What kind of FE instrumentation for Pre-OBD2 Diesel

[meelis11]

With some modifications in mpguino hardware and software it should be possible to use mpguino for this purpose too. No need to invent bicycle (mpguino) again.

It already has VSS input logic similar like we want here - it counts VSS pulses.
So we need to modify injector logic to measure pulses instead of pulse length. MPGuino uses two input pins (and two interrupts) for injector measure - one for pulse start and other for pulse end detecting. Currenty arduino pin 2 and 3 are connected together - here we need to separate them in schematic again.

[AndrzejM]

Originally Posted by meelis11

It already has VSS input logic similar like we want here - it counts VSS pulses.
So we need to modify injector logic to measure pulses instead of pulse length. MPGuino uses two input pins (and two interrupts) for injector measure - one for pulse start and other for pulse end detecting. Currenty arduino pin 2 and 3 are connected together - here we need to separate them in schematic again.

I thought the same, but counting pulses can be tricky.
For example - engine is idling and using 0.5 litre/hour when actual fuel flow trough the whole system is around 2.5 litre/min. Lets say that fuel flow meter counts 1000 pulses/ litre so one pulse is 1ccm

Now some maths:

First fuel flow will count 2500 pulses per minute = 150000 pulses/hour
Fuel used will count as -500 pulses / hour so second flow meter will count 149500 pulses per hour

If we want to update LCD screen once per second we'll get:

150000/3600 = 41.66666666666667 pulses/second from FM#1
149500/3600 = 41.52777777777778 pulses/second from FM#2
so the difference between those two numbers will be: 0.1388888888888889

So we need 7.2 seconds to see 1 pulse difference in flow!

As you can see that's not so easy to have instant reading from flow meters.

I'm thinking that best option will be to count time between pulses on both FMs
So for FM#1 we'll get 1 pulse per 24000us and 24082us for FM#2 accordingly

The difference is 82us (pretty small IMHO), anyway I think that would be the most accurate way of measuring fuel efficiency in a real time.

Time between pulses will allow us to get to those numbers above with pretty good accuracy and in a real time.

Then math is pretty simple

One liter for FM#1 will pass trough in 24 seconds and 24.082 seconds for FM#2
So fuel flow in liter/hour is accordingly:

3600/24 = 150 for FM#1
3600/24.082 = 149.5017 for FM#2

150-149.5017 = 0.4983 l/h

Combining that with VSS signal will give us l/100km or mpg

Error will be ~0.34% so it's not so bad for an instant FE gauge.

Of course tank average or trip average will be way more acurate, after some calibration.

[meelis11]

What about this flow meter?
Low flow flowmeter, mini - Q= 0,025- 3,0 LPM, 6.800 pulses/Litre
There are no prices though, maybe somebody can contact them (i dont actually need flow meters)? 6800pulses/liter makes instant reading easier when counting pulses.
Anyway - for instant reading, we can use time between pulses, for cumulative reading we can count pulses.

Low flow flowmeter, FCH-m-POM -3 LPM, 97478350: B.I.O-TECH Flowmeter

[AndrzejM]

Originally Posted by meelis11

What about this flow meter?
Low flow flowmeter, mini - Q= 0,025- 3,0 LPM, 6.800 pulses/Litre
There are no prices though, maybe somebody can contact them (i dont actually need flow meters)? 6800pulses/liter makes instant reading easier when counting pulses.

3.0 LPM can be a bit low for big diesel. I think it's best to do the bucket test on a return line and see how much fuel can run trough the system at various engine speeds. Then we can talk about getting the best flow meter for a given engine.

Anyway - for instant reading, we can use time between pulses, for cumulative reading we can count pulses.

That makes sense. Good idea.

[Hilly-Billy-13]

The hardware mods are very minor, add a 1 pin connector, 5.1 Volt zener diode & resistor as per the other 2 inputs. Cut the trace between pins 4 & 5 run a jumper from from the disconnected pin (depending on circuit board it could be either 4 or 5) to the junction of the resistor & zener diode. Run a jumper from the other end of the resistor to the added connector. Connect the 2 flow transducers to the inputs for pins 4 & 5.

