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mpg display for mechanical diesel

Not sure if this is the right newsgroup....

i'm doing some experiments with the engine of my motorhome (turbo boost levels, intercooler cooling via water misting, injection pump timing and flow rates etc)

what i really am after is the best fuel economy for power tradeoff, and it'd be best if i could have a display on the dash to show the fuel being used per mile.. average and instiant.

i know you can buy a gauge for boats, but they need a gps plotter nema input for the distance bit, and cost a fortune, but even then there are not many options, since electronic diesel injection, you can get the info needed from the obdi2 port.

i know i will need 2 flow meters, one in the supply and one in the return line, i can get speed pulses either from the electronic speedo or fit a hall effect sensor and magnets to the prop shaft.

what i can't do is the electronics to take the speed and flow meters outputs, work out how much fuel has been used and display it in mpg (uk mpg units, 4.454 litres to the gallon)

i can solder, etch pcb's, but can't program pics and suchlike, but i'm sure i can find someone to do that if i can get the code.

Reply to
Gazz
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On Tue, 15 Jun 2010 00:33:57 +0100, "Gazz" wibbled:

Counter incrementing on the (presumed pulse output) flow sender and decrementing on the return sender. Then count and display the number of prop shaft pulses for a particular and fixed number of fuel-difference counts? 7400/4000 series logic territory possibly? Probably need some dividers to arrive at a real MPG reading.

If it were me, I'd whack an AVR/PIC in there and either learn to program them in C (AVRs are IME very easy beasties - you'll be able to poll everything and totally ignore setting up fancy submodules, timers and IRQ handlers for something like this, bar enabling the IO port directions, which google will lead you to virtually boilerplate code for), or subcontract that bit.

This solution over the raw logic would make "instantaneous" + averaged readouts much easier and you can add a boat load of other standard car dashboard crap in there too, like average trip speeds[1] and so forth for no extra hardware.

[1] OK, now you need the internal timer/counter circuit too and a reasonably decent clock crystal - but setting that up is not hard.

You can download AVR Studio for free from Atmel's website and have a play

- the simulator is pretty good for messing around in.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.
Reply to
Tim Watts

Which engine? Is there an electronic TPS on the injection pump? The short answer, subject to limitations of accuracy, if you have or can rig a TPS you can estimate the MPG of a mechanically injected diesel engine.

Injection pumps are rather simple in how much fuel they provide for a given throttle angle, though it is not exact (they limit to a certain extent to prevent over fueling to limit obnoxious black smoke).

Using two flow meters might work, but the precision needed will be a problem, compared to total flow.

Reply to
PeterD

"PeterD" wrote

it's an iveco turbo daily, the 2.8 litre 100 horse direct injection lump, but i've added the intercooler and pump from the 120 horse unit, upped the boost pressure etc, hence my messing about to tune it all in,

absolutely no electronics at all on this engine, as long as it has over 7 volts to the shut off solenoid it'll run till the fuel runs out.

not sure, i tow a car on an a-frame with the motorhome, giving me an all up weight of over 5 tons, so any hill i find my self with the pedal to the metal, i dont need it right down, but it's easier to do that than find the spot where it's making power and hold it there whilst increasing it as the speed builds up,

gotchya, that explains why the boat mpg readouts using flow meters, gps speed logs and all that cost almost 4 figures,

Reply to
Gazz

For a diesel that's easy: pedal to the metal at low RPM.

The flow meters won't work right away. The diesel from the return is much hotter so you'll have a considerable error if you do not compensate for temperature.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------
Reply to
Nico Coesel

"PeterD" wrote

it's an iveco turbo daily, the 2.8 litre 100 horse direct injection lump, but i've added the intercooler and pump from the 120 horse unit, upped the boost pressure etc, hence my messing about to tune it all in,

absolutely no electronics at all on this engine, as long as it has over 7 volts to the shut off solenoid it'll run till the fuel runs out.

not sure, i tow a car on an a-frame with the motorhome, giving me an all up weight of over 5 tons, so any hill i find my self with the pedal to the metal, i dont need it right down, but it's easier to do that than find the spot where it's making power and hold it there whilst increasing it as the speed builds up,

gotchya, that explains why the boat mpg readouts using flow meters, gps speed logs and all that cost almost 4 figures,

Reply to
Gazz

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