Diesel instrumentation

[diesel_john]

Originally Posted by consaka

Ok this is just ingenius. I love it.
questions and suggestions. Id love to see a scope reading off of this.. part and full throttle.. pretty please?

I'd like to see it too. i miss all the test equipment where i use to work.
I don't have a storage scope, so am fixin to use an old pc and sound board to time capture. I read that the max volts for line in, is 2.8 peak to peak, so i need to voltage divide. don't know how much just yet.

[consaka]

Originally Posted by dcb

Find a flowmeter first, then we can discuss

I already have an old zemco. How many do I need?

[dcb]

For typical diesel you need two, one to measure fuel going into the pump and one to measure it going out.

I thought briefly that you could use one flowmeter, but the pumps (bosch at least) have internal bypasses that make it difficult, as John points out.

Rather than timing the injection pulse lengths, you just count the number of pulses from the flowmeter, as each pulse represents a certain volume of fuel (more or less). If you have one on input and one on output then you subtract the output count from the input. With the flow rate of the output it might have reasonable resolution. You might still want to time the length between pulses for more predictive instantaneous readings, but for the longer term trips you really just care aboout the total pulse count.

Though the flowmeter approach is probably better suited for the Carb thread since that is a single sensor solution for carbs, just don't have a solid on flow sensor sources.

I am liking the chances with the dual knock sensor approach for the diesels. I'm sure the price can come down later since knock sensors are glorified peizos, and piezos are cheap.

[consaka]

Originally Posted by dcb

For typical diesel you need two, one to measure fuel going into the pump and one to measure it going out.

I already explained how to do this with one flow meter and to bypass the return line. But yes ideally two would be nice with a logic board to do the math for the output to the mpguino

I thought briefly that you could use one flowmeter, but the pumps (bosch at least) have internal bypasses that make it difficult, as John points out.

It can bypass internally all it wants since internally isnt a resevior with air in it it will make no difference on fuel demand from the tank. Any bypass or leakage internally is either going to stay in the pump or more likely go back to the tank on the return line. The only thing making it difficult is if they have more then one return line going back to the tank.

Rather than timing the injection pulse lengths, you just count the number of pulses from the flowmeter, as each pulse represents a certain volume of fuel (more or less). If you have one on input and one on output then you subtract the output count from the input. With the flow rate of the output it might have reasonable resolution. You might still want to time the length between pulses for more predictive instantaneous readings, but for the longer term trips you really just care aboout the total pulse count.

What you just described is what I have explained a few times already. As for the instantaneous reading the zemco was very precise in that regard. You are either using fuel or you aren't. Personally I dont think those old computers that computed the data from the zemco's was all that great, compared to the mpguino, but even on a carbed engine the response and accuracy was right there.

Though the flowmeter approach is probably better suited for the Carb thread since that is a single sensor solution for carbs, just don't have a solid on flow sensor sources.

You are right about a good source for flow sensors but I think if someone with a few pesos wanted to have some made in china cheap there would be a good little market for it similar to the mpguino market.
I personally think a zemco would be more accurate then trying to measure the pulsewidth. As your injectors get old and get deposits built up it can change their flow characteristics. If that happens then your accuracy went out the window. As we are all guessing our settings to some extent our calibration is a bit suspect as it is. With an accurate flowmeter or two none of that kind of thing would affect it at all. Once calibrated it shouldn't need calibrated again. The trick is to come up with a really accurate high resolution design that can be outsourced cheap enough.

[dcb]

no further comment.

[diesel_john]

[QUOTEIt can bypass internally all it wants since internally isnt a resevior with air in it it will make no difference on fuel demand from the tank. Any bypass or leakage internally is either going to stay in the pump or more likely go back to the tank on the return line. The only thing making it difficult is if they have more then one return line going back to the tank.QUOTE]

the internal bypass concern involved a concept using pump rotations and fuel control rod position a few pages back.

if the ball melts in the old zemco a 6mm BB works nice.

i check calibration each tank full any way.

there probably is an inexpensive impeller in a fish bowl pump or
something that would make a good flow meter, we just haven't found it yet.

[consaka]

the internal bypass concern involved a concept using pump rotations and fuel control rod position a few pages back.

I thought it might be something like that. fuel rate from the tank, compensating the return line of course, is still going to reflect fuel demand by the engine. Sooo the zemco's or a pair of zemcos would still work.

if the ball melts in the old zemco a 6mm BB works nice.

You know that is interesting. I have heard of that happening but the last one I rebuilt had a very hard plastic ball with a fairly thin skin. Id say pretty roughly the same mass as the fuel and I would think that would be important for universal positioning.
If i remember correctly there is a rubber piece that acts as a nozzle inside. Perhaps that could be sized for the engine? It is enough of a restriction that larger engines can be starved for fuel.
Do you happen to have one on hand? My father has one that I fixed and I am going to see if he can bring it back from Idaho the next time he visits. See if I can't figure a way to improve or dupe the design by cast or machine.

there probably is an inexpensive impeller in a fish bowl pump or
something that would make a good flow meter, we just haven't found it yet.

You really think that would stand up to gasoline and hot diesel fuel?

[diesel_john]

check out my photo gallery for a snap shot of the signal from the home made injection line sensor. Could work to trigger a timing light but the noise floor becomes a concern at higher speeds for use as an injection duration sensor.

[max_frontal_area]

those are dogs. spend the xtra $$$'s for one with a snail. upgrade it to something with a bigger compressor wheel and add an water to air intercooler to keep egt*s to a minimum. best yet get a vnt (variable vane) turbo.
now you will be able to drive uphill also!

[Christ]

mod?