The "Devils in the Details" in this case it's the code, as some one pointed out for quick readout you need to count the time between pulses from the flow transducers, and use this to figure short term fuel consumption. For long term calculations you may want to keep track of the number of pulses. The MPGuino code already does this for the vehicle speed. I figure I'll get the hardware going then see what can be done for software.

I'm more of a hardware person than software, I can appreciate nice clean code, and I try very hard to write it when I do so.

Bill

Originally Posted by meelis11

With some modifications in mpguino hardware and software it should be possible to use mpguino for this purpose too. No need to invent bicycle (mpguino) again.

It already has VSS input logic similar like we want here - it counts VSS pulses.
So we need to modify injector logic to measure pulses instead of pulse length. MPGuino uses two input pins (and two interrupts) for injector measure - one for pulse start and other for pulse end detecting. Currenty arduino pin 2 and 3 are connected together - here we need to separate them in schematic again.

[Hilly-Billy-13]

I've been looking at another of Bio Techs offerings, the fch-m-pom-lc-08-lpm-97478617-LC FCH-m-POM-LC -0,8 LPM 97478617 : B.I.O-TECH Flowmeter In the North American market, they sell direct, I'm not if they have a Rep for Europe.
Bill

Originally Posted by meelis11

What about this flow meter?
Low flow flowmeter, mini - Q= 0,025- 3,0 LPM, 6.800 pulses/Litre
There are no prices though, maybe somebody can contact them (i dont actually need flow meters)? 6800pulses/liter makes instant reading easier when counting pulses.
Anyway - for instant reading, we can use time between pulses, for cumulative reading we can count pulses.

Low flow flowmeter, FCH-m-POM -3 LPM, 97478350: B.I.O-TECH Flowmeter

[AndrzejM]

Originally Posted by Hilly-Billy-13

I've been looking at another of Bio Techs offerings, the fch-m-pom-lc-08-lpm-97478617-LC FCH-m-POM-LC -0,8 LPM 97478617 : B.I.O-TECH Flowmeter In the North American market, they sell direct, I'm not if they have a Rep for Europe.
Bill

Flow range min. / max. LPM

0,015 LPM 0,8 LPM

0,8 l/m can be too low for a passenger car's engine with "old" injection pump. The fuel flow can reach up to 4 l/m, try the bucket test first to see what you are dealing with. Then you'll be able to choose correct F-meter.

[94-turbo]

I'd like to add a MPGunio to my truck with a 6.5 turbo diesel. I haven't found a place to purchase one. This thread is describing what I've been designing, but without a read out I'm out of luck. Anyone have a lead on a MPGunio or other gauge? Thanks!

[meelis11]

Originally Posted by 94-turbo

I'd like to add a MPGunio to my truck with a 6.5 turbo diesel. I haven't found a place to purchase one. This thread is describing what I've been designing, but without a read out I'm out of luck. Anyone have a lead on a MPGunio or other gauge? Thanks!

Link is also in my signature:
MPGuino trip computer - MPGuino - get assembled mpguino from here!

[AndrzejM]

Originally Posted by 94-turbo

I'd like to add a MPGunio to my truck with a 6.5 turbo diesel. I haven't found a place to purchase one. This thread is describing what I've been designing, but without a read out I'm out of luck. Anyone have a lead on a MPGunio or other gauge? Thanks!

Hi, before you purchase MPGuino you have to be aware that it will require some wiring changes on the board itself and definitely changes in the code. So maybe it would be better for you to buy Arduino clone and build MPGuino on your own? It's not so complicated, and I'm sure you'll find lot's of informations and assistance if needed here on EM.

And remember to make a bucket test of fuel flow on return line before you'll purchase any flow meter. It's crucial to get FM that will be counting small enough amounts of fuel to be acurate, and big enough to not strain itself with maximum fuel flow in the system.