct again. Plug and play it is not. I only said it was as the "closest to Plug-n-Play old cars can get" to that. Obviously, anyone can "rig" up their own custom device and then make it possible to move, for instance, the display unit from car to car-- but I think what the plug-play poster meant, was that IF such a standardized interface existed, it would be more "LIKE" the plug-n-play scan gauge for newer cars. That having been said, I am painfully aware of the "dangers" of taking something simple and effective, and making it complicated-----purely in the name of technological elegance. I am just as cognizant that one "intended" consequence of the status quo, is by definition, to throw sand in the engine of change.

[andylaurence]

The great thing about OBD for older cars is the other things you can do with it. There's lots of applications (not just in the ecomodding world) that would find OBD useful. For example, I may be ecomodding my Smart Roadster but I have a track car that doesn't have OBD and would benefit greatly from being able to interface with RaceChrono, which supports logging RPM and otehr parameters via OBD. I'm sure there's many more potential areas of use, too.

[mwebb]

if the purpose of your invention is to

"be cheap "
and provide feedback to the driver so that the driver can adjust his / her driving habits to improve fuel economy .

why not just monitor the load sensor , depending on the system the load sensor will be ;
either MAP sensor
or
MAF sensor

at any given condition a lower value on either will result in "better" fuel economy than a higher value .
so the driver adjusts driving habits to keep load value low .

that's it , simple and frugal
K.I.S.S.
it will not function with early ford digital MAP sensors or
GM digital MAF sensors

[racprops]

Sorry but there is such a gauge, a Vacuum Gauge...

Rich

Originally Posted by mwebb

if the purpose of your invention is to

"be cheap "
and provide feedback to the driver so that the driver can adjust his / her driving habits to improve fuel economy .

why not just monitor the load sensor , depending on the system the load sensor will be ;
either MAP sensor
or
MAF sensor

at any given condition a lower value on either will result in "better" fuel economy than a higher value .
so the driver adjusts driving habits to keep load value low .

that's it , simple and frugal
K.I.S.S.
it will not function with early ford digital MAP sensors or
GM digital MAF sensors