Mechanical Injection: measure fuel flow?

[Dalez0r]

Anyone know of a proven way to measure the realtime fuel consumption of a older distributer-pump style diesel? Is a flowmeter the best option, and what type, installed exactly where in the system?

[dkjones96]

I'd say a flow meter in the line to the injection pump if it is a return-free system. If it does have a return you'll have to measure that too.

[jeep45238]

If you know the orifice size and pressure of the fuel going through the hole it won't be too hard to figure out at all.

[Lug_Nut]

The flow rate of consumption will be quite low at idle and moderate flow at WOT (I know, no "throttle" in a diesel, but you know what I mean). Trying to find one meter with sufficient accuracy at these minimal flow rates will be tough.

[Dalez0r]

Originally Posted by jeep45238

If you know the orifice size and pressure of the fuel going through the hole it won't be too hard to figure out at all.

Doesn't that also require knowing the viscosity of the fluid to work? Could vary wildly with this stuff.

It appears VW's have a return port coming out of the distributer pump (fuel cools the distributer?) So, I'd have to measure both the fresh fuel and return fuel lines, and take the difference.

So, I need to find out how many GPH the pump is rated for, and find flowmeters that work in that range that are fairly accurate in the middle...?

So much harder than reading pulsewidths... >>.<<

[jeep45238]

Yes, it requires the viscosity. You will be able to find the viscosity on various engineering websites, a high and a low.

Otherwise you'll be dealing with adding flow meters to the fuel rails.

Either way, it's not going to be easy. The easiest thing to do would be looking for a replacement fuel pump and keep you eye out for one that has specs on it

[Lug_Nut]

Originally Posted by Dalez0r

It appears VW's have a return port coming out of the distributer pump (fuel cools the distributer?) So, I'd have to measure both the fresh fuel and return fuel lines, and take the difference.

The TDI, yes. The older idi from the generation 1 and 2 Rabbits, Jettas, pickups, Dashers and such don't have the bypass and return.

[Dalez0r]

Think a power steering pump with a high resolution encoder wheel on the shaft could measure the range of fuel consumption on this engine? What's the idle fuel consumption on these little things? The smallest diesel engine I could find data on was a 7.3L powerstroke, they apparently burn as little as .8gph, but that's almost what I'll be burning going down the highway...

[Lug_Nut]

Idle consumption is down around .13 gph for the 1.9 liter TDI.

[OldBeaver]

Hello all there. This is my first post in this forum.

I have a 1989 MB car, to which I installed a RD28 6 in line diesel, of 2.8 liters.
It is a naturally aspirated diesel.

I am developing a system for mesuring diesel fuel consumption. As my engine has fuel return flow I installed two fuel sensors.

The idea was to measure diesel consumption in three ways, and validate and calibrate them with each other:

1. Install a couple of fuel sensors on each fuel flow pipes, one on the fuel injector pump pipe and another in the return pipe. Then measure both signals, digitalize them and make the difference to account for the net flow.

2. Measure throttle position and rpm signals and make a model to estimate fuel consumption in relation to these two variables. The specs of the fuel pump are necessary for this method. I already developed the math model.

3. Measure fuel tank curve and the distance of a trip. One can do it always by refuel the tank full after each trip, you would say. No, no. What I am talking about is having a almost "real time" measure of tank. For that, I filled the fuel tank and recorded the digitalized signal of the fuel sender every time it changed. (It proved to change in jumps, approx. every 5 liters of fuel. This is necessary as the fuel tank isn?t linear in capacity).
At the same time, one need a digitalized signal of the distance. Dividing the distance by the liters every minute or so, you will have a measurement of "real time" consumption.

For the digital part of it I am using an Arduino board and a LCD screen.

Please see: http://www.flickr.com/photos/oldbeaver/4116160742/
and : http://www.flickr.com/photos/oldbeaver/4115242131

At present, I am in the phase of getting this to work.

The Arduino Board and the LCD screen are conversing ok.
I have 7 signals already wired to my system.

However, one of the fuel meters are broken, cause no signal is coming out from it.
The second problem I have is the impedance of the voltage dividers that must be used for each signal before entering to the Arduino board, as car signals are always close to 12 volts and Arduino maximum input is 5 volts.

So I am stopped at this point.

Need a lot of time to test suitable impedances for each signal, as I am not electronic (just a forester), cause they may be different. Besides, I need to replace the broken fuel meter.

What I want with this project is to provide a fuel meter system for old diesel engines like mine and many others.

Any ideas or any help?

Best,

OldBeaver