Diesel instrumentation

[99metro]

For an older non-turbo, non-OBDII diesel, I think I would have to agree with you Gravedigger. Keeping your foot out of it and monitoring your EGT would be a way of helping with fuel economy. 600 degrees is a good start, but you'd have to experiment to find your 50 mph (+/-), flat-road EGT. Then keep your EGT at or below that, even on acceleration. My happy spot on my 96 F250 PSD just happens to be 600 degrees also. I'm not sure what else you can do with it for instrumentation other than an Inlet Air Temp (at the filter) or air pressure/vacuum on the inlet manifold (?).

Obviously, you know the tricks for HP. I'd at least change the intake setup and maybe the exhaust if it has a cat and/or muffler. I'd love to have a little diesel to play with!

[instarx]

Originally Posted by dcb

I have suggested measuring throttle position and RPM to get a relative measure of consumption. Then combining those signals and a speed in an mpguino like device for display. Can anyone think of why that is worse than nothing?

The reason there are no mpguino-style gauges for older diesels is because the recirculating fuel system makes it impossible to measure how much fuel the engine is using at any point in time. Noting that there is a relationship between throttle and rpm doesn't change that. How would you calibrate all the different combinations of throttle and rpm to their fuel use - that's the original problem.

[americasfuture2k]

older (mid 80's) diesels dont use a TPS either. their throttle is flow control of the fuel output. and that regulates RPM.

[dcb]

From the diagrams I saw, it should be linear. The largest share of the return fuel is from the feed pump, but what gets forced through the injectors is controlled by the position of the control sleeve (controlled by the throttle) and the plunger moving back and fourth.

One could describe the control lever position to control sleeve with a function, or make a good guess at the demands at idle and at full throttle and come up with a formula that way. Alternately one could pop off an injector and measure how much fluid comes out of the injector after X revolutions for different throttle positions and map it that way. You might have to add a tps and an rpm signal though.

http://ecomodder.com/forum/showthrea...html#post63034

[dcb]

Ok, maybe not Those tension lever things might have some springiness in them and be active with the flyweights. So control sleeve position is a function of rpm AND throttle position (and "smoke screw" position to a lesser extent).

Hmm. If you could get a fix on the control sleeve position, it would be simpler. Otherwise you have to measure and build a rpm/tps to gph fuel consumption map.

[dcb]

Hmm... the piezo fuel line tach sensor approach is looking better.

You can derive rpm. You can probably also tell how long the pulse was, which is a function of rpm and control sleeve position (effectively stroke). Still need to determine the range but should be able to get a relative reading anyway.

fuel delivered = rpm * pulse duration * k

[instarx]

Originally Posted by dcb

Hmm... the piezo fuel line tach sensor approach is looking better.

You can derive rpm. You can probably also tell how long the pulse was, which is a function of rpm and control sleeve position (effectively stroke). Still need to determine the range but should be able to get a relative reading anyway.

fuel delivered = rpm * pulse duration * k

But how are you going to measure pulse length? I think you are confusing new, OBDII engines (for which gauges are no real problem and determining pulse length is relatively easy to do) with older engines. The older diesel engines like the 190D, for which there are no gauges, just use mechanical injection timing.

If you have electrically controlled injection timing there is already an Australian company that makes a device that measures the length of the injection event to determine instantaneous fuel usage data. I can't remember it's name but I found it on Google a year or so ago. I posted about it on a 6.5L diesel engine forum, so if anybody is interested I can probably find it in their archives..., but it won't work on older diesels with mechanical injector timing.

[dcb]

Originally Posted by instarx

But how are you going to measure pulse length?

Originally Posted by dcb

piezo fuel line tach sensor

It is something DieselJohn had mentioned a while ago. The steel fuel lines actually expand during the injection on the old diesels, and it can be sensed with a clamp on sensor that came with some tachometers.

Edit: found a reference, don't know what the signal looks like though.
http://www.onosokki.co.jp/English/hp...ve/ge1200.html

[instarx]

Originally Posted by dcb

It is something DieselJohn had mentioned a while ago. The steel fuel lines actually expand during the injection on the old diesels, and it can be sensed with a clamp on sensor that came with some tachometers.

Edit: found a reference, don't know what the signal looks like though.
ONO SOKKI - GE-1200 Diesel Engine Tachometer

Those steel-tubing fuel lines expand!? I suppose that's possible, but it sure wouldn't be by much.

Oh - I read the reference. The sensors measure vibration of the fuel line, not expansion. That seems more doable. You'd have a lot of work to do since it counts vibration events - not length of the events. Its response time appears to be 0.5 seconds, which is way slower than you would need. Still, you might be able to use some sort of piezo-electric sensor with different electronics. You could also use a microphone to detect the sound of the injector firing (which in its own way is detecting vibration). This is getting so complicated it might be easier to just buy a new car with OBDII.

[dcb]

"The sensors measure vibration of the fuel line"
Nope, not according to Diesel_John. I found his original post and he says he saw the whole pulse on a scope:

http://ecomodder.com/forum/showthrea...html#post34033

A lot easier to clamp a piezo on a line than to retrofit obdII if you happen to otherwise like your old diesel . And even with obd you are not guaranteed fuel consumption feedback, I've heard a few reports about MPG on scangauges not working on diesels. So worth exploring a bit more anyway. Anyone want to donate an old vw diesel to me